pics of piston and crank damage

[adz_244]

hi as you know from my last threads ive been tryin to get to the bottom of my,spluttering problem at low revs.Well today i took off the top end for replacement and found this a damaged piston on the intake side,the rings and barrel are good(i suspect someone has tryed to reuse this piston:crazy: ) as the bore has no damage to the coating,the second problem i saw was on the sides of the crank the plastic looks like its broken off,ive added some pics for you to see,ps do you think this was the reason to my spluttering

[adz_244]

and heres the crank

[studboy]

It looks like that bike got hot! Looks like it was maybe jetted a little lean. What does the exhaust side of the piston look like? It looks like your crank stuffer melted. Are you sure that your crank is OK? Usually they melt when the big end heats up.

I'd definitely take a real close look at things before putting it back together.

[adz_244]

ive decided to replace it to be on the safe side i just dont understand the lean issue cause its standard jetting,or would something else cause it to run lean forgot too add exhaust side is good

[studboy]

You shouldn't be running lean with standard jetting. A few more possibilities that I can think of:

1. Oil separation from the fuel.

2. Base gasket leak.

Scarring that bad on the intake side only usually indicates that the motor lost lubrication at some point.

[adz_244]

there was actually a tear in the side of the base gasket i noticed when i got the bike home.

[USED YZ426F]

ive decided to replace it to be on the safe side i just dont understand the lean issue cause its standard jetting,or would something else cause it to run lean forgot too add exhaust side is good

Anything that would allow air into the engine between the carb and cylinder can cause a lean condition.

- Loose / damaged carb-reed cage boot

- Cracked / damaged reed cage

- Torn / missing base gasket

Just some things to look for / check.

[adz_244]

i think the base gasket was the problem then as it was split on the left side but stupidly i thought it would still be sealed as the cylinder was all tourqed down.plus i think the previous owner was riding it like this

[USED YZ426F]

It won't take a big gap to cause a tiny air leak. A little air can really alter the jetting.

[adz_244]

thanks time for a full rebuild,before ive even rode it for more than ten minutes ha ha,the most expensive ten minutes of my life cheerz dirtjunky

[studboy]

i think the base gasket was the problem then as it was split on the left side but stupidly i thought it would still be sealed as the cylinder was all tourqed down.plus i think the previous owner was riding it like this

Looks like you found your problem. ?

[FFRacing79]

That piston scarring is not from a lean condition. As stated earlier, it is from lack of lube. Possibly from water entering the intake??? The gasket probably tore on cylinder removal.

The bottom end definately got hot, again from lack of lube.

Remember to do a leakdown before teardown to better diagnose the problem and just don't throw new parts at it. Tdub

[adz_244]

thanks ff,*edit*(the gasket was torn when i first got the bike didnt notice till i got it home)its already apart now,im putting the blame on the previous owner as i only had ten minutes on the bike with the correct premix mixture and standrd jetting,i litteraly rode about 400 yards and returned because of the missfire it had and was greeted by that piston and crank when i tore it down last night,on the plus side i got a cracking deal on a complete wiseco crank and mains kit from your side of the pond,everything so much cheaper there,and better riding areas and weather...........................hold on i NEED to move lol

[honda_best_789]

exact same thing happened to my crank, the stuffers melted, pics r in my garage.... i thought it coulda been from a worn down needle bearing maybe? if it is because it is running hot what can i do to keep it cooler?

[KJG15]

can you replace the stuffers? the plastic on mine did the same thing.

[adz_244]

can you replace the stuffers? the plastic on mine did the same thing.

i really dont know but i thought id replace the crank assembly and do a totall motor rebuild for insurance:ride:

[honda_best_789]

yea thats what im doing i just need a crank and then i can put it back together and go rippin

[adz_244]

yea thats what im doing i just need a crank and then i can put it back together and go rippin

there were a few on fleabay if your stuck for one

[KJG15]

if you send you crank out to be rebuilt do they replace the stuffers?

has any body on there done this?

[shrubitup]

if it is because it is running hot what can i do to keep it cooler?

If you want to run cool you should jet rich as the extra fuel actually lowers cylinder temperatures. However, get ready for spooge.?