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Need help with unidedtified carb part!!!!!!

  • Thread starter Thread starter Schwebel
  • Start date Start date
S

Schwebel

Guest
Hello all, my friend has an 81 Gs550 he got it for free, it was siting in a co-workers field for about a year. We have it running on starter fluid but it doesn't seem to want to suck in gas from the carbs. There were only two hoses from the carbs when we got it, the gas and gas tank vacuum line. There seems to be two hose conections between the #1 and and 2 and also between the #3 and 4 carbs. I have no idea were the hoses would go from those connections and was wondering if that had something to do with it not drawing in fuel. The carbs are Mikuni's. Thanks for any help:-D
 
Carb vent tubes?:-k

What bike is it? That will get you a lot more educated answers.
Also, losen the drain plugs on the bottom of the carbs and set the petcock to prime to see if fuel is getting from the tank to the carbs.
 
It is a GS550T, the bowls were full and I also tried cleaning out the mains, and sprayed some carb cleaner through the other jets. I'm thinking it is some kind of vacuum issue. Could these hose connections be some kind of vacuum assist type thing?
 
Pilot and idle circuits on the carbs have very small orifices, most people don't realize this and don't go far enough when they "clean the carbs" - thus they have to do the job twice. Small rubber o-rings inside the carbs dry out and don't seal well either thus allowing air leaks and/or fuel leaks. Number one source of air leaks though is not the carbs themselves but rather the carb boot O-rings sandwiched between the head and the boots. I't almost certain that they are dried out and WILL LEAK unless you replace them. Don't shortcut or you will not get the bike to run right, or at least it won't run right for long.
 
First thing you need to do is to pitch the starting fluid. It is far too easy to do damage with that stuff. It may get the engine running, but it won't fix anything and keep it running, so you may as well find the problem and fix it.

Since the bike was sitting in a field for a year, you can easily plan on cleaning the carbs and replacing the o-rings.

The hoses on the carbs sound like they are correct. The two between 1&2 and 3&4 are vent tubes. They are usually routed over the airbox, under the seat. The two to the petcock: the larger one is fuel and goes to a "T" between 2&3, the smaller one goes to a nipple on the engine side of #2.

Remove the hoses from the petcock, connect a temporary hose to each fitting. Place the other end of the fuel hose in a container that can catch the gas, suck on the vacuum hose. If things are working well, gas should flow from the fuel hose and you should not get a mouthful of gas through the vacuum hose. If you don't get gas through the fuel hose, the petcock is stuck. By carefully disassembling it, you might find that the o-ring in the valve is stuck. It might be cracked, which requires replacement. If you get gas through the vacuum hose, the diaphragm needs to be replaced. Probably better off to just replace the entire petcock, as rebuild kits for them are of questionable quality.

Now that you are assured that gas is getting to your carbs, clean them as outlined in the links I gave you above to be sure that gas is getting through them, too.

While you have things apart, it would also be smart to check the valve clearances. Not hard to do, you will already have the tank off, and you will then have a good starting point for proper operation of the engine.

Ditch the starting fluid.
Check the petcock.
Adjust the valves.
Clean the carbs.
Synchronize the carbs.
Enjoy the bike. \\:D/


.
 
Steve said:
First thing you need to do is to pitch the starting fluid. It is far too easy to do damage with that stuff. It may get the engine running, but it won't fix anything and keep it running, so you may as well find the problem and fix it.

Since the bike was sitting in a field for a year, you can easily plan on cleaning the carbs and replacing the o-rings.

The hoses on the carbs sound like they are correct. The two between 1&2 and 3&4 are vent tubes. They are usually routed over the airbox, under the seat. The two to the petcock: the larger one is fuel and goes to a "T" between 2&3, the smaller one goes to a nipple on the engine side of #2.

