VM Carb Reassembly Questions

[iammulva]

Before I reassemble my carburerors I have some questions that I'd like to get addressed to avoid (I hope) having to go back and re-do any of the work that I've already done. So, without further ado and in no particular order:

(using this as reference http://www.thegsresources.com/files/vm_carb_rebuild.pdf)

1. The instructions say that I can re-use the washer on the float needle valve seat. Mine looks thin/worn. Should I replace it? If so with what? I don't see those washers in the rebuild kits. Also, how do I tell if float needle valve itself needs to be replaced?

2. The pilot air screws were pretty much bottomed out. Each one had about 1/8 turn at the most. Is that "right"? Is it indicative of anything? The main reason I am rebuilding the carb is because I thought it was running rich (based mostly on smell, running poorly, and bowl drain screws leaking).

3. The pilot fuel screws are between 1 1/4 & 1 1/2 turns out. I'm assuming that I should use the 1 1/4 "default" setting. Is that as good a place to start as any? I read that with a non-stock exhaust it might be different. I have a muzzy muffler but I think the exhaust pipes are stock.

4. How do I know if I've set the fuel screws correctly? I'm guessing run/no run is the first indication, but if it runs then how will I know whether another 1/4 turn more or less would be "better"?

5. I have the fuel lines that go between each carb body by tubes that have non-replaceable o-rings. The reference says that if they are removed they might not re-seal. I've already pulled mine so should I just "give them a shot" or is there a way to ensure a seal?

6. The carb bodies are dirty/grungy/oxidized, but not really shellacked. I'm dipping the body, bowl, and top in merrimans overnight but don't see an appreciable difference after the dip. Do the insides have to be pristine?

I think that's all I have for now.

Appreciate all the help!

Chris
'79 1000E



4.

 

[Nessism]

1) If the washers are worn they should be replaced. Not sure what to suggest about new ones.

2) Air screws should be set at roughly two times that of the fuel screws - try 1.75 turns to start.

3) Fuel screws should be set to about 3/4 of a turn, maybe one turn.

4) Tweak the fuel screws and air screws to provide the highest idle speed and best running. Sorry but I can't give any more specifics than that.

5) I've heard about people wraping the fuel Tee with teflon tape to assure a good seal. You can also make one from brass with replaceable O-rings if necessary. These are available for purchase as well on ebay I think.

6) As long as there is not noticable grunge inside the carbs I think you will be okay.

Good luck.

 

[Steve]

1. The instructions say that I can re-use the washer on the float needle valve seat. Mine looks thin/worn. Should I replace it? If so with what? I don't see those washers in the rebuild kits. Also, how do I tell if float needle valve itself needs to be replaced?
Please don't tell us you wasted money on "rebuild kits". Too often, they have parts that are sub-standard quality and still don't contain all the parts you need.
The float valve needle can wear and get a groove around the tip, where it seals in the seat. By the time you see a groove, it needs to be replaced.
You will get better results if you simply re-use your stock brass pieces and use an o-ring kit from cycleorings.com. The guy that runs that place is a member here and has put together kits for our carbs.


2. The pilot air screws were pretty much bottomed out. Each one had about 1/8 turn at the most. Is that "right"? Is it indicative of anything? The main reason I am rebuilding the carb is because I thought it was running rich (based mostly on smell, running poorly, and bowl drain screws leaking).
1/8 turn is not "right". As Nessism mentioned, the air screw should be about double the fuel screw.


3. The pilot fuel screws are between 1 1/4 & 1 1/2 turns out. I'm assuming that I should use the 1 1/4 "default" setting. Is that as good a place to start as any? I read that with a non-stock exhaust it might be different. I have a muzzy muffler but I think the exhaust pipes are stock.
The stock setting for the fuel screw is between 1/2 and 5/8 turn. For better running, it is better to use 3/4 to 1 full turn out. If you still have the stock airbox in place, start with 3/4. For pods and a header, go with 1 turn.
This means that the air screw should then be about 1 1/2 to 2 turns out, start with 1 1/2.

4. How do I know if I've set the fuel screws correctly? I'm guessing run/no run is the first indication, but if it runs then how will I know whether another 1/4 turn more or less would be "better"?
When all is said and done, you should be able to do "plug chops" and read the color of the spark plugs. That will show you exactly what is going on inside the cylinder.


5. I have the fuel lines that go between each carb body by tubes that have non-replaceable o-rings. The reference says that if they are removed they might not re-seal. I've already pulled mine so should I just "give them a shot" or is there a way to ensure a seal?
Try test-fitting the tubes into the carb bodies. Is it a snug fit? If so, you are good to go. If not, apply 3 or 4 wraps of Teflon tape.


6. The carb bodies are dirty/grungy/oxidized, but not really shellacked. I'm dipping the body, bowl, and top in merrimans overnight but don't see an appreciable difference after the dip. Do the insides have to be pristine?
Actually, it's the inside of the carb that you should be worried about. The outside can be positively caked with grunge without affecting the way the carb runs. Inside the carbs are all the little passages where the fuel gets mixed with air. They are the ones that really need to be "pristine". Unfortunately, you can't see any of them, so you are relying on the chemicals and compressed air to clean them out.

