Carb rebuild qusetions

[GS750GUY]

Dear fellow GS'rs,
I have a 1978 GS750EC. It has 11M original miles on it but was horribly maintained. I should say NOT maintained. The prior owner left 1/2 a tank of gas in it and then let it sit for two years. Well......you know the rest.
I'm getting ready to rebuild the carbs and found the excellent article in the GS Resources site titled VM Carb Rebuild by Paul Musser. It is the most comprehensive and well written instruction on the subject I have been able to find yet. I have a few questions though about the article.

Paul uses the term "blipping the throttle". What does "blipping" mean?
Should I use gasket sealer when installing the new bowl and carb cap gaskets?
Nothing is mentioned about what to use to clean the needle passages with. Do I use wire of some kind? Does anyone have any suggestions? Is it necessary that I spend the bucks to buy one of the carb cleaning wire sets for possibly the one and only set of carbs I will ever rebuild?
On these bikes the fuel system is gravity and vacuum feed. The fuel tank has a filter in it. Is it necessary or even recommended to put an in line fuel filter in the gas line? Could I be harming fuel flow since this is the one and only fuel line servicing four carbs? Would I be possibly starving my carbs by adding the filter?
Thanks!! Your wisdom is greatly appreciated guys and gals!!
GS750 Guy:-s

 

[ikazuki]

gs750guy: welcome to the world of the satisfaction of working on your own ride. it works out to be , if all goes as planned, a rewarding experience. now to the good stuff.
blipping means quickly twisting the throttle on and letting off.
no sealer.
wait til you break your carbs down to get logistics.
q-tips, carb cleaner, toothbrush make a good start.

a screen in the tank and a screen in the carb keep the fuel clean. however, a dirty air filter and cheap gas will contribute to a dirty carb.

one rebuild? i wouldnt count on it. mine has under 15,000 and they are pretty dirty. many of the problems we have are due to tiny specks of dirty build up blocking air, air fuel or fuel passeges. but this experience will prepair you for the next time. good luck and good riding

 

[SqDancerLynn1]

Start by cleaning the tank & make sure the petcock is working properly
Get a set of O rings from www.cycleorings.com
Go to work cleaning the carbs The VM are actually easer to clean than the BS type. During testing ---- IT WILL NOT run properly without the airbox & filter installed. I WOULD NOT add an external gas filter

 

[GS750GUY]

Thanks

Thanks

Thanks guys for the tips. I will get the O-ring set. I hear it is highly recommended. I will also forget about installing an in line fuel filter. Sounds like there is no need and could cause fuel starvation problems.
One more question for you: I had the air box off the bike to do some work elswhere on the bike. I know for the bike to run properly the air box must be in place. I replaced the air filter with a new one and now am having a HECK of time getting the boots for the air box connected to and seated properly on the carbs. Are there any tricks to this? I'm doing all but stand on my head!!!

GS750GUY

 

[Dave8338]

I used silicone spray, loosened all clamps almost all the way open and started the boots on the bottom of the carbs first. Lift up while standing over the bike and push forward...some wiggling a swear word or two and they should slip on. Also, make sure that the clamp that holds the manifold to the airbox is good and loose and also sprayed well with the silicone spray.

 

[Jethro]

With the carbs and boots removed, install the air box. Then mount the carbs to the air box. Then push the whole assembly back as far as you can and install the boots. That's how I do mine anyway, and the carbs have been off over 2643 times.

 

[KEITH KRAUSE]

Just to answer some more of your original questions...
"Blipping" the throttle is just a quick twist of the wrist, any throttle amount but generally 1/4 or close.
Gasket sealer is generally not needed for the bowl gaskets but sometimes it helps. Apply a thin coat that won't cause excess sealer to squeeze into the carb when tightening the bowl screws. Permatex 2B black form-a-gasket works well. The top gaskets never need sealant to help them seal out dust/moisture.
Berrymans is a good carb cleaner. I also use carb cleaner with a jet spray tube and follow that with high pressure air, about 150 psi works well. I've never tried using wire to clean passages, never needed to. Be careful of wire because you can burr up the soft passages if you poke too hard. Monofilament line works well but be sure the kind you use is fuel proof. I still say the carb cleaner/high pressure works fine and poking things in there shouldn't be needed.

 

[denydog]

I just want to make a note about my own carb cleaning experience. After dipping in Gunk brand carb dip which appeared to work very well, and spraying with carb cleaner, and poking with a wire brush bristle as directed in the other carb cleaning series, my bike would still not run worth beans. It wasn't until I aggressively scraped out the main jets with the wire, that I got the VERY crusty deposits out of the main jets.

I guess it depends on how hard the crud has set up. Mine was like dried glue, but that was from thirteen years of drying up.

