Vintage and Classic Hondas

idle problem

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750boy1995

idle problem

hey I have a 1981 cb750 and I cleaned the carbs,rejected them, and changed the needle height and it is still idling up and when I rev it in neutral the bike pops and stays idled up at about 3000 for a while it also does this when coming to a stop after riding it. I was wondering if anyone has any ideas on what could cause this or how to fix it.

TOOLS1

Re: idle problem

Administrator

Two things, one is you have a vacuum leak. Two is your carbs are way out of sync.
TOOLS

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1976 CB 750-A X 2
1977 CB 750-A X 4
1977 CB 750-K
1976 CB 750 F
1981 CB 750
1966 Kawasaki SG 250
1981 KZ 750 LTD
1973 CB 350
1979 CM 185 Twinstar
1982 Honda XL 80
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gkmaia

Re: idle problem

In reply to this post by 750boy1995

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Re-run

Re: idle problem

Administrator

In reply to this post by 750boy1995

As tools said, check those 2 things first. A high idle that slowly comes down is almost always caused by air leaks or poor sync. it is usually caused by the engine running way too lean.

The ride IS the adventure. The destination is just to get gas!

SoonerRon

Re: idle problem

In reply to this post by 750boy1995

The rubber insulators get hard, cracked and leaky. Sure cause of a high idle problem due to loss of vacuum. Also, a poorly adjusted choke cable can cause a high idle.

1979 CB750K
1978 CB750 Four SS (gone but not forgotten!)