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Post by henri on Jan 16, 2015 20:28:13 GMT
you say both ya cases have same inlet track shape ,i'm sure all my recent builds (2 px's included)have had regular rounded corner rectangle openings ,with the exception of a cosa lump that had a hole on rear edge like yours but angled back not straight down like yours .its either a later px-e/efl improvement by piaggio or a local tuners trick ,no matter which ,i'd say smooth out the sharp edges/ridges where round meets squarish . if you decide to go 150 way theve got to be around unless everybody who's kitted there scoots is using them as doorstops , ive got 1 with piston an head ,i'm not sure of condition but will hook it out n check if ya interested ,but i'd probably go with a dr or other kit if it was my lump, the new 5 port barrels from india are about 50 quid cheaper than a dr kit an a polini/mallosi kit bout 50 quid more than dr , i personally dont rate olympia's an have had bad luck with dykes rings on other engines so have never tried pinasco's but vespaco seems to rate his 1 . tho that dr kit is well cheap ,usually i thought they where 130 , an i'm suspicious of that 3 port barrel as theve got it fitting lots of 2 port engines ,it would fit but the rear port would be unused , H
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Post by sime66 on Jan 17, 2015 7:31:18 GMT
The Inlets are a good little investigation and fine-tweaking job; just what this build is for. Maybe it’s just opened up a bit for a 150 and we’ve found a difference between 125 and 150 casings! Maybe they whacked an extra hole into the ones in the pile intended for a 150 barrel and gearbox? I posted the ’83 and ’82 (both PX150) engine inlet photos yesterday (previous page), I don’t have a photo on the inside surface of the ‘83, but you can see the round cut-out on both from the top. It’s nothing local; they’re both ‘imported’ to Cornwall by me! (Special licenses, revenues and quotas observed, of course). I'll definately have a good look into the holes. I was taking the relaxed and budget approach with the barrel, and waiting to see what the tide brings in cheap. I definitely don’t want to buy a 2-port by mistake, I don’t know if there is a 2-port DR180, H, and I can check that listing; anyway I’ll take a look at all options. New wasn’t my initial intention, but if buying new, I would certainly be thinking might as well be a 180, and I’d certainly be interested to see what you, or anyone else, has in the batcaves/bins/sheds/wardrobes/under beds and floorboards - or bedroom ornaments, if you’re inclined to dig. Don't really want the faff of finding someone here to pay them to rebore though. There are loads of 2nd hand 125 barrels around; I’ve seen no 2nd hand 150s in the last month or since I've been looking. Were there ever loads of PX150s in England? Mines an Italian import (about 10 yrs ago). I think most of the old PXs here are 125/200. Then there was the new PX150, which didn’t find a market here, and now there’s the new 125s, which seem to be the source of loads of 2nd hand PX125 stuff now (esp. barrels/exhausts) as people start to tweak those, as the warranties expire, I suppose. Two thoughts occurred overnight about the intention for this engine: · Ultimately I will probably be selling it (hopefully to get a 200 lump (more reliable?) to fiddle with when I get my full licence). When I’ve been looking at 2nd hand engines recently, I’ve always been put off a bit by casings that are already chopped about by persons unknown. I think mine would be easier to sell if it was unmolested. · The idea of this engine was to have it inside for me to fiddle with, when I'm in the mood, whilst still having a good engine in my scooter for the summer, and to do everything thoroughly, and take plenty of time with no real deadline (ideally autumn though). So I ought really to take the opportunity to do some Dremelling while I’ve got the luxury of time and a blank canvas. But I'm not spending this year preoccupied with this job either; it's an out-in-the-sun fun year, after the aggro of 2014. Those two thoughts contradict each other though, so I still don’t know, but I have time to think about it when I have the full story of what would be involved. There is no hurry; might still just wait to see what crops up and what I can do with it. Morning ponderings completed; other jobs to do…………
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Post by pxguru on Jan 17, 2015 8:14:40 GMT
The only thing you dont have is the barrel/piston. Either will be ok for your needs but the bigger bore of the 180 is easier to tune. The 20mm carb and old crank will be just fine. Using the same clutch will save some money as you would need another 21 tooth.