 

[GS750GUY]

Carb cleaning and air box installation

Carb cleaning and air box installation

Thanks guys for all the great suggestions. Part of my problem with the air box is that I didn't know how aggressive I could get with installation. It seemed that my attempt to wiggle and force the air box into place was causing me to also jerk around excessively on the carbs and boots that connect the carbs to the cylinder heads. They appear to be pretty heavy rubber and probably pretty tough but I don't know how aggressive I could get with the boots that go between the carbs and the cylinder heads without breaking them.
GS750GUY

 

[ikazuki]

you may find a second soaking and cleaning to be advantageous depending on how dirty the carbs are. i sit and scrub with the q-tips and yes it takes about 300 to do a set of four not to mention if you get one stuck in a passage and have to remove it a couple of strands at a time. but the main point of the whole process is to clean the carb to such a degree that it will get the keith krauss stamp of approval. that means no speck of dirt, no trace of varnish and as deny noted the incredible amount of crud build-up in the main. wear eye protection, as you are blowing air through the passages you will be surprised at where the air/carb cleaner/dirt etc. exits.
unless you have a photographic memory do one carb at a time and try to get them finished in a reasonable length of time else you start forgetting. we all assume you are buying carb kits, z1 enterprises 17 to 18 dollars, dennis kirk 22 to 24 dollars. there are many well qualified guys and gals who are more than happy to pass on their vast knowledge base .good luck and safe riding.

 

[GS750GUY]

More Carb Cleaning questions.

More Carb Cleaning questions.

Thanks to everyone of you for taking the time to to advise and guide amatures like myself. The fact that many of you have already been down these same paths before and have as a result created a wealth of knowledge is proving to be tremendously valuable to us that are new at this. I hope to repay all of you by eventually having a photo of my basket case project on this site so you all can see what all of my fuss was about. I've got the O-ring and gasket kits on order, the carbs back off the bike and am going step by step through Paul's instructions. However, I came to a snag and I don't know how to proceed. My Haynes book illustrates and describes the fuel line connectors between each carb. The book says the prefered kind of connector has O-rings that can be replaced to assure a good seal between carbs. The book says the least prefered connection is the type that has no O-rings but just has raised hard ridge rings moulded in the tube to make its seal. The book recommends that the later type without O-rings not be taken apart because reassembly could cause a weak seal and thus fuel leaks. Paul's instructions does not address this difference. Without removing these and seperating the carbs how can I do a deep submerged cleaning in the carb soak? If I leave all four carbs assembled and soak them all as a connected unit will I be risking that the carb cleaner may harm these hard plastic (rubber) fuel line connector seals between each carb?
Thanks again!!
GS750GUY:?

 

[Dave8338]

Pull them apart, then you'll know. And yes, if you try to soak them with the fuel couplers in place, for sure you'll be looking for replacements. Some here have mentioned that they were able to make the non o-ring type work with o-rings if they shaved down the rubber ridge and found the right sized o-ring to fit. You may not have to do this, if they are not leaking now. If they are the o-ring type, you've got it made. :-#

 

[KEITH KRAUSE]

You most likely have the "T" fitting with the rubber coating/built in o-rings (raised ridges).
You can see the rubber coating easily where it contacts the carb body. If you can't see it, you have the replacement T with the separate o-rings that sit farther inside the passage.
The T isn't sold by Suzuki anymore but a new one with separate o-rings can be special ordered/built at at least 1 website (name escapes me at the moment...Motorcyclecarbs?) for about $45? You can also get a T from some Kawasaki's that used the better T design, late 70's KZ650's is one example. A couple of members here have come up with their own fixes if you get to that point.
Just how dirty do you think the carbs are? Is total tear down necessary?
You can usually do a good cleaning by using carb spray, then rinse with gas, then immediately follow with high pressure air. I don't believe the spray cleaner will do any damage to the rubber coating if you rinse it off as I said. The only thing to gain by separating the bodies is if you believe the large main fuel passage could be excessively dirty or blocked by something such as spider webs, (yes, I've seen webs before) etc. Most of the time, a basic cleaning/flush through will be enough for this large passage. Other than that reason, you can do a good cleaning without separating them.
I've cleaned/rebuilt several VM carbs and the longer the carbs were sitting dry, the higher the chances are that the T will fail if taken out. Some fail without being taken out. The rubber just dries up and shrinks on carbs that sat dry too long. Upon admitting gas, they leak.
Paul did a great service by setting up that VM section. It was something I always wanted to do but my computer skills don't allow it. He did ask me to screen it for him. It's hard to mention every little thing that can come up with these carbs and Paul may want to add info at some time(?) I've made many comments about these carbs over the years and perhaps some of them should be added sometime. You can always search and probably find more things that may come in handy. You'll find more detailed info about separate parts of these carbs and what you need to know. One thing that has helped some people is the detailed bench synch info that I provided at another thread but isn't part of Pauls write up. I always suggest getting hold of a factory manual whenever you get a bike though. Then you don't have as many questions but things like the leaking T still won't be brought up.

 

[SqDancerLynn1]

9 times out of 10 you do not need a complete rebuild kit to clean the carbs. IF YOU DO MAKE SURE TO COMPARE THE NEW & OLD JETS make sure they are the same

 

[txironhead]

I don't understand how a fuel filter is not recommended. Screens do a crappy job of filtering compared to a cheap paper element. If it does cause starvation due to the vacuum activation, then I'm tossing the factory petcock. I've never run any of my vehicles, motorcycles included, without a filter. Plus it would seem that not running a filter would lead to most of the carb problems listed here.

