Will XJ750 Carbs work on a XJ650?

In article <76d6c1dc2144e@uwe>, "Albrecht via MotorcycleKB.com" <u33665@uwe> wrote:
>noreply@noreply.com wrote:
>>Will carbs from a 1982 XJ650 work on a 1982 XJ650?
>
>Yes.
MAYBE-if you rejet correctly and the volumetric flow is adequate.
it will not be bolt and go.
>
>But your subject line asks a different question.
>
>>Is the carb body the
>>same?
>
>They seem to be very similar. Is the XJ750 a bored out XJ650?
no.


>
>In that case the carburetor spacing would probably be the same. The typical
>spacing of carbs on an I-4 is that the pairs of carbs on left and right are
>close together and there is a larger space between pairs.
>
>You can shoe horn carbs into place even if the spigots are larger and the
>spacing is off by 2mm or so because the rubber boots will yield to force and
>lubrication.
>
>http://www.powersportspro.com/pages/parts/home.aspx
>
>XJ750:
>
>Carburetor Ass'Y 1 (15r-14901-00) 1 --
>3 Carburetor Ass'Y 2 (15r-14902-00) 1 --
>4 Carburetor Ass'Y 3 (15r-14903-00) 1 --
>5 Carburetor Ass'Y 4 (15r-14904-00
>
>
>XJ650:
>
>2 Carburetor Ass'Y 1 (5n8-14901-00) 1 --
>3 Carburetor Ass'Y 2 (5n8-14902-00) 1 --
>4 Carburetor Ass'Y 3 (5n8-14903-00) 1 --
>5 Carburetor Ass'Y 4 (5n8-14904-00)
>
>I dunno if "15r" and "5n8" are just some Powersportspro model designator or
>what?
>
> > I figure I need to check all the jet sizes and so forth...
>
>http://www.powersportspro.com/pages/parts/home.aspx
>
 >> Stay informed about: Will XJ750 Carbs work on a XJ650? 

Thanks.

Sorry about the typo - I meant to ask if XJ750 carbs would work on a XJ650,
and if the carb body's are the same.

I have a XJ650 that I can't get to start well. I've cleaned the carbs
numerous times. I know it is the carbs, because I have put a set on from a
friends XJ650 and it ran great. I am looking at a used set of XJ750 carbs
on e-bay and was wondering if I could use those.

Thanks again.

Kyle
 >> Stay informed about: Will XJ750 Carbs work on a XJ650? 

noreply.DeleteThis@noreply.com wrote:

>I have a XJ650 that I can't get to start well. I've cleaned the carbs
>numerous times. I know it is the carbs, because I have put a set on from a
>friends XJ650 and it ran great. I am looking at a used set of XJ750 carbs
>on e-bay and was wondering if I could use those.

Well, it sounds like you might have some gum and varnish in the idle ports
and passages.

I won't go deep into telling you how to clean those passages out, because
I've typed it out a few hundred times and posted it in rec.motorcycles.tech.

What you need to know is that the starting enrichener won't work unless the
throttle butterflies are almost completely closed. And, if you have dirty
passages inside your carbs, you have probably turned the idle speed knob to
get the engine to idle.

So, you've unknowingly sabotaged your carburetors.

--
Message posted via http://www.motorcyclekb.com
 >> Stay informed about: Will XJ750 Carbs work on a XJ650? 

It is good to be conversing with someone knowlegible. And I appreciate you
looking and researching.

Your description of the pilot screw is correct. I was lucky that mine were
not under a brass plug, but rather were covered with red silicone, I think
from the factory. Apparently some years had the brass plug, while other
years they used red silicone. I have had the pilot idle mixture screws out
and cleaned all of them, and made sure the outlet port is clear. After
looking closer at the factory service manual that I have, and reading online
about cleaning the carbs, I was confusing the "pilot screw set" with what I
thought was other parts under the pilot jet, in the bottom of the carbs.

I am pretty sure the idle mixture port is clear, because I have blown
compressed air and carb cleaner through it. Also, the butterflies were
closed when I remounted the carbs on the bike, and I have only made minor
adjustments to sync the carbs. I have also tried reducing the idle screw to
close the butterfiles. I can't get it to die by backing down the idle
setting, it just goes down to about 1000 RPM's and then sits there, idling
fine, even though I continue to turn down the idle. Because of this, I
think it is fine getting fuel through the idle circuit.

I don't think the problem is compression because when I borrowed by friends
carbs, it started fine.

I think the starter bypass circuit is ok. If the bike is warmed up and
running, starting to open the bypass circuit even a little causes the motor
start to sputter and eventually die (too rich I assume). The starter jets
in the bowls are clear because I can easily shoot carb cleaner through them.

This is really baffling me. I have got so many hours of labor in this bike
now, the thought of giving up now makes me cringe. I've been looking at
used carb bodies on e-bay, but with that you are just getting someone else's
problems.
 >> Stay informed about: Will XJ750 Carbs work on a XJ650? 

Yes, that's it. Any suggestions? I have cleaned and cleaned. I think it
must be a vacuum issue, because all the passages are clear.

kylentz.RemoveThis@mchsi.com
 >> Stay informed about: Will XJ750 Carbs work on a XJ650?