Topic: Cam Chain Replacement

[81cb650]

Hey folks--

I've snapped my cam chain on my 1981 cb650.  I opened it up and verified that it is indeed snapped.  With a magnet, I'm able to pull the snapped chain up and out.  Does anyone know if it's possible to replace this without a full teardown? 

for instance, do the new chains come with a master link? and perhaps then I could tie the 2 chains together and snake it through the bottom of the motor around the crank?

[70CB750]

These chains exist for CB750 but I never used one. 

[seanbarney41]

What were you doing when the chain snapped?  The engine running at high rpm?    ...if so you may as well continue disassembling the engine and put in a correct endless chain as well as all the rest of the damaged parts that you have not found yet.

[81cb650]

hm. fair point.  I had pulled over in the middle of a ride to buy some fruit from a farmstand and the chain actually snapped immediately upon starting the bike back up. The motor wasn't revving high at the time

[seanbarney41]

well, you may have lucked out then as far as valves contacting pistons...still probably need new tensioner and guides for the chain to ever get that bad.  It is extremely uncommon for these to break, unless their is something different about the 650's that I don't know.

[PeWe]

Open chain with master link not properly riveted?

[Oddjob]

I seem to recall the 650 uses a hyvo camchain not a regular figure 8 chain.

[Nicklopic]

K&L makes a cam chain with a river style master link for the 650

[Oddjob]

After checking and confirming my suspicion that the camchain is in fact a hypo type I must warn you that the likelihood of you finding all the pieces of the chain is low. The chain is a 9 plate affair, my experience of one of those types of chain breaking is that they almost explode in the break area. Small pieces fly everywhere and plates are flung around the engine. You may succeed in threading a new chain onto the crank only to find the engine seizes as soon as you start it or when it’s put in gear. It broke for a reason, they usually break when the engine drops a valve for instance, you need to find the reason it broke not look to cut corners and just fit another, it’s almost certainly thrashed the tensioner and the guide. You were lucky it snapped at low speed or you’d be looking at major damage if you aren’t already.

Sorry to say but the safest way is to pull the engine apart and see what the damage is. Anything else is just throwing good money after bad imo.

[HondaMan]

^^^ What he said...