Rubber to be removed for carburetor cleaning

[ZacharyB]

Is there a sequestered seal somewhere on my '78 750's carbs that I will miss when I dunk them in Berryman? I know to remove the float bowl gasket and adjustment cap gasket, possibly the mixture screws poking out the top at angles (?) , but is there anything else?

 

[SqDancerLynn1]

The choke assembly should be removed if you are dipping them.
Check with robert www.cycleorings.com he has a O ring kit for the older slide carbs

 

[satchmo]

If you're going to dip your carbs, I would recommend completely disassembling them. Remove the mixture screws, seat assemblies, jets, chokes, gaskets, etc.

If you've got the VM carbs -- all of these parts of rubber o-rings on them. If your o-rings are cracked, or if you forget to take some out, they can be replaced fairly easily.

Make sure you know how many turns out the mixture screws were (turn them all the way in until they touch bottom lightly -- counting the turns as you go).


Satch

 

[KEITH KRAUSE]

Re: Rubber to be removed for carburetor cleaning

Is there a sequestered seal somewhere on my '78 750's carbs that I will miss when I dunk them in Berryman? I know to remove the float bowl gasket and adjustment cap gasket, possibly the mixture screws poking out the top at angles (?) , but is there anything else?

Your VM carbs have an o-ring for the bowl drain bolt, the side air screw, the pilot screw (underneath, engine side of bowl), the needle jet, the choke plunger assy'. The choke plunger assy' must come out too. The plunger bottom is rubber.
Keep a record of how far out each pilot screw turns EXACTLY. The sides of the screw slot may be in line with a "nick" on the carb body? Seat them LIGHTLY first. Use a good fitting tool. They can be tight and the heads easily stripped. This goes for the side air screws too. They are not as sensitive but record them too. If you mess up the side air screws adjustments, just set them using the highest idle method which is where they need to be anyway.

 

[ZacharyB]

Thanks, I could have missed those, especially the jet needle.

This is going to sound really newbieish, but how do I disassemble the slide? I see there is a cap on the side of the carburetor top that could prise off or? I have the bike bandit parts diagram to help me see what needs to be taken apart, but of course, there's no directions.

 

[satchmo]

In order to completely dissasemble the carbs you'll need to remove the throttle rod to get the slides out. Their should be two rubber caps on the ends of your carb bank. Remove those.

If you've removed the caps on top so you can see the adjustment mechanism, you'll see the bolts that hold on to the throttle rod. Loosen those. There will also be a throttle plate which needs to be removed before the rod will come out. Once it is removed, the throttle rod should slide out (depending on the condition it may take a bit of lubricant).

Then the slides should be able to come out.

It's a lot easier to visualize if you use a haynes or clymer manual.

Of course there are some guru's on here who can describe things much better than I can.

Good luck and keep firing the questions if need be.

Satch

 

[satchmo]

Here's a thread on cleaning carbs that might help.

http://www.thegsresources.com/_forum/viewtopic.php?t=19145&start=0

 

[KEITH KRAUSE]

Thanks, I could have missed those, especially the jet needle.

This is going to sound really newbieish, but how do I disassemble the slide? I see there is a cap on the side of the carburetor top that could prise off or? I have the bike bandit parts diagram to help me see what needs to be taken apart, but of course, there's no directions.

An o-ring goes on the needle jet, not the jet needle. The main jet screws into the needle jet/bleed pipe. Remove the needle jet and you'll see the o-ring.
You don't really have to remove the throttle valves (slides) to properly clean the VM carbs. Of course, you can clean things easier if they are removed. If you do remove the slides, or even disturb the throttle shaft bar, you'll have to re-synch the open and closed positions of the throttle valves. Then follow this with a carb synch using a vacuum tool. If you don't synch these carbs by eye, the vacuum synch can be a lot harder to do. And if you don't do the vacuum tool synch, you'll almost certainly have mixture problems and uneven cylinder combustion.
As Satch said, check out the thread posted earlier this year. I explain how to manually synch the carbs, both open and closed positions. This will make the vacuum synch much quicker and easier.
You really should get a factory Suzuki manual or at least a Haynes or Clymers.

 

[ZacharyB]

It's ok. Thanks for bearing with another guy who want to use others' experiences in order to help prevent a screw-up!

I have the carb that is closest to the choke completely apart. The slide has been taken out (I didn't bother getting to the tiny screws that would disassemble the needle in the slide, I just took the whole slide out and put it aside). The jets and gaskets were removed successfully, no tears, thank goodness. The one thing that bothers me is that I was able to get the pilot screw out but not the air screw on the topside of the carb. I can turn it in and it will seat in two turns, and I can turn it out, but then that will make it seat again in one and a half turns. It's disturbing. I want to dunk this thing but this issue is holding me back. I don't want to force it out and then have to buy a new carb.

I have vacuum tools (the motionPro tubes), the adapters, an RPM multimeter (for the fuel fine tune 50 rpm drop test), and I know about the wire sync, so I don't have to worry about that. It just has to run after I put it all back together... :lol:

My main remaining question is, is my carb undippable with that stuck air screw?

