BETA EVO 2009 carb problem?

[copemech]

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.

Something did strike me! Wonder if he has the needle on top of the plastic thingie where the spring sets into the slide, rather than below it?

[srfallsallot]

Something did strike me! Wonder if he has the needle on top of the plastic thingie where the spring sets into the slide, rather than below it?

It is below The plastic keeper.

[srfallsallot]

My friend brought his carb from his 96 BETA. We put it on and it runs great. SOOOO it is a Carb problem. It has got to be a float problem. I am just stumped. Do I have to buy a new carb?

Thanks so much to all of you who have read this saga and offered sugestions.

[copemech]

My friend brought his carb from his 96 BETA. We put it on and it runs great. SOOOO it is a Carb problem. It has got to be a float problem. I am just stumped. Do I have to buy a new carb?

Thanks so much to all of you who have read this saga and offered sugestions.

Ok , so it is a carb problem. So lets start over, now that it is not p****** fuel out the vent, What I get is it still seems to be running rich and blubbery?

Not sure exactly what you have done with the floats levels as compared with the posted diagrams. As they should run about paralell or slightly above when held at a 45 deg angle.

[srfallsallot]

Ok , so it is a carb problem. So lets start over, now that it is not p****** fuel out the vent, What I get is it still seems to be running rich and blubbery?

Not sure exactly what you have done with the floats levels as compared with the posted diagrams. As they should run about paralell or slightly above when held at a 45 deg angle.

I have set the levles to theeven at 45 to more and less. It still runs fat with absolutely no bottom. A new carb is on its way.

[copemech]

I have set the levles to theeven at 45 to more and less. It still runs fat with absolutely no bottom. A new carb is on its way.

Ok then, flat with no bottom, which generally leads me to a lack of fuel still yet caused by a restriction in the low speed circuit(idle jet) yet not neccessarily in the jet itself.

If you look at the carb, there are two tiny holes in the bore,one just behind the slide(engine side) as you look down through the slide hole. This is a transition circuit. The other is miniscule, and angles up toward the engine side as viewed through the engine side(idle circuit). Soo tiny anything even the smallest spec could block it!

I would think these the culprits, and a backwards blow out with shop air and carby cleaner after removal of the slow jet and airscrew would be called for to try and dislodge anything in there. Once again a fine wire could help to some extent. though I would have to hunt for one to fit the small hole myself.

Simple view of the size of these holes reinforces the need for inline filters if one does not have it installed.

Even with a new carb, one would want to ck and verify the float height prior to install. It is critical.

Edited November 3, 2010 by copemech

[dan williams]

OK this is a longshot but it all sounds vaguely familiar. Last year I worked on a bike that was a whole pack of woe. Never really got it completely sorted as I think the stator packed it in but before it finally quit the bike ran sporadically and in much the same way you describe. I swapped carbs and did the multiple rebuild thing. What I finally found was the rod on the choke plunger was bent (don't ask me how). In any case the bike would start hard and run poorly at low throttle settings and bog but clear up at higher throttle settings even though it still wasn't quite right. The bent rod was causing the choke to stay partially on. So I guess the practical upshot is make sure your choke is closing all the way. Next time you are in debug mode stick your finger on top of the choke and push down to see if it helps.

[srfallsallot]

Ok then, flat with no bottom, which generally leads me to a lack of fuel still yet caused by a restriction in the low speed circuit(idle jet) yet not neccessarily in the jet itself.

If you look at the carb, there are two tiny holes in the bore,one just behind the slide(engine side) as you look down through the slide hole. This is a transition circuit. The other is miniscule, and angles up toward the engine side as viewed through the engine side(idle circuit). Soo tiny anything even the smallest spec could block it!

I would think these the culprits, and a backwards blow out with shop air and carby cleaner after removal of the slow jet and airscrew would be called for to try and dislodge anything in there. Once again a fine wire could help to some extent. though I would have to hunt for one to fit the small hole myself.

Simple view of the size of these holes reinforces the need for inline filters if one does not have it installed.

Even with a new carb, one would want to ck and verify the float height prior to install. It is critical.

I will do this again. I have done this several times with no result.I have even run fishing line through to make sure all the holes are open.

[srfallsallot]

OK this is a longshot but it all sounds vaguely familiar. Last year I worked on a bike that was a whole pack of woe. Never really got it completely sorted as I think the stator packed it in but before it finally quit the bike ran sporadically and in much the same way you describe. I swapped carbs and did the multiple rebuild thing. What I finally found was the rod on the choke plunger was bent (don't ask me how). In any case the bike would start hard and run poorly at low throttle settings and bog but clear up at higher throttle settings even though it still wasn't quite right. The bent rod was causing the choke to stay partially on. So I guess the practical upshot is make sure your choke is closing all the way. Next time you are in debug mode stick your finger on top of the choke and push down to see if it helps.

Yes I have thought of that too. I did the push on it thing to see if it made any difference. It did not. I have checked the rod to see that it moves freely. Thanks

[copemech]

Just to hit once again on this float height thing, you see in the illustration from JL, he suggests parallel, whilst holding at the 45deg angle, yet gives no actual measure.

I think the parallell would likely be the seam edge of the float as example, ant not the top edge of the hump in the bottom(top when inverted).

I believe the actual measure to the top middle of the hump on the float should probably fall to within 20-21mm using a precision rule from the sealing base.

Mind you, I am running an Oko(copy) on the Sherco, yet the same basic principles apply. Direct mounting angle of the carb may vary a bit with the beta, but you need to be in the ballpark here, as things go. I have a Kiehin here in front of me for quick ref!.

As you have narrowed this down it seems, I am not quite sure what else to suggest?

What was your pilot jet size?

[trialsnutterman]

Have you checked the overflow tube that sticks up into the float bowl is not catching the floats.

It is really easy to bend this tube when assembling or disassembling the carb and if your unlucky you can bend it so it rubs on the floats making it difficult for them to close the float valve.

After checking that try a new float valve, then I guess you will have to buy a new carb as the float valve seat cannot be replaced.

[dan williams]

Took me quite a while to figure out the only way to get the damn float bowl back on was to hold the carb upside down so the floats were out of the way.

[srfallsallot]

Thanks all for the advice. I have done everything that anyone has sugested. None of it worked.

My new carb arrived. It is not a perfect match but close enough. I used the original top plate,slide, needle, jets, and the bowl from my old carb. I plugged an extra hole on the engine side of the carb. I did not mess with the float. I kicked it once and it fired right up. It runs smooth and has huge bottom end power and top end too. I am not able to ride this extensively at home so I do not know how it will perform in a real trials but I hope this weekends 2 day trials at Roswell New Mexico USA will turn out OK.

Many thanks to all of you who took the time to think about and offer advice.

Special tahnks to Bob Rowland, Adrian Lewis of Lewis Sport, and Tim Pilg of American BETA. These great people went way beyond anything I could ever have expected in there efforts to help me out of this maddening problem.

I guess I will never know what the problem really was.

Thanks All

[duggan]

Happy days glad to hear it all work out

[dan williams]

If you'd like me to take a look at it I'd love to take it into work and throw the carb body under the microscope. The curiosity is killing me.