Motorcycle Repair: ZXR250 valve clearance adjustment, leaky valves, leak down test

Question
QUESTION: Hi,

I have a question regarding valve clearance on a ZXR250

On the manual it is stated that it's clearance should be between 0.15 to 0.24... if a ZXR250 engine has quite a few valves with clearances less than 0.15 .. and a couple as low as 0.06 ... will this be a really bad situation?? I know obviously it will need new shims for proper clearance.. but would it be fine to use for few months before attending to the problem??

The bike starts fine with choke when cold... I know that the valves can end up getting burnt as it's too tight... but does this happen in short term??

Thanks buddy

ANSWER: Oc,

Smaller engines can live with less clearance.
Around .06 mm is small but some smaller bikes
run this much clearance on both valves.
The exhaust is usually a bit hotter and
may expand more requiring a little extra
clearance.
Was it correctly checked at room temp?
Don't worry about the ones a little under
.15 mm, they are okay.

Were you checking with a mm feeler gauge?

If it has some clearance it is not too
big a worry, but get it checked when
you can or just do the valves
in the winter for next year.

A leak down test can check for leaky
valves.

---------- FOLLOW-UP ----------

QUESTION: It was checked at room temp.. not sure how it was checked as my mechanic let me know of this (assuming mm feeler gauge) ... how do i know when this problem need definite attention or when I definitely need to fix it before I'll be burning valves ..etc..??

Summer is coming up here in my country ... will this be a higher risk.. as it will be hotter??..with some of the 0.06 clearance??

So 0.06 clearance as u said is not too big of a worry.. what if these are on the exhaust valves?.. should i worry about it.. will it be enough clearance when it heats  up...

Thanks for your previous reply.. it was very helpful

Answer
Oc,

It is always better to have things set
on the factory recommended settings.
I don't think you will have much problem
as the valve system you have
does not expand very much.
The clearance you have is okay but
in time it will get tighter as the valves
and valve seats wear. The only way
to be sure is to set them a little
closer to the right specs.
It gives some peace of mind when
things are set correctly.