Jump to content

'92 with hole in right piston


xrjoe

Recommended Posts

a buddies problem, running mostly stock motor, with Toomey t5's, stock carbs with 350 main jets, stock needles, weisco pistons, cool head. hes run it all over glamis, not counting numerous trips, then under a good warm daytime load, it scorched the right piston. he got the motor top end redone, new weisco's, and out in similar conditions, with a slow relatives daughter riding it, same clutch side piston comes out with a hole and top  ring landing melted down, supposedly she never rode hard, he never had a chance to check the plugs for any lean condition, im having trouble beliving a hole could melt at lower power level activity, theres no visible vacuum leaking around carbs, if the crank seal was pulling air it would include oil from the trans right? anyway im helping to hopefully prevent reoccurrence, talked to Toomey about correct jetting, his needle kit has slimmer needle and 280 main, for sea level operation. so im wondering if im overlooking something else, to check seal integrity, would pouring solvent in case to monitor for any loss indicate seals ability,  well enough to rule out failure?

Link to comment
Share on other sites

Most air leaks aren't visible. The fact that a mostly stock motor needed a 350ish main with toomeys and a couple bolt ons, That tells me there was an air leak. If you did just the top end and it happened again, I would lean toward crank seals.

 

I'm normally not one to preach the leak down as I'm advocate for checking the details twice and assembling once and that type of practice usually builds a solid engine assembly. However, it seems you guys are still trying to sort this out, so I reccomend tearing it all the way down. Split the cases and start over. Once you guys got it back together, a leak down would be wise.

Link to comment
Share on other sites

Most air leaks aren't visible. The fact that a mostly stock motor needed a 350ish main with toomeys and a couple bolt ons, That tells me there was an air leak. If you did just the top end and it happened again, I would lean toward crank seals.

I'm normally not one to preach the leak down as I'm advocate for checking the details twice and assembling once and that type of practice usually builds a solid engine assembly. However, it seems you guys are still trying to sort this out, so I reccomend tearing it all the way down. Split the cases and start over. Once you guys got it back together, a leak down would be wise.

Link to comment
Share on other sites

for what its worth, I filled the crank case with diesel solvent 2 days ago, both cylinders, and theres no loss from the initial level, if the seals were leaking under load, I would suspect they wouldn't hold liquid either, test obviously not under pressure, but being the clutch side, a pull of air would include trans oil, there was no sign of loss on dipstick.

Link to comment
Share on other sites

for what its worth, I filled the crank case with diesel solvent 2 days ago, both cylinders, and theres no loss from the initial level, if the seals were leaking under load, I would suspect they wouldn't hold liquid either, test obviously not under pressure, but being the clutch side, a pull of air would include trans oil, there was no sign of loss on dipstick.

Oh, looks like you got that figured out..... At least post pics the next time it melts down.
Link to comment
Share on other sites

Join the conversation

You can post now and register later. If you have an account, sign in now to post with your account.

Guest
Reply to this topic...

×   Pasted as rich text.   Paste as plain text instead

  Only 75 emoji are allowed.

×   Your link has been automatically embedded.   Display as a link instead

×   Your previous content has been restored.   Clear editor

×   You cannot paste images directly. Upload or insert images from URL.

Loading...
×
×
  • Create New...