Honda-SOHC
SOHC.co.uk Forums => CB350/400 => Topic started by: martyn1061 on April 12, 2022, 06:03:33 PM
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Hi guys
My carbs have been recently ultra sound cleaned and rebuilt with new original jets, but when running sometimes it will rev at about 3000 revs and then won't tick over at all. I'm at a loss, if anyone got any idea what the cause will be great.
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Could be an air leak in the rubber mounts,
Are they soft?flexible?
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Hi
They are new mounts and seals so they should be ok.
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Not really possible to get "NEW" original jets these days, well not cheaply anyway. The original jets are by Keihin and the copies are made by Keyster and such. Although they look the same, are the same size etc they just don't perform the same as they are not made well enough IMO.
Even though people say it's been ultra sonically cleaned it can mean nothing, you have to test each circuit in the carbs to see if the obstructions it was ultra sonically cleaned to remove have actually been removed. Whilst ultra sonic cleaning is fine it cannot for instance clean everything, ok on organic deposits but not so good on small stones, pieces of metal filings etc that can sometimes find their way into air circuits, most noticeably the idle circuit. Lots of reports of finding out that ultra sonic cleaning failed to remove stuff lodged in there, sometimes the only thing that works is compressed air.
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The jets came from david silver and quoted as original and your right they are a lot more expensive
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Oh DS, well it's never been known for him to mislead people with the old "Original" description.
Were they stamped on the side with Keihin?
Did you replace the O-rings on the inlet manifolds?
Try removing the throttle cables and setting the idle with the idle adjusting screw.
Presume you synced the carbs after?
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Thanks. I will try to set the tickover with throttle cables disconnected, i have not balanced them yet as it has been difficult to get it to tick over at a steady 1200 rpm. Yeah new rings on manifold mounts.
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Hi
Had a stumble all over the years when opening throttle from fully closed.
New rubber-manifolds with new O-rings - in my opinion everything should have been tight. Tests with brake cleaner didn’t show airleaks.
Last year I smeared some threebond between manifolds and head and oh boy stumble is no longer here and the engine revs up like a turbine.
You might give that a try.
Is your ignition spot on? Advancer moves freely?
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Thanks for the tip.