Fuel And Oilmixture

[betachap]

hi everybody i am new to this so bare with me.

i am looking to see what petrol mix people run at im useing castrol tts 2 stroke but bike acts like its running out of fuel sometimes when queing for a section on tickover and also keeps fouling plug.

any info on carb/air mix would be great as well.

the mix im on is 100ml to 5 litre of petrol bike is a 07 250.

cheers.

[dougie pumpkin]

hi everybody i am new to this so bare with me.

i am looking to see what petrol mix people run at im useing castrol tts 2 stroke but bike acts like its running out of fuel sometimes when queing for a section on tickover and also keeps fouling plug.

any info on carb/air mix would be great as well.

the mix im on is 100ml to 5 litre of petrol bike is a 07 250.

cheers.

Lampkins and Pennine advisese 75 ml to 5 .

[betachap]

cheers for that have you any idea wot the carb settings should be on the mixture screw i.e how many turns out it should be.

bike running very rich.

[shercrazy]

THATS A BETA! I ALWAYS RAN HALF VP RACING FUEL AND HALF 93 PUMP GAS, KEEP THE NEEDLE ABOUT THE MIDDLE, I RAN MINE AT 100:1. (THATS U.S. MIXTURES) BUT MY BIKE RAN GREAT, YOU JUST HAVE TO FOOL WITH THE FLOATS AND THE MIXTURE SCREWS, IT'S A PROCESS BUT YOU WILL LEARN TO KNOW YOUR BIKE A LOT BETTER, AND YOU CAN LEARN TO CLEAN YOUR CARB IN A FLASH! THERE IS A PAGE ON HERE UNDER BETA THAT SHOWS YOU HOW TO SET THE FLOATS AND ALL THAT, HOPE THIS HELPS...........................................JOHN

[shercrazy]

Beta Rev3 Carb Problems can all be sorted by going through the info below...

Mikuni Carb Setup By Billy Traynor

The first area of urban legend is the two little brass outlets with the pink hoses attached. You may know these as the "over flow tubes".

In reality they are not overflow tubes. While they may allow fuel to escape from them that is not there sole purpose of design.

They are in fact atmospheric tubes.

The main purpose of these tubes is to allow the fuel to reach atmospheric pressure.

This means that when the pressure in the carb body (slide area) drops due to the negative pressure in the engine the atmosphere pushes (@ 14.7 PSI) on the fuel surface helping it go up the jets.

click to enlarge..

There are two adjustments on the float level.

1. The tangs set the fuel level.

2. The little tab sets the travel of the tangs.

The "brass tang" level should be set accordingly.

Remove the float bowl and slide. Place the carb on a flat surface. Get down to eye level with the carb body and you will see two towers sticking up. One tower is the main jet tower the other is the pilot jet tower. Due to casting imperfections I will not supply an actual measurement.

(This settings is visual and will vary from carb body to carb body that is why I will not supply an actual measurement)

The brass tangs should project itself to the extreme left hand top corner of the lower tower or pilot jet tower. This sets the float level.

We will now set the little tab that sticks out perpendicular on the brass tangs.

The purpose of this tab is to stop the actual travel of the tangs downwards.

This is important, as it will alleviate many anomalies once set correctly. One must know that the small pointed plunger that the brass tangs pushes up acts like a light switch. The gas is either on or off. With this in mind one need only have this plunger move enough to allow the gas to flow freely and then close when the tangs act upon it pushing up.

Think of this! When you land off a large rock the weight of the floats push quite rapidly down inside the float bowl. This is known as gravity. The extended movement of the floats downwards tends to do two things. It moves the floats way down inside the float bowl allowing more gas than needed and it also causes some of the excess gas to be pushed up into the jets and into the engine. It also if not set correctly allows the float tangs to travel down to far.

It is kind of like being inside a fast moving elevator and when it reaches this bottom it kind of makes you bend your knees. In other words the elevator has stopped but you are still going downwards.

So how do you set this travel tab?

Adjusting the travel tab on the carb will not stop the floats from going down but it will stop the float level tangs from traveling all the way down. This is important as the further they travel the more they are likely to stick.

