Engine failure - seizing - what happened?
- Bomberpilot
- Posts: 45
- Joined: October 29th, 2010, 6:04 am
Engine failure - seizing - what happened?
I experienced an engine failure yesterday
I was going about 70 miles per hour when a strange sound appeared - like a scratching and I expected the piston rings to make this sound.
The sound began a few rides before - but only at the higher speeds. Even if the sound wasn't nice I was not too afraid because I just opened the engine and looked at the parts and measured the piston ring gap (it was 0.4mm-0.45mm) and everything looked good (the whole setup had about 1500-2000 miles on it and never made any problems and looked good as I said).
At the last inspection I mentioned I changed some parts:
I got now the Sudco PWK 41 pro Series with a 190 main jet and a 52 pilot jet and a DGK needle. Could that be too lean?
I added also a cylinder head with a raised compression and only little squish height but I couldn't hear any pinging...
The piston is a Wiseco (Seizeco?) 636M09050 4229E 90.50mm.
What the fuck happened here? I run 1/33 Motorex GP (very expensive Racing) oil.
Here are the pictures - what are your thoughts about all that?
I was going about 70 miles per hour when a strange sound appeared - like a scratching and I expected the piston rings to make this sound.
The sound began a few rides before - but only at the higher speeds. Even if the sound wasn't nice I was not too afraid because I just opened the engine and looked at the parts and measured the piston ring gap (it was 0.4mm-0.45mm) and everything looked good (the whole setup had about 1500-2000 miles on it and never made any problems and looked good as I said).
At the last inspection I mentioned I changed some parts:
I got now the Sudco PWK 41 pro Series with a 190 main jet and a 52 pilot jet and a DGK needle. Could that be too lean?
I added also a cylinder head with a raised compression and only little squish height but I couldn't hear any pinging...
The piston is a Wiseco (Seizeco?) 636M09050 4229E 90.50mm.
What the fuck happened here? I run 1/33 Motorex GP (very expensive Racing) oil.
Here are the pictures - what are your thoughts about all that?
- Bomberpilot
- Posts: 45
- Joined: October 29th, 2010, 6:04 am
not that I know... ok I got the (bigger) KTM radiators and the pressure relief valve openes from what I know at 1.2 bar (more than stock) but it didn't open - so I guess it wasn't that hot (also the wheater wasn't that hot - about 15°Celsius, 60°F).
The power of the bike at that day was very good before the engine broke down. I heated the bike up for about 4-5 miles and than I hit WOT. Not even one minute later the engine broke down (not all the time WOT).
The power of the bike at that day was very good before the engine broke down. I heated the bike up for about 4-5 miles and than I hit WOT. Not even one minute later the engine broke down (not all the time WOT).
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- Posts: 4394
- Joined: July 4th, 2007, 6:57 pm
its easy to see what happened but the question is why. i dont have a concrete answer. i can tell you i dont like the looks of that wristpin, sucker looks badly scorched. i would say the topend lost lubrication somehow and then the temp skyrocketed ? or maybe the temps were so high the oil just boiled off ? whats underneath the piston look like ?
have you considered a castor type oil ?
sorry man but i cant say exactly what happened
have you considered a castor type oil ?
sorry man but i cant say exactly what happened
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- Joined: July 4th, 2007, 6:57 pm
- britincali
- Posts: 8207
- Joined: May 31st, 2007, 7:10 pm
- Location: Barstow, CA
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- Posts: 4394
- Joined: July 4th, 2007, 6:57 pm
- Bomberpilot
- Posts: 45
- Joined: October 29th, 2010, 6:04 am
thanks for your answers!
so as I said I was in last gear and went about 70 miles/hour when that strange scratching sound came up. And this sound came up before but only at the high speeds when I had full load for a few more seconds.
I also sealed up the exhaust pipe at the flange but I don't think that this is bad...
I did not make a leak down test after assembling the engine
Yeah, really looks like high temp. and then the clearance went away - but really, the question is why as you all said. I never had overheating issues before.