If you are going to open out the inlet then that old crank will need to be cut as well.
Whether its a 150 or 180 about 8000 rpm is where you should be aiming. The rev limit is 10,000rpm over that the reliability becomes questionable. Otherwise if the engine is built well, reliability is about set up of carb, compression and timing.
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Post by sime66 on Jan 17, 2015 11:04:21 GMT
Thanks, pxguru; that’s pretty much as planned, and simple for now, but with an extra tweak to achieve 8,000, and spending some extra time and care on carb set-up and timing. I’m not sure if you meant decent compression, or adjusting compression ratio, but that’s down the line anyway. (Unless I need to take care with the head when buying, but I don't think that's what you meant?) So: · I’m still on the lookout for a decent 2nd hand 180(pref) or 150 barrel for the time being, but if I do end up getting new, I’ll get 180. · I’m still on the lookout for EFL driveshaft half-gearbox – to make it EFL, for reasons already covered. · I’m using the rest of the PX/E gearbox I have, so I will have (21)/86x21,17,13,12 – 35,38,42,57. · I wasn’t thinking of opening the inlet in the way I think you mean, or messing with the crank (inlet timing?) I was just going to tidy the flow up from carb outlet, through carb box and crank inlet – leaving the size of sealing pad opening the same. · I’ll give the Dell’Orto 20 an overhaul and use it. It’s the one off my scooter when I bought it, and was working fine before I put the 24 on. · 21T clutch; probably use the same one – not bothered about the cost really; more thinking about having a clutch in an engine not being used. For the lack of agro swapping now I’ve got it right, I’d rather have one in each. Doesn’t matter right now. For now, the bits I’m after are as planned then; we can talk about Dremelling casings nearer the time, or whether this is port adjustments, or both for the 8,000. (I think matching casings to barrel, checking/adjusting port heights for 8,000, and keeping an eye on C.R.?) H, I’ve sent an email to check that DR from Italy . I’m sure there isn’t a 2-port DR177, but it’s easy to check anyway – that KT00017 reference is on the box for the full kit, not motortime’s listing reference. It’s a KT00017 wherever you look at it; I’ve seen it this morning on Italian, French and German listings. I don’t think it’s a problem. I’ve been pretty happy with that kit too, so would consider this option; I’ll see what they have to say anyway. I’ll also keep an eye on how many they sell, and what feedback they get. German KT00017: Thanks for input chaps; I’ll be back when I’ve made some progress with it……..
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Post by henri on Jan 17, 2015 16:34:47 GMT
from the piccy you can see the rear cut-out in the spigot so its def a 3 port , i was just questoning there fitting guide as half the engines in the list are 2 port,thats all. an if i was you i wouldnt mess with cutting a crank ,it would cost the same as buying a mazzy race crank an worsen the balance factor,ive a set of cosa cases coming an will take photo's which will show how piaggio lengthened the inlet timing without cutting the crank,an it works,i occasionaly knick the managements cosa 125 for a blat an it out performs any px125 easy ,ans prob got the edge on my 150cc, a tad embarrassing but true.thats why i'm counting pennys n delaying getting leggys/floor as that dr kit is priced mighty tempting , H
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Post by sime66 on Jan 18, 2015 8:33:43 GMT
There’s no 2-Port, there’s loads of chat on Net about using it on 2-Port engines. Chappy replied to my email within the hour yesterday; not conclusive from him – bit of a language barrier, but I’m sure now anyway. I’m also tempted to grab one, but trying to wait a while, see what else is about. And once I’ve got my gruppo termico sorted, all I’ll need to find is the cambio di velocità and I’ll be più veloce di merda fuori una pala! I’m not cutting my crank; don’t know how this one cropped up and grew; lets nip it in the bud. Going to look at my flow through carb to inlet though – make some templates; see what can be done. Yes mate; give us some photos of Cosa inlet – you know you want to. Short and sweet this morning; just been out for a ride and have a few winter maintenance jobs to do on my scoot while it’s dry outside…..
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Post by henri on Jan 18, 2015 17:00:23 GMT
i didnt think dr did a 2 port kit, polini do an i think some others use to, the net chat is people reckoning they can carve a 3rd port in there cases , not enuff meat on itialian cases to do it proper but lml can be changed , know what ya mean bout language ,bought my last dr kit from italy on a photo as description as "unit to change calorific value" suggested it was dieting advice , i'm cruising german e bay at mo, ya want to see what google translate mangles that into, when ya think carbs i'll turn you onto sum cheap german alternatives if ya like , H
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Post by sime66 on Jan 18, 2015 18:29:18 GMT
Pinasco do a 2-port 177 in Alu and CI. scootercentre is good for details of barrels and stuff; even some port maps, but not for the DR; no idea what they're like to buy from though - not cheap. This is quite interesting if you're into that sort of malarkey: blog.scooter-center.com/en/177cc-cylinder-options-for-2-and-3-ports-sprint-engines/Generally, when emailing Germany or Italy, their english is better than my Italian/German, so I don't criticise - Or India for that matter. I'm not looking for a carb unless one passes under the radar on Ebay, and I get a good'un cheap again; I have proper Dell'Orto Si24 in scoot and another proper Dell'Orto Si20 in spares. I've just got me feelers out for two main bits at moment, (barrel & gears) and any odds and sods as they crop up.
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Post by pxguru on Jan 19, 2015 9:43:51 GMT
It will go ok with a standard inlet like everyone elses does but opening it out will make a differance. Standard inlets are tuned with just economy in mind. Measure the inlet degrees you have on your standard crank and cases and compare it to what a touring tuned scooter should have and you will see what I mean. Inlet degrees are quoted as before and after TDC like 130/70. When cases are in pristine condition its a tough decision to cut them
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Post by vespasco on Jan 19, 2015 21:14:48 GMT
If you get a kit then youre probably going to have to attack them nice clean cases Scooter Centre are cool! Somethings are more expensive, others not so much! Their data is pretty conclusive too, unlike some of SIPs data which can be very vague. Ive used them quite a few times. No worries. €5 post with tracking, Similar to sip really. You can get a good few € for your £ at the moment too, so its a good time to buy anything from europe My spider senses keep telling me theres a spare (late) drive shaft in my shed which i thought i sold last year... Ill check that out when im a bit more agile. (Im still off work)! If youre really lucky theyll be attached to a set of 200 gears too?!?! Dont get ya hopes up just yet tho'! I do need to double check that. Memory's fading fast!
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Post by sime66 on Jan 19, 2015 22:29:04 GMT
Would you believe it vespasco, I just landed a good old PX150EFL driveshaft today! Proper Piaggio, out of a dead Vespa, cheaper than Indian, but needs a crux and rod, so a decent price. I’ll Post it up properly when it arrives, but here’s a sneak preview; no need to dig in your shed, think I'm sorted: With that in mind, for the last big bit I’m leaning towards going for a 180 kit, not a 150, and being led through some cutting, but my mind changes with the wind on that one; the DR from Italy keeps calling me, but I’m trying to keep some money in my pocket for a bit. Interesting what you say about scootercentre/prices/exchange rates; i just noticed SIP's price for DR has gone silly (and scootercentre is a bit more, I agree they are good for data though - good source of info): www.sip-scootershop.com/en/products/racing+cylinder+dr+by+sip+_10003000Hope your leg isn’t giving too much gyp; not really scooting weather though, I was pretty chilly yesterday morning even with my muffs. Brrr!
