Topic: 1981 CB650 Runs rough, valve timing?

[gilesclement]

Just replaced the cylinders on a recently purchased CB650. The bike never ran very well during my ownership which I attributed to a pitted cylinder and oil blow by. Now with new cylinders and decent compression and just cleaned carbs it's still running like my grandmothers ass.

- I've static checked the timing but don't have a light handy to check at higher rpms
- pilot screws set to where the manual suggested but haven't synced the carbs.
- One plug looks a bit white, the rest are slightly sooty but nothing horrible.
- Checked valve gap and adjusted.

I'm wondering if, when replacing the head, i somehow managed to get the timing chain off by a notch or two. It runs rough and has some lag from idle up to about 4000 then goes fairly well albeit still a bit piggish then at about 6000 the power just seems to drop.

Any suggestions as to what I could try and if there's some surefire way of determining whether the chain is off before pulling everything and cursing a lot. Would it run at all if the chain was off by a notch?

Thanks.

[WFO]

what year?

[gilesclement]

Sorry, 81

[martino1972]

did you check the timing advance if it moves freely...?

[WFO]

Well if you think it's one tooth off you better start there and take the rocker assembly off and make sure (did you read the shop manual?) 1.4 TDC and line up the notch up on the cam with the cylinder head?

[gilesclement]

I'll check the timing advance.

I'm almost certain that I set the timing chain correctly, 1.4 and set the notch to line up with the casing, aligned the little dots on the top sprocket. Just trying to determine what would cause the horridness and that seems like one possibility

[Spanner 1]

I think valve timing off by 1 notch of the chain would be pretty obvious when re-building...I think that you may not be done with your carbs!, carbs, like the ladies, wont give you what you want if you don't give them enough 'quality' time ....!

[gilesclement]

ugh, i hate that quality time certainly when all the effort doesn't result in a happy release.

Any suggestions on what to try with the carbs? They've got new gaskets and looked pretty sparkly when i had the open a week ago.

Could this be a valve adjustment problem where it reaches a certain rpm and the valves just stay open?

[gilesclement]

new discovery, apparently the#2 & #3 cylinder aren't firing at idle, pulling the plugs wire has no effect on rpms. slight change when you pull the plug wires on inside cylinders at higher rpms. I've tried swapping the coils from side to side in hopes that one was bad, no dice. Checked the gap on the spark generators thingies, they were way out and I've adjusted them in a bit, no difference.