Lumpy Big Reds

[broook]

:? [2] 1986 Big Reds both start easily when cold but when warmed up they start to run lumpy and eventually shut off. They will restart with a bit of throttle but idle rough and eventually shut off again. If I let them run and turn off the gas, after about 10-15 seconds they will eventually run and sound perfect until the gas runs out. It makes me think the float level is too high but with a new needle valve in one of them and a new float and carb kit in the other i am lost. It seems like they are getting too much gas. :oops:

[broook]

Cmon guys, somebody out there should know. How do I lower the fuel level in the carb? They run smooth when the gas level starts to lower. :?:

[TimSr]

If you let them sit, with the gas on, not running, do you get a puddle of gas on the floor? If not, your floats are not set too high. If your floats are too low, when your cruising along at high RPMs, it may suddenly dog down (out of gas) for a half dozen seconds until more gas fills the float bowl, and then it will take off again. Float setting have very little to do with how it runs, or carburetion in general.

Beyond that, much more information is needed. I dont know what running lumpy is. Are you riding the machine when it dies, or is it sitting and idling the whole time? When it dies, pull your plug. Is it black, wet, dry? Does the plug have spark when its dead? Pull your gas line off the carb. Does it maintain good flow? Is it venting properly?

[broook]

Thanks very much for the reply. I will try to answer your questions one at a time.

If you let them sit, with the gas on, not running, do you get a puddle of gas on the floor?

No there is no gas comeing out of the overflow and the overflow is clear.

If your floats are too low?

Bike runs good when moveing so I eliminated low float.

I dont know what running lumpy is?

Sorry for the poor terminology. Lumpy should probibly be irratic. Slows down and boggs and eventually shuts off.

Are you riding the machine when it dies, or is it sitting and idling the whole time? When it dies, pull your plug. Is it black?

Rides good but problems start after it is warmed up and idling. Runs good when cold. Plug is black.

Does the plug have spark when its dead?

I assume it does as it will start right up again if it is given some throttle.

Does it maintain good flow? Is it venting properly?

Good flow of gas. Tried with the gas filler off altogether.

Just thought of something. Do the rubber carb vent tubes have anything to do with this.????

Once again thanks for the reply.

Bob

[broook]

The thing that has me thinking it has a high gas level is that when i come to a stop, I can shut off the gas and keep it reving for a few seconds to drain the fuel from the supply line and then it sounds and idles perfectly until the gas runs out. This happens to two 86 big reds I have here right now. One is mine the other belongs to a friend.

I put a new float and needle in one and a complete carb kit in the other less the float.

They both have new cam chains.

[Tri-Z Pilot]

Do you have the stock carb and settings? It sounds like you are running rich, because you said that if you turn the gas off it will idle pefect for a few seconds, which means it is getting less gas and leaning out the carb giving the engine the correct air/fuel mixture. Have you tried playing with your fuel mixture screw?

[broook]

Yes I have the stock carbs and I started with the two complete turn out settings on the idle adjustment screw.

[if you turn the gas off it will idle pefect for a few seconds, which means it is getting less gas and leaning out the carb giving the engine the correct air/fuel mixture.]

Exactly. That is the problem I have, but how do I correct it?

Most motor cycle carbs I have worked on have a metal tap for slight float adjustment but these are plastic non adjustable.

[Tri-Z Pilot]

Did you turn the idle speed screw, or the idle mixture screw?

[broook]

The idle mixture screw. A new one comes with the kit.

I failed to mention that when it is idleing over perfect with the gas off, as soon as I turn the gas back on again, after 2-3 seconds it stalles right out again as soon as the carb fills up. :?

[ejc042]

Remember if you are using stock jets that altitude can have an effect on the air/fuel mixture, as well as climate.

[bayougrizz]

I'm not trying to insult anyone's intelligence here, but have you checked your air intake? do you have water in the airbox? is your filter VERY dirty, is it over oiled?


also, everyone is leaning toward rich, but I have had the same experience with a VERY lean bike after i snorkeled it, and the plug was showing black. it just would not run long enough to give a lean indication on the plug. take your hand and half cover your intake and see if it falls on its face or tries to run good. it doesn't happen often, but you may be going in the wrong direction thinking its rich. Just suggestions.

another thing, is the carb seated well in the boots on both sides?

[Tri-Z Pilot]

it cant be lean, he said when you shut the gas off it will idle perfect, shuting the gas off will lean the jetting, so it cant be lean. I agree though, did you check your airfilter/airbox?

[broook]

OK. Yes the friends, [customers] bike does have a dirty looking air filter.
A lot worse than mine. That would obviously enrichen the mixture. :oops:

We will try to clean them tommorrow.

I will also try mine without the filter [inside the shed] just to see if there is any difference.

Thanks guys. I really appreciate the time and consideration you are giving this. :-D

Regards.

Bob

[Tri-Z Pilot]

Make sure you are in a very, (and I cant stress this enough), very clean enviroment, you dont want any dust or dirt getting inside your engine.

[bayougrizz]

so what ever happened?