Honda-SOHC

SOHC.co.uk Forums => CB350/400 => Topic started by: Winterfield on May 27, 2020, 09:36:43 AM

Title: Need to rejet carbs for megaphone style exhaust?
Post by: Winterfield on May 27, 2020, 09:36:43 AM

Hi all,

Due to budget constraints I've opted to get a cheap megaphone silencer from Classic Bike Shop (https://www.classicbikeshop.co.uk/short-universal-megaphone-silencer.html).

Will this be likely to change the back pressure enough to warrant re-jetting the carbs? I'd prefer not to, with the intention of buying a replica 400 silencer when (if?) they become available again. Would adding a baffle change the back pressure?
 
Cheers.

Title: Re: Need to rejet carbs for megaphone style exhaust?
Post by: Johnwebley on May 27, 2020, 10:34:52 AM

Possibly.

Try it

Do a couple of plug chops.
To check

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Title: Re: Need to rejet carbs for megaphone style exhaust?
Post by: K2-K6 on May 27, 2020, 07:24:05 PM

As John says, you'd only see by trial and error.

If there's any evidence of it running lean at first appraisal,  lift the needle jets by one notch (circlips lower) and use higher numbered spark plugs from NGK 8 to a 9 to give some margin for error.