modpx
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Post by modpx on Jan 2, 2013 21:13:34 GMT
Hello guys, i took a ride on my kitted 225 PX yesterday, JL pipe freshly mounted..and after 20km this was the result... now besides the causes (air intake from the cylinder head?, troo tight carburator screw? Damaged mixer..?) what i'd like to know is if in your opinion the cylinder can be saved..i dont have much of hope in the piston...  Attachments:
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Post by modpx on Jan 2, 2013 21:14:45 GMT
Hello guys, i took a ride on my kitted 225 PX yesterday, JL pipe freshly mounted..and after 20km this was the result... now besides the causes (air intake from the cylinder head?, troo tight carburator screw? Damaged mixer..?) what i'd like to know is if in your opinion the cylinder can be saved..i dont have much of hope in the piston... Attachments:
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modpx
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Post by modpx on Jan 2, 2013 21:17:26 GMT
Hello guys, i took a ride on my kitted 225 PX yesterday, JL pipe freshly mounted..and after 20km this was the result... now besides the causes (air intake from the cylinder head?, troo tight carburator screw? Damaged mixer..?) what i'd like to know is if in your opinion the cylinder can be saved..i dont have much of hope in the piston... Attachments:
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Post by sbwnik on Jan 2, 2013 22:53:38 GMT
Can you find an oversize piston for it? Looks like nothing that isn't recoverable with a rebore. It may even polish out with a quick hone.
As a rough rule of thumb, if you can catch a nail on the damage, then it's too far gone to reuse as is, but a rebore will often recover the barrel.
Pistons fukked though...
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modpx
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Post by modpx on Jan 3, 2013 0:13:21 GMT
Can you find an oversize piston for it? Looks like nothing that isn't recoverable with a rebore. It may even polish out with a quick hone. As a rough rule of thumb, if you can catch a nail on the damage, then it's too far gone to reuse as is, but a rebore will often recover the barrel. Pistons fukked though... Hi thanks for the tips! The rectangle shaped stain that you see under the cylinder ports is flat, smooth as well as the rest of the cylinder, there are some scratches of course but nothing you can catch a nail on  could you make me an example of oversize piston that would fit my purposes? I maybe found a used pinasco piston but the guy doesnt have the pinasco rings (which are quite expensive, 45€ from Sip) I have two brand newpiston rings for the original px200 piaggio piston instead, would they fit into the Pinasco piston? Is the quality approx the same? thanks |
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Post by kru251 on Jan 3, 2013 0:23:10 GMT
Well if that 'damage' on the bore could be honed out (as you say it's more visual than actual damage) then you'd get away fitting whatever size this nipped up piston was (std?) I'd reckon.
Think I'd chance it provided the hone removed the 'damage/scuff'. It has picked up on that now scrap piston, but not scored the bore by the looks of it. Score = rebore at least.
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modpx
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Post by modpx on Jan 3, 2013 1:00:49 GMT
Well if that 'damage' on the bore could be honed out (as you say it's more visual than actual damage) then you'd get away fitting whatever size this nipped up piston was (std?) I'd reckon. Think I'd chance it provided the hone removed the 'damage/scuff'. It has picked up on that now scrap piston, but not scored the bore by the looks of it. Score = rebore at least. Is there any chance i can just polish out the cylinder without taking it to rebore? And if yes, what's the procedure for a home made polish? |
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Post by pxguru on Jan 3, 2013 5:43:04 GMT
Its always a bit gutting on a new bore. 2013 might be your lucky year, as it looks like you got away with it  Only the top 2cm of the bore ever need to be fully score free. It might look awful but it will run fine after a clean up. If it was mine I would get some 600 grit wet and dry paper and rub out the worst of the bruise in the barrel (careful!) and the same on the piston (less careful). The ring groves on the piston have burred slightly, so clean those out. If you get the rings off without breaking them they will go back ok too. Check the piston for tiny cracks. If ok I would put it back in! I doubt the barrel liner is cracked but if it is...... Now the important bit. Why did it seize? Assuming you weren't wringing it's neck. I think you were very lucky. This is is exactly the type of seize I was talking about in the post "Running In". It is called a "lean seize", recognisable from all the other types by a big bruise near the exhaust port and a small complementary bruise on the opposite side of the piston. It is caused by the main jet being too small (rule of thumb; if it heat seizes on an SI carb the main jet is at least 10 points too small). If you really don't know how to jet in a 2 stroke just ask any of us on here  Don't forget to set your barrel height to exactly suit your engine when you re-assemble it (re- Which pipe on a Pinasco 225?) |
