SOHC.co.uk Forums > CB500/550
CB 500 K1 running issue
Oddjob:
Fading at low speeds sounds like a fuel issue.
Have you checked the vac gauge adapter screws are secure and fitted with an alloy washer?
Have you checked the inlet manifold rubbers for cracks. I suspect an air leak somewhere, enough for it to overwhelm the mixture at low speeds and why high throttle openings still work, as it would on choke.
Also check the manifold clamps, possible a screw has failed allowing the clamp to become loose.
Try the carb cleaner trick, start the bike and spray carb cleaner around the inlet side and see if the revs increase, if they do, you have a leak.
Beefington1975:
--- Quote from: Oddjob on September 19, 2022, 02:55:54 PM ---Fading at low speeds sounds like a fuel issue.
Have you checked the vac gauge adapter screws are secure and fitted with an alloy washer?
Have you checked the inlet manifold rubbers for cracks. I suspect an air leak somewhere, enough for it to overwhelm the mixture at low speeds and why high throttle openings still work, as it would on choke.
Also check the manifold clamps, possible a screw has failed allowing the clamp to become loose.
Try the carb cleaner trick, start the bike and spray carb cleaner around the inlet side and see if the revs increase, if they do, you have a leak.
--- End quote ---
Thanks for responding.
I thought fuel at first, so took the carbs off and on again, stripped and cleaned them and checked the rubbers and clamps - all look in good condition. Will try carb cleaner as you suggest.
Beefington1975:
--- Quote from: Beefington1975 on September 19, 2022, 03:05:27 PM ---
--- Quote from: Oddjob on September 19, 2022, 02:55:54 PM ---
Fading at low speeds sounds like a fuel issue.
Have you checked the vac gauge adapter screws are secure and fitted with an alloy washer?
Have you checked the inlet manifold rubbers for cracks. I suspect an air leak somewhere, enough for it to overwhelm the mixture at low speeds and why high throttle openings still work, as it would on choke.
Also check the manifold clamps, possible a screw has failed allowing the clamp to become loose.
Try the carb cleaner trick, start the bike and spray carb cleaner around the inlet side and see if the revs increase, if they do, you have a leak.
--- End quote ---
Thanks for responding.
I thought fuel at first, so took the carbs off and on again, stripped and cleaned them and checked the rubbers and clamps - all look in good condition. Will try carb cleaner as you suggest.
--- End quote ---
Tried the carb cleaner trick - didn't change the idle speed.
deltarider:
Inline fuel filters are a no no. Please read:
http://forums.sohc4.net/index.php/topic,190857.msg2220841.html#msg2220841
Beefington1975:
--- Quote from: deltarider on September 19, 2022, 03:30:06 PM ---Inline fuel filters are a no no. Please read:
http://forums.sohc4.net/index.php/topic,190857.msg2220841.html#msg2220841
--- End quote ---
Thank you. I'll take them off, but only added them after this issue developed in the hope it would help. I wondered if it sediment was blocking the idle circuits
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