Hi guys, my first post.
I have a CB750K '76 US model. Lovely bike with just 10k miles (think it's genuine). Recently had it in part ex for a Datsun Z. I've spent a few weeks checking over the bike and sorting a few things before I tried to run it. I've had the carbs apart and checked/cleaned everything, ignition timing is fine (electronic upgrade), new plugs etc etc. Compression is 170,170,168,168. Valve clearances 3 and 4 thou (1 thou large after reading the internet)
The bike runs fine (static on stand) and seems ok however when I checked carb sync with a new set of vacuum gauges the reading is 10 (across all cylinders) instead of the advised 20 Hg expected. According to my research that indicates a valve timing or air-leak problem. I don't think I have air leaks and if I did would all cylinders be the same?
The other issue is that the slow running airscrews make no difference, I can even screw them all the way it. However the bike will tickover ok at 1000rpm.
So guys how can I check the valve timing without removing the engine. I have access to a dial gauge but I'd rather try to see the cam timing marks. What have you guys done and can I lift the cam cover enough to see the marks?
Do you think my problem is cam timing anyway? Taking the engine out is a huge issue just to check the marks.
Anybody used an endoscope (just ordered one) i.e. lift the cam-cover and insert a scope?
I have a CB750K '76 US model. Lovely bike with just 10k miles (think it's genuine). Recently had it in part ex for a Datsun Z. I've spent a few weeks checking over the bike and sorting a few things before I tried to run it. I've had the carbs apart and checked/cleaned everything, ignition timing is fine (electronic upgrade), new plugs etc etc. Compression is 170,170,168,168. Valve clearances 3 and 4 thou (1 thou large after reading the internet)
The bike runs fine (static on stand) and seems ok however when I checked carb sync with a new set of vacuum gauges the reading is 10 (across all cylinders) instead of the advised 20 Hg expected. According to my research that indicates a valve timing or air-leak problem. I don't think I have air leaks and if I did would all cylinders be the same?
The other issue is that the slow running airscrews make no difference, I can even screw them all the way it. However the bike will tickover ok at 1000rpm.
So guys how can I check the valve timing without removing the engine. I have access to a dial gauge but I'd rather try to see the cam timing marks. What have you guys done and can I lift the cam cover enough to see the marks?
Do you think my problem is cam timing anyway? Taking the engine out is a huge issue just to check the marks.
Anybody used an endoscope (just ordered one) i.e. lift the cam-cover and insert a scope?
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