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Post by pxguru on Feb 23, 2015 3:17:01 GMT
H - how could anyone ever say modern petrol is any good? My point was if it starts pinking after filling with different petrol then there is something making it too sensitive. This is not normal on a non highly tuned Vespa. Should be able to run it on any old cheap c**p and it wont detonate!
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Post by pxguru on Feb 22, 2015 5:51:12 GMT
21 degrees timing is much more like it. The flat spot is probably the MJ. Is the float bowl all standard height? No packer on it? When you find the bits carefully reduce the MJ. Always check the temperature to verify what is happening. Seat of the pants only gets it so far. Keep that 190 air corrector lost. Running that on your set up will hole your piston. I suspect there is something funny with your head causing the pinking. It shouldn't be so sensitive to petrol. Do you have dowels fitted to exactly centre the head over the piston? This is more important with tighter clearance (about 1.8mm or less) and the squish starts to perform properly (doing actual squishing). Pinascos have big 69mm pistons and if the head is not centred then this could be the whole issue. It will need a little more out of that exhaust port before it sets up really well. You will see on the MD curve it still flattens off a little too early. Sounding like good progress overall though. 55/160 160/BE3/~135 and 21 degrees should be about it
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Post by pxguru on Feb 22, 2015 5:34:44 GMT
Unlucky but not uncommon. The crank will clean up ok just be careful not to damage the slot when you get the old half out. New crank with an old flywheel is the issue. Get all the burrs and rust off the crank and in the flywheel. Do up as tight as you can. Run it for 15 minutes on the spot then tighten up the flywheel again. Expecting it to be fine
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Post by pxguru on Feb 18, 2015 5:06:32 GMT
IMHO nothing any of us do on here revs high enough to need any more oil than 2%. How you get it in just comes down to personal choice, do you trust autolube or do you prefer taking ages in the petrol station?
If you post a picture of the scores in the barrel and condition of the piston we can advise. You need to really look very closely at the piston for hair line cracks as these may not show in a photo. Depending on how bad it seized, sorry to say, it might need new piston rings already!
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Post by pxguru on Feb 18, 2015 4:49:16 GMT
As you are happy with it now you might as well leave it until its apart again or you decide it needs some more top end. You are still quite a few mm away from having trouble with a 3rd to 4th gear gap (similar to what always happens with those Malossi 210s). Have to keep remembering yours is a Rally frame as well, even less suitable for motorway speeds than a PX!
On an engine tuned for high rpm power, the programmable CDI is one of the many little tricks needed to help get the mid range back up to normal. I've had this type of CDI about a year and after a few seasons of tinkering and porting, I have pretty much finished my Polossi. It will now go up hill at 30mph in 4th like a standard engine or roll on to over 8000rpm, overtaking the cars on the motorway (only if there's no cross wind, as that can get properly scary and tries to do something like a tank slapper, when overtaking white van man!).
Hopefully you won't need any of the different slides or anything but BE3/160 as that would be unusual for a set up like yours. The 140 jet is not 'way' to big, so be careful to get it really hot and watch the temperature as you hold it at wot. Only reduce the size of the MJ if the temp drops while holding at wot. Otherwise leave it alone. On an SI the main jet affects the mid range too (as adjusted by the air corrector) so looking for slightly rich colour as always. Check the plug colour at 1/4, 1/2 and 3/4 when you are done. Then ride all summer without touching anything more!
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Post by pxguru on Feb 16, 2015 12:10:25 GMT
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Post by pxguru on Feb 16, 2015 7:08:20 GMT
Glad to hear it was running so much better that you didn't want to take it home!
It should really have another 0.5mm out of the exhaust port before it is near enough to minimum blowdown to leave it. Don't worry about the slight tool slip, if it's just near the exhaust port, won't make any difference at all.
If you are happy with it as it is then get some use out of it for now. I doubt another 0.5mm will affect the bottom end enough to notice but is probably costing a few HP at higher rpm. Often as the high rpm gets more powerful and later the mid torque starts to feel weak but isn't really. Run the MD and I expect you will see what I mean. If you do get a programmable CDI then the mid range could be improved further. On my programmable CDI I have the static ignition timing set at 26.5 degrees, when running up to 4000rpm to max the mid range. After that the timing reduces progressively to avoid any melting anything.
