BETA EVO 2009 carb problem?

[srfallsallot]

Hi all

I was having an occasional stall. It seems like it would just run out of fuel. Totally not reproducible deliberately.

Plenty of spark on the plug.

I checked the fuel line.

I checked the petcock.

I checked the vent hoses.

I have dissembled the carb more times than I can count. I can now take the carb out in less than 1 minute.

I have cleaned the carb many times after first taking it apart. All the orifices are open.

I have checked the float level.

It now hardly runs at all! I can start it but now there is no bottom end and it runs very fat.

Help

[liviob]

Have you checked the reeds. Cracked or chipped reeds will cause hard starting and poor bottom end responce. If you have alot of time on the motor the rings could be worn. This will cause the bottom end to be soft and the rich condition you mentioned.

[srfallsallot]

Have you checked the reeds. Cracked or chipped reeds will cause hard starting and poor bottom end responce. If you have alot of time on the motor the rings could be worn. This will cause the bottom end to be soft and the rich condition you mentioned.

Thanks

I do not think that this is the case because it is a low time bike but I will check this out.

[dan williams]

OK a couple of thoughts, sometimes an intermittant electrical fault like a bad kill switch or leaky high voltage lead can seem like a carb issue. I've seen it several times and it's always a surprise. The Keihin has a tiny exit hole for the pilot circuit bleed air. This causes the carb to be very sensitive to getting water stuck in the circuit and unless you make a concerted effort to blow it out with high pressure air it won't come out. The specific hole that gets blocked is the TINY drill hole on the bottom of the venturi chamber just behind where the flat slide touches down in the groove at the bottom of the chamber. To really blow out the pilot circuit you need "security" torx driver to remove the central tower from the underside of the carb and have at the orifaces with a high pressure air line.

[duggan]

I had a problem with my 2010 running weak after six months running fine, found it was a wire from the coil which had rubbed through so was getting a poor spark. Might be worth a sight?

[slickgolf_0]

Hi

Check with Beta UK web site , they have a carb mod listed in the technical menu

My 290 would not lift properly at the bpttom end , I was advised to change the pilot jet , it made all the difference but will have to change back for the colder weather , the guys at Beta are very helpful , give them a call.

[srfallsallot]

I have done all that you all have suggested except the electrical ideas. I will do that next. The fuel is clean. I have cleaned out the exhaust system. The reeds have been checked. It is still flooding with a lot of fuel running out of the vent tubes. The needle does not seem to shut off properly. I have had my favorite professional mechanic work on it and he does not seem to be able to make it run correctly.

I am at a loss as what to do next. Hope fully I can solve the flooding problem. I will check the electrical system. Maybe I have multiple problems?

Thanks all.

[stork955]

Gday, you are on the right track. If fuel is running from the breathers its a float/needle issue. You can check that the float is OK by putting it in a jar of fuel and seeing that it floats "high". If it is puntured it will float low (under the surface) or sink. Its unlikely since the bike is relatively new but something I would check since you have already looked elsewhere. Double check the float level as well - you must do this by tilting the carb on its side to a point that the float just closes, not all the way upside down. This loads the spring in the needle and will give you an inaccurate level setting. Hope this makes sense,

Cheers,

Stork

[srfallsallot]

I removed the carb again.

I have removed the valve petals to check for damage. They are perfect.

I dissembled the carb completely (I have security torx drivers.)

I polished the seat of the float needle.

I have cleaned out all passageways with carb cleaner, compressed air, and mono filament fishing line several times..

The float does float in a bowl of gas.

The float is now set so that it closes much earlier than shown in the attachment. If it is set at the attachment specification it floods horribly with fuel running out the vent tubes.

I can now get it started.

After starting and warming up.

It runs fat at higher revs.

It will not run at all at low revs where the pilot jet should be on.

If I turn off the petcock as the fuel is used up in the carb it begins to run like it should until the fuel runs out completely.

It starts easily with a few kicks and a partially open throttle with the fuel on.

This problem just does not seem to be an ignition problem. I do have a new kill switch and will put it in and disconnect all accessory electrical connections if you really think that is electronic. If it was electronic why when the fuel is turned off it begins to run correctly?

I do not have access to another carb from a running bike to try as others have suggested.

I have been working on it for the last 12 hrs. The needle and seat are shutting off. Slowly working up from an empty bowl so that there is more fuel in the bowl. This is most difficult as there are few good surfaces to measure from. At any rate fuel is now 17mm below the split line with the floats out.