Remove the hoses from the petcock, connect a temporary hose to each fitting. Place the other end of the fuel hose in a container that can catch the gas, suck on the vacuum hose. If things are working well, gas should flow from the fuel hose and you should not get a mouthful of gas through the vacuum hose. If you don't get gas through the fuel hose, the petcock is stuck. By carefully disassembling it, you might find that the o-ring in the valve is stuck. It might be cracked, which requires replacement. If you get gas through the vacuum hose, the diaphragm needs to be replaced. Probably better off to just replace the entire petcock, as rebuild kits for them are of questionable quality.

Now that you are assured that gas is getting to your carbs, clean them as outlined in the links I gave you above to be sure that gas is getting through them, too.

While you have things apart, it would also be smart to check the valve clearances. Not hard to do, you will already have the tank off, and you will then have a good starting point for proper operation of the engine.

Ditch the starting fluid.
Check the petcock.
Adjust the valves.
Clean the carbs.
Synchronize the carbs.
Enjoy the bike. \\:D/


.
Click to expand...
Your recipe for success Schwebel. No more than an afternoon's work if you go about it right. You can let carb parts soak while you run valve clearances. Be careful with spray cleaners and rubber parts. It's okay to use the spray cleaners to blow out passages. Don't use it on seals and slide diaphrams though.
 
Billy Ricks said:
No more than an afternoon's work if you go about it right. You can let carb parts soak while you run valve clearances.
Click to expand...
I might argue that point with you, Billy.

First, I like to keep all the carb parts to one carb with that carb. Yes, that means four separate "dips", but it makes me more comfortable. If you were replacing everything with new parts, it would not matter, but the wear marks on the slide of #2 will not match those in #3 and may cause problems. Also, it's nice to have at least one carb that is still together for reference if you get lost re-assembling another.

Second, although the can of 'dip' says to immerse the parts for 15-30 minutes, I have had minimal success with that, and prefer to dip them for 15-30 hours. Yes, that means one carb per day, which slows down the process, but you are guaranteed that the carbs are CLEAN.

This is, of course, assuming that you are doing this for yourself. If you are doing this in a shop environment with the constraints of the flat-rate manual, you do whatever you can. I have found that if I am doing something for myself, my personal 'shop rate' is very flexible and tends to vary with my interest in the project. Since the intent is to get the bike running, and running well, I don't care how long it takes. 8-[


.
 
Steve said:
I might argue that point with you, Billy.

First, I like to keep all the carb parts to one carb with that carb. Yes, that means four separate "dips", but it makes me more comfortable. If you were replacing everything with new parts, it would not matter, but the wear marks on the slide of #2 will not match those in #3 and may cause problems. Also, it's nice to have at least one carb that is still together for reference if you get lost re-assembling another.

Second, although the can of 'dip' says to immerse the parts for 15-30 minutes, I have had minimal success with that, and prefer to dip them for 15-30 hours. Yes, that means one carb per day, which slows down the process, but you are guaranteed that the carbs are CLEAN.

This is, of course, assuming that you are doing this for yourself. If you are doing this in a shop environment with the constraints of the flat-rate manual, you do whatever you can. I have found that if I am doing something for myself, my personal 'shop rate' is very flexible and tends to vary with my interest in the project. Since the intent is to get the bike running, and running well, I don't care how long it takes. 8-[


.
Click to expand...
My Flatslides at one time were in horrible shape after a round of extended mods and failing to drain the carbs. It probably sat for a couple of years with only an occasional starting. I had green varnish hardened in all the jets and smaller passages. With small gauge wire and spray cleaner you can make quick work of cleaning a set of carbs. You do have to be careful with the rubber parts. If you spray carbs you need to wear eye protection and a long sleeve shirt is a good idea. If he needs o-rings and disassembly he certainly won't get it done in an afternoon. If he doesn't already have fuel oozing everywhere he may only need to replace the rings on the float seats. I need to go through my carbs and run valve clearances again since it has sat through another round of butchering. I'll do it all in about 3 hours including replacing manifolds and cleaning all four carbs. I need to replace the o-rings on my float seats and clean up the bore they fit into. I may replace the exhaust cam and a rocker while I am doing the valves. Still just a long afternoon of work..
 
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