LCGB Forums

I need to replace a Pro X, possibly Mitaka, Yamaha RD350 YPVS 64mm piston, for use in a 186 Imola kit. I have it on good authority (Soullad) that they are the same ones used in the GT kits from Richard Taylor.

Mine seems to have exploded.

If any one could point me in the right direction, I would be most pleased as I need to purchase one, proper sharpish, like.

In a bit of a hurry, however, the weather is crap, and it is warm in the garage......

Does it look anything like this?

That looks like it, but will need to check. Looks like this at the mo.....

Exhaust gasket had blown. Do you think this could have caused the failure? Lots of carbon in the combustion bowl is proving a bastard to get off.

Kerist! That got hot!

The exhaust gasket failing could well have caused the piston meltdown, but from those images I wouldn’t be surprised if the bore & crank suffered as well.

Sorry to suggest that & hope to be proved wrong.

Are you sure the head was not leaking as well or have you partly cleaned the sealing face?

Warkton Tornado No.1 wrote:Kerist! That got hot!

The exhaust gasket failing could well have caused the piston meltdown, but from those images I wouldn’t be surprised if the bore & crank suffered as well.

Sorry to suggest that & hope to be proved wrong.

Are you sure the head was not leaking as well or have you partly cleaned the sealing face?

Agree with that but the mounting surface on the crank mouth doesn't look too clever near the barrel stud, porous weld possibly too?

Re the piston, your imola barrel will be 'graded' A, B, or C but I don't think the GT ones will be as they are for an iron bore

I didn't notice it getting hot (I have a SIP Speedo with CHT). It had been running for only about 10 minutes, which was lucky as I only had about a mile to push it home!

I always keep an eye on the CHT and never give her the beans until she is warm, but c'est la vie!

Anyone know where I can get a piston, then?

As Coaster said, your barrel & piston would have been a match via the grade. They certainly aren’t now!

However, before you rush to get a new piston, you need to look for clues as to what the grade was via a identification mark on piston &/or barrel.

Sorry to be ‘p*ss*ng on your chips’ but in my mind, it’s as important to check other components likely to have been affected too

BTW I'll PM you a supplier but I haven't checked with them.....

I used to get mine from yambits. You will find them if you do a google search. They are the same piston as in the GT186.

Cheers everyone, that is a great help.

I'm taking all this info in, and will try and get some details off the piston, but to be honest, its too buggered to glean much info off it.
The inside of the cylinder looks ok, but had better get it checked I guess. I want to do it right first time, as I have not got time to do this twice. Its going to Mull in about 7 weeks!!

This didn't happen on route to Kelso National rally did it? lots of holed, siezed and melted piston on route, suspected dodgey fuel.

dscscotty wrote:This didn't happen on route to Kelso National rally did it? lots of holed, siezed and melted piston on route, suspected dodgey fuel.

Wasn't the fuel at Jedburgh was it Scotty

dscscotty wrote:This didn't happen on route to Kelso National rally did it? lots of holed, siezed and melted piston on route, suspected dodgey fuel.

This anInteresting read Daz to what we were on about!
& the combating dodgy fuel earlier m8

http://www.fuelexpert.co.za/canirunavgas.php

Wasn't the fuel at Jedburgh was it Scotty

Not sure, but a few people had issues on route and returning, some usually solid motors suffered seizure/holed pistons including a few standard p200's