another starting problem

[lowside]

Before you start messing with valve clearances do a wet compression test. Squirt a few pumps of oil into the bores and recheck the compressions. If the reading goes up by a marked amount then your problem is bottom end not top. I would have thought that any clearance will insure the valve is closed and will stay closed at canking speed.

Why, the op has already shown that the clearances are way too tight, they Need doing regardless. After that look at other things if it still isn't right or running right.

But why spend time and money on valve clearances if the bottom end is shot? for the sake of half and hour and a shot or two of oil.
He could spend time and money only to find the valve clearances do not improve the compressions. As i said if the valve has a clearance it should be fully closed, yes it could cause issues with engine running when hot and expansion causes the valve to not fully close, but that should not cause low compression with a cold cranking engine.It's also possable that if the valve has been holding open when hot the seat could already be damaged.

[popkat]

Well first post says starting problems, nothing about it running too bad when running, tight valves can cause starting problem, infact they will cause starting problems. I have a VFR where the valves clearance had closed, compression was way down, done clearances and bike runs fine, compression is up, not to full spec (it is 28 years old) but pretty even across all cylinders which is more important in ruling out a major problem.

As a rule the VTR engine is reliable, a problem has been found that can easily be fixed, I still say do the valves then look further if needed.

[lowside]

Ok, i don't dispute what you're saying. The TRX has the same issue with tight valves causing starting problems, but it never gives that low compression. I can't see why a tight clearance will cause low compression. It will advance the valve timing and effect the over lap, but i can't see that being far enough out to cause a valve to stay open long enough to cause the compression issue. Can anyone enlighten me? Maybe the readings are wrong OP did say his tester was not ideal.

[chaz]

thanks for the input all.
the bike runs well enough but the problem is starting. he is using the bike during the week so we have to look at it at the weekend.
cct's were changed before christmas , starting has only been a real problem after christmas. does get run low on fuel a lot as only getting around 75 miles to the tank.
valve clearances will need doing as I doubt they have been looked at over 40+k miles. not much history.