It still has no bottom end.

If I had access to a machine shop I would fabricate a gauge that would screw into the bottom of the bowl with a tube so that I could measure fuel level in the bowl with the carb in the bike.

At this point I am wondering about the electrical system too just because I am ignorant about the real technicalities of engine design and electrical system. As it is I have a very expensive piece of junk. I still love this BETA but this is the most trouble I have ever had.

[stork955]

Gday, it still sounds rich. If you have to start it with some throttle, this is a clue. The spark plug is probably partially fouled at this stage, so it may pay to slip in a new one unless you can clean it properly (so the porcelain is white again). Something in the back of my mind says there is a weird thing you can do to those Keihins which makes them run like this... I'll have to think on it today and get back to you there.

Cheers,

Stork

[copemech]

Well, if the float is set correctly and the needle is sealing, it should not(cannot) pee fuel out the vent(lower attachment to bowl) unless the tank is pressurizing or there is a casting flaw in the carb body leaking fuel into the bowl.

That vent on the lower bowl, as well as the one on the side of the carb need to go to free air. Do not attach one to a manifold vacume source! I have seen this!

[srfallsallot]

Well, if the float is set correctly and the needle is sealing, it should not(cannot) pee fuel out the vent(lower attachment to bowl) unless the tank is pressurizing or there is a casting flaw in the carb body leaking fuel into the bowl.

That vent on the lower bowl, as well as the one on the side of the carb need to go to free air. Do not attach one to a manifold vacume source! I have seen this!

It does not "pee fuel" since I polished the seat for the float needle.The vent holes are to air.

Thanks

[srfallsallot]

Hi all.

Thanks for all the advice.

Update.

Our importer American BETA Tim Pilg with consultation with a good friend and long time Trials rider, mechanic and dealer Adrian Lewis of Lewis Sport sent a box of parts to try. A new coil, Black box,stator and a carb used carb body.

I replaced the coil with no change.

I replaced the black box with no change.

I replaced the tower in the my carb with the tower from the sent carb. The pilot jet sits in the sent carb tower 1/2 mm less deep than the the original. No change.

I have not replaced the stator yet. I am loth to do that as I hve no experience with this and I fear making more problems.

Again thanks for all the advice.

[dan williams]

Usually when the stator is crap it's the trigger coils that have gone out so it's unlikely to run better as the fuel is running out. This may be a stupid question (I'm full of them) but have you checked the jet sizes? The more screwy the problem often the more basic the answer. Maybe somebody at the factory grabbed a carb for an enduro bike by accident. Monday bike? Even if it says it's the correct size it is possible to have misdrilled jets. Worth replacing as an experiment. If you got an oddball pilot or needle jet or even incorrect needle you could be chasing your tail for months. It certainly sounds like a fuel issue and I'm impressed with your diagnostic work so far. See if American Beta will front you a set of jets.

Just as an afterthought, was the little O-ring gasket thingy that isolates the jet cicuits in place at the base of the jet tower?

Edited October 31, 2010 by Dan Williams

[srfallsallot]

Usually when the stator is crap it's the trigger coils that have gone out so it's unlikely to run better as the fuel is running out. This may be a stupid question (I'm full of them) but have you checked the jet sizes? The more screwy the problem often the more basic the answer. Maybe somebody at the factory grabbed a carb for an enduro bike by accident. Monday bike? Even if it says it's the correct size it is possible to have misdrilled jets. Worth replacing as an experiment. If you got an oddball pilot or needle jet or even incorrect needle you could be chasing your tail for months. It certainly sounds like a fuel issue and I'm impressed with your diagnostic work so far. See if American Beta will front you a set of jets.

Just as an afterthought, was the little O-ring gasket thingy that isolates the jet cicuits in place at the base of the jet tower?

Thanks for thinking of me. First off the bike ran very well for several trials. So it is not a jet size problem. Yes i checked the jets to make sure they are clean.

I have replaced the coil, black box, and the stator. Each on individually. The problem has not changed. I have put all the original parts back and it runs just the same as with the new parts.

A friend is bringing over a carb from an 96 BETA that runns ver well just to try. I am also going to put all mey carb parts into the Carb body that American BETA sent.

I wish I new what I was doing.

Again thanks for your time.

Edited November 1, 2010 by srfallsallot