With carb back on the table and the float tangs set to the previous mentioned setting (top left hand lower tower) you should be able to lift the float tangs about 1/16 NO MORE.

This bit of play allows the tangs to move away from the plunger jet safely. You will notice that the plunger jet has a springy feel to it. This is allows the float level tangs to still travel up and press continual against the plunger jet for a good seal. The first contact of this plunger will not necessarily close the plunger jet off that is why there is some additional travel afforded.

The bottom line is that if the gas is coming out of the atmospheric tubes (overflow tubes to you) then the gas level is way to high to begin with. It is not that they are not shutting off it is purely that they are set to high. Keep in mind we are taking about the bike in static upright position with or without the engine running.

The other thing I would highly suggest is that the pink hose ends be cut on a very sharp angle and small holes placed in the pink tubes. This will help alleviate the siphoning action if it does tend to flow out of the tubes. After all the levels and tangs are set correctly. There is still the possibility that gas will come out of the tubes in some rare circumstances. By cutting the ends of the tubes on a very sharp angle and piercing small holes into the tubes that siphoning action is somewhat cut off. This siphoning action can even after the floats have settled down keep it self self-going.

Also you should withdraw the pivot pin (the pin the float level pivots on) about 3/8 of an inch and pinch it with some side cutters about 1/8 on an inch from one end and then slide/push it back in. This notched pin will help it stay put in its housing.

These pins tend to vibrate out and hit against the side of the float bowl (look at the inside of the float bowl for witness marks to this happening).

One other area of concern on the Beta is the two vent hoses coming out of the engine are far to near the float bowl. In fact mine were pushing against the float bowl this caused excess vibration into the carb body, which in turn plays havoc with the float levels.

I solved this by cutting the cable tie and having them go around the carb float bowl.

Thanks again to Billy T and to Brian Curran (kinell on TC forum) for the photos.

I also have completed the modification of the overflow hole in the body of the carb as described HERE from KD Mototrials in Australia ... all has so far been perfect.

Another link ... this time for routing of the overflow and atmosphere pipes. scroll down to the 2nd page.. mikuni pipe routing

Visit the Trialscentral Forum from the above link...

[the addict]

I use TTS on my 06 270, I had too rich problems (popped plugs etc etc) I now use 65-70mlitres in 5 litres of super unleaded (Shell V Force) 27.5 pilot and 145 main jet, lowered needle one notch. Bikes runs really clean, good plug colour and no bogging low down.

[dougie pumpkin]

cheers for that have you any idea wot the carb settings should be on the mixture screw i.e how many turns out it should be.

bike running very rich.

The advise i was given, was that if the plug was oily black after running the bike in , was to lower the needle 1 notch and this should solve the problem.

[totalshell]

for every 5 litres of super unleaded use 70/75ml of something like PJ1 or Ipone , the 100 ml of castrol that your using will probably smoke a bit and give the feel of running rich when infact the bike will be lean with all that oil in it

[ssiegmund]

I use TTS on my 06 270, I had too rich problems (popped plugs etc etc) I now use 65-70mlitres in 5 litres of super unleaded (Shell V Force) 27.5 pilot and 145 main jet, lowered needle one notch. Bikes runs really clean, good plug colour and no bogging low down.

Glad to hear this. I just pulled the carb on my new to me '06 250 last night: Pilot 27.5, Main 145, Needle middle position, air screw out 2.5 turns. I almost dropped the needle one position since it appears slightly rich and ideally I would like to have the air screw in the 1.5 - 2.0 range. I ride at 440' ASL, 55-65* F, running 100 octane (RON), Castrol TTS at 80:1, smokes a little, but not bad.

Sounds like dropping the needle one clip will clean it up nicely.

Where's your air screw at Betarev3?

[the addict]

Mines usually 1.75-2 turns out depending on how the weather and sections are going, the needle drop should work nicely mate

[ssiegmund]

Mines usually 1.75-2 turns out depending on how the weather and sections are going, the needle drop should work nicely mate

Thank you very much! Exactly the air screw setting I was hoping for, