Honda XR650L 2017
So here’s the wiseco piston.
It’s a 102.41 mm piston. I was told to put a .008 gap on the top ring and a .014 gap on the 2nd ring. The oil rings are supposed to have a .015 gap last I remember. I may be wrong. I just know I compared the ring end gap with the manufacturers instructions and ensured it was wide enough. I know I did the top and 2nd ring and the oil rings didn’t need to be filed after checking the ring gap. The oil rings had more than enough gap. A lot more than was recommended via wisecos instructions.
I do not have the best tools for checking ring end gap. I just through them in the cylinder, peeled them off and checked the ring end gap with a feeler guard and made sure the ring end gap was at least a thousandth of an inch wider than was recommended.
I had the cylinder bored out for the new piston and was told it had 004 clearance but I can’t verify that on my own.
Why did this happen to my piston and how can I keep this from happening again?
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Typically when you have scoring on the intake side but not the exhaust side; that is indicative on debris.
https://preview.redd.it/agkafoergz7g1.png?width=700&format=png&auto=webp&s=4037845edf56e6dc783693933e9c7fee8a830fc1
Damage was on the intake side of the piston.
I should add I only rode the bike for about a mile before it soft seized. The bike warmed up to operating temperature and then seized. It cooled down again and I could start it but when the bike was hot it was getting compression issues. Wouldn’t start until it cooled down and then kicked over no problem at all.
You don't want the gap to be larger than what is recommended. You want it to get as close as possible due to the exact issue you have. I'm going based off what you are saying. It's entirely possible to have other things causing your issue, but most likely, it's the incorrect gap in this case.
I’m not saying you’re wrong. Just explaining my process.
Wiseco recommends .00045 times the circumference of the bore.
In this case it comes out to 0.018144 in for the ring end gap. The person that recommended the .008 in gap works on this specific bike and does this specific mod piston mod professionally and never has a problem.
Based on what wiseco recommends and what the professional recommended I just used the two and gave myself a target range between .008 and .018 for ring end gap.
I’ve seen some aftermarket pistons require unique ring gaps, not factory. Keith Black pistons have you gap the compression rings much larger.
The ring end gap is supposed to be .0045 times the bore. It comes out to .018 in. The reason I did a .008 ring end gap was because someone who installs these professionally like this specific piston in this specific bike uses a .008 in ring end gap. The scoring along the cylinder walls comes up only until the oils rings and the oil rings had a huge ring end gap. Much larger than .0035 which was my widest feeler gauge.
I’m not too sure it was ring end gap but I do appreciate your input and am considering it may have been the ring end gap. I should have more throughly explained the issue outside of just posting my piston and asking what was wrong. That’s on me.