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New (to me) '83 GS750E, I think I need some help with the carbs.

  • Thread starter Thread starter 83GS750E
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83GS750E

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So I just bought this 83 GS750E last week and it needs some work. I've done the carb. rebuild, r/r replacement and relined the fuel tank. Everything's back together now and I can't seem to get it idling properly. It revs up great, and holds whatever I set the idle screw at for about 30 seconds then drops off and stalls unless I give it some throttle. Also, there's a bit of black smoke from the tailpipe. Any ideas? Is there an adjustment on the carbs. that I'm missing? Any help would be great.
 
Are you running an gravity inline filter? I bet some of the junk from lining the tank got into the carbs.
 
Well, ... if you did a full carb rebuild, you should have seen the idle mixture adjust screw on the top of the carb outlet. :-k

IMG_2958.jpg


Those screws should be between 2 and 3 full turns out from lightly seated, if you have a basically stock bike (stock airbox/filter and exhaust). You also need to be sure that the float height was set properly. You need to measure the height from the bottom of the step on the float.

IMG_2161.jpg


You also need to make sure that the carbs are synchronized, which will require a set of gauges to measure the vacuum levels in each intake throat.

.
 
No fuel filter, however there should't be any junk in the tank as I spent 2 days soaking it with the different Kreem products to remove a very small amount of rust and left the final coat to dry for 24 hours. It seemed very clean, dry and tough, I couldn't scratch it off with my fingernail so I doubt that the gas would remove it. I'm thinking that I should play around with the air screws to see if that makes a difference, is this a good idea or a bad one?
 
Thanks Steve, I did see the screws, wasn't sure what they did and couldn't figure out how to set them. :confused: When I replaced them after the rebuild I just screwed them in the same number of turns as when I took them out (14). Sounds like I should have screwed them all the way in then backed them off a couple turns. I'll start there. Thanks again.
 
Thanks Chef, yeah, I went through the carb rebuild pictures from the link that you included in your post. Everything got soaked and blown out with the air compressor including the pilot circuit.
 
Be careful when you screw them in. The factory had them set about 1 to 1 1/2 turns out, and you don't want to bottom them too hard, the points might break off. In fact, remove them first, to make sure the points are not broken off now. Then put them back in (I use a drop of oil on the o-ring to keep things smooth) and seat them lightly. Now back off at least 2 full turns. When the bike warms up, tweak each of those screws a bit, listening for highest engine speed. When the engine is running the fastest for each screw, it is getting the best mixture. If you can't find a setting where the engine speed is highest, turn the screw in until the engine starts to slow down a bit, then back it out about 1/4 turn. Do this for each of the carbs to see if your situation improves.

.
 
Make sure the o-rings and washers come out with the screws too. You don't want to leave them in the bore then replace the screws and mangle stuff.
 
Thanks guys, I adjusted the screws today and got her running just right. Took it out for the inaugural ride and now something else has popped up. I'll post a new thread, but there appears to be some play in the front forks.
 
Steve said:
You need to measure the height from the bottom of the step on the float.

IMG_2161.jpg
Click to expand...

Steve,

do you know if this applies to all the BS series carbs or just the BS32s?
I setup my 550 floats measuring to the top step and I've noticed some
bogging down when I go up a steep hill. Last time it happened I pulled
over and found gas dripping out the airbox. Carbs were overflowing.

Now it all makes sense.

Problem is the factory manual and Clymers don't show a clear picture
of where they are measuring from.

thanks!!!
 
Last edited:
DimitriT said:
Steve,

do you know if this applies to all the BS series carbs or just the BS32s?
I setup my 550 floats measuring to the top step and I've noticed some
bogging down when I go up a steep hill. Last time it happened I pulled
over and found gas dripping out the airbox. Carbs were overflowing.

Now it all makes sense.

Problem is the factory manual and Clymers don't show a clear picture
of where they are measuring from.

thanks!!!
Click to expand...
Yo Spanky :p
You measured wrong.
:D
This does apply to all BS carbs.
 
chef1366 said:
Yo Spanky :p
You measured wrong.
:D
This does apply to all BS carbs.
Click to expand...

Yep, last night I went in and redid them. Today I'm gonna do a test ride
and see if it fixes my uphill problem.

BTW, the Mikuni CV manual on BassCliff's web site clearly shows
the right way to measure the float heights.
 
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