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Post by modpx on Jan 3, 2013 10:17:56 GMT
Its always a bit gutting on a new bore. 2013 might be your lucky year, as it looks like you got away with it Only the top 2cm of the bore ever need to be fully score free. It might look awful but it will run fine after a clean up. If it was mine I would get some 600 grit wet and dry paper and rub out the worst of the bruise in the barrel (careful!) and the same on the piston (less careful). The ring groves on the piston have burred slightly, so clean those out. If you get the rings off without breaking them they will go back ok too. Check the piston for tiny cracks. If ok I would put it back in! I doubt the barrel liner is cracked but if it is...... Now the important bit. Why did it seize? Assuming you weren't wringing it's neck. I think you were very lucky. This is is exactly the type of seize I was talking about in the post "Running In". It is called a "lean seize", recognisable from all the other types by a big bruise near the exhaust port and a small complementary bruise on the opposite side of the piston. It is caused by the main jet being too small (rule of thumb; if it heat seizes on an SI carb the main jet is at least 10 points too small). If you really don't know how to jet in a 2 stroke just ask any of us on here Don't forget to set your barrel height to exactly suit your engine when you re-assemble it (re- Which pipe on a Pinasco 225?) Hi, i show you also the other side of the piston that is what makes me think that the piston is gone, there's that crack in between the ports in the lower side, well that you can catch a nail on...i'll definitely try to clean the cylinder upplike you said then. Ii'm very interested in knowing the cause too since i wouldnt like this to happen again. I can't diagnose exactly so any help is very appreciated. What i can certainly do is upjetting the carb indeed that i actually took up to 132. Here''s a video of the pipe just mounted after a little a ride i took to test the spark plug. I also post it in the "which pipe on a 225" to complete the post. Well it was super "rich", all black and oily. So i screwed in the screw under the carburetor to make it poorer. Yesterday i wanted to take a longer ride and test it again but...it was probably too long... Attachments:
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Post by pxguru on Jan 3, 2013 11:49:11 GMT
Ahhh......you will be needing a new piston then. You must be an actor as you only show your best side to camera. The sieze mark is bigger on the cold side so could be more like overheating. If you are positive the mixture is rich (132 isn't so big) and you are using the autolube, are you sure it is working? The other thing that can cause poor lubrication is a leaking oil seal or gasket. Silly question, do you pressure test the crankcase after final assembly? The black and oily could be gearbox oil? Check you still have some in there. |
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Post by sbwnik on Jan 3, 2013 20:27:32 GMT
Definately a hot seize.
I'd guess the timing is set at standard from that damage.. how can I put this... 'It looks familiar!'
Over sized pistons are made by the same manufacturer - you generally find them in stepped increments. buy the next size up, check what the tolerances are and give the piston, cylinder and tolerances to a machine shop to do the work.
If it'll polish up, then I'd get a new standard piston. That one is definately past its use by date.
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modpx
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Post by modpx on Jan 3, 2013 20:39:15 GMT
Definately a hot seize. I'd guess the timing is set at standard from that damage.. how can I put this... 'It looks familiar!' Over sized pistons are made by the same manufacturer - you generally find them in stepped increments. buy the next size up, check what the tolerances are and give the piston, cylinder and tolerances to a machine shop to do the work. If it'll polish up, then I'd get a new standard piston. That one is definately past its use by date. No the timing is set almost on IT... im trying to figure out what that might depend on... if it was intaking air from somewhere should´ve shown some signs like "accelerated idle" or something... i see that the pinasco piston rings are 1 standard and 1 extra, do you know the measures? cause i have 1 pinasco (the lower) that is ok and 2 piaggio 66,5mm that are new..would it be possible to mix them or it´s insane? |
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Post by pxguru on Jan 4, 2013 4:28:47 GMT
On the IT mark sounds fine to me, Nik. The cold side seize mark looks bad enough to be a pinking seize but the piston crown doesn't have pits around the rim from what I can see. Maybe a picture of the head (from the business side!) would confirm it.
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Post by sbwnik on Jan 4, 2013 14:10:38 GMT
If it's around the IT mark, it's definitely in the right area, but it's one of those things that can be a little trial and error in my experience - tuned engines are never perfectly the same by their very nature.
