SOHC.co.uk Forums > CB350/400
IDLE PROBLEMS CB400/4
PatM:
It reads that your bike is running weak for some reason- I guess the plugs are a good colour. Most of the things you can check won't need to throw money at it, which can be annoying as well as costly.
i had a lack of power problem which turned out to be the ruddy seat blocking the air-intake. took ages to find as it was so intermittent.
My petcock was in a poor state- but allowing fuel flow into a can didn't reveal it- I've tried to attach a photo of the state of it- [ Guests cannot view attachments ]
mike the bike:
That clogged up fuel filter may be indicative of rust in the tank. Been there, had a superdream tank hammered to fit for a while until I found a replacement. Not a pretty sight.
PatM:
Mike- The bike was awarded a better tank due to internal corrosion and the fact i got one that had a better paint-job. However, the tank its running on had a poor attempt some years back by the look of it- bits flaking off. So, I fitted an inline filter and so far, so good- and that was about 3 years ago (I've owned the bike since 2009).
To the original post- Ive got a spare set of carbs that i brought off ebay for about £70 one winter, as I thought my bad running was carb related- even though Id replaced a full jet-kit to ll carbs (turns out it wasn't, but its good to have spares for these 40-year old machines if you can come by them!) To my spare set, I also fitted a jet-kit...just in case. From memory, as they were not on the bike more than a couple of hours- they ran like you described- poor idling and that was after complete cleaning using the old fashioned method of carb cleaner and air-gun.
mike the bike:
What does it run like after you clean the filter? My was so clogged with rust particles it run rough and was a pig to start.
PatM:
Bike runs fine now , but back to the original query for help.
My rebuild was only successful after curing previous problems
1. The battery must be working correctly in terms of static 12v measurement and charging
2. The fuel supply/carbs must be working correctly- preferably with new jets and seals- the prime offender is the main-jet seal, which if defective will cause incorrect mixture because fuel runs down the side of the jet, rather than being metered correctly
3. Air supply- i ignored this to my peril!
We are all different- i prefer mine to run properly, start etc and am less concerned about it looking pretty. I therefore concentrate my efforts on what i can!
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