Have I had a Rebuild or Not?

Well my trusty '04 is showing inconsistant signs of burning a bit of oil.

After a ride or two the dip stick tells me it needs an couple of ounces. It did this twice this season...normally I never need to "top up". But...after the last two rides...all looked OK in terms of oil level. I am consistant in the process of checking the oil...IE a good ride...stop the bike on level ground and within 30 seconds I have a clear reading on the dip stick.

I asked the guys I ride with if they notice any sign of blue exhaust coming from the bike when were on the trails and they say no.

WHen I started last week from cold (about 55 farenheit) after 2 weeks of sitting... it blew out some messy black fumes just briefly immediately after start up (choke on...several estart tries) but also a bit of blue smoke as well when I tweaked the throttle a couple of times. This went away very quickly as it started to warm up. Not sure if I should ascribe this to "burning oil" in a real way or just to the fact that a well used '04 has sat around for a few weeks and was cold on startup.

Looked at it with a knowledgeable guy I ride with and he pointed out that the head has already been removed at least once based on a small tab that extends out from the front of the head gasket..see picture below...his conclusion was that this was not the OEM headgasket..therfore the head must have come off at least once.


My questions is....is this "gasket tab" a definite sign that the head has been off at least once and that therefore the valves/valve guides etc have likely been replaced at least once...OR is this gasket "tab" just part of a standard OEM head gasket?

Trying to gauge the likelyhood of how much long term wear there is on the valve components to try and decide if I should seriously think about spending the money to rebuild it....It is an '04 after all....and I am a little reluctant to tackle a job of this complexity myself even though that would make it a lot cheaper.

Any thoughts/ideas/musings/speculations welcome.


Edited by travertt

If you are unsure of the bikes maintenance history....like the bike....intend on keeping it....start now with your own maintenance schedule, strip down & rebuild.


Just realized that I had the answer to my question at my fingertips....just checked the Yamaha parts fiche for the bike and indeed there appears to be a tab on the head gasket at that location

So from this i learn the following...

1- Should have given it more thought before posting...apologies

2- The likelihood of a non-OEM head gasket now seems very remote...having given it more thought.

3- I haven't the faintest idea how much maintenance has been done.

Too soon old...too late wise!

A little blue smoke on start is indicative of worn rings/plating. Unless you are racing, you can probably go another season on it. But I'd plan to get a new piston and rings and possible a replate.

I just rebuilt my'06 with new piston & rings because it has over 200 racing hours on it. Conclusion, it didn't need it. There was no measurable difference between old & new!!! There's a device that can measure wear on a four stroke without tearing it apart. It's called a leakdown tester, and an adapter threads into the spark plug hole and then air is pumped into the combustion chamber. A gauge on the device will indicate how much leakage is present , telling you how worn out your engine is. With a careful ear, you can listen to locate where it's leaking even! Leaking out the exhaust pipe, tight exhaust valve. Leaking out the carb, tight intake valve. Leaking out the crankcase breather is worn piston & rings.

The oil burning could also be the valve guide seals. It is exactly what my 426 did. Once the seals were changed, no more burning oil.

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