Run the MD again and compare to the original and see how the curve shape is now.
Edit: If you raised the exhaust port another 6.1mm from where it is now then you would be on the limit of your transfers. Another 3.1mm from now would be tuned for thrashing on the road.
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Post by pxguru on Feb 14, 2015 12:01:55 GMT
It always makes me smile when someone says a kit bolted on blind and rough out the box, is more reliable than one that has been tided up, ports chamfered top & bottom and the deck height set to where it was intended on your engine. They will go fine just bolted on, nothing wrong with that, just don't kid yourself its the most reliable it can be. There are many levels of tuning and two stoke engines are far more complex than their few components would have you believe. As Sime implied, knowing what to do and how much, is the key when it comes to tuning for reliability and we are all here to help each other
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Post by pxguru on Feb 12, 2015 15:35:09 GMT
Keep an eye on this as H says. Running in this c**p state could make it go pop. For a fast road or sporty tune on your transfers of 127 you need something like 185. This doesnt suit what you are after and like you say, as low as possible exhaust is best for you. About 177 will be about your minimum for power to peak near 7500. Once this is sorted the pinking should reduce. The reason your power drops off at 6500, yet the transfer ports could do 9500, is because the exhaust gas can't get out in the time (degrees)available. With higher compression and so much old exhaust fumes in the new mix it will overheat and detonate. Once you raise the port to get up to minimum blowdown of 177 degrees (max being about 190 degrees!) I expect this pinking to get much less. And a whole load faster
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Post by pxguru on Feb 11, 2015 16:06:18 GMT
The pinking could get better once the blowdown is raised to minimum. Might be something to do with the trapped exhaust gas at higher rpms
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Post by pxguru on Feb 9, 2015 18:27:43 GMT
So you raised the exhaust port by 0.6mm I wouldn't worry too much about the chamfer yet. There is still 1.9mm more to remove yet. A high chamfer is best but a some barrels (see sime's new barrel) run without any and get away with it. If you do run a 190 air corrector on the main jet stack then that will make it pink! Its way too much air for yours. And messes up the mid range atomiser too. After raising the exhaust port the rest of the way try the jetting at; 135 main jet 160/BE3 55/160 pilot I.T. mark timing And go from there. Its all about plug colour and engine temperature. As the transfers wont go any lower 8,000 rpm has to be the target. What packer is needed to cover the dykes ring at BDC? And how many transfer degrees is that? 10.3:1 compression is not really so high. With good squish angle it is possible to have more compression and still not pink or overheat. The SIP Road II should be fine at 8,000 rpm. When its finished it will have more power with an expansion exhaust but its not compulsary! If you like the SIP Road II then will be better round town
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Post by pxguru on Feb 9, 2015 8:52:01 GMT
Vespasco, How many mm did you raise the exhaust port? Sounds like not so much yet but going in the right direction if the HP is going up. If the plug is running rich when up to temperature and still pinking at WOT then its not jetting. Do you have pinking marks on the piston? Is it only at WOT?
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Post by pxguru on Feb 8, 2015 8:21:56 GMT
Still looks pretty rough whatever way its sloping Plenty of work that can be done to that barrel to make it go better. Finishing the casting and chamfering all the ports seems like too much work for many of the factories to do. When looking from the exhaust stub you should be able to see clear out of the additional exhaust ports. There is plenty of metal to allow this. 1mm could be taken out of the dividing pillar for a start. All those square edges in the exhaust need to be smoothed to avoid turbulance, which would restrict the flow as the 3 streams merge. Once the transfers are set your squish will be about 3 to 4mm. Taking 3mm (approx!) off the head will be the simplest way for you. A local machine shop with a big lathe and greasy old guy should be able to sort it easily and cheaply. All the cutting in the right places is what is going to make it pull. Just bolted together it is unlikely to be any stronger than the other engine! I don't think anything we have talked about is beyond your power tool ability, as there is no drilling involved
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Post by pxguru on Feb 7, 2015 8:29:57 GMT
It will never not amaze me how rough new barrel/head kits are. A sloping roof on an exhaust is not good and way up the c**p end of the scale. Those fantastic additional exhaust ports are probably very narrow too. Whole lot should be opened out. I guess there is plenty of metal? Moving all the transfers is a lot of work for a beginner. A packer is the easy way. You will need to work the exhaust now anyway. Might as raise it up a bit while you are at it. And as Vespasco said the bottom of the exhaust should really be flush with the piston. Exhausts dont need to be as accurate as transfers. Skimming that barrel 3mm you will lose the top fin. Maybe better (and more reversable) to get the head machined to go inside the barrel.
