Valve Clearances and headache

[ross01505]

Hello all,

Where does everyone measure their valve clearances from?, inbetween:

Cam lobe and rocker arm or..
directly on top of the Shim.

I have just reshimmed a cyl head according to the manual i.e. between cam lobe and arm, as I found no valve clearances on the inlet valves and all tight on the exhaust (project build). Managed to get it running today but a comp test showed up low compression on all cyls with cyl no.2 <20 psi. I did the old trick of a teaspoon of oil down the bores and hey presto good compression readings i.e. around 130 to 155 psi with still nothing in cyl no.2 however. The bike would run after a bit of oil down the bores but once this was burnt off it wouldn't start again - piston rings I believe to have been changed and new, this i will now investigate.

I do have another zxr400 at the parents house and managed to get my Dad to check the valve clearances today, he did it without reading the manual and did it between the shim and rocker arm, all were in spec however found no to little clearances between the cam lobe and rocker arm. This is a good running bike and starts with no problems. So now confused as how to proceed with the project build.

I wonder if this is a case of 6 and half a dozen...

The race manual states greater valve clearances as it is measured on top of the shim but measured between the cam lobe and rocker arm this reduces due to cam lobe profile and brings it down to the same clearances as the road manual.

Hope my ramblings are understandable and any guidance is appreciated.

Cheers,

[RedexRobB]

I measure between the lobe and the rocker.

Has the head gasket blown?

[ross01505]

Yes I believe the head gasket was blown and the head got skimmed, to the max but not sure how to check this.

[ross01505]

This might be of interest, I've found that measuring the valves directly on top of the shims gives a consistent 0.05mm increase in clearance.

Also i now have the cycl head off and found a couple of interesting anomalies. I will post pics up hopefully later tonight.

Cheers

[banner001]

finished off my valve clearances last night...dead easy once i had made a shim-magnet-lifter

i have one that i bought, but the magnet end was very big, i have made a new one from a 3mm neodymium magnet (can lift over 700g), an old allen key and a bit of JB weld...jobs a good un! Did all 16 valves in a hour, not bad for a first timer!

I have made a proper shim chart for myself so i can do the next lot a lot faster as i will already know what shims are fitted, so its just a case of measuring clearances and ordering new shims.

Ill post a pic of my magnetic tool later, also if anyone wants one of these little magnets i have 9 here that i can 2nd class post for free, im never gonna use them for anything else.

[banner001]

bike runs SO much better with the valves in clearance

plus ive gone back to my old setup of 2 shims per needle and 100 mains and it seems a lot better, i also had a piece of the airbox upper (the bit that normally hides the snorkel) removed previously as it had a piece missing, but i put it back as i was finding more water in my airbox drain pipe than usual, ive now repaired this bit of plastic so it shouldnt be sucking quite as much air in on WOT...there is a nice straight road outside work, might have to see what the crack is sometime

my next job will be to lap the valves back...but for someone who's never done it before im imaging it being a lot of work, 2-3 weeks maybe as i would like to keep the engine in the frame if possible, might give the top of the piston crown a small tidy-up at the same time...a job for this autumn if i can get my hands on a replacement bike for a few weeks.

[banner001]

this is my home made shim-lifter, better that the inspection magnet i bought by a mile!