A forum for owners of Yamaha TTR250 trail and enduro bikes!

TTRfan · Super Guru

Base Gasket issues

ttr steve · Super Guru

RE: Base gasket gasket

TTRfan · Super Guru

If you do use sealant, an old trick is to put it just on the barrel side of the gasket and smear grease on the crankcase side such that if, God forbid, you have to take it apart in the future, the gasket will come away whole sticking to the barrel wink

heffh084 · Veteran Member

Hi Brian and Steve, went with a tiny amount of sealant on the barrel just to seal the imperfections and left the crankcase side dry. Hopefully if I keep my breathers clear, I'll get no cheeky leaks.

On another note, the circlips that came with the piston pin had little tangs on one end of the ring. I was always told that the small cutout in the gudgeon pin circlip grooves (to aid removal on the pin clips) was to be kept free of the circlip ends. But with these particular clips, you can't help but to seat the tang in the cutout. Does this sound right?

Looking forward to the new parts Steve, especially the shorty header pipe. Hope that helps this 325 kit breathe!

leigh · Senior Member

Base gasket and sealant?

TTRfan · Super Guru

Hi Leigh

I am not a fan of sealants and only ever grease gaskets (both sides) in the vain hope that they stay in one piece on any future tear down biggrin

A mate who doesn't like to take any chances always uses Wellseal on everything but it's a bit expensive! Example here.

I confess to using sealant on my BSA A10 though and I use Blue Hylomar on one side of the chain case gasket and grease on the other so it stays in one piece when the cover is taken off - usually....

It is unusual for TTR head gaskets to blow and there is usually something "fixable" that causes it.

I had it happen twice on one engine before I realised that the front LH head bolt wasn't torquing down on the head but binding on its threads. The solution was to run a thread cleaner down the crankcase holes and spin the head bolt in and out until it ran totally free.

Also, where a base gasket has leaked, the RH front bolt hole can fill up with oil and, if my memory serves me correctly, it is a blind hole so make sure there is no oil in it before fitting the bolt else it will hydraulic.

Good luck!

Brian

mossproof · Super Guru

I use a very fine smear of flange sealant on both sides of the base gasket. I would rather spend time cleaning the surfaces much later than have a leak sooner.

JOHNYBOY · Super Guru

silicone & such sealants drop into oil & block oilways mr honda yamaha etc did not use them clean up the surfaces just my opinion john

leigh · Senior Member

All good points gentleman

I recently removed the clutch side engine cover and the gasket took hours to get off and again, using a razor blade and brake cleaner and summoning the patience of mother Teresa it still left a less than smooth surface. The gasket sealed and no leaks but wonder if I am doing something wrong? Just seems to easy to score and mark the aluminum surface. I just think how many times can you do this before the surface is really stuffed. But then gasket sealant would sort that nicely you would think? I'm dreading it as I need to remove again to adjust or replace the clutch on this new TTR so it's like, how many times can I do this before the surface is ruined.

Removing gasket sealant is way easier (in past experience) than these gaskets that seem to get superglued down. I like the idea of using grease both sides thats gotta help in removing it but I really like the idea of using sealant with gasket and doing the job once.

I think most (and I have in the past) use way too much sealant and it squeezes out and can cause problems (I guess) as you say Jonyboy. I feel if you use a fine amount, there is minimal chance of that occurring. Mr Yamaha certainly uses it on the cases though, and I know 3 bond is used OEM by most bike manufacturers so feel confident in using it.

Can only experiment I guess, but next time I do this I will use a fine amount of sealant both sides of the gasket as you say Mossproof and hedge my bets.

Do you smear it on the gasket itself, or the metal surfaces? Prob doesn't matter.

Cheers Leigh

leigh · Senior Member

Base Gasket issues

Jeff B · Senior Member

Hello,

Was the cylinder o-ring and base gasket replaced with Yamaha OEM parts?

If so, then it sounds like warping due to overheating or frequent and prolonged cold water quenching of the cylinder or case.

cyl base.jpg

TTRfan · Super Guru

Hi Leigh

Assuming the base gasket was new and the O ring was fitted, there is another possibility that caught me out back along.

The two "outside" head bolts can be very tight in the casing threads and give false torque readings. I have had this before and blew two head gaskets before I realised what was happening. The bolts seem to thread in OK before the build but seem to seize a bit when under pressure.

It is really important to check the two outside head bolts run easily in the threads and if not run thread cleaners over the bolts and in the casing threads. They need to bolt all the way in.

Brian

Tommy Young · Member

Good evening,

Looking for a bit of advice. After a ride I noticed a patch of oil on the exhaust side that had been seeping out. Checked the oil and all is fine there so its not losing a lot. Looks to me that the base gasket has gone. Dry side just showing its not all the way round.

New base and head gasket set from Totally TTR's?

please excuse the mud. Photos straight after a ride

leigh · Senior Member

That's where I get my gaskets from.

For the new base gasket I've done around 2 months ago, I've followed all the tips above and used sealant, I think sealant will be the deciding factor - we will see.

I've seen quite a few leak from that same corner, I've had 3 leak from that spot - gut feel is the gasket can be easily pinched in that spot, I'm not sure, but I was ultra careful this time and used sealant. Time will tell.

Also the side cover gasket leaking there can look like that, clean and ride on the road to find out :)

Cheers Leigh