But if the jetting is right (wrong kind of seize anyway) and there is no seal damage showing, then what else? Too small a squish band? I'm reaching the limits of my knowledge here, but my 207 is built on a 1.4mm squish, bang in the middle of the 1.2-1.6 I was advised to use.
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modpx
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Post by modpx on Jan 4, 2013 20:37:53 GMT
On the IT mark sounds fine to me, Nik. The cold side seize mark looks bad enough to be a pinking seize but the piston crown doesn't have pits around the rim from what I can see. Maybe a picture of the head (from the business side!) would confirm it. Hello guys, well, i polished the cylinder, i first sandpaper it with water sandpaper 1200 then i polished it...the visual marks are still there, actually there´s a little scratch that i can feel with the fingertip but nothin major it´s really little, the piston... well i decided to buy a new one i found one including shipping bills for 108€ not bad... it´s useless to recicle the old. the performance will go down and i love too much the kick of my pinasco to give it up like this. This is the head, looks ok to me. About the squish i dont know ... my knowledge is limited to plug and play, when it comes to work the cases match the ports or more "tecnical" things i usually pass it to more skilled mates ;D Attachments:
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Post by kru251 on Jan 4, 2013 22:25:52 GMT
Be careful with 'skilled mates' as they aren't paying your repair bills are they?  |
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modpx
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Post by modpx on Jan 5, 2013 8:20:17 GMT
Be careful with 'skilled mates' as they aren't paying your repair bills are they? ahahaha you're right but what d'you expect when you use 12 packs of beer for payment method! ;D ;D This time thou i guess was my fault since the problem was (most probably) in the carburation... When the new piston will arrive, i'll upgrade the jet to 135 and keep it richer, a bit of smoke and a black and oily spark plug is better than a seized cylinder after all.. thanks for the tips i'll keep you posted! Next thing to be tested, the new Megadella pipe for Pinasco! |
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Post by pxguru on Jan 5, 2013 12:12:23 GMT
1st the good news. It isn't pinking (pre ignition). With real pinking a few millimeters round the edge of the head would look like it was all pitted like something loose got in there. More good news. I know you are inexperienced but you are learning fast. 2 stroke plugs are supposed to be dark coloured (like chocolate apart from the end of the cone) and they do smoke a bit this isn't the head of a scoot running rich. This is the head of a scoot that is overheating. Start with a 140 main jet. Barrel sounds like it cleaned up fine. A few scuffs way down the bore won't have any affect on performance. What the F*@K is that blue stuff doing on the head! clean it off and don't ever put it on there again...If you want it to seal well, tape down some of that 1200 paper on a sheet of glass spray it with WD40 and polish it for 5 mins (same for the top of the barrel). Don't touch the timing. Too far retarded causes a different kind of seize up! Everything in a 2 stroke is a balance. You dodged the pressure test question. And the one about the autolube! Exactly what spark plug is in it? Post a picture of the one that seized up (looking into the electrode) just for final confirmation. |
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Post by pxguru on Jan 5, 2013 12:31:24 GMT
If it's around the IT mark, it's definitely in the right area, but it's one of those things that can be a little trial and error in my experience - tuned engines are never perfectly the same by their very nature. But if the jetting is right (wrong kind of seize anyway) and there is no seal damage showing, then what else? Too small a squish band? I'm reaching the limits of my knowledge here, but my 207 is built on a 1.4mm squish, bang in the middle of the 1.2-1.6 I was advised to use. Nik, at 1.4mm your squish is a bit on the safe side. 1.2 is like the max really. Like Kru said your mates aren't paying for the repair and yours gave good advice erring on caution. If the squish is too tight it will cause pinking (and you will see the marks, when you take it apart to put a new piston in!). If it doesn't pink then its fine. When you are setting up a squish band it is worth remembering that the fuel compressed in the area of the squish band doesn't add any power to the stroke. A standard PX200 has a squish around 2.7mm (double the max). How much of the 198cc is that?..........45cc of the uncompressed volume going straight out the pipe!! Just putting a 60mm crank in a totally standard PX200 with a standard base gasket (0.2mm) will up the squish to perfect at 1.2mm...funny that isn't it? And only losing 18cc ;D |
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modpx
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Post by modpx on Jan 5, 2013 15:13:12 GMT
