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SOHC.co.uk Forums => CB350/400 => Topic started by: paul G on March 27, 2017, 01:01:12 PM

Title: CARB JETS
Post by: paul G on March 27, 2017, 01:01:12 PM
Hi all,
            Took the 400/4 in for its MOT at the weekend as I can change the tax to historic from the 1st April.
It sailed through the MOT but I have an issue with the jetting now.
I fitted a Silvers aftermarket silencer and it now runs crap, won't pull and won't rev through the range (you have been warned if you are looking at one).
Checked the plugs and as I thought it is running weak. Looking to get some oversize jets if anyone can recommend somewhere or has anyone tried these .
http://www.motorradbay.de/jet-c-97-2.html
Just in case anyone is wondering, I have packed the mint original exhaust system away under the bed  ;D ;D
Title: Re: CARB JETS
Post by: philward on March 27, 2017, 03:26:25 PM
Have a look at this company - don't know about 400 carbs but they seem to have a huge range of jets - http://www.allensperformance.co.uk/carb-kit/keihin-jet-identification-chart/

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Title: Re: CARB JETS
Post by: paul G on March 27, 2017, 04:16:48 PM
Have a look at this company - don't know about 400 carbs but they seem to have a huge range of jets - http://www.allensperformance.co.uk/carb-kit/keihin-jet-identification-chart/

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Cheers Phil.
Title: Re: CARB JETS
Post by: Bryanj on March 27, 2017, 05:01:47 PM
Same type of jets as 500/550 as I remember(push in held with a clip) Siriusonic in Canada do all of them and even a box of several sizes
Title: Re: CARB JETS
Post by: Trigger on March 27, 2017, 05:58:58 PM
Seems like the exhaust has no back pressure, I would try a bit of wadding.
Title: Re: CARB JETS
Post by: mike the bike on March 27, 2017, 06:22:33 PM
Make sure you've got fresh juice in it.  Modern juice goes off after a couple of months and the engine won't pull the skin off a rice pudding.
Title: Re: CARB JETS
Post by: paul G on March 27, 2017, 07:43:03 PM
Make sure you've got fresh juice in it.  Modern juice goes off after a couple of months and the engine won't pull the skin off a rice pudding.
Fresh that morning Mike.
It's just down to the crap silencer, I bought it last summer or I would be back on the phone to them.
Title: Re: CARB JETS
Post by: andut on March 27, 2017, 07:43:10 PM
You could always try raising the needle a notch or 2, and you can get fine metric drills if you have spare jets available to increase in 0.05 increments.
Title: Re: CARB JETS
Post by: paul G on April 03, 2017, 07:39:20 PM
Stripped the carbs down and went up a size on the jets.
80 main and 45 on the slow jets.
Double checked the float levels and new rubbers all round.
Took it out for a quick spin and it bogs down on initial acceleration but then pulls like a train.
Didn't go far enough to check the plug colour or do a chop.
What do you think rich or weak. ;)
Title: Re: CARB JETS
Post by: andut on April 03, 2017, 07:57:53 PM
Paul, if it's initial accel, try adjusting idle mixture screws maybe 1/2 turn at a time and see if it makes a difference - should give you an indication of rich / lean and a damn sight easier that pulling the carbs on and off which gets pretty tedious if you're chasing carb settings !

Andy
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