SOHC.co.uk Forums > CB350/400
Won't return to idle/slight oil seep...
Mikep328:
My new to me CB400 does the "won't return to idle" thing. I noticed this the first time I rode it. It will idle OK after starting/warmed up but when out riding, it will hang at 2500+ RPM. Blipping the throttle doesn't help. I have found extensive posts here re that issue so I'm going work my way through the suggestions/opinions.
I had a Norton Commando that did the same thing and it turned out the mechanical advance weights were sticking in the advanced position when the throttle was reduced to the idle position. So I'll check it with a strobe light and verify that the weights are functioning properly.
I don't know if the carbs were worked on previously. There are receipts and mechanic's notes for an engine rebuild but no mention of carbs and no parts receipts for carb parts. So I need to at least check them for proper linkage adjustment, etc. Also will check sync though when it is idling at 1200 RPM after start up, it runs smoothly so I'm thinking the sync is reasonably close. Popping the throttle open when running down the road at say, 3000 RPM will result in a major bog; opening the throttle less aggressively it pulls well. I should go through the carbs I guess but if I can sort out the not-returning-to idle with external adjustments, I'll delay that..
Also noted a seep from the oil pan gasket. I checked and all bolts were all adequately/evenly tight so seems like a new gasket is in order.
A problem I have for mechanic work is that our bikes and car are in an apartment building multi-car garage. So there is no workbench or electricity and everything I do has to be contained within the parking slot which also contains our MiniCooper and two other motorcycles. Obviously, things like the carbs can be removed and worked on indoors but much care has to be taken with any operation that might end up with oil or fuel being spilled on the community garage floor. Replacing that oil pan gasket might be tricky under the circumstances... :(
Nurse Julie:
Double check to make sure it is the sump gasket that's leaking. I chased the same leak years back only to find it was an oil seal, gear change I think, that was leaking and weeping down and around the join of the sump pan.
Also, if you do take your carbs apart, I sell complete O ring kits in Viton which you will need to prevent issues with Ethanol in fuel.
Where do you live?
Mikep328:
Thanks! I'll check to verify where the oil is seeping from. We live in Bath.
Nurse Julie:
--- Quote from: Mikep328 on July 22, 2023, 10:31:22 AM ---Thanks! I'll check to verify where the oil is seeping from. We live in Bath.
--- End quote ---
Not local to us then 😂😂😂. I was going to say if you live fairly local you could come and work on your bike in our workshop but Bath to Lincolnshire is a bit far 🤣🤣🤣
Laverdaroo:
Im in Compton Martin near Chew Valley Lake (BS40) and Multiman Tim isnt far from you either. Let me know if you need a help or bit of space, we're all here to help and youre smack in the middle of both Tim and me if youre struggling.
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