Topic: cam installation problem-cb650

[davesee]

finishing up my rebuild and having a good ol' time trying to get the cam back on.

i followed the FAQ instructions, threading the chain onto the cam, installing the cam and then walking the sprocket over the cam. the first few times i tried there was simply not enough chain slack (i know, everyone says this), so i double checked and tried to decompress the cam chain tensioner fully. on the cb650 this involves undoing the lock bolt and physically pushing the tensioner back, then retightening the lock bolt. as you can imagine, with the head, this is tricky.

i still don't seem to have enough chain slack. do i need to take the head back off to decompress the cam chain tensioner fully, or is there something i'm missing? i've done this before and it was a major pain, but i forget how i did it!

[Vincent P]

Hello Davesee,

Just did the upper half of my CB750; I removed the chain tensioner completely so that it was not in the way. The gear on the camshaft has 2 bolts which allowed me to remove the gear; this needs to be dropped and then the chain can be slipped around the gear. Note: it may still have some tension, but you should be able to slip it back on.

[davesee]

vincent, did you put the cam chain tensioner on after the cam chain went over the sprocket? my manual shows it going in before the head goes back on, and i'm not sure it'll be possible to install with the cam in place.

[ShermanPain]

It installs better from the right hand side i believe. I struggled with mine for a good hour from the left before i realized this. i didnt remove the cam chain tensioner just loosened the lock bolt.

[Vincent P]

I removed it firs and  backed it as far back as it would go then bolted it back up; I then installed the came chain with a bit of effort then let the tensioner back out.

[crazypj]

650 and 750 are completely different tensioners, ignore anything about 750.
Most likely cause is either a new chain (real tight until motor has been run) or, 'loop' on crank sprocket.
Usually have to remove head, have someone hold chain as far 'open' as possible and maintain slight upward pressure then 'rock' crank to get chain tight on bottom sprocket.
One other thing I've come across, damage to hyvo chain links, particularly when someone tried to fit chain by 'rolling' it onto sprocket (gear?) like you would with a bicycle

[tomkimberly]

The cam gear sets on a shoulder. Install the cam from the right side (as you sit on the bike), slip the cam through the chain, then the sprocket. After you get the cam in position, slide the chain over the gear, then move the gear and chain onto the shoulder of the cam. Make sure you have aligned the cam gear correctly so the two bolt holes line up correctly and make sure the slot on the cam is in the correct position.

Tom

[davesee]

well here's one for the books...the 650's cam chain tensioner attaches to the engine at two points: one is the set bolt about midway up the tensioner, and the other is a locating bolt near the top. i had somehow mixed up the locating bolt with another bolt that was twice as long.  the extra length of the bolt kept the tensioner from decompressing.

once the proper bolt was in place the cam and sprocket went in and were bolted up in a bout a minute. seems like my cam chain is very loose after readjusting the tensioner though, meaning i've stretched the chain or i've ...wait for it... installed the cam chain tensioner wrong. two steps forward and one back, or vice versa.

thanks for everyone's input.

[Vincent P]

I would lean more towards the tensioner incorrectly installed; the bolt would have damaged before the chain stretched.

[ji107]

If you have taken the cylinders off, and the front cam chain guide, did you replace it on the inside of the cam chain?
If the guide is on the outside of the chain, you can't get the chain on the sprocket.

[davesee]

i think the 650 tensioner is quite a bit different...the guide can only go outside the chain.

at any rate, i had a happy ending. i verified the installation of the tensioner by pullinbg the oil pan. it was right on, so i gave the crank a few quick spins and the tensioner popped out a bit, and now everything is pretty snug. phewf.

[ShermanPain]

I always like a happy ending

[Vincent P]

Awesome; not get riding!!!