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Post by pxguru on Feb 5, 2015 20:29:12 GMT
Impressive graphics. To put some meat in the sandwich if you are not doing anything with the barrel then you are going to need a 1mm packer and not much more or the blowdown will be far too short. This will leave it a bit compromised but will be ok. With the 1mm packer and that new head the squish will be about 2.5mm, which is a bit c**p. In my ideal world; 2.5mm packer, raise the exhaust port 1mm and skim 3mm off the top of the barrel
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Post by pxguru on Feb 5, 2015 20:13:38 GMT
Could also be a slight crankcase airleak
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Post by pxguru on Feb 4, 2015 17:44:44 GMT
While you are doing some shopping; the Pilot jet is too big. Should be a 50/120 at most.
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Post by pxguru on Feb 1, 2015 7:14:11 GMT
While it just had the 60mm crank in it was just a few mph quicker top end. The most noticable though was it rode better and didnt slow down so much up hill. Main jet was 128, no barrel packers and timing 23 degrees.
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Post by pxguru on Jan 29, 2015 16:41:43 GMT
One of the most common reasons for pinking is that the head doesn't fit the barrel. As you say a narrow squish carries less mixture and is less likely to pink but if the head squish overhangs the edge of the barrel it holds an extra ring of fuel right at the edge. This can add to the problem. If the head is correctly profiled to the piston the squish can be as tight as you dare for mechanical contact. On my own scooters I often use less than 1mm, without any issue. Pinking can usually be fixed by properly jetting across all throttle positions. Ignition timing often gets the blame but is rarely the real reason
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Post by pxguru on Jan 29, 2015 6:47:07 GMT
When I did one it had more power and revved higher. Torque about the same on standard exhaust. Was noticably faster
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Post by pxguru on Jan 28, 2015 19:16:07 GMT
Dosent overheat with high compression, just goes better. Any problems are all due to jetting. 60mm crank and nothing else. No head gasket or base packer. Even the timing is ok at 23 degrees. Its the easiest tune you can do to a stock P200
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Post by pxguru on Jan 27, 2015 18:51:41 GMT
Sime, Sounds like the right conclusion to me; you don't want a race crank if it has too much ATDC. 125/55 or there abouts will suit your needs
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Post by pxguru on Jan 27, 2015 18:25:59 GMT
Without any other change just fitting a 60mm crank in a P200 and no packer goes well. I've done it before. Will need to upjet about 5
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Post by pxguru on Jan 25, 2015 16:01:21 GMT
I think maybe you are over complicating this a little but at least it irons out all the wrinkles The area of the narrowest part of the inlet hole just needs to be bigger in area than the carb. The timing of the rotary inlet is related to the porting of the barrel being used and the purpose it is being used for. Standard inlet timing doesn't suit anything else but a standard barrel being used for driving around an Italian city, with a girl riding side saddle on the pillion
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Post by pxguru on Jan 24, 2015 10:26:21 GMT
Not much time right now but just to clear up one point. Vespasco, your blowdown duration is a few degrees under the allowable absolute minimum. This will cause a power loss in from low mid range to high rpm. Fixing this will increase power everywhere
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Post by pxguru on Jan 23, 2015 9:40:09 GMT
Just had a quick read. Considering the whole tuning job to make all aspects compatible will give the best results.
Good you found the overlap. This is normal. About 10 degrees max overlap for a tourer, where the power band starts low down. For something that revs 10,000+ with a later power band this can be a lot more.
That inlet table in Bell's book is for a piston port inlet. These numbers are not at all related to a rotary inlet. Piston port inlets have many flaws and have to run less degrees, all of which are corrected, and then some, when changed to a reed valve.
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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 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 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 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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