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

threshold · Senior Member

Leaking head gasket should I get the piston done too?

katana · Senior Member

IMHO a set of rings is never a bad idea, it saves the barrel and piston for longer. The piston should still be fine. Unless the motor ate a lot of dust.

TTRfan · Super Guru

An interesting question on such a low mileage TTR Glen wink

It begs the question as to why the head gasket has blown confuse

Do you know its history and whether the 6,500km are genuine?

Have you or a previous owner had the head off for any reason? It's just that it is very rare for the head gasket on a TTR to blow.

It is a bit of a faff to get the head off (not difficult but a tad long winded) - see http://www.ttr250.com/Removing_Cylinder_Head/TTR_head_removal.htm

If your TTR had a higher mileage on it then I would normally recommend lifting the barrel to examine the piston and bore for possible damage and, if none, replace with new rings.

I would also recommend dropping the valves out to examine them for any possible damage (such as pitting on the faces), thoroughly de-coking and cleaning the valves and head, lapping the valves back in and fitting new valve stem oil seals.

Brian

PS If you were to need a rebore and new piston - see http://totallyttrs.com/epages/699105d9-e4cc-4b32-b236-84e72cd67f84.sf/en_GB/?ObjectPath=/Shops/699105d9-e4cc-4b32-b236-84e72cd67f84/Products/TTR-0355

Plus a gasket set - http://totallyttrs.com/epages/699105d9-e4cc-4b32-b236-84e72cd67f84.sf/en_GB/?ObjectPath=/Shops/699105d9-e4cc-4b32-b236-84e72cd67f84/Products/TTR-0134

If you need new valve stem oil seals whilst you have the head off (if they are worn and letting oil into the bore) - see http://totallyttrs.com/epages/699105d9-e4cc-4b32-b236-84e72cd67f84.sf/en_GB/?ObjectPath=/Shops/699105d9-e4cc-4b32-b236-84e72cd67f84/Products/TTR-0173

threshold · Senior Member

Unfortunately I don't know it's history. If the speedo was bodged thats a bit upsetting, but the bike is pretty clean especially for its age.

According to my mechanic a few bolts underneath the head were missing so I assume it has been off at some point for some reason.

TTRfan · Super Guru

Your mechanic might be able to get an idea as to the mileage done from the wear in the bore.

I wonder why the head was taken off previously confuse

I am guessing the PO left off the two 12mm "side" nuts but am still surprised the head gasket blew but, if the guy was that slack, he may not have torqued the 4 main head bolts down correctly.

I think you need to be guided by your mechanic on this one and wait to hear what he finds when he removes the head.

Brian