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Post by henri on Jan 20, 2015 7:46:11 GMT
you'd of stuck a new cruccy in anyway so a really good score there ,an ive tended to use sip more as scooter centres site tends to stick in german an get mangled more by google translate ,tho i'm slowly changing as sip seems to of gone downhill a tad recently ,for a dr kit i'd keep to italian sellers as thats where sip are buying an putting a mark-up on , i dug out my reciept for the smallie kit i bought 4 months ago ,memory was saying 130 as that was e bay n sip price at time but with postage it was 90 quid ,DOH, havent photo-ed the cosa inlets yet but if ya scope german e bay theres loads of cosa cases an the sellers mostly take photo's of the sealing pad which will give ya a idea of what i mean by piaggio's improvement , an as vespaco says the exchange rates good at mo so prices for new or used px/cosa stuff is well cheap ,tho postage robs the cream ,but all cosa boxes are efl as far as i know ,worth a look for ya rod/gears or even the better 24/24h cosa carb ,H
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Post by sime66 on Jan 20, 2015 8:05:08 GMT
From reading about, I believe it's wise to use proper Piaggio parts for crux and rod - yes I'd have done crux anyway. If I use pucker stuff, it's another £30, but I'm much happier putting old Piaggio in, rather than LML or Indian. I think that attitude will have to change though, as old parts become harder to find, and more listings are from india, or obviously Indian/Far-East sourced - even from renowned suppliers. So I'll be hanging on to my other PX/E driveshaft for sure - into the spares! I think buying direct from Italy, Germany, India is the way to go.
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Post by sime66 on Jan 21, 2015 6:47:41 GMT
Lovin’ Ebay Deutschland H, quick to replies to my questions last night too; quite a few bits into my watched list…… Found a couple of Cosa inlet photos there too; their extra hole is at the other end of the inlet to mine – haven’t yet got my head around which way it spins and whether this is early or late, but all stuff to add to the list of things to look at (I can see crank is same rotation direction as wheel and primary is opposite, so it seems later inlet, but I haven’t got time to think about it this morning; it’s payday and I’ve got €€€s to spend!!)
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Post by henri on Jan 21, 2015 9:40:33 GMT
weird ,your right ,i hadnt noticed that ,must be a 200 thing as the 125's at tother end ,same as your vertical round hole but slanted towards back of lump, damm piaggio imps /always got to mix it an you up , H
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Post by vespasco on Jan 21, 2015 12:23:10 GMT
Are you referring to the 'drilled' hole of the inlet, that looks like an after thought...? Pointing towards the front end. I thought that was normal for all px. Its normal for the 200 at least. Or am i missing something?
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Post by sime66 on Jan 21, 2015 14:37:19 GMT
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Post by pxguru on Jan 21, 2015 14:43:37 GMT
Another differance between 200 and 125/150 casings! The drilled part on both is like you say, an after thought. The cast hole is too short and the drilling corrects it. there is nothing special about the shape it makes they just dont bother to smooth them out.
The best info I have had heard over the years is its part of the casting process. The casting pulg that makes the inlet hole has to be withdrawn from the cast from the outside and will only make a parallel sided hole. I'm sure they could be a bit more creative to do a proper job though.
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Post by pxguru on Jan 21, 2015 14:59:08 GMT
That's some nice info Sime but no conclusion Quickly calculating in my head from your data your casings and cranks work out at 109/43. Thats 109 degrees open before TDC and 43 degrees after. For a pretty average tourer set up 125/55 would be fairly normal. Something very special (and on the race track) would be nearer 150/70. The basic idea is that, the longer the inlet is open the more mixture gets sucked into the crankcase. ps. you didn't really need the 24/24 but if it makes you happy
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Post by vespasco on Jan 21, 2015 20:25:37 GMT
The casting process sounds correct to me. Its a handy way to change the inlet timing in the factory!
Ive often toyed with the idea of smoothing out the drilling. It must aid in getting a little more gas to the crank case a little faster. Ive also read that the not so smooth surface of the casting actually aid, in a positive way, to how the fuel actually flows into the cases, keeping it in smaller, faster moving particles, rather than large drops clinging to the surface. Like a lot of people, ive not really attempted to alter this too much. But i have a feeling my mind may be expanded soon... ऊँ
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Post by sime66 on Jan 21, 2015 22:09:17 GMT
After a bit of head-scratching, and some drawings, I worked out how you got 109/43. I know it's obvious if you done it loads of times before, but I got there in the end. I'm having a look around now for some crank timing info, and I’ll suss it all out at my own pace. Am I right in thinking that the unused area on the pad is the limit to increase the timing before having to cut/change crank? (The extra few degrees room for cutting before and after the opening as it is now). Re: the 24/24 – I’d have got it whether or not I thought it might be right for this engine, got a bit of a thing at the moment for grabbing some of this old stuff that’s not being made any more before it disappears. (Into your sheds; you lot with Alladin’s Caves full of old bits – you know who you are). Anyway, now when we get to it, I have a choice of carbs. Also it came with box and lid, bolts and stuff, which I needed, so was a bit of a bargain for £21.
