My bike is a 72 Roadster (not combat), grey import from the USA 10-15 years ago. Good compression, feels like it should have more torque. I've measured valve lift on 1 exhaust and 1 intake valve, about 160 thou for both. This means the cam needs replacement?? Can't do this without splitting the crankcases ?
Hi Mick, I just checked my workshop manual, it says 332 thou inlet and 322 thou exhaust max lift for standard cam. So looks like your cam could be worn down. Yes crankcases need to be split to replace the cam.
My 72 750 still ran when one exhaust valve was only lifting 40 thou. Engine wouldn't pull higher than 4,000 revs though!
Thanks Alan, confirms my suspicions. Will pull higher rpm, but not much grunt, time to pull it down.
Pick up a copy of the clubs engine strip very good.
...sounds excessive. Rocker Spindle bearing all good? How do the adjusters look? Well extended?? I trust they are gaped properly???
Close out the gap on the back side of the cam and measure at the top of the push rod to see what stroke you get there...
How does the oil look?
If it is the cam send a pic when its out. Someone will spot something....
Hi Jon. Rocker spindles and adjusters seem fine but will recheck, oil comes out in reasonable shape at changes, which are done regularly.
I'll do some rechecking before I commit myself to a rebuild, just in case I've missed something obvious...