Carb experts wanted!

[Joep]

Ethonal, man eats the rubber right out of some of the old carbs, Disolved 175 bucks worth of diaphrams in my Vulcan, replaced the float bowl gaskets in the Interstate and shut of the fuel and run the carbs dry. Can't be helped since we are forced to burn the combustable water downed crud.

Randakk's kits use a different compound in the tips and gaskets that should stand up to the ethonal aditives.. check his site out...

 

[vulkan 95]

Ethonal, man eats the rubber right out of some of the old carbs, Disolved 175 bucks worth of diaphrams in my Vulcan, replaced the float bowl gaskets in the Interstate and shut of the fuel and run the carbs dry. Can't be helped since we are forced to burn the combustable water downed crud.

Randakk's kits use a different compound in the tips and gaskets that should stand up to the ethonal aditives.. check his site out...

Checked out the website, many thanks Joep for pointing me in direction of Randakks

 

[jjones0187]

the oil pressure looks like it drops off to much for the engine to be revved that high, could be the oil pickup screen in the side of the engine is stopped up, I don't think the oil pressure should change just by leaning the bike either, and that knocking sounds is probably due to low oil pressure. the oil pickup screen could be getting stopped up due to clutch wear, its no easy to get to I think you have to pry the frame away from the engine to remove the cover to clean it, its on the right side of the bike below the headers. just a thought

 

[mcgovern61]

the oil pressure looks like it drops off to much for the engine to be revved that high, could be the oil pickup screen in the side of the engine is stopped up, I don't think the oil pressure should change just by leaning the bike either, and that knocking sounds is probably due to low oil pressure. the oil pickup screen could be getting stopped up due to clutch wear, its no easy to get to I think you have to pry the frame away from the engine to remove the cover to clean it, its on the right side of the bike below the headers. just a thought

Hey jjones0187, welcome to the site!! :clapping: :clapping:

Right after I did this test, I cleaned the oil pickup screen which really wasn't clogged. After cleaning and changing the oil, I repeated the test with the same result. I agree that it sounds like oil pressure drop, just cannot figure out which parts are banging to make the knocking. i do believe that wrist pins or main bearings might be worn because of the sand. But it does still have 160's compression in all 4 cylinders.

 

[jjones0187]

if the carbs are out of syc it will cause a bad knocking sound, though im sure you have been through that part already, hard to diagnose something like that but I would probably narrow it down to carbs out of wack or low oil pressure.

 

[mcgovern61]

Well, it happened again! Gas in the intake plenum and trickling into the intakes. The petcock is off and I have checked it with the gas line off and it does not leak. I pulled the carbs and found gas in the bottom of the plenum and intakes #1 and #2 are wet with gas as well as spark plugs 1 & 2. The bike is on the center stand and was started last Wednesday and run till hot.

A separate observation. Since I have had this engine, it knocks or sometimes pops on startup until the oil pressure is up. If I throttle up from say 2500 rpms while riding and push real hard it seems like it detonates, but the plugs are ok with no signs of detonation. The PO claimed they were rebuilt and re-jetted. I had them rebuilt over the winter last year, but did not have the jets changed. Is it possible that gas is dribbling out not metered correctly?

I still have to admit, carbs are a mystery to me, and I can't seem to get a handle on them. (I am going to find some fuel injectors!! I wonder if the throttle body MPI unit from an old Suburu boxer engine would work?)

 

[dan filipi]

I wonder if there could be some capillary action going on, maybe caused by heating,cooling or...

What doesnt make sense is if there is no gas supply then where is it coming from?

Could try running it as normal to hot like you did, shut it down and disconnect the gas line between the carbs and fuel pump.
That would at least rule out gas coming from the tank.

 

[mcgovern61]

I wonder if there could be some capillary action going on, maybe caused by heating,cooling or...

What doesnt make sense is if there is no gas supply then where is it coming from?

Could try running it as normal to hot like you did, shut it down and disconnect the gas line between the carbs and fuel pump.
That would at least rule out gas coming from the tank.

The '81 engine is out and on the garage floor! (Can't start it now.) I also would like to know where the gas is coming from and why it is in the bottom of the plenum? The carbs are out and also sitting on the floor. I'll see what happens by tommorrow. I'm preaching in the morning so I will not be able to get to them before 2 pm.

 

[joedrum]

when its back firing and poping it can blow gas back to plenum where it can collect. i dont know about 1100s but 1000s gas delivery is though the air box maybe something there. whats the point if your changing motors. is your daughter i mean helper home for a visit just kidding gerry. may the words of truth flow from you in the morning. my bike had gas in air box and never went away till i got it running sweet and the gas quit collecting there and gas mileage increase. so i think its just cause its not right probably from several causes. if you dont like messing with the 4 carbs consider one carb with the LD manifold and carb mod. im giving it quite the consideration like dan ive got one carb body in pretty bad shape.

 

[mcgovern61]

when its back firing and poping it can blow gas back to plenum where it can collect. i dont know about 1100s but 1000s gas delivery is though the air box maybe something there. whats the point if your changing motors. is your daughter i mean helper home for a visit just kidding gerry. may the words of truth flow from you in the morning. my bike had gas in air box and never went away till i got it running sweet and the gas quit collecting there and gas mileage increase. so i think its just cause its not right probably from several causes. if you dont like messing with the 4 carbs consider one carb with the LD manifold and carb mod. im giving it quite the consideration like dan ive got one carb body in pretty bad shape.