Thanks for the link Satch, and Keith (who supplied the breakdown therein). And everyone else who responded

 

[KEITH KRAUSE]

I'm not sure what's going on with that air screw.
The small washer and spring can't tilt or come off by turning the screw until seated and then backing it out 2 turns. The only reason the screw would go in 2 turns, come out 2 turns, but then only go back in 1 1/2 turns, would be if the o-ring broke and a piece of it is sitting near the base of the hole or the factory sealant has balled up and jammed the threads a bit. The o-rings usually stay in their groove, but I guess a piece could break off and cause your problem. Hopefully, it's the sealant.
To remove the screw, did you try seating it and then cleaning the exposed threads? I use a toothpick or straight pin/safety pin tip to carefully pick out any sealant in the threads. I know you don't want to strip the head trying to remove it, but you would like to know if the o-ring is still in one piece.
If you dip the carb in a strong cleaner for a long time, you will harden the o-ring. Who knows what condition the o-ring is in now? If you use carb cleaner with a spray tube, you can still do a good job of cleaning the carb. Then squirt some fuel up there and rinse off any cleaner on the o-ring. This would help not damage the o-ring further.
The side air screw is supposed to be adjusted for the highest idle possible and then you re-set the idle using the idle adjuster knob. In my experience, the side air screw always ends up between 1 1/2 and 2 turns out to achieve highest rpm, with 1 3/4 turns out being the most common.
Since your screw WILL turn out this far, you can be sure that it's going to be able to be set properly.
If the threads will clean out and allow you to replace the o-ring, that's great, but you run the risk of stripping the screw and not be able to adjust it at all from the stripped point. I would try, counting as I turn it out but that's up to you.
If you decide to just leave the screw alone, you can just turn it out to 1 3/4 and see how it responds after you start it up. If turning the screw effects the rpm's the same amount as the other 3 carbs, then it's working and the "possibly" damaged o-ring is not causing a flow problem. Hope this helps.

 

[ZacharyB]

Thanks Keith. I got the air screws out, it was the threads. They were gummed up with some of the "this has been set properly" paint. I removed everything rubber and then dipped each carb. It was uneventful until carb 4 (farthest from the choke).

This one was hiding a real nightmare, and not just for a newbie. The pilot screw tip had sheared off at one point and lodged itself in the exiting orifice. The screw came out but not the tip. I have tried many things to get this tip out, probably ruining the orifice diameter in the process.

I tried taking an old honda pilot screw I had and using that to force the tip out from the top (so it would fall towards the floats) but the hole is oblique to the top of the carb and it was hard to get a bead on the tiny hole with the equally tiny honda pilot screw tip. I ended up bending and breaking the tip.

Then I tried sewing needles, small nails... Filing down nails to make them sharper... I even tried taking a small hand saw, caulking a small nail to the blade, running the blade through the tunnel of the carb, aiming carefully, then forcing downward at both ends of the saw when the nail was in the hole. The nail bent! My next step is to drill; I wanted to avoid it due to the risk of damage but I've been completely defeated. What a disappointment. I may be looking at a new carb body, I hope it isn't too expensive. Or I hope I can find a 1/64th", 2.5 inch long drill bit.

 

[KEITH KRAUSE]

That's too bad. That hole is a secondary passage, meant for fine tuning the pilot circuit. If the hole gets widened much, I don't think the screw would be able to do its job anymore. That cylinder would run rich at idle and up to 1/5 throttle. It's always possible, after getting a new screw, that turning in the screw further may help compensate for the larger hole but I would look for a new carb body. The carb is probably ruined and trying to use it will just make more work. Of course, you still don't have the tip out. Just my opinion.
Just be sure to get a replacement body that has TWO HOLES, just like yours. There are some carbs out there that only have one hole and the other secondary hole is capped and uses a dull-tipped "dummy" pilot screw that doesn't do anything. I learned this the hard way. I think the last of the (U.S.)'79's came with these modified carbs, maybe for smog reasons. I don't know. Just be sure to inspect what you buy.
Also, the 750's and 1000's use the 26mm carbs. There are jetting differences, but you can swap parts.

 

[ZacharyB]

Hey Keith, there's a set of suzuki carbs on e-bay now.

http://cgi.ebay.com/ebaymotors/ws/e...ry=35581&item=2494717861&rd=1&ssPageName=WDVW


The only thing is that they have ribbed towers while mine are smooth. Despite the auction title, are these the '79 carbs you are talking about?

 

[KEITH KRAUSE]

Hey Keith, there's a set of suzuki carbs on e-bay now.

http://cgi.ebay.com/ebaymotors/ws/e...ry=35581&item=2494717861&rd=1&ssPageName=WDVW


The only thing is that they have ribbed towers while mine are smooth. Despite the auction title, are these the '79 carbs you are talking about?