If it's around the IT mark, it's definitely in the right area, but it's one of those things that can be a little trial and error in my experience - tuned engines are never perfectly the same by their very nature. But if the jetting is right (wrong kind of seize anyway) and there is no seal damage showing, then what else? Too small a squish band? I'm reaching the limits of my knowledge here, but my 207 is built on a 1.4mm squish, bang in the middle of the 1.2-1.6 I was advised to use. Nik, at 1.4mm your squish is a bit on the safe side. 1.2 is like the max really. Like Kru said your mates aren't paying for the repair and yours gave good advice erring on caution. If the squish is too tight it will cause pinking (and you will see the marks, when you take it apart to put a new piston in!). If it doesn't pink then its fine. When you are setting up a squish band it is worth remembering that the fuel compressed in the area of the squish band doesn't add any power to the stroke. A standard PX200 has a squish around 2.9mm (over double the max). How much of the 198cc is that?..........45cc of the uncompressed volume going straight out the pipe!! Just putting a 60mm crank in a totally standard PX200 with a standard base gasket (0.2mm) will up the squish to perfect at 1.2mm...funny that isn't it? And only loosing 18cc ;D So..you're saying that is possbile to calculate the squish approximately... and that a stock PX200 waists 45cc of its own power by using its original settings? and a PX200 with 60crackshaft has 1.2 squish and 1.2 squish is ok? hmmm so... a pinasco 60cranckshaft how much squish should have to be perfect? And how do i get there approx without calculating the PMS and the PMI (i dont know their names in english) and all that booring stuff? Could you simplify/clarify? Try to explain it like if you were explaing it to a kid. |
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Post by modpx on Jan 5, 2013 15:21:28 GMT
ahh by the way..what do you mean by "pinking" exactly? and where should i check those marks to verify if my settings are alright? Sorry for the too many questions..
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Post by pxguru on Jan 5, 2013 15:47:58 GMT
You have to lose some mixture in the squish. Just keep it to the minimum. Which for yours with that head will be about 20cc
I wouldn't advise for you or anyone to calculate it. If you get it wrong it will break a lot more than your piston! You must measure it.
To get the most out of yours you need to decide how many base gaskets you need first. Your barrel must be at the correct height for maximum torque (47.5mm, top of stroke to top of main transfers).
When you are ready to put it together put the piston on without the rings. Slip the barrel on with the base gaskets you will use. Get some solder wire and lay it on top of the piston (a cross of twisted wire works well). Put the head on an nip the nuts down (no need for tight). With the piston only going up, force it gently past the top, (only once). Take off the head and measure the squashed solder at the four ends. All should measure about the same. This is the squish, 1.2mm.
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Post by pxguru on Jan 5, 2013 15:55:51 GMT
Pinking is Pre Ignition k Noc KFor a scooter its the sound of imminent death  Sounds like a tin full of pins being shaken and will melt your piston quicker than a cold shower. Mild pinking is little dents around the edge of the piston crown and under the head in the squish area. Medium is a melted top ring groove. Severe is a big hole and molten aluminum all over your crankshaft! |
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Post by pxguru on Jan 5, 2013 16:03:52 GMT
You can do all this with your old piston right now. Get the barrel height right, come back with the squish you measure and we can go from there.You can check and correct on final assembly later |
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Post by kru251 on Jan 5, 2013 17:41:18 GMT
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modpx
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Post by modpx on Jan 6, 2013 18:38:06 GMT
You have to lose some mixture in the squish. Just keep it to the minimum. Which for yours with that head will be about 20cc I wouldn't advise for you or anyone to calculate it. If you get it wrong it will break a lot more than your piston! You must measure it. To get the most out of yours you need to decide how many base gaskets you need first. Your barrel must be at the correct height for maximum torque (47.5mm, top of stroke to top of main transfers). When you are ready to put it together put the piston on without the rings. Slip the barrel on with the base gaskets you will use. Get some solder wire and lay it on top of the piston (a cross of twisted wire works well). Put the head on an nip the nuts down (no need for tight). With the piston only going up, force it gently past the top, (only once). Take off the head and measure the squashed solder at the four ends. All should measure about the same. This is the squish, 1.2mm. Ok, let's try to put some order 1) Squish: A) This is the PMS of the piston into the cylinder, now, where do i have to put exactly the solder wire? cause once i slip the head on top of ithe cylinder, either i put the wire through the spark plug hole (that's one method i've heard) nor lay the wire on the piston head, the wire doesnt get squashed anywhere when i rotate the flywheel and move the piston up and down. B) In the second picture there's the base gasket i used when i made the engine, it's 0.25 mm like visible from the display in the picture. According to what parameters i have to choose which and how many gaskets to use? 2) In the third picture there's the seized spark plug. 3) If the blue paste is crap, how about red sylicon for warm temperature to seal? Attachments:
