GPZ500 - Valve Clearances, timing wrong ?

[Nipedley]

Hey guys,

My friend noticed his gpz500 had a rocker cover bolt broken off inside one of the cam caps (neither of us the guilty party) so I said I'd take the cam cap out and get it sorted for him, and while I'm in there do the valve clearances. I've done clearances before but only on a shimmed bike where these are locknut and adjuster

Question no. 1 - While following the Haynes manual to check the clearances, I set it to the T mark however the cam lobes on cylinder 1 are not pointing up at that point like the Haynes manual says they should be. I'm quite confused about this. I have attached photos of the bike at position T with the cam lobes pointing down, forgive the bad photos it was very sunny (!) Is the timing wrong or should I be doing Cylinder 1 from a different mark? The bike was running fine and strong so I can't imagine the timing could be out that much and be running surely? Setting the bike at mark C as listed in Haynes for Cylinder 2 is fine, the cam lobes are pointing up as they should be

Question no. 2 - Should I set the clearances to the higher end or the lower end of the limits? Haynes says intake is 0.13 to 0.18mm and exhaust 0.18 to 0.23mm

Many thanks guys

[Kickstart]

Hi

Can't really tell from the pictures, but the crank turns twice for every turn of the cams. So try turning the crank once and then check the cam lobes positions (they will move 180 degrees).

All the best

Keith
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Traxpics, track day and racing photographs - Bimota Forum - Bike performance / thrust graphs for choosing gearing

[Nipedley]

Hey Kickstart,

Thanks for the reply, so I should just be able to try it around to T again on another turn and they will be in the right position?

I'm surprised I didn't have that earlier as I rotated it many times to check I wasn't doing something stupid, but I probably alternated between checking T and C on different turns

[Kickstart]

[Nipedley]

Thanks Keith,

I figured it had to be something like that because the engine runs fine and very well

Any idea on whether to aim to get the clearances closer to the higher or lower end of the spectrum (if any need adjusting)?

Many thanks guys

[Kickstart]

Hi

Screw and locknut valves normally widen a bit with wear so if a choice from the tight end of the clearance to the lose end I would go for the tight end. But not something I would worry about too much and would probably just go for the middle setting.

With screw and locknut it is easy enough to adjust them (90% of the work is getting at the valves which you have done to check them anyway).

All the best

Keith
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Traxpics, track day and racing photographs - Bimota Forum - Bike performance / thrust graphs for choosing gearing

[blurredman]

These valves are fiddley. When I last tried to do them on mine it was a little frustrating.

Taking the oil line off allows easier access. Though, remember to put it back on before putting it back together! And give it a good few cranks on the motor before starting.
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CBT: 12/06/10, Theory: 22/09/10, Module 1: 09/11/10, Module 2: 19/01/11
Past: 1991 Honda CG125BR-J, 1992 (1980) Honda XL125S, 1996 Kawasaki GPZ500S, 1979 MZ TS150.
Current: 1973 MZ ES250/2 - 18k, 1979 Suzuki TS185ER - 10k, 1981 Honda CX500B - 91k, 1987 MZ ETZ250 (295cc) - 40k, 1989 MZ ETZ251 - 51k.

[stinkwheel]

Bent feeler guages makes it a whole lot easier.

Get a set of feeler guages, clamp the tips as a bundle in a vice (not too tightly, just enough to hold them) and put a 45 degree bend in them.
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“Rule one: Always stick around for one more drink. That's when things happen. That's when you find out everything you want to know.”
I did the 2010 Round Britain Rally on my 350 Bullet. 89 landmarks, 3 months, 9,500 miles.