These are not the carbs I was warning you about. The carbs that only have one pilot passage to the main bore are otherwise identical to the carbs with two passages, that's why you have to look in the bore AND take the screw out to be sure. The carbs I warn you about are not nearly as common as the two passage type, but they are out there.
I would like to see better pic's, but from what I can see of these E-bay carbs, they look like there's some corrosion going on (the white stuff). The pilot screws are missing too. Besides that, I think they're off a '77. I wouldn't use one of these "ribbed" carbs even without these problems.
Wherever there's white corrosion, the metal is being eaten away. It could also be corroding in the places you can't see.
E-bay is a gamble in buying used carbs. You have to ask questions. If the seller can't answer the questions, beware. You don't want butchered carbs.
Can you show a pic' of your carbs? They have the thumb lever choke, correct?

 

[ZacharyB]

That's true, they have the thumb lever choke. They are identical to the Mikuni smoothbore carburetors on the SUDCO parts index page, http://www.sudco.com/catalog/Page 128-131.pdf

My father took pity on me and went seeking a carburetor specialty shop. A mechanic was exploring the carb carefully with a dental pick when he left. I'll see tomorrow if he was able to remove the tip. If not, it's no big deal. The bike ran with the pilot screw plugged, it just had some bad idling habits that I was trying to fix when I pulled everything. I am coming from a 250cc bike so the power is impressive enough. I can live with something not perfect, that's the way it's been for a while. At least the bike looks OK.

And all I have to do is find someone parting out a 78 750, then ask to see the carb farthest from the choke. He couldn't charge me more than $100 for the carb body, so in the end, it will be OK. Actually, I have to make sure it is the carb the farthest from the choke and not the one NEAREST to the choke... I hope I didn't mix those up.[/url]

 

[KEITH KRAUSE]

They sell entire carb banks for $100 at the only salvage yard we have out here, when they have a set. You should be able to find a carb body for less, but it might have to be on a bank of "parts carbs". A member here may be able to help you out if you place a request in the "parts wanted" section?
I just hope you get the correct carb. I don't have the factory manual for your 750. There MAY be certain jetting differences from the 1000 carbs. It's possible the 1000 carbs would also work, but the air jet (not removable) would have to be the same. The other jets you can remove and swap.
Which carb is it? 1 or 4? I doubt I have a spare, but I can look or ask a friend.

 

[ZacharyB]

I was correct, it's the carb farthest from the choke. I don't know if that means 1 or 4. Sitting on the bike, it's the carb at the extreme right.

I have all the jets and everything. All the components looked brand new (especially the floats) when I opened up the float bowl. I had a hunch this bike was serviced just before I bought it. If only it weren't for that pilot screw tip that someone probably botched up and kept a secret.

Thanks for the offer, it's ok if nothing turns up. I've never seen a pick-and-pull around here in metropolitan NY, all the junkyards have become "used parts dealers". That first guy had no luck getting the tip out but we're trying someone else tomorrow.

 

[KEITH KRAUSE]

Hi. No one I know has a spare for that type of carb body. I did drop by our only salvage yard. I work throughout the city, so I had a little time. They didn't have a parts carb, but they did have a complete bank. They marked it '78 GS750 and it looks correct to me. They wanted $125 . I took out the pilot screws on 1 and 4 and they were fine. I didn't inspect further. We both know you can find these carbs cheaper from other sources. I still think someone at this site can help if you ask.
"wiredgeorge" a member here, may be able to help you out. He works on carbs for a living. He sounds knowledgeable and would give you the RIGHT carb. I don't know if he'll sell you just a carb body. He repairs entire banks, etc. Bet he's worth a try. Give him a PM, it can't hurt to ask.
If you go with E-bay, ask questions! You may even try just living with it?You said the bike didn't run too bad before? You would run lean on the pilot circuit, but you may be able to install a larger 17.5 pilot jet and get close to a correct mixture? Just a thought.
I could always send you those salvage carbs I found, but I really think you can do better. With shipping, they would run you $140. Try 'george or the parts wanted here. Good luck and let me know what you find.

 

[ZacharyB]

OK, thanks again Keith. I'd just have to live with less-than-satisfactory idling, that's all. :wink: If something happens I'll post to this thread again or PM you. I'll wait on the other shop to see if they're successful, if not then I'll get wiredgeorge's attention.

 

[KEITH KRAUSE]

OK. Good luck. If you have any questions about re-assembly/synching/jetting, let me know.
PS: Don't forget to replace the manifold o-rings (unless they're fairly new). This should be done any time it's been "awhile" since the carbs were last serviced. They're cheap and if you try to replace the old ones you'll probably get intake leaks.
To help the new o-rings last longer, apply a coat of hi-temp' bearing grease to them. I also suggest getting rid of the stock manifold Phillips screws and replace with Allens. Torque the new o-rings to 6 ft/lb.
O-ring Suzuki part # 09280-32006.
Robert Barr, a member here, may save you some money if you order the o-rings through him.