Jetting

Hi one and all. I’ve been a member awhile now with little or no interaction. I’ve been away from this project for sometime but getting close now. Age old question bs32’s on xs 250 open intake open pipes. Any experiences please

Carb is way too big for that if truly only a 250. Open intake just makes it worse.

The bs32 was stock for the xs250. I would try and take to someone in your neck of the the woods as they were never sold here in the u.s. There have been members on the this forum in the past with those bikes. But not much posting anymore. I would try to do a search on the forum for xs250.

Yes, eating crow, tastes good. Got to thinking as in 'surely not?' and went looking and found it out. I'm very surprised and firmly convinced the slide action in those will be modded to the hills to make them open fully. Or maybe they don't. That is even bigger than a race carb for that size cylinder. All for bragging rights as to who has the biggest carbs.

I'd love to see the slide activation holes in the bottoms of the slides.

Mornin' from the UK.
Thanks for the input. I have alot of information to say that these are the correct carbs from the factory
back in the early eighties. It's interesting to hear you say they are too big for the cylinder cc amc49. If you were to start from scratch, what would be your choice of carburettor?

Something from 24-28 max VM Mikuni type and non-CV.

You are right, they are the original barbs as I said higher up. Yamaha picked those for bragging only, they are in a normal world way too big for a 125 cc. cylinder, the 250s use 30 in non-race engines and those are 2 strokes with more flow. My 550 Honda uses 22s on 130 cc. cylinders and widely known to be slightly too small, Honda could have gone up to at the least 24 and maybe more but chose not to to pick up more lower end on that particular setup. My '80s 750 only uses 30s with 182 cc. size cylinders.

So maybe a pair of linked 26's would work. Or make/modify a two into one manifold for a single 30mm.
Triumph T110 had a single Amal before it became the twin carb T120 Bonneville.

You absolutely do NOT want to use one carb only on that engine if the crank layout is like the 400, it is not a 360 degree crank like the Triumph is and what allows good sharing of a single carb. The Yamaha is 180 crank and will not work well at all like that, one cylinder messes the other one up, you will never get it jetted right as the two intakes flow totally different.

Even though the carb bores will be OK you do not want to go willy nilly and simply start all over with new unknown carbs, The factory spends a million dollars tuning whatever carb(s) they use to work and you cannot hope to duplicate that, The main jetting is not hard but that is not nearly all the jets there and the rest will likely drive you nuts.

You're right about "driving me nuts" that process has begun already!