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Post by modpx on Jan 6, 2013 18:39:06 GMT
You have to lose some mixture in the squish. Just keep it to the minimum. Which for yours with that head will be about 20cc I wouldn't advise for you or anyone to calculate it. If you get it wrong it will break a lot more than your piston! You must measure it. To get the most out of yours you need to decide how many base gaskets you need first. Your barrel must be at the correct height for maximum torque (47.5mm, top of stroke to top of main transfers). When you are ready to put it together put the piston on without the rings. Slip the barrel on with the base gaskets you will use. Get some solder wire and lay it on top of the piston (a cross of twisted wire works well). Put the head on an nip the nuts down (no need for tight). With the piston only going up, force it gently past the top, (only once). Take off the head and measure the squashed solder at the four ends. All should measure about the same. This is the squish, 1.2mm. Ok, let's try to put some order 1) Squish: A) This is the PMS of the piston into the cylinder, now, where do i have to put exactly the solder wire? cause once i slip the head on top of ithe cylinder, either i put the wire through the spark plug (that's one method i've heard) nor lay the wire on the piston head, the wire doesnt get squashed anywhere when i spin the flywheel and move the piston from down to up. B) In the second picture there's the base gasket i used when i made the engine, it's 0.25 mm like visible from the display in the picture. According to what parameters i have to choose which and how many gaskets to use? 2) In the third picture there's the seized spark plug. 3) If the blue paste is crap, how about red sylicon for warm temperature to seal? Attachments:
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modpx
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Post by modpx on Jan 6, 2013 18:39:55 GMT
Ok, let's try to put some order 1) Squish: A) This is the PMS of the piston into the cylinder, now, where do i have to put exactly the solder wire? cause once i slip the head on top of ithe cylinder, either i put the wire through the spark plug (that's one method i've heard) nor lay the wire on the piston head, the wire doesnt get squashed anywhere. B) In the second picture there's the base gasket i used when i made the engine, it's 0.25 mm like visible from the display in the picture. According to what parameters i have to choose which and how many gaskets to use? 2) In the third picture there's the seized spark plug. 3) If the blue paste is crap, how about red sylicon for warm temperature to seal? Attachments:
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Post by sbwnik on Jan 6, 2013 21:22:59 GMT
Just skimming through here, so I may have missed something... You're using sealants? DO NOT USE SEALANTS!!!! It'll blow out eventually, then the engine will run lean, then you'll be back here again. Hmm.....
1.4 squish is deliberately on the safe side on mine. I don't want to break anything unnecessarily!
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Post by modpx on Jan 6, 2013 22:48:59 GMT
Just skimming through here, so I may have missed something... You're using sealants? DO NOT USE SEALANTS!!!! It'll blow out eventually, then the engine will run lean, then you'll be back here again. Hmm..... 1.4 squish is deliberately on the safe side on mine. I don't want to break anything unnecessarily! The thing with the squish is that i don't know if is so necessary to measure it, i start to think that Pinasco set the kit (that includes also the head and the crankshaft 60) already with the perfect squish... probably if i start to thicken the base in order to make it rev higher then the squish is important..but for a torquey kit like Pinasco maybe not? hmmm  about the sealants... i was suggested to put the red silicon at the cylinder base together with the gasket...Pxguru suggested wd40 for the cylinder head but is it ok also for the cylinder base? |
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could you make me an example of oversize piston that would fit my purposes? I maybe found a used pinasco piston but the guy doesnt have the pinasco rings (which are quite expensive, 45€ from Sip) I have two brand newpiston rings for the original px200 piaggio piston instead, would they fit into the Pinasco piston? Is the quality approx the same? thanks
Only the top 2cm of the bore ever need to be fully score free. It might look awful but it will run fine after a clean up.
about the sealants... i was suggested to put the red silicon at the cylinder base together with the gasket...Pxguru suggested wd40 for the cylinder head but is it ok also for the cylinder base?