Taking stock; here’s where I think I’m at with the plan for this engine at the moment; say if I’m going wrong: · 180 barrel; probably new, probably DR from Italy. · Match casings to barrel · Raise barrel for transfer timing, but don’t cut barrel. (Still 8,000 for the 180?) · Cut inlet to open up for an increase in inlet timing. · Don’t cut crank, but investigate different cranks. · Bit of cutting on top of engine too for better airflow from carb. · Got my EFL gearbox now, so that’s all sorted up the back-end and inside the gearbox. (As long as we don’t change any single gears, which I don’t imagine we will). · Got a choice of carbs. Will do thorough job of understanding all the jets and setting up properly. · When I do the flywheel, got to decide whether to take the start-ring off to lighten, and want to do a thorough job of setting timing with strobe. I’ll also have a bash at rewiring the old stator off my scooter, which I replaced. I've got a new stator anyway. So I’m cutting the casings, but not the barrel or crank. As well as making me a spare engine, I’ll be putting into practice all the barrel stuff we did last year, learning and applying inlet timing stuff, matching casings with the Dremel, doing some case mods to inlet, doing timing properly, and generally doing all the building stuff, slow and steady and thoroughly, taking as long on each bit as we need to have a good old natter about each bit. AND keeping a record of it all on here for anyone else who’s interested. AND then putting this one in me scoot, and doing it all again on the other one!!
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Post by sime66 on Jan 22, 2015 7:25:15 GMT
This is the inlet timing as it is with these casings and this crank: I know this is an over-simplification and there’s the whole picture to consider (which I have to first understand item-by-item to be able to do that); just trying to get an idea of the numbers, and how the hole effects the inlet timing. I looked at the pad, and how much more hole could be cut, still leaving a decent border (amount TBA – used 2mm as that’s what’s there now). So I did a little sketch and calc and reckon there’s room to get close to the touring inlet timing stated above: 110° + 61° = 171° 123° – 5° = 118° (BTDC) 171° – 118° = 53° (ATDC) So I could get close to 118/53 with this crank, and opening the inlet? Or is that nonsense? Got this to think about too:
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Post by henri on Jan 22, 2015 11:09:43 GMT
in reference to vespaco's earlier comment on "rough wall inlets" ,the current thinking from silent sub then racing yacht research is that sharks skin isnt smooth but rough to create a "micro climate" of turbulence close to the object that being of water has less friction/resistance to moving thru water , before ya groan an say henri's "off on 1 ,again" ,this has transferred to modern inlets that use to be as smoothed as poss to being patterned/dimpled or roughened with coarse sandpaper ,giving the same effect even tho its the medium moving not the object ,with the added benefit of the micro-turbulence encouraging the incoming charge to scavenge any fuel load thats condensed n settled on the tract wall, Aaah, an now breath , thats better ,sorry lads but "had to be done" back on thread ,from a read thru your plan above sounds do-able with a good result that is what ya want , i'd prob tune to 7000rpm myself or halfway between there n px guru's 8000,as your running a sip ,either way the higher the revs the more important the crank balance ,so not cutting is a wise choice ,but if changing crank buying a race/pre-cut better inlet crank would make sense , just my opinion tho, H
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Post by vespasco on Jan 22, 2015 12:11:28 GMT
So if you , for example, opened the inlet in the cases, to open earlier and/ or later, would this slow down the velocity of the incoming mix? Is this why its better to cut the crank rather than the easier to do inlet. Otherwise i cant see what difference it would make so long as the inlet opened and closed at the correct moment? I was wondering if anybody else would agree with the 'rough surface being better' theory!! Cheers H
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Post by sime66 on Jan 22, 2015 12:13:09 GMT
