Hello!
I just finished replacing the exhaust camshaft on my 1979 CB750L and now I’m having issues where the bike won’t idle or stay running without the choke lever pulled fully out and doesn’t seem to rev above 4000.
I ran the bike before doing the replacement and it started up great (forgot to pull the choke out, but it fired right up) and stayed running until I hit the killswitch.
When I pulled the cover and put it on “T”, I noticed that the notch on the end of the intake camshaft was one tooth behind the exhaust camshaft. I corrected this issue and now the notches on the ends of both camshafts line up the same.
Initially, I thought it might be the slight difference in lobe size on the “new” exhaust camshaft and change in valve clearance. Then I thought it might be a fuel delivery issue, but I just cleaned and rebuilt the carbs, so probably not that. Then I started thinking about the adjustment I made on the intake camshaft and how that could have made significant difference in my timing.
I’m leaning towards a timing issue, since the bike started right up and revved strong before the adjustment.
I am looking for some feedback on where to start digging, before purchasing a bunch of tools/parts I don’t need to diagnose/correct my issue. I have ordered a compression test kit, but it won’t be here for a couple of days. I am trying to get my timing light back from a buddy, but I don’t have it yet.
I’m new to motorcycles and motorcycle troubleshooting, but in general, I would say I’m mechanically inclined and intuitive. Any feedback or suggestions would be greatly appreciated.
Thanks
Matt
I just finished replacing the exhaust camshaft on my 1979 CB750L and now I’m having issues where the bike won’t idle or stay running without the choke lever pulled fully out and doesn’t seem to rev above 4000.
I ran the bike before doing the replacement and it started up great (forgot to pull the choke out, but it fired right up) and stayed running until I hit the killswitch.
When I pulled the cover and put it on “T”, I noticed that the notch on the end of the intake camshaft was one tooth behind the exhaust camshaft. I corrected this issue and now the notches on the ends of both camshafts line up the same.
Initially, I thought it might be the slight difference in lobe size on the “new” exhaust camshaft and change in valve clearance. Then I thought it might be a fuel delivery issue, but I just cleaned and rebuilt the carbs, so probably not that. Then I started thinking about the adjustment I made on the intake camshaft and how that could have made significant difference in my timing.
I’m leaning towards a timing issue, since the bike started right up and revved strong before the adjustment.
I am looking for some feedback on where to start digging, before purchasing a bunch of tools/parts I don’t need to diagnose/correct my issue. I have ordered a compression test kit, but it won’t be here for a couple of days. I am trying to get my timing light back from a buddy, but I don’t have it yet.
I’m new to motorcycles and motorcycle troubleshooting, but in general, I would say I’m mechanically inclined and intuitive. Any feedback or suggestions would be greatly appreciated.
Thanks
Matt