CB750 Valve timing
 

I have been trying to sort out running problems on my 1981 CB750CB It was running badly spitting with odd backfire.It was also breaking down with wet plugs,The carbs on the bike were VB52C jetted P68 S75 They were butchered and only scrap I have tried a set on VB42A carbs with no improvement.I have replaced Ign coils,leads,and plug caps.Compression is from 120 to 150.On checking the valve timing I find that With the Dots on Cam chain sprockets lined up with the Cyl head the F mark is lined up not the T as in the Manual. Can I reposition timing by loosening Cam chain tensioners or do I have to loosen Camshafts.

Re: CB750 Valve timing
 

Typically, all you need to do is pull the chain tensioner to loosen the chain enough to reposition the cams. Are you sure the crank is @ TDC when you checked the camshaft position?

Also, if it's an automatic type tensioner, remove it and reset it before reinstallation. Your manual should have the details.