Primary/HY-VO adjustment screw?

Hi,

My 80 XJ650 has a bolt and lock nut that goes into the case directly below the cam chain tensioner. I can't find any reference to it online or in any manuals I've come across. I was under the impression the hy-vo chain was tensioned by oil pressure which is why you might hear a rattle at first straight up?

Someone set me straight haha

 

That bolt and locknut holds the rear cam chain guide. There is no provision for adjusting the Hy-Vo alternator chain (the shaft driven bikes all have a gear primary drive).

You are thinkng of the XJ550, which does have a primary drive chain that is tensioned by a hydraulic tensioner.

If you have a chain rattle on startup you likely need to adjust the cam chain tensioner (your year of 650 has a manual adjuster).
If after adjusting the tensioner, you still have a rattle, then there are other things to be looked at.

 

Well that clears that up!

I noticed it because I was adjusting the cam chain and it looked exactly like the bolt and lock nut on the cam chain tensioner. It only rattles for 2 seconds tops on the first cold start of the day. Running 20W50 oil dino oil.

 

It shouldn't rattle at all.
Have you ever encountered any difficulty when shifting?

 

Unless you ARE thinking of the bolt, and locknut, that holds the primary chain guide, inside the engine, that bolt and locknut should NOT be loosened, or removed, as stated Hy Vo Primary chain is non adjustable....if anything, the Hy Vo chain almost never wears out, the guide blade, however can break up with age+mileage......regular oil change inspections, looking for small black/hard rubber bits ( I believe it's a hard rubber coated steel blade) might be a sign this is happening

 

no difficulty shifting, there's no plastic in there either. I've read all about the primary chain guide falling apart.

 

It happened to me, twice, but..well North of 125K......, stuck in 1st gear and the second time 2nd gear...all the way home!!.
had to strip both motors though, Primary chain itself had barely 'stretched' 1mm!!!

 

There is no external bolt that holds the alternator chain guide (there is on the Xj1100, but that uses an XS1100 engine). There is no primary chain on the XJ650/750/700. They have gear driven primaries. The Hy-Vo chain spins the alternator, and allows the starter to spin the engine on startup.

At this point mileage isn't the issue. The alternator chain guides are failing due to age now.

 

* thanks, meant the Hy Vo chain, NOT primary.....

 

Doesn't the locknut and bolt, on the top crankcase, hold part of the hy vo chain guide?
I seemed to remember it did.....

 

On the XS 1100 and Xj 1100 it does. On all the other shaft-driven machines it holds the rear cam chain guide.

 

Just pulled the side cover (shifter) and it's clean as a whistle in there. Nothing remotely resembling plastic. There was also nothing in the oil when I did the oil change a while ago. Once back together. started it and no noise because I ran it for 5 seconds this morning. Could possibly be in the starter clutch, who knows.

I think I'm going to drive it for the season as the bike had been parked for 12 years with the previous owner. Once igloo season hits up here, if I have to tear the cases down, then so be it. I'll have 6 months of winter lol.

 

I adjusted this by mistake instead of the camchain tensioner. Could I have messed anything up

 

Probably not. Did you hear or feel any signs of cracking? Is the cam chain still running in the rear guide?

 

No I didn't hear or feel anything but I do think the rattle in the top and got worse. Still runs.
Going to do the cam chain tensioner correctly soon as it cools down

 

It's fine then. That bolt literally just holds the cam chain pivot in it's recess. You might want to back it off a tad just to make sure that it's not causing the rear guide to bind. It has to pivot freely or the adjuster will just bend the guide, instead of it swinging to take up the slack.