KZ900 Valve adjustment shim question.

Well, now that I have had my bike on the road for a couple of months I still couldn't get it to run perfectly. Runs pretty good, but I get some misses and and I feel it could idle and and run smoother. So, I plan on purchasing a Morgan Carbtune as opposed to taking it to have it done Anyone have one for sale?. Price for the tool as opposed to the cost to have it done seems worth while. Anyhow, decided to first measure the valve clearances since the bike seems better run a bit better before it gets very warm. Once hot, I get popping once in awhile and it misses from time to time at cruising speed. I found the following measurements in mm:

Cyl___Intake__|_Exhaust
1_____< .038__|__.076
2______ .076__|__.064
3______ .058__|__.102
4_____< .038__|__.076

So the number 1 and 4 intakes are out of spec. The smallest gauge I have is .038mm (.0015 in). So there seems to be no clearance at all in these two intake valves (1,4). I have taken out the number one cylinder intake shim so far and it is a 2.55mm. My question is, should I go with a 2.45mm to increase the clearance by .10mm, or should I go with a 2.50mm for a .05mm clearance? Would just like to get some opinions before ordering the shims. I don't want to play around with swapping with any of the others shims on the bike. Not worth the time for the price of these things considering all the rest are within spec.

Joe

If you can spin the buckets, you can get away with 1 shim size. If not, go at least 2 sizes down.

Personally, I set the valves at max loose with the lobe straight away. .006"

If choosing between shims, I always go for the wider (in spec) value, not the tighter one. A shade loose won't hurt, a shade tight can ruin a head.

If you have some so tight the lifter won't mode, assume it's zero. If it spins freely, probably between zero and .001".

LarryC wrote: If you can spin the buckets, you can get away with 1 shim size. If not, go at least 2 sizes down.

Personally, I set the valves at max loose with the lobe straight away. .006"

bountyhunter wrote: If choosing between shims, I always go for the wider (in spec) value, not the tighter one. A shade loose won't hurt, a shade tight can ruin a head.

If you have some so tight the lifter won't mode, assume it's zero. If it spins freely, probably between zero and .001".

OK, I went back and checked both the 1 and 4 intakes, The buckets do spin on both so there is some clearance. So Cyl. 1 intake has 2.55 mm shim with less than .038mm (.0015") clearance. And Cyl. 4 intake has 2.40 mm shim with less than .038mm (.0015") clearance. So from what I gather you are both telling me is that it would be OK if I go down two sizes by .10mm (.004") to 2.45mm and 2.30mm shims respectively. Is that correct? That means I would end somewhere between a .004" to .0055" clearance. My service manual indicates my bike should be between .002" and .004". Larry, you said you like going up to .006";which sounds good. Does that apply to the KZ900 as well? If so, does it add much valve noise?

KZ900 spec is as .05 - .1mm for intake & exhaust...

As provided to me, due to exhaust running hotter...

Exhaust .10mm - .15mmm
Intake .05mm - .10mm

Basically as Larry taught me, if you run into a shim/clearance measurement that's border line, go loose versus tight on the clearances...

Example for an intake, let's say you measured .06mm, still in spec right...
But knowing this clearance is shrinking on you, better go with a thinner shim size and be at .11mm.

Also, measure your shims, don't just go off their stamping especially on used shims... You'll be surprise on how due to wear, they vary in actual thickness... I've run into this many times where next size (.05mm) placed me above spec by stamping but in measuring found it was slightly thinner....

OMR

Old Man Rock wrote: KZ900 spec is as .05 - .1mm for intake & exhaust...

As provided to me, due to exhaust running hotter...

Exhaust .10mm - .15mmm
Intake .05mm - .10mm

Basically as Larry taught me, if you run into a shim/clearance measurement that's border line, go loose versus tight on the clearances...

Example for an intake, let's say you measured .06mm, still in spec right...
But knowing this clearance is shrinking on you, better go with a thinner shim size and be at .11mm.

Also, measure your shims, don't just go off their stamping especially on used shims... You'll be surprise on how due to wear, they vary in actual thickness... I've run into this many times where next size (.05mm) placed me above spec by stamping but in measuring found it was slightly thinner....

OMR

Thanks OMR, that's a great point you bring up about the actual vs. stamped spec on the old shims. I will measure them before ordering. In which case, if they are truly thinner than stamped, it would make my going thinner by two sizes even more OK. Thanks guys, all great info!

KZJOE900 wrote: My service manual indicates my bike should be between .002" and .004". Larry, you said you like going up to .006";which sounds good. Does that apply to the KZ900 as well? If so, does it add much valve noise?

My KZ750 manual says .002 - .004", but I have read it was opened up to .006" high end. I shoot for .003 - .005 but .006 does not worry me. Worst it could do is maybe click a little.