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'06 EG YZ 144 piston / cylinder wear

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Nov 14, 2000
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#1
First off I love the bike but I can't figure out why every piston has scrap marks on the exhaust port side.

The damnage is centered mainly right under the exhaust bridge and the piston damnage is mainly right where the lubrication holes are on the piston. Every time I change the top end I've been swapping them every 38 - 40 hrs soon as I feel it drop off in compression.

It's leaving alittle bit of the piston on the cylinder wall everytime I have to clean it up with scotch brite pad it cleaned off and smoothed out. Cept this last time there is a small nick in the bore.

I've been extra careful in making sure it's properly warmed up keeping the cylinder torque'd down using good fuel n premix keep the fliters clean in fact my jetting is alittle bit on the rich side. The bike runs great when its running just the wear on the piston n cylinder seems alittle abnormal yes my crank is within spec.

It's to the point now where I'm probably gonna send it back to eric with the last 4 pistons and ask to have it diagnosed I don't think the cylinder plating will go another top end after this one not without at least a honing at minimal.

Is what i'm experiencing normal ? I'm starting to wonder if it has proper clearance in this part of the cylinder wall.
 

_JOE_

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#2
Get ahold of Eric. The rm 265 he did for me has some issues with intake port rub. There is a 1 year warranty on the plating, and he will work with you if it's a bore issue. He is a great guy who is very concerned with customer satisfaction.
 

Rich Rohrich

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#3
You need to relieve the exhaust bridge a little bit. It expands from the exhaust temps, and presses out against the piston. The lube holes will help cool the skirt in that area but on some cylinders you still have to relieve the bridge. You can do it by hand, or Eric can do it quickly with the porting tool.
 
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#4
I'll send it back to eric the plating on the clyinder is saying it's had enough and the whole heat exspanion etc makes sense it's the hottest part of the cylinder. the rest of the piston looks great btw I wouldn't even care if I had to pay him to do that this time around. I just can't afford it right now 2 stroke street bikes are draining my wallet.
 
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#5
What kind of 2 stroke street bikes? The cr134 I half built had similar issues. Fresh it went 10 hours,pulled the top end and wtf! Could have been to long on the ring,also suggested it could have been the mix. Xamax & 537@32:1,that ended that. Fresh top end,bridge relief at .0015,15 minutes with similar results. Sent back for professional analysis,with the pistons and rings. The exhaust bridge has issues,its wide and tight. Well I will see the bore tonight with about an hour on it. I am ready to strangle the owner,from day one I insisted on a new bottom end. Old,used and abused,same engine I discovered the: swirl taper bored carb,seemingly modified intake,at least 1.5 lbs of aluminum removed from cylinder,squish clearance removed. Gm went shooting off on a thread about the right crankseal causing this type of abnormal wear. I would think that relieving the bridge .002 from the bore would be sufficient. What else causes the bridge to get hotter than its mating parts?
 
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#6
1991 Suzuki RGV 250 - what I like to call the black distraction (its got black fairing OEM) yes it's plated.