By the way, I have never heard of "merrimans", hope you mean "Berryman's".

.

 

[iammulva]

Thanks - I feel better now

Thanks - I feel better now

1. The instructions say that I can re-use the washer on the float needle valve seat. Mine looks thin/worn. Should I replace it? If so with what? I don't see those washers in the rebuild kits. Also, how do I tell if float needle valve itself needs to be replaced?
Please don't tell us you wasted money on "rebuild kits". Too often, they have parts that are sub-standard quality and still don't contain all the parts you need.
The float valve needle can wear and get a groove around the tip, where it seals in the seat. By the time you see a groove, it needs to be replaced.
You will get better results if you simply re-use your stock brass pieces and use an o-ring kit from cycleorings.com. The guy that runs that place is a member here and has put together kits for our carbs.

No - didn't buy rebuild kit. Did buy o-rings and fasteners from cycleorings. Don't remember whether float valve needle has a groove or not, but will look tonight. Still wondering where to get replacement washer for the float valve seat though.


2. The pilot air screws were pretty much bottomed out. Each one had about 1/8 turn at the most. Is that "right"? Is it indicative of anything? The main reason I am rebuilding the carb is because I thought it was running rich (based mostly on smell, running poorly, and bowl drain screws leaking).
1/8 turn is not "right". As Nessism mentioned, the air screw should be about double the fuel screw.

Ok - good - that's what I needed to know.


3. The pilot fuel screws are between 1 1/4 & 1 1/2 turns out. I'm assuming that I should use the 1 1/4 "default" setting. Is that as good a place to start as any? I read that with a non-stock exhaust it might be different. I have a muzzy muffler but I think the exhaust pipes are stock.
The stock setting for the fuel screw is between 1/2 and 5/8 turn. For better running, it is better to use 3/4 to 1 full turn out. If you still have the stock airbox in place, start with 3/4. For pods and a header, go with 1 turn.
This means that the air screw should then be about 1 1/2 to 2 turns out, start with 1 1/2.

I have stock airbox so I will use 3/4 on fuel and 1 1/2 on air.

4. How do I know if I've set the fuel screws correctly? I'm guessing run/no run is the first indication, but if it runs then how will I know whether another 1/4 turn more or less would be "better"?
When all is said and done, you should be able to do "plug chops" and read the color of the spark plugs. That will show you exactly what is going on inside the cylinder.

Related to the above fuel air screw settings.... once the fuel screw is set initially then do I only adjust the air screw or is it possible that I'm going to have to tear down the carb again to get to and adjust the fuel screw?


5. I have the fuel lines that go between each carb body by tubes that have non-replaceable o-rings. The reference says that if they are removed they might not re-seal. I've already pulled mine so should I just "give them a shot" or is there a way to ensure a seal?
Try test-fitting the tubes into the carb bodies. Is it a snug fit? If so, you are good to go. If not, apply 3 or 4 wraps of Teflon tape.

Perfect - thank you.

6. The carb bodies are dirty/grungy/oxidized, but not really shellacked. I'm dipping the body, bowl, and top in merrimans overnight but don't see an appreciable difference after the dip. Do the insides have to be pristine?
Actually, it's the inside of the carb that you should be worried about. The outside can be positively caked with grunge without affecting the way the carb runs. Inside the carbs are all the little passages where the fuel gets mixed with air. They are the ones that really need to be "pristine". Unfortunately, you can't see any of them, so you are relying on the chemicals and compressed air to clean them out.

By the way, I have never heard of "merrimans", hope you mean "Berryman's".

I was not clear, but I was referring to the inside of the bowl and top and what I can see on fully disassembled carb. The inside of the bowl has "stuff" on it, but whatever it is it is on there good. Berryman's (yes Berrymans - I wrote that post last night in bed right before going to sleep) doesn't seem to be doing too much to it. It's like thin splotches of paint here and there. Haven't inspected the internal passages of the carbs super closely yet, but initially nothing jumped right out at me as being gunked up.

 

[Big T]

1. Try Z1, Bike Bandit, Suzuki dealer, SUDCO in no particular order

4. Maybe, but a short, small blade screwdriver from below works for some (the right tool for the right job, check Sears or Harbor Freight)

 

[Guest]

Just another note. The fuel screw can be adjusted with the carbs on, no need to disassemble to adjust them, you just need a short screw head that will fit, just takes a bit of ingenuity. The air screws can be adjusted using the "best idle" method, just do a search and you'll find lots on the subject. The fuel screws are adjusted doing plug chops, or I use a carbtune myself. On my own VM carbs that use the plastic non o-ring fuel connectors, I use fuel safe gasket sealer bought from Canadian Tire. Just a bit on each end does the trick. Used it multiple times, never had a leak and on repeated tear downs it cleans off easily. As to the 'gunk' inside your carbs you could always post a pic, but really Berryman's should get any internal\external slug off. Hope this helps.