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S1W jetting for mikuni
https://www.ukbeg.com/forum/viewtopic.php?f=8&t=23087
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Author:  HowardRD [ 20 Apr 2018 19:03 ]
Post subject:  S1W jetting for mikuni

My recent purchase of a S1W is testing me now, its fitted with a mikuni 42 carb a force winder filter and noisey as fooook pipe, it's flat as below 3k then pulls great above it, where should I start with the jetting , i.e. pilot ,main and needle position .
Would like to get it somewhere close then get it set up on a dyno , anybody recommend a decent mechanic or garage in the Yorkshire area ?

Author:  pash [ 20 Apr 2018 21:22 ]
Post subject:  Re: S1W jetting for mikuni

Take it to Maz. He knows what works...

Author:  DaveH [ 20 Apr 2018 21:25 ]
Post subject:  Re: S1W jetting for mikuni

I can recommend one in Lancashire. He's called Maz. He seems to know what he's doing. When he's not spannering buells he's a part time comedian......... I lied about the last bit. But he's the bloke you need to see. Find him here http://ukbeg.com/forum/viewtopic.php?f=7&t=18897

Author:  pash [ 20 Apr 2018 21:32 ]
Post subject:  Re: S1W jetting for mikuni

Main 170
Pilot 25
Needle 97 with clip on #2
Accel nozzle 60

Author:  Maz [ 21 Apr 2018 11:31 ]
Post subject:  Re: S1W jetting for mikuni

Hmmm, pretty sure all my own Mikuni's run....

Pilot 30
Main 160
Needle 96
Jet 70

Seem to remember this is how the 42-11 kit comes as standard ?.....bikes run great lOl

Author:  pash [ 21 Apr 2018 14:21 ]
Post subject:  Re: S1W jetting for mikuni

The only things I changed from the 42-11 kit were main and pilot so I’m guessing the needle and accelerator pump jet have changed in the kit at some point.

Author:  HowardRD [ 21 Apr 2018 15:15 ]
Post subject:  Re: S1W jetting for mikuni

Thanks for the replies guys, I've spoken with Maz and will be taking it over to him once I get the bike rideable but at the mo it's just no right.
Stripped the carb again ,
Pilot 25
Needle 97 2nd notch from top
Main can't read it but it's big , I've measured it against my LC350 mikuni mains and it's much bigger than my biggest 360 main jet.

Author:  HowardRD [ 21 Apr 2018 17:16 ]
Post subject:  Re: S1W jetting for mikuni

Been to buy new jets and could only get main jets , when I measured the new 160 main I bought it's not that much different from the old one and I couldn't get a new larger pilot .
The bike is still running like sh*t and won't rev cleanly , I'll try a new pilot next week and if that doesn't work the bike going to the back of the garage or ebay , pissed off with it now!

Author:  Maz [ 21 Apr 2018 17:26 ]
Post subject:  Re: S1W jetting for mikuni

Bit drastic....just fetch it in and I'll sort it.

Author:  Jill Brown [ 21 Apr 2018 18:09 ]
Post subject:  Re: S1W jetting for mikuni

HowardRD wrote:
Been to buy new jets and could only get main jets , when I measured the new 160 main I bought it's not that much different from the old one and I couldn't get a new larger pilot .
The bike is still running like sh*t and won't rev cleanly , I'll try a new pilot next week and if that doesn't work the bike going to the back of the garage or ebay , pissed off with it now!


Don't give up on it yet. If you can't ride it to Maz, get it taken there in a van, you know it makes sense. Maz knows a guy with a van whose job is couriering bikes who is reliable and reasonably priced....or you may have a great mate who will deliver it for you. 👍

Author:  HowardRD [ 21 Apr 2018 18:20 ]
Post subject:  Re: S1W jetting for mikuni

Spoke with Maz in the week and he was very helpful but he also said he was very busy and I would like to get it sorted asap really , I do have a van myself for moving my bikes so transport isn't a problem.

Author:  pash [ 21 Apr 2018 18:49 ]
Post subject:  Re: S1W jetting for mikuni

How did it go with a big glug of RedEx in the tank?

Changes in jet sizes from what you have fitted will not fix the issue you have. Don’t waste your time...

Author:  HowardRD [ 21 Apr 2018 19:21 ]
Post subject:  Re: S1W jetting for mikuni

Sorry pash I haven't tried the redex treatment yet but I'll buy some tomorrow from Tesco they always have it on offer , do you think it's worth me trying a standard carb ?
There's a few on ebay at the mo and the guy selling his S1w has a standard carb for £120.

Author:  pash [ 21 Apr 2018 19:29 ]
Post subject:  Re: S1W jetting for mikuni

I would say don’t buy a standard carb cos the Mikuni will work better. My bets are on blockage of the emulsion tube, Redex will (at least it has done for me) clean this out.

This is all based on the assumption that it is a fuel issue and not ignition (did you confirm that the tacho is stable?).

I would be happy to lend you the carb off my S1 or jets out of my collection (pic to follow).

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Author:  Maz [ 21 Apr 2018 19:36 ]
Post subject:  Re: S1W jetting for mikuni

Dont waste your money on a standard carb :roll:
Assuming that the fault is carb related, it will just need a thorough cleaning.

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