80 GS750 lives- now the hard part

[Texatl]

So the GS750 I bought for $200 is now running.

Recap- it had a burnt electrical ground to the accessory circuit. Replaced 7-8 inches of wire and most is good. I think she sat for 18 months to 2 years. Gas is good and nothing looks gummed up.

In the past I've got her to turn over using the starter button when all ancillary stuff was plugged is (headlight, lights, etc...). Finally charged the battery enough, primed the carbs, and she started by jumping the solenoid posts. She's idnled for a while so I would beleive shes running on the tank gas, did have a little leakage out of the left side drain tube, but not now.

Thats the good news.

The bad- she runs fine and fast under choke (a little stumble and a bit of backfire but the backfire went away after a bit). I won;t say she's idling smooth. Won't run without choke. When she warms up a bit I can give her a little throttle, but any decent turn (more than a 1/8th or so) she just bogs. Choke all the way up she jumps up to 4-5K rpm.

Won't start with the button, but I didn't have all the lights attached. But something tells me the ground needs to be more complete 'cuz- shouldn't it start without...

So I need to chase down the starter button issue and the fuel flow issue.

Any ideas on the throttle bogging or starter button.

I did some searching but have not found the answer yet.

Thanks in advance,
Texatl

[Nessism]

Sounds like you need a carb rebuild. Not sure about the starter.

[Steve]

Throttle 'bogging' is usually caused by not enough fuel. You say "Gas is good and nothing looks gummed up." Is this FRESH gas that YOU have added? How deeply did you look for 'gum'? If the bike has been sitting for anywhere near as long as you suspect, you really should do a thorough tear-down, dip the carbs overnight, then put them back together with new o-rings from cycleorings.com. If you only looked in the float bowls for 'gum', you looked in the wrong place. When you had the bowl off, did you notice a long brass tube that stuck out from the carb body? Did you notice the size of the hole in that tube? Did you do anything to clean out that tube? Hey, that one's the easy one. There are many more passages in the carb body and other jets that are just as small and they are the ones that get gummed up. A simple look in the float bowl is only good for determining rust content, not gum.

Since you will have your carbs out again to to a proper refreshing, it will also be a good time to install new o-rings on the intake tubes. You can get them from cycleorings, too.

Oh, that long tube that was so easy to clean ... that's your 'choke' inlet. Apparently that is the only thing that is able to pass gas, so that's why it only runs on 'choke'.

.

[Texatl]

Is this FRESH gas that YOU have added? How deeply did you look for 'gum'?

Yes and kinda 8-[


Fresh gas with stabil (for the time I had it sitting over the winter). Cursory look for gumming.

Kinda new to the carb thing so, apparently, my "gum" inspection skills are not up to snuff. But I have no problem tearing down and rebuilding.

Here's a dumb question- what should they be dipped in overnight (whats the best solvent for the job)?

[Griffin]

Go to Advance Auto, Pep Boys, Autozone, etc.. and ask for a bucket of "Carb Dip". The store will have some, maybe behind the counter depending upon the state laws about things like that. The brand name will be Berryman's, Gunk, Gumout, etc... It's pretty much all the same stuff.

Totally tear down each carb body and soak the body, bowl, and any metal parts that don't have rubber on them for 24-48 hours. Do this for each carb.

Order a Carb o-ring kit from Robert Barr at www.cycleorings.com for reassembly. You don't have to worry about the intake o-rings, the '80-'82 GS750 doesn't use that style of boot.

[Texatl]

OK- ordered o-rings and picked up some carb-dip. No big surprise here, but 2 of the o-rings were already cracked and fragile on the fuel fittings. The snapped at the slightest touch. Hmmm- 28 year old bike. Yep its time for new o-rings.

So tore apart 1 carb last night and there is a bunch of grime in the fuel passages. One thing I noticed thats odd from the carb rebuild pictorial is on the bottom of this item...



Is a very small domed plastic mesh filter. On this particular carb it was very clogged up. I cleaned the screen off by hand, but cannot get the dome off the valve seat and I surely won't dip this (as it would probably kill the filter).

Any advise??? clean by hand??? Use spray carb cleaner (prolly not a good idea)???

I'm pretty sure based on the condition of this carb the gunk/grime is in all the carbs (as it was in the passages).

