XS750 carbs on a 650? (obviously only 2 of the 3...)

joestella28 · Aug 19, 2016

Hi All,

I'm about to start a build and have everything to get the engine running... except for the carbs...

the XS650 was taken apart 10 years ago and as usual, some things have gone walkies, the carbs being one of them. Now as with most of us, I have grand ideas and don't intend keeping the engine standard for long and had always intended upgrading from standard carbs. As such, I have a set of (three) XS750 carbs kicking about, with some re-jetting would two of the three be suitable to get the bike running in standard form?

Many Thanks,

Joe

weaselbeak · Aug 19, 2016

They both ran BS38 carbs, so why not?

fredintoon · Aug 20, 2016

Hi Joe and welcome,
like weaselbeak sez, why not?
You could also solder up some copper plumbing fittings into a manifold to run just one of them.
Or go t'other way with the manifold and run all three.

grizld1 · Aug 20, 2016

OK, here's (maybe) why not. Center-to-center spacing of XS650 carburetors is 120 mm., which does not translate to any spacing you can get out of an XS750 bracket, choke rod, and throttle shaft. So you'll need to either fabricate a custom bracket (easy), choke rod (moderately easy), and throttle shaft (very hard), or scavenge those parts from a pair of 1976-79 BS38s for the XS650.

5twins · Aug 20, 2016

I'm pretty sure the 750 carbs are BS34s, not that it matters much for 650 use. As Griz said, the main stumbling block will be correcting the spacing between the carbs.

If you did get some 650 carbs, the 750 set could be a good source for some extra parts. The alloy tops are a nice upgrade for the 650 BS34 "tin tops". The #135 butterfly plates also match the 650 BS34s.

weaselbeak · Aug 20, 2016

By son has an XS750 he bought as a donor bike for tractor pulling stuff. It has BS38's.

angus67 · Aug 20, 2016

If you put those alloy tops on 34, be mindfully that they are a lot thicker than the tin tops. I put a pair on my 34s, and started it. The thicker tops made the throttle open 1/8.....throttle cables need to be adjusted looser, almost as loose as they would go.

joestella28 · Aug 22, 2016

Cheers guys, I've got nothing to loose so might as well give it a go

scabber · Aug 23, 2016

Another 10 year project.

stuyvpc · Aug 31, 2016

Hi Joe, I fitted GPZ500 carbs to my tracker, very easy mod, much lighter than the originals and I found them very easy to set up, also can be cheap on Ebay. I'm near Swindon - where are you in the UK?

joestella28 · Aug 31, 2016

Hi All, I've been surprised with how straightforward it is to space them out to be honest. Like I said, I'm only going to use them to get the engine running on a stand before the real mods start. After that point I'll get either some more modern CV carbs of some VM's.

I'm based in Norfolk and am a long way off being able to ride the old XS

XS750 carbs on a 650? (obviously only 2 of the 3...)

joestella28

XS650 Member

weaselbeak

XS650 Junkie

fredintoon

Fred Hill, S'toon.

grizld1

Grumpy old man

5twins

XS650 Guru

weaselbeak

XS650 Junkie

angus67

Welder's penetrate deeper!!

joestella28

XS650 Member

scabber

XS650 Guru

stuyvpc

XS650 Member

joestella28

XS650 Member

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