Cheers, H. I see you're online, Vespsco, so i'm trying to slip a quick one in.. I was originally talking more about smoothing out/removing edges and corners, not actually making the finished surface smooth. I do agree about not making a smooth polished surface though; it’s done a lot in sport; making big smooth surfaces in to multiple smaller surfaces, with rough materials and dimples (lots of little eddys, rather than one big ‘sticky’ surface): I reckon I might be able to handle cutting the casings (inlet, and at barrel - matching); I’m hoping not to have to play with the crank, which is why I looked at it as it is – as part of the getting to understand how the changes effect the numbers. I know I could get a better crank, rather than using this one, and I could get a longer crank too, but that’s not really my intention. I’m hoping to raise the barrel, but not cut it. This is still meant to be more of a budget build than a full-on-jobby, and I don’t want the full-on-jobby anyway, which is why I’m taking stock of it at the moment to make sure I’m taking on work that is ‘doable’ for me, and that I’m still making the engine that I want - before moving on. I’m also intending not to take on any jobs that I can’t do myself, which rules out cutting the crank anyway. All this stuff is good to know; it doesn’t mean I have to do it all in one go on this engine; I need to understand it to try to make some decisions. It’s only January; still planning, which involves the learning first, and as part of it. I'm pretty happy with the ways it's going, just checking the plan. (You beat me to it vespasco - I think the idea is same velocity x bigger area = bigger volume and same velocity x longer time = bigger volume - I think we know a man who might enlighten us.............................)
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Post by pxguru on Jan 22, 2015 15:42:30 GMT
To get the most fuel in the crankcase the inlet needs to be open as early as possible and close as late as possible. So, longer time (without going over)is what is needed here. The area of the inlet hole is a limitation on Vespas. With the hole as big as possible on a 200 this is about the area of a 30mm carb (Any carb bigger than 30mm should have a reed valve conversion (and and carb smaller than 30mm shouldn't!!)). On this 150 job to get a reasonable inlet time, the maximum inlet hole size and a little ground off both ends of the crank should do it. If you really don't want to do what everyone else does with cutting the standard crank then just the inlet hole will have to do. If you search the forums you will see many impressive examples of home crank cutting/polishing. The actual surface texture is really fine tuning. Getting the port timing right makes way more differance than the surface finish any day
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Post by henri on Jan 22, 2015 16:36:29 GMT
def agree with timing over finish , finish is formula 1 tech level really ,a 2 strokes inlet timing has set limits from the suck/blow of moving piston so within those set parameters a bigger/smoother inlet can phsyically move more gas at a set airflow speed ,laws of physics ,an as the suck is predetermined by size n travel off piston the only 2 parameters to play with are size of tract n timing .people use to try n change primary compression til a suzuki ?or yamaha ?engineer proved that 1.5 to 1 to 1.6 to 1 is optimum , an going outside this is counter productive , i think its bell who stated the research n findings in his "bible" if not jennings, well it wud be 1 or tother,safe bet. H
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Post by pxguru on Jan 22, 2015 16:54:59 GMT
Yep, crankcase compression was sorted in Japan, they proved the rule that less is more. I think this is in Bell's book. The slower the mixture goes up the transfers, results in more of it staying on top of the piston after the exhaust is shut.
If the inlet timing is too long for your barrels transfer ports then the velocity up the transfers has to increase and more can be lost out the exhaust. Important for the inlet timing to suit the barrel.
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Post by vespasco on Jan 22, 2015 21:56:52 GMT
This is getting v interesting I've kinda been waiting for this inlet and timing thang to crop up Ive a few questions in mind but I'll wait to see if you add them in your follow up sime. Ive some revision to do!