Unfortunately, my daughter is still in Florida (BigAndrew, keep and eye out for her!). She is coming home for Easter, but I have to go to Sacramento and Seattle Easter week for sea trials on a high speed fast ferry that I have been overseeing the construction of. I told her that I have to get started now before the weather gets too nice not ro ride!

The detonation happens while riding, but the gas showed up in the plenum while the bike was shutdown.

 

[dan filipi]

I would get the engine in then deal with the other problems.

The detonation could be an over advance. Mine does the same thing.

You could check the carb float needles and float adjustments to see if they're leaking by if you rig a gas container with a 1/4" hose fitting out the bottom higher than the carbs and connect. Gravity feed pressure 3 feet or so above the carbs should be enough to test and turn up any problems.

 

[mcgovern61]

I would get the engine in then deal with the other problems.

The detonation could be an over advance. Mine does the same thing.

You could check the carb float needles and float adjustments to see if they're leaking by if you rig a gas container with a 1/4" hose fitting out the bottom higher than the carbs and connect. Gravity feed pressure 3 feet or so above the carbs should be enough to test and turn up any problems.

Great idea! I have them out and on the floor now. When I turn them 45 degrees on end (side to side) gas comes out of #1 and #2 into the intake plenum, but #3 and #4 stay dry.

 

[BigAndrew]

Unfortunately, my daughter is still in Florida (BigAndrew, keep and eye out for her!).

Whats her address? :smilie_happy: :salute:

 

[mcgovern61]

She's in Fort Lauderdale, a hop, skip and a jump from you!

 

[mcgovern61]

Well, after coming back from an out of town trip to the West coast, I finally took a look at the carbs.

When I drained the bowels, I got different amounts in each one. I pulled the float bowel covers and checked the floats. They were all different. Worse yet, the individual floats were different with one side higher than the other(twisted?).

I first leveled out each individual float set and then set them to 15.5 mm each. The #1 float was really off (by as much as 3mm). Next I will put gas back in and see if it leaks while setting on the floor.

The insides were looking real good, no gum or debris. (I did have them rebuilt last winter).

Is there any way to tell if I have OEM jets? The PO said the carbs were "re-jetted" before I bought it.

 

[dan filipi]

These were redone by Pistol Pete right?
Strange that the floats were that far off.
Have the carbs been dropped or jarred? Only thing I can think of could throw the adjustment and twist them.

Can't help on the jets because I don't know the stock size.

 

[mcgovern61]

Yes they were redone by Pistol Pete. The only thing I can think of was a possible drop while shipping back to me, particullary if they were upside down while in the truck. A portion of the trip may have been air freight and you know how careful the airline handlers are with baggage and freight. Since they were re-installed back on the bike, I have not hit anything hard that could have caused the tabs to bend.

 

[mcgovern61]

First shot with gas back in them and they still leaked into the plenum. I opened them up again and pulled the float needles and pins. Gave them a cleaning and tested them to see if they were actually sealing. They worked fine after some cleaning. Got a better ruler and made a float gage by marking 15.5 mm on the new stainless ruler and adding a tab that was 90 degrees to 15.5 mm and then rechecked and readjusted the floats. Put the carbs on the floor, topped off the gas tank and gravity feed the carbs from the petcock. I let them sit for 48 hours and no more leaks. Turned them up 45 degrees in both directions and no more leaks.

I believe that what happened originally is that between the floats not being set right, the pins not sealing correctly, the bowels became overfilled. The petcock was off but the fuel pump was still pressurized from running and with several changes in temp in the garage, the gas expanded and started leaking into the plenum. (Seems plausible to me under the circumstances :smilie_happy: )

 

[danf]

That's great you figured it out, might help the next guy...

 

[mcgovern61]

mcgovern61 » Sun Mar 21, 2010 9:02 pm[/url]":2afexp5n]
First shot with gas back in them and they still leaked into the plenum. I opened them up again and pulled the float needles and pins. Gave them a cleaning and tested them to see if they were actually sealing. They worked fine after some cleaning. Got a better ruler and made a float gage by marking 15.5 mm on the new stainless ruler and adding a tab that was 90 degrees to 15.5 mm and then rechecked and readjusted the floats. Put the carbs on the floor, topped off the gas tank and gravity feed the carbs from the petcock. I let them sit for 48 hours and no more leaks. Turned them up 45 degrees in both directions and no more leaks.

I believe that what happened originally is that between the floats not being set right, the pins not sealing correctly, the bowels became overfilled. The petcock was off but the fuel pump was still pressurized from running and with several changes in temp in the garage, the gas expanded and started leaking into the plenum. (Seems plausible to me under the circumstances :smilie_happy: )

Reading this next quote from the Randakk website seems to confirm that the gas CAN siphon back! (Good information!)

https://www.randakksblog.com/floats-101/

To protect against the possibility of float valve failure when parked, always use the petcock to shut off the flow of fuel every time you shut off the engine…that’s why it’s there. Yes, I’m well aware that the fuel tank is below the seat on GL1000s and that a mechanical fuel pump is necessary on these bikes to feed the carbs. However, the fuel pump can come to rest in a certain mode that allows fuel to flow when the tank is full or near full. At lower tank levels, siphon action can do the same!

I always closed my petcock, but the floats and needle seats were not correct. Reading this blog just helps me to understand that siphoning does happen!