Topic: 81 CB650 with a bent valve!

[lowd239]

Hey all,

I just picked up a 81 CB650 for cheap...previous owner said he had it running last year.  He put a new battery in but couldnt get it to turn on...when I got it home I realized he didnt put acid in the new battery!

So I sorted the battery, cleaned the carbs and it fired up but it was down on a cylinder.   I checked compression and there was hardly any compression on cylinder 1.  Ahhh!  So much for an easy fix.  As I was taking the valve cover off...on the one over cylinder 1, the longer and shorter allen bolts were swapped so that the longer bolt was actually hitting the intake rocker.  And then after taking the cylinder head off it was revealed that the intake valve was bent from hitting the piston. 

I also noticed the camshaft and rockers are pretty worn which seemed odd as I could still see the cross hatching on the cylinders.  Perhaps it was rebuilt previously?  Its only got 13000 miles.

My question is...do I replace just the bent intake valve or since the rockers and camshaft are quite worn, find another cylinder head to swap??    Any suggestions are appreciated!

Jeff

[69cb750]

Head looks nice, replace the valve

[lowd239]

What about the cam and rockers?  I know the cb650 has a desirable cam so I thought maybe it'd be best to just get the entire head.

[Don R]

 I'd go with a better head if there was one reasonably priced. 

[lowd239]

I'm not finding much as far as good cams and rockers go.  Some on ebay are just as bad as mine with pitting on the lobes.  Mine has groves you can feel with your fingernail.  I've only found one head that comes with the camshaft and its $250

[Scott S]

I'm not finding much as far as good cams and rockers go.  Some on ebay are just as bad as mine with pitting on the lobes.  Mine has groves you can feel with your fingernail.  I've only found one head that comes with the camshaft and its $250

 That's not a horrible price, seeing as how the 650 cam sells for $100+ itself.

[lowd239]

Ok thanks, good to know. 

Also when taking the head off I noticed that not all the 8mm bolts for the rocker box had washers... Is this correct?  Also only two of the head bolts had washers.

[DaveBarbier]

Not all valve cover “rocker box” screws have copper crush washers. Only the ones that are through holes into the valve/cam cavity.

All head bolts should have washers. I bet they are in there but just stuck real good to the head.

I have a good method to unstick those washers. Look at my build thread in the table of contents and you’ll see it.

[lowd239]

Awesome, super helpful!  I see what you were saying about the head bolt washers...gladly they're all there!

[Scott S]

 I can't see any of the pics you posted.