Could that be that I make too much power now after all the changes and tuning I made and that the cooling system cannot cool that down? (the big point here I guess is the much higher compression!)
so as I said I was in last gear and went about 70 miles/hour when that strange scratching sound came up. And this sound came up before but only at the high speeds when I had full load for a few more seconds.
I also sealed up the exhaust pipe at the flange but I don't think that this is bad...
I did not make a leak down test after assembling the engine
Yeah, really looks like high temp. and then the clearance went away - but really, the question is why as you all said. I never had overheating issues before.
Could that be that I make too much power now after all the changes and tuning I made and that the cooling system cannot cool that down? (the big point here I guess is the much higher compression!)
Just curious - how long were you holding it WFO?
IIRC Golden Rule with any 2T is never hold it WFO for too long. Always on/off, on/off. At least thats what I was taught - has worked well for me so far.
And x2 on the 927! 44:1 is all I run.
If you are planning on WFO for long periods of time, you may want to consider adding a powerjet.
IIRC Golden Rule with any 2T is never hold it WFO for too long. Always on/off, on/off. At least thats what I was taught - has worked well for me so far.
And x2 on the 927! 44:1 is all I run.
If you are planning on WFO for long periods of time, you may want to consider adding a powerjet.
The CR500 is an acquired taste. If you don't like it, acquire some taste...
- Bomberpilot
- Posts: 45
- Joined: October 29th, 2010, 6:04 am
my engine builder said that he did a clearance of 9/100mm or other 0.09mm or 0.0035".
as I already wrote - i used the Motorex Racing GP 2 Stroke Oil at 1/33.
My main jet in the PWK 41 Pro Series is 190, pilot jet is 52 and needle DGK - do you guys think that this is too lean?
I was on WOT for just about 3-5 seconds when the noise appeared. Then I let off the throttle and hit it again and let off and again... so I don't do WOT for too long, too.
so do you guys think that I can not just replace the cylinder and piston (got another set here)? do you think some of the other parts are damaged too? could I soo that without disassembling the bottum end?
as I already wrote - i used the Motorex Racing GP 2 Stroke Oil at 1/33.
My main jet in the PWK 41 Pro Series is 190, pilot jet is 52 and needle DGK - do you guys think that this is too lean?
I was on WOT for just about 3-5 seconds when the noise appeared. Then I let off the throttle and hit it again and let off and again... so I don't do WOT for too long, too.
so do you guys think that I can not just replace the cylinder and piston (got another set here)? do you think some of the other parts are damaged too? could I soo that without disassembling the bottum end?
What does the plug look like?
No longer have a CR500.
07 Yamaha YZ250, 17 Husqvarna 701 Enduro
Get on with riding or get on with dying.
https://www.youtube.com/mojoscojo
07 Yamaha YZ250, 17 Husqvarna 701 Enduro
Get on with riding or get on with dying.
https://www.youtube.com/mojoscojo
the plug will tell you if you to lean should be a coffee color any lighter and you too lean if you like full throttle ridding then make your main jet a lil richer than perfect color your main jet works mainly at WOT...well you could get away with the top end but make sure you find the cause ...if you were riding WOT then closing off and coasting meaning the motor spinning with the throttle shut off that could also cause it because the oil is fed with the fuel as you know and with the throttle shut off but the motor still spinning with the momentum of the wheel speed you could cause a seize. if you notice an increase in engine vibration then you know you have damaged you bottom end ...hopefully notBomberpilot wrote:my engine builder said that he did a clearance of 9/100mm or other 0.09mm or 0.0035".
as I already wrote - i used the Motorex Racing GP 2 Stroke Oil at 1/33.
My main jet in the PWK 41 Pro Series is 190, pilot jet is 52 and needle DGK - do you guys think that this is too lean?
I was on WOT for just about 3-5 seconds when the noise appeared. Then I let off the throttle and hit it again and let off and again... so I don't do WOT for too long, too.
so do you guys think that I can not just replace the cylinder and piston (got another set here)? do you think some of the other parts are damaged too? could I soo that without disassembling the bottum end?
- 2strokeforever
- Posts: 1524
- Joined: November 13th, 2009, 1:04 pm
- Location: Vernon B.C Canada