Carb rebuild qusetions

[GS750GUY]

Thanks!!

Thanks again to all of you for taking the time to respond. Denydog, your before and after photo's are awesome. You have convinced me to definetely dip.
I know what you mean. I would talk about bikes all the time if I didn't have to feed myself.
GS750GUY (HAROLD)

[GS750GUY]

Thanks

Thanks again guys!!
I've taken your advice regarding dipping and took a chance on the fuel tubes. I found they are the kind without seperate rubber seals. But I'm going to take the chance anyway. They were a very tight fit and I'm going to hope they go back together with a good leak-proof seal. One of you mentioned having the carbs off of your bike five times before you achieved a cleaning that worked. AS much as I love working on my bike I can't imagine doing this carb cleaning job that many times without a certain amount of frustration. I'm anxious to move on to other parts of the bike.
I found Berrymans at OReiley's auto parts for $14.95 per gallon. A bargain to me since I was hearing the $20.00 range. This stuff is great!! Two float bowls in the basket for 30 minutes and they came out looking like brand new. Way better than any result I was getting from any spray carb cleaner.
Thanks again for all the help!!
GS750GUY.

[GS750GUY]

Ooooo Nooooo. Back yard mechanic panic.

GS750Guy here again. I'm in the midst of my "78" GS750EC carb rebuild project. Guys & gal's here is one to test your experience & wisdom:
I know you guys and gals that have been at this for a long time could probably tell some real dooozies of stories regarding what you have discovered when tearing into a bike project.
I completed three carbs and got to my #4 carb and was about to remove the Pilot Fuel Screw when my first inclination that something was wrong was when I noticed the head of this screw was set waaaaay lower into the shaft than the other three I had removed. The head of this Pilot Fuel Screw was probably half way down into the shaft that it screws into. The heads of the other three were very near the top of the shaft. As I removed the screw it was apparent what had taken place. I suspect someone had put some undue force on this screw in the past and broke off the tip in the shaft. In their attempt to correct this and still use the broken screw they filed a new point on the screw and then in order to get the screw to seat further into the hole to accomodate its new shorter length they filed off the bottom four rows of thread from the screw so it would seat further into the hole. When I inspectecd the hole in the carb throat that this screw services I noticed the hole was three to four times larger than the same hole in the other three carbs. It appears they may have enlarged this hole by either drilling out the broken tip or forcing the broken tip out through the hole enlargening the hole. Ironically, cylinder #4 was operating when I had the carbs on the bike. It was running very rich but it was running.
In light of the expense of buying carbs is there any way I can continute to use this carb? Could I just buy a new Pilot Fuel Screw to replace the broken one? I realize that due to the enlarged hole I would need to set my screw deeper to fill the larger hole and adjust from there. Since this screw is mainly a fine tune screw for the fuel mix does this sound mechanically doable? I don't know if I can buy just one carb or not. I've only seen them in sets and are very very expensive.
Again your wisdom is appreciated. You are probably getting tired of hearing from the GS750GUY.
THANKS!!!!!!!!

[t3rmin]

If the hole is bigger as you're looking at it from inside the throat, you are gonna have to replace that carb body. You could try to repair it with JB Weld and re-poke a smaller hole or something but it'll never be right. Get a carb or set of carbs off eBay or in the forsale section here on the forums. You may be able to find a carb from a different size bike but as long as it's the same style of carb you should just be able to swap the jets out to make it match your other three.

Good luck.

[ptm]

Bummer. I'll have to defer to more experienced carb folks for a definitive answer. I'd guess that with the right shape tip, you could adjust it so that it has the same effective opening and allows the same flow as the other carbs, but it would add a large unknown to your efforts to get the whole system tuned properly and running smoothly. Finding a new #4 carb body would be the preferred solution. A lot of Kawasaki's from that era also used the Mikuni VM carbs, so that might expand the possibilities.

[t3rmin]

Exactly. While technically possible to repair or work-around the problem, it's highly impractical and likely you'll never get it "just right". And any time you have trouble, you'll never know if it's a result of that messed up carb since it'd be an unknown.

[txironhead]

There might be someone here who's willing to seperate a bank of carbs for you. Myself, I have a bad set of CV's, but with a little work the #2 & 3 carbs could be salvaged, so I'd be willing to break them up and send one to someone who needed it, or send them the whole set since 1 & 4 are shot. Maybe someone here has a similar set of VM's. Post under the parts wanted and see what turns up.

[KEITH KRAUSE]

I can't give a solid opinion unless I saw how much the hole is enlarged.
A replacement body would be the best thing but if you don't mind experimenting you can try to make it work. If you don't like the results, then look for a replacement. Depends on how big the hole is and how important your time is. I'd look for another carb but I'm trying to consider you may want to be more practical about it? Don't forget that separating the carbs may create a leak at the infamous "T" fitting or tube couplers. It has to be another #4 carb too.
I suppose in theory, if the hole was enlarged up to a certain amount, that amount could still be filled by turning in the screw more. The pilot fuel screw assists the pilot jet. It's the fine tuning for each cylinder. It has a noticable effect on the pilot circuit. You'll notice any problems mostly at warm up/idle and lower speeds. Up to about 1/4 throttle position will be effected though until the jet needle takes over completely. The smaller the throttle opening, the more the effect.

[GS750GUY]

#4 Pilot fuel screw..THANKS

Thanks again guys for your insight concerning this. The hole is not huge....maybe three to four times it's normal size. They are slightly bigger than a hair anyway. Based on what an old Zuzuki mechanic told me about the situation Keith's theory makes sense. The mechanic told me that if the hole is still small enough that it can still be filled with the screw then the screw can still be adjusted for correct fuel mixture. He said the purpose of the screw adjustment is to meter the amount of fuel and air mixture to the carb throat and that as long as the hole is small enough the taper of the screw will be able to meter this flow by resetting the screw position. He said the screws primary purpose is to fine tune the fuel burn and you can tell if it's doing the job by looking at the plugs.
I guess the worse that can happen is that I will eventually have to replace the carb. I'm debating if I should go through the headache and expense to find another #4 carb body.....or just buy a new screw and see if an adjustment to the screw will do the trick.
THANKS AGAIN!! IT REALLY HELPS TO BOUNCE THINGS OFF ONE ANOTHER.
YOU GUYS ARE THE BEST!
GS750GUY

[edbot]

I've got a rack of VM26 carbs off my 79 750E that I've been cannibalizing. You can have the #4 carb body and pilot fuel screw if you want them. Let me know.

[GS750GUY]

Thanks Ed!!

Ed, thanks so much for the offer for the #4 carb & screw!! Please let me know how much you want for them. Your a life saver!!\\/
GS750GUY (Harold)

[edbot]

Just sent you a PM.