SOHC.co.uk Forums > CB750

F2 running problem

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brianm:
Hi Guys

I am new to this site and to Honda's in general.
In the summer i bought a 1978 CB 750 F2 from ebay and put it all together and got it MOTd. Now it runs well but will not idle below 2000rpm. Also when it gets to about 70 mph it is almost at red line on the rev counter. I am presuming this is not right.
The tappets have been set, the compression checked on each cylinder, new ignition coils fitted, new spark plugs fitted, timing checked, checked for leaks around the carb rubbers, and the carbs have been balanced.
Can anyone give me any ideas as to why the revs are so high?
Cheers
Brian

SteveD CB500K0:
What revs does the rev counter say at 70mph? (Others on here with F2s will advise as to whether this is correct)

Honda rev counters are not necessarily interchangeable (even though they may look similar) and run on different ratios.
There's a FAQ on the US site which gives the different ratios.

Show us a photo of the clocks.

Steve

brianm:
When doing 70 mph the revs are about 8000 rpm.
Brian

Bryanj:
8,000 at 70 is not right, what sprockets are fitted.

Would guess that bad idle is the pilot jets blocked

brianm:
The rear sprocket is 0333 43, don't know about the front. The carbs have all been stripped and cleaned.
Brian

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