[Nessism]

I think you will be okay with a quick sprits out with the spray cleaner but I agree with your assessment to keep the seat out of the dip. For my carbs I took a piece of fine scotchbrite pad and twisted it into the needle seat to make sure there was no scale on the inside. Use a flashlight to look down inside, or a magnifying glass if you have one. It's best to keep the needles and seats together also since they wear together.

Hope this helps.

[Texatl]

Yes actually my thought process was to keep all parts together from the carb they came from. That and since each carb body will be dipped separate, I'll rebuild one while I'm dipping another. I have plastic bags labeled 1-4 to keep the parts separate.

Good call on the light/magnifiying glass. I'll clean the seat separately tonight.

Now to find my drill to get the air screw cap off and that bugger out so I can actually dip the first body (parts being dipped now, body tonight). :-D

[cbrophy22]

the screens do pop off I used a razor to pop them off. when I dipped my carbs I made little pouchs out of some window screen so all the stuff from number 1 carb went back intoo number 1. All so pull your petcock and clean and test it.

It will get you buy until you can get a new one.

[Texatl]

OK here's the next problem. The Air/Fuel screw will not come out! I drilled the cap off, got the right screwdriver and she won't budge. Soaked with PB blaster, still no movement. I can't dip the carb body until this comes out (O ring inside). What do I do!!!!!!!!!

HELP

[basic]

well....theres a couple things you can try....

a) soak longer....
b) keep soaking
c) they are probably oxidized in the threads and won't come out easily so make sure you have the perfect screwdriver, sit the carb up where it won't move, put some torque on it and gently tap the area the air screw screws into with a small rubber hammer. the tapping helps break loose the oxidation.
d) if you put too much torque on it, you will strip the head off. if/when this happens (happened on 2 of mine) you have 2 options - cut a line across air screw area with a dremel or something and cut a new slot in the screw and try again (damaging your carb body in the meantime) or use a screw extractor. if you use a screw extactor you will need to replace the air screw. z1enterprises sells them for like 6 bucks each i believe.

[Griffin]

I've got the same problem on my wife's 550L. Two of the air mix screws will not come out. I've tried about everything, and am ready to get out the screw extractor kit.

I had the same problem on my GS700 when I refurb'ed it a few years ago. I had one stuck air screw, and ended up destroying it getting it out. I ordered a replacement from the local Suzuki dealer, it cost about $8, I believe, and took a week to get.

Not too high a price to pay to ensure that the passage is clear and to get your idle mixture set right.

[Texatl]

Damn it all!!!!!!!! Well its half way to destruction. Extractor isn't working either. Trying 2 different types. ARGH!!!!!

OK- so whats my options??? Drill through will smaller bit??? I don't want to destroy the threads. Obviously the head is now stripped smooth, so I need a way to get it out and perserve the carb.

OR (blasphemy, I know) Leave it in at the factory setting and deal with getting the other three set correctly? #2 carb came out and apart no prob and is being dipped now. #3 tomorrow. Hopefully #4 on Monday. Thats leaves this PITA #1.

[Griffin]

Damn it all!!!!!!!! Well its half way to destruction. Extractor isn't working either. Trying 2 different types. ARGH!!!!!

OK- so whats my options??? Drill through will smaller bit??? I don't want to destroy the threads. Obviously the head is now stripped smooth, so I need a way to get it out and perserve the carb.

OR (blasphemy, I know) Leave it in at the factory setting and deal with getting the other three set correctly? #2 carb came out and apart no prob and is being dipped now. #3 tomorrow. Hopefully #4 on Monday. Thats leaves this PITA #1.

You can't leave it in at factory setting, and expect the bike to idle well if you adjust the others away from factory spec.

You can dip it in the carb dip with the air screw (and o-ring beneath it) in place. It will ruin the o-ring, but it may free up the screw as well.

I've done it before, and it did help me get a stuck air screw out once. The o-ring was soft and trashy, but I got it out.

By the way, I have a spare air screw from a junk set of carbs if you need one. You can have it for a buck to cover postage and the envelope.

[Texatl]

By the way, I have a spare air screw from a junk set of carbs if you need one. You can have it for a buck to cover postage and the envelope.

Yes I agree leaving it in is a bad idea. Thank you- fro the Super excellent on the offer of the spare part! But I gotta get it out first.

I really really really need some guidance on the best way to drill it out and preserve the threads.