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Post by sime66 on Jan 23, 2015 5:39:59 GMT
Morning shift, clocking on……….4:00am; coffee, slippers and dressing gown. I’ve had to get the books out too, got a bit lost in there as usual, and had a jolly good read-up on the Net last night; found loads of interesting threads on other forums on inlet timings, opening cases, cutting cranks etc; the highlights of which are listed at the bottom if anyone fancies a read. Remembering that I am not after the max, revviest, fastest, thirstiest, break-easiest engine; but also that I want to make something to make the modest(ish) expense and effort worthwhile, and I do want to understand and do these jobs; I was wondering if it was too early to start at the other end, establish some target transfer port timings (and then blowdown & exhaust?) for what I’m trying to achieve, and work backwards to decide whereabouts my ideal (not necessarily maximum) intake port timing might be. We can then decide if this inlet/crank combination is likely to meet it, or if I’m looking at cutting or replacing this crank; and if so, how much needs to come off and how. This will clear up two matters where there’s a slight deviation in opinion, which are: 1) Whether cutting crank is necessary or wise. H has mentioned crank balance a couple of times; pxguru has said everyone cuts the standard crank; a little ground off both ends of crank should do, but if not just the inlet hole will have to do. I’ve read it’s a specialist job; pxguru reckons it’s something that can be done – by me? Without splitting crank? I did find some pictures, but nothing that inspired me. I definitely got the impression from yesterday, pxguru, that without doing something with the crank, I was going to have something adequate, but not ideal (but ideal is not necessarily max – for me); making something adequate is not really what I want to do, so it’s worth spending some more time understanding the real difference between my figures and ideal figures, how doable the job is (for me), and if I need to decide to do it or not. If we compare mine with the Tourer figures, are we looking for 180-171; about 10° off this crank? 2) What rev range I’m aiming for (for what is going to be a 180). H is saying nearer 7,000, and I think suggesting my exhaust is the limiting factor; pxguru is saying 8,000. I’m thinking reliability, economy, wear, keeping the emphasis on what I need, which is my low-end grunt more than top speeds. I have read several times last night that too much inlet timing has a negative effect on the lower range too. Keep in mind that my goal might be different to the normal just make it rev as high and go as fast as it can target. What I started doing was looking at race/touring crank options for my engine – not to buy, but to see if I can get some data together to see what sort of timings they would give. I have the figures pxguru gave a couple of posts above this (page 2), so adding mine in, so far I’ve got these, and I’ll add some in with manufacturer’s part references later (ran out of time last night): · Mine as it is now: 109/43 (from measurements) · Mine with case mods: 118/53 (from measurements/calcs) · Mine with Case mods & crank mods: TBA · Case mods & crank x: TBA (for comparison) · Case mods & crank y: TBA (for comparison) · Case mods & crank z: TBA (for comparison) · Average Tourer: 125/55 · ‘Something Special’: 150/70 I also had a look at the good book, and referred back to last year’s work too, and for the moment working on 8,000, which is transfer duration of 124° I think, the best info I could find (so far; I’m still looking) was a table which isn’t really for our engines, but might be close, and seems to suggest 155-160, which is pretty much where I am, but I know isn’t really the right table, and is not what we’re aiming for (mine with case mods is approx 170, Tourer figures is 180): I know this is wrong; I’m scratching around a bit to find decent figures: So what I want to do now is do a port timing diagram, using these rough figures (T=124, E=TBA & I=125/55), as a start point for discussion and tweaking, to try to end up with some target figures for this engine: ...no diagram because I got confused; if using Transfer 124° (62°) & Inlet 125°, there's 7° overlap, which I thought was wrong, so I'm just leaving it here for now; see what the clever blokes say: Here’s some interesting threads on the subjects we’ve been discussing; ours will obviously be far more worthwhile once we’ve finished chewing it all over; I’m getting loads out of it already, having a project on the back-burner and discussing each aspect in detail as we come to them is really useful; we seem to have found ourselves another mega-thread to get stuck into; worthy of the allnighters and early starts again (Half-way down) – Inlet Porting: www.scooterhelp.com/tuning/vespa.malossi210.porting.htmlIs opening pad same as cutting crank: modernvespa.com/forum/topic116074Race crank Vs Stock: modernvespa.com/forum/topic81652rotary valve inlet timing on PE /PX range vespas www.scooterotica.org/forum/viewtopic.php?t=26997&p=195790I know you’ve started talking about velocity in the transfers, but I’m waiting to see if anyone expands on that, or points out if and where it’s something I need to be thinking about at the moment. That’ll do for now; I’ll post it as it is, and I’ve still got time to do some more and maybe edit again before the nonsense of the day starts here….
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