[jjr57]

My 96 CR has been running well all summer, with the exception of a low idle (1k) and occasionally dying at stoplights. So I tried to raise the idle by turning the idle screw clockwise. For some reason there seems to be little change in idle, and now it gets hung up at 3k only to come down to 1k after 30 seconds or so. I tried going back an forth, but its either no hang up and eventual stoplight death, or 3k hang up and 1k idling.

Carbs are in sync and have been cleaned and rebuilt recently. Choke/throttle cables are returning. Turning steering lock to lock does nothing for rpm hang up.

Where should I start looking?

Thanks

 

[pat1098]

This may be a symptom of an air leak on the intake side, between the carbs and the heads.
Or the carbs may not have been set up correctly. Or you may have a leaking slide diaphragm (presuming you are running the original carbs).
And check the valve clearances if they haven't been set recently. If they are out your changes to the idle may only be trying to compensate for a loss of compression due to exhaust valves 'riding'.
Getting the valves correct should be the first step towards tuning these. And fitting stronger coils is also a good idea, as the stockers were weak. This aids both starting and low-speed running.
THEN you adjust the carburetion..

 

[jjr57]

Sounds good. I need to learn how to check the valves anyway. I actually just re tensioned my belts before this started happening if that means anything.

 

[pat1098]

Make sure you haven't over-tensioned the belts.

You should be able to lift the belt away from the idler wheel quite easily.

I'm all in favour of you developing your skill set, but it may be worth paying someone with experience to set the valves and belts correctly.

It can be a false economy to learn these skills on your own bike.. There is no substitute for doing this type of work for your whole working life.

Adjusting the valve clearances is a process unique to Ducati, requiring some special tools, insights, and a set of shims.

Particular attention needs to be paid to the rear exhaust valve, which is harder to access (requiring the rear shock removing) and gets hotter than the rest. This is the valve which is usually the farthest 'out' of setting.

 

[jjr57]

As always, thanks for your reply Pat.

At this point I plan just to measure valve clearances, which were set by a duc dealer a few hundred miles ago, before she sat for a spell. If they are out of spec I'll go from there.

I'll recheck belt tension while I'm at TDC as well.

 

[jjr57]

Pat, you mentioned to me a while back that I should check my valves because my bike sat for 4 years, despite the fact that they were adjusted by the shop before she was put up. I was just curious, how could the clearances change from just sitting?

I'm realizing what is involved and would rather not go there unless I'm sure i have to.

 

[jjr57]

So, I replaced the stock 37.5 pilots with 40's and turned out the idle mixture screws 1/2 turn. This allowed me to turn in the idle speed screws without the motor dying. Now she idles at 1100 with improved 1/8 throttle response.

I also just noticed my stock cans have been cored at some point, (thought they were all that loud!) but she is running fine with the otherwise stock jets and needle settings, so I appear to be in good shape.