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SOHC.co.uk Forums => CB750 => Topic started by: 750rideruk on April 18, 2014, 06:37:53 PM

Title: cb750 cam timing
Post by: 750rideruk on April 18, 2014, 06:37:53 PM

On rebuilding my cb750 K1 I find that on lining the T mark 1-4 up the cam line is slightly out of level but not as much as one tooth on the camsprocket. I have fitted a new cam chain. Anyone with any ideas or is it OK to continue?

Title: Re: cb750 cam timing
Post by: Bitsa (Ralph Wright - RIP) on April 18, 2014, 06:59:35 PM

Is this with the tensioner fitted?Photos of the T mark and the cam would help.If you have not got the tensioner on with the difference you describe could be it.
Cheers
Bitsa

Title: Re: cb750 cam timing
Post by: 750rideruk on April 19, 2014, 11:15:28 AM

Only very slightly out of line. is this OK

Title: Re: cb750 cam timing
Post by: tom400f on April 19, 2014, 12:45:11 PM

Bitsa is suggesting that backlash in the chain, if it is not tensioned, might account for the discrepancy. Perhaps wind the engine backwards some way then approach the timing marks in the correct direction of rotation only. Do they line up then?

Title: Re: cb750 cam timing
Post by: 750rideruk on April 19, 2014, 04:26:40 PM

I have tried that to no avail. Atiming disc show about 15 degrees out but not as much as one tooth on the camsprocket. Starting to think its a faulty chain but seems a bit far fetched

Title: Re: cb750 cam timing
Post by: Bitsa (Ralph Wright - RIP) on April 19, 2014, 06:59:36 PM

Photos and will let you know.Why are you using a timing disc for?Hondas have it all there for you.
Cheers
Bitsa

Title: Re: cb750 cam timing
Post by: 750rideruk on April 27, 2014, 12:51:41 PM

Job sorted.
Cam chain had come off the crankshaft sprocket. Removed barrells and heads replaced and hey presto everything aligns

Title: Re: cb750 cam timing
Post by: Bitsa (Ralph Wright - RIP) on April 27, 2014, 02:10:55 PM

Yep
Had that happen to me once but with a lot of poncing about got it back on the crank without removing cylinders and head,
Well done hope all goes well for you,
Cheers
Bitsa

Title: Re: cb750 cam timing
Post by: steff750 on April 27, 2014, 08:32:56 PM

 ;) yes we all done it I think at some time, but knowing it is off the sprocket is the trick I always try and keep tension on the chain so no slack is at the bottom of chain
 as bitsa says a lot of poncing about .
but it will go back on no problem without removing  the head or barrels
 but that being said you need to know that it is off the crank anyways ::)

Title: Re: cb750 cam timing
Post by: Bitsa (Ralph Wright - RIP) on April 27, 2014, 08:37:12 PM

Steff
Spot on mate I test it by pulling on the chain if its not on the crank it justs keeps pulling without any thing moving and hurts your hand like fury.
Cheers
Bitsa