I have a valve adjustment question.

[zrx479]

I just got done checking the valve clearances on my bike "98 ZX6". There are a few that are out of spec on the tight side and the rest are at the very lower limit according to the manual.

It's been my experience in the past that valves get tighter not looser as the valve seats wear. I'm inclined to go ahead and
switch the shims on the ones that are at the min. clearance while I'm in there.

That will put them at the loose side of the adjustment range, but still within spec. I don't want to have to go back in mid-season if I can help it! Incidentally, the bike has about 7000 miles on it and this is the first adjustment.

I'm looking for a second,and maybe 3rd and 4th opinions on this.

Gonna order shims on Tues. so speak up quick!

Thanks!!!

[down&out]

I ran a 98 ZX6 for a season and never had to adjust the valves. I ran the intake and exhaust a bit tighter than spec to get more lift out of it. This tip came from a guy that worked at Muzzy's and built Aaron Yates 600 engine when he was on a Kawie.

[fastfreddie]

if you really want to get anal about it...you can grind the shims to exactly the spec you want. just make sure they're ground 'square'.

[zrx479]

Originally posted by down&out
I ran a 98 ZX6 for a season and never had to adjust the valves. I ran the intake and exhaust a bit tighter than spec to get more lift out of it. This tip came from a guy that worked at Muzzy's and built Aaron Yates 600 engine when he was on a Kawie.

Actually I'm more interested in the longevity of the engine than wringing the last little bit of power out of it.

The downside to running valves tight is that as the engine gets hot they may hold open and burn.

Obviously from your experience you can cut it pretty close!

Thanks for the tip!

[zrx479]

Originally posted by fastfreddie
if you really want to get anal about it...you can grind the shims to exactly the spec you want. just make sure they're ground 'square'.

I don't think grinding will be necessary. Either of the two shim choices will still be within spec, I just need to decide which end of the range I want to be at.

Thanks!

[Don Nees]

Actually I'm more interested in the longevity of the engine than wringing the last little bit of power out of it.

The downside to running valves tight is that as the engine gets hot they may hold open and burn.

Obviously from your experience you can cut it pretty close!

Thanks for the tip! [/B][/QUOTE]

From personal experience with my son's FZR 400, and longevity, I would go for the greater clearance (within spec) for the following reasons:
1. As the valves heat up, they're going to expand, thus decreasing the cold clearance measurement.
2. You're right, in that with engine time, the valve seat wear will cause the clearance to tighten up.
3. A leaking valve due to tight adjustment will burn out that valve seat in no time. Now your into a whole new issue.
4. I agree that setting the valves tight will produce a longer lift time, HOWEVER, there is a standard spec that involves timing the cams with the valve at "Check Lift Height" of .030 in. I have been told that this is because no meaningful Intake/Exhaust gas moves at less than that clearance (other than leakage burning the valves/seats). Therefore I suggest that unless I had one or two backup motors in my hauler (and the money to build them identically), I wouldn't risk adjusting on the tight side, but would opt for longevity and seat time for my rider to get faster, as opposed to that possible extra 1/2 HP.

Just My Humble Opinion,
Don

[apexspeed]

I think those shims are hardend, I wouldnt grind them.

keep an eye on the clearances. the tight specs could be seat/valve wear or it could be valve stretch too. if it gets tight soon after after you re-set them again, it may snap a valve if it gets too streched.

/////

[zrx479]

Well, I went ahead and set them on the loose side of the tolerances. Everything went well and the engine sounds good!

I'll find out this weekend how she runs!

Thanks for all the advice!

Mike

[headbanger]

One thing to remember next time is if you take the shims that are out of spec to your dealer they may trade you for the ones you need. When they do a valve adjustment at the dealership they usually swap with other used shims they have rather than buying new ones all the time.

[zrx479]

Originally posted by headbanger
One thing to remember next time is if you take the shims that are out of spec to your dealer they may trade you for the ones you need. When they do a valve adjustment at the dealership they usually swap with other used shims they have rather than buying new ones all the time.

I tried that and neither of the two local dealers will trade shims UNLESS they do the work.

Sorry, but I'm not paying them $300 in labor just to save the cost of shims!