Carb Frustration. I'm goona shoot it!

[Sheradan]

After being fed up with carb issues and running on 3 for awhile, I finally got another set of carbs from a member who was parting out and had redone carbs. I installed carbs and it was great to run on all four again. Seemed to stumble a bit at low RPM so I put the sync to it and got it all staighted out. Ran great for about 50 miles, then started running like crap. Seems to fall on it's face and die when you give it gas. Runs great at 5k-7k rpm.. The diaphrams and slides are all in great shape. Fuel filter is new, idles great. No air leaks I can find. Any ideas O' Venture guru's? A BMW 1200 LT is looking appealing right now, but I still love the 1st gen look and power (when it runs right).

[Yammer Dan]

Sea -Foam??? Sounds like you picked up some crap. Try draining bowls and see what you get.

[rhncue]

Could be rust/debris in the fuel tank and now has worked back up into the new carbs. Drain the carbs through some cheese cloth or such and see what you catch. I had the same problem with an old KZ11. Had to clean and reseal the inside of the tank.

 

Dick

[Black Owl]

Not intended to be insulting, but are you sure the fuel filter is installed correctly?

[jasonm.]

The fuel filter will NOT catch everything. But the bits of rust it misses are usually too small to clog anything. I suggest you drain the tank completely. Then remove the fuel "sender". And look in the tank. I had a bunch of random rust spots and SAND in the tank. I got 90% of the stuff out. Using WD40 which does break the rust down. ANd clean white rags(Tshirts and socks) on end of a stick. A vaccum I also used ONLY around the strainer. Do all cleaning w/petcock OFF. The little bit of WD40 will not hurt anything when you start it. ALSO how is the petcock strainer? EVAPORUST is a water base product that does a great job on rust. BUT MUST be flushed w/water. Making the job a BIG one.

[GeorgeS]

Completly drain your tank at the petcock, and start with new fuel, and Sea-Foam.

 

Drain all 4 carb bowls seperatly with the bowl drains, letting fuel pump run fuel thru the bowls.

 

Go for a good hard ride with the Sea-Foam in new gas, see if anything changes.

 

Pull the plugs and see what they look like. You might have an ignition problem on one cylinder. Try a new set of plugs.

 

Screw the plug caps off the Ignition Wires, make sure the copper strands are not chewed off at top of Resistor caps.

 

Find the Pull apart plug from the Pick up Coiles going to the TCI, and clean the Pins. This is a known trouble spot.

 

Pull both plugs from the TCI unit, and clean the pin contacts. ( might help )

 

And of course !!! Check for Intake Air Leaks, Above, and below the Carbs. Also, check the two bolts holding each Intake Manifold to the Cylinder heads, you might have an In-Take air leak. These engines do NOT like Intake Air Leaks !!

 

Manifolds, have an O-Ring, at the heads. Also use sealant if you replace the O-rings.

 

Those Clamps above and below the carbs are fairly chezzy clamps, I had to get a new set of them. Old ones were stretched, and would not seal.

[Sheradan]

This issue is new with these carbs. Ran Seafoam, new plugs. will try draining the bowls. Fuel in new filter is clear and clean. Last carbs ran good except one, not at all.

[CrazyHorse]

After being fed up with carb issues and running on 3 for awhile, I finally got another set of carbs from a member who was parting out and had redone carbs. I installed carbs and it was great to run on all four again. Seemed to stumble a bit at low RPM so I put the sync to it and got it all staighted out. Ran great for about 50 miles, then started running like crap. Seems to fall on it's face and die when you give it gas. Runs great at 5k-7k rpm.. The diaphrams and slides are all in great shape. Fuel filter is new, idles great. No air leaks I can find. Any ideas O' Venture guru's? A BMW 1200 LT is looking appealing right now, but I still love the 1st gen look and power (when it runs right).

Fuel pump?

[Sheradan]

I'm gonna take the air box apart and check that out. Might as well try the easy stuff first.

[TonyLudwick]

I don't know about your model, but some bikes have tubular strainer screens attached to the petcock tubes that stick up inside the gas tank, one for the main tube and one for the reserve tube. Dump the gas out of the tank, remove the petcock from the tank, inspect and clean strainers with spray carb cleaner, verify that flow is good through the petcock. It sounds to me like this is a fuel delivery problem between the tank and the carbs. Could be a faulty fuel pump if your bike has one. Hope this helps and Good Luck!

 

Regards,

Tony

[Sheradan]

Wouldn't a fuel starvation problem keep it from running great at high RPM?

[Condor]

Since the fuel line is after the filter check to see if it's not breaking down on the inside. You might be getting small bits of rubber blocking the main jets and Sea Foam ain't gonna touch it....

[Snaggletooth]

If it is just one carb that is suffering from lack of fuel it might be the one filter that is a bear to change.

 

In the body of the carb, on top of the body, by the fuel intake elbow there is a plug. It looks like a casting mark at a glance but it is the plug that seals the hole to remove and replace the needle seat itself. If you remove that plug there is a small net filter under it and on top of the needle seat.

 

Not many folks replace the seats as it's not an easy job and few realize there is a filter in that position.

 

It's possible that the filter itself may be plugged with debris. To check it, open the carb and blow air back through the needle seat from the inside of the carb and watch to see what comes out of the fuel intake elbow.

 

Maybe...maybe not. Just a thought.

 

Mike

[bkuhr]

If it is just one carb that is suffering from lack of fuel it might be the one filter that is a bear to change.

 

In the body of the carb, on top of the body, by the fuel intake elbow there is a plug. It looks like a casting mark at a glance but it is the plug that seals the hole to remove and replace the needle seat itself. If you remove that plug there is a small net filter under it and on top of the needle seat.

 

Not many folks replace the seats as it's not an easy job and few realize there is a filter in that position.

 

It's possible that the filter itself may be plugged with debris. To check it, open the carb and blow air back through the needle seat from the inside of the carb and watch to see what comes out of the fuel intake elbow.

 

Maybe...maybe not. Just a thought.

 

Mike

 

I never realized this about the screen, but might be possible to open drain screw and blow air up thru drain and out intake elbow with fuel hose off:confused07:. With drain open, float should be down opening needle port. Put paper towel around fuel inlet to catch anything that comes out. Just a thought.

[Snaggletooth]

I suppose it would be possible using low air pressure. My concern would be the possiblity of damging the spring loaded plunger in the needle itself using too much pressure.

 

But that would show if you are getting flow through the intake elbow and the net filter.

[Sheradan]

Filter is correct and clean. Did many airbox repairs. It had many leaks and they are all sealed. Drained carbs and got clean clear fuel from all of them. Now bike idles nice, starts well when started with choke, completely dies if you give it gas. Going to the shop on Tuesday. If it's a big deal I'm just gonna shoot and be done. It ran better than this on three carbs. I'm starting to hate this thing.

[Condor]

Filter is correct and clean. Did many airbox repairs. It had many leaks and they are all sealed. Drained carbs and got clean clear fuel from all of them. Now bike idles nice, starts well when started with choke, completely dies if you give it gas. Going to the shop on Tuesday. If it's a big deal I'm just gonna shoot and be done. It ran better than this on three carbs. I'm starting to hate this thing.

 

It's a love-hate relationship. When it's running right there ain't nothing better, but when it gets a glitch somewhere it's an SOB..... Sounds like you still have jets plugged up, or?? you're not getting enough fuel to the carbs. Enough to idle, but not enough to supply the main jets... What is getting there may be clean, but not enough. From your original post you had a second set that ran great for 50 miles and then went south. You're sucking something into the bowls that's plugging the jets. I still think it's the fuel line breaking down....