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KH250 more power?
Posted: Fri Dec 27, 2024 7:01 am
by Ace Collins
Has anyone ever tried putting bigger carbs on an S1 or KH250?,if so how did they go about sourcing the bigger carbs with the right specifications i.e clamp on, choke position and tick over screw position?,can someone let me know please,thanks.
Re: KH250 more power?
Posted: Fri Dec 27, 2024 7:50 am
by scouse
S2/400 carbs are bigger, however bolting on a 350 top end and carbs will deffo give you more power
Re: KH250 more power?
Posted: Fri Dec 27, 2024 8:06 am
by Ace Collins
Hello scouse,
Thanks for your quick reply,i know that bolting S2 barrels and carbs will give me more power but trying to get hold of that sort of stuff for reasonable money is much harder to do unless you know of someone who can help?,all i was thinking of doing was bolting on some slightly bigger carbs say 24mm or there abouts just to give it a tad more power but knowing how to get hold of the right thing to do that is not easy ether,anyway thanks again for your help.
Re: KH250 more power?
Posted: Fri Dec 27, 2024 9:33 am
by SAM
350 is way to go. My KH350 & S2B both gone that route.
My two run standard 350 top ends. 350 carbs. Early airbox with K&N filter. Set up to run 8,500 revs @ 90mph. Will out sprint most if you catch them un aware.
Re: KH250 more power?
Posted: Fri Dec 27, 2024 9:34 am
by SAM
Contact Gary Ckarke.

Re: KH250 more power?
Posted: Fri Dec 27, 2024 11:30 am
by Triple Parts
Say you get 10% improvement, which is a lot just for a carb swap, you will gain 2 or 3hp. Is it worth it?
As others have said, 350 top end or a 400 engine. You can fit 400 barrels, but would need to bore your top case. You may also need to upgrade your clutch, which will start slipping with the extra power.
Re: KH250 more power?
Posted: Fri Dec 27, 2024 9:04 pm
by Kezsam1
As Ace has said getting hold of 350 top end is not that easy.
However, a decent set of chambers, carbs, programable ignition and a set up on a dyno would probably get the best out of the 250, not cheap but all easily obtainable.
Just my thoughts

Re: KH250 more power?
Posted: Sat Dec 28, 2024 10:14 am
by Triple Parts
Given that 250 barrels were originally designed as 350, we need someone to start producing 350 liners and re-sleeving them.
I wonder if PJME would do it? …
https://www.pjme.co.uk/acatalog/Cylinde ... eving.html