 

[GS750GUY]

Carb cleaning cont.

Carb cleaning cont.

Thanks guys for you valued input. I think since I'm only gaining access to the interior of the fuel connecting tubes that I will just leave the connecting tubes in place and save myself the possiblity of having the headaches of fuel leaks later. I know the fuel connection tubes between carbs must be open because I don't seem to have any problems with the system filling all four bowls.
Regarding the fuel filter issue: I read somewhere where it was not recommended that an aftermarket in-line fuel filter be added between the tank and the carbs. The authors reasoning was that there is only one fuel line feeding all four carbs and any possibility of any additional restriction to fuel flow could possibly starve the carbs. I agree that it seems that a lot of junk could still get by the in-tank filter and on into the carbs causing problems and wondered why an in-line filter was never a factory installed item.
I would like to know if any other GS'rs out their have ever experienced any problems with fuel starvation as the result of installing an aftermarket fuel filter. I could understand that happening if the filter were getting dirty and plugged. If they do work it would be a nice addition to have in order to keep the carbs cleaner longer and greatly lengthen the time between carb teardown.
Thanks again guys!! It is sure great to be a part of a group that is just as interested in this as I am. MY WIFE JUST DOESN'T SEEM TO CARE FOR SOME REASON.:-D

 

[denydog]

I had a small fuel filter in my gas line for years, apparently without any problem. But after seeing the in-tank filter, I think it should do an acceptable job all by itself. The fuel passages in the carbs look to be larger than the screen material in the tank filter, so any very fine particles that might get through the filter, should pass through the carb as well.

So after cleaning my carbs, I left the extra filter off. If the fuel was delivered by a fuel pump, I think the extra filter would be fine. But seeing that the fuel on the bike is gravity fed, and from a short distance at that, we're not talking about a lot of pressure. I don't want any extra restrictions that I don't really need.

 

[KEITH KRAUSE]

I had a small fuel filter in my gas line for years, apparently without any problem. But after seeing the in-tank filter, I think it should do an acceptable job all by itself. The fuel passages in the carbs look to be larger than the screen material in the tank filter, so any very fine particles that might get through the filter, should pass through the carb as well.

So after cleaning my carbs, I left the extra filter off. If the fuel was delivered by a fuel pump, I think the extra filter would be fine. But seeing that the fuel on the bike is gravity fed, and from a short distance at that, we're not talking about a lot of pressure. I don't want any extra restrictions that I don't really need.

I agree. Fuel filters aren't necessary and can cause fuel flow problems. If the reason for a filter is a rusting tank, I suggest sealing the tank, not extra filtering.

 

[GS750GUY]

Bench sync.

Bench sync.

Thanks!! All of you have been very helpful. Keith, can you please tell me how to find the detailed bench sync info that you mention above?
Thanks!!
GS750GUY

 

[ptm]

I've been out of town and not checking the forum as closely as I usually do so I missed this thread. A few comments etc...

Thanks for your kind words about the VM write-up. It was a lot of work, but also a lot of fun to do. I keep thinking about adding some info to it, but other things are taking my time. Maybe this winter...

Regarding the tee and other fuel connectors between the carbs. Maybe I got lucky, but I have the non-o-ring type and after a complete disassembly, I have had no problems in two years and 9,000 miles. There are several ways to deal with them if they do leak, the best I've heard (from someone on the forum) is to take an exacto knife and cut slots in the sleeve where the o-rings should go and then use the standard o-rings (with the rest of the sleeve to keep them in their place). I haven't tried it but it seems like a good way to go. Although I like to get the carbs completely stripped down for cleaning, I did notice that the spray carb cleaner seems to be much stronger than the dip (Berryman's in my case), so you might be able to do a sufficient job without dipping.

If the rubber sleeves have shrunk from being dry for a long time, try soaking them in gas for a day or so. They may swell enough to seal again. That was an issue for this guy -http://www.ronh.org/mcpage.htm . First check out his collection (that includes several GSs) then his writeup about getting them out of storage and running again. The biggest problem he has is with rubber fuel seals that have shrink.

As far as using wire to clean the jets and passages, if you really have to, I'd get some brass wire. It is much less likely to enlarge the extremely precise holes in the carbs.

I've haven't had much difficulty putting the carbs and airbox back on. I put the carbs on the head, then slide the airbox in. The main issue I've had is snagging a wire with the tab where the side covers bolt on. You do have to squish the rubber intake on the back of the airbox a lot but it goes in fairly easily for me.

The bench sync info is in the write-up, but it's probably not as clear as it should be. As Keith says, do a search on the forum and you will find several explanations. You should also get a factory shop manual. If you can't find one, PM me. I have a spare I can get to you for a reasonable cost.

Thanks again for the compliments on the write-up, I'm glad it's been useful. Good luck getting your bike running - it's a sweet machine once it's sorted!