Honda-SOHC

SOHC.co.uk Forums => CB350/400 => Topic started by: cliff7 on June 09, 2021, 07:48:53 PM

Title: 400 f2 carbs
Post by: cliff7 on June 09, 2021, 07:48:53 PM
My bike starts first time and seems to perform cleanly through the revs. It idles fine at 1200rpm and will idle slower although a touch lumpy. However the idle mixture screws do not seem to make a lot of difference when adjusted. Is this normal? The carbs were professionally rebuilt last year.
Title: Re: 400 f2 carbs
Post by: K2-K6 on June 09, 2021, 08:46:04 PM
Where do you have the screws set now?

And how far do you move them? Going down below 1/2 (not to set them but to judge if there's any change) and up to near 3 turns out should at least let you hear a response from each cylinder if adjusted while running.

Doesn't sound too bad though from your description of how it runs at idle.
Title: Re: 400 f2 carbs
Post by: cliff7 on June 10, 2021, 10:02:43 AM
Thanks for response. I have screws set about 2 turns out and even when screwed right in (gently) the bike still idles. Does a plug check on idle help as previously I have only done this on more open throttle settings? Maybe a colourtune!
Title: Re: 400 f2 carbs
Post by: K2-K6 on June 10, 2021, 10:30:52 AM
Slightly odd signals it's giving you.

Are you confident there's not an air leak?  Spray something like WD40 around carb to head rubbers while running to see if you get a change in speed. Also can the tickover idle speed master control be turned down enough so that it stalls at idle?
Title: Re: 400 f2 carbs
Post by: cliff7 on June 10, 2021, 10:43:12 AM
Thanks. I'll try that and yes, it will stall when main idle screw is set low. Rubbers are a bit hard but no problem fitting carbs. Also trying to work out how to upload a video so maybe someone can help me identify a mechanical noise (clutch?) on idle.
Title: Re: 400 f2 carbs
Post by: philward on June 10, 2021, 11:01:27 AM
I don't think you can upload a video Cliff, I have a youtube account (easy to open) - post the video on youtube, then cut and paste the youtube link (of your uploaded youtube video) to your forum post - hope that makes sense
Title: Re: 400 f2 carbs
Post by: cliff7 on June 10, 2021, 11:08:11 AM
Right, I'm not very computer savvy but know a man who is. He's out on his FJ1200 at mo but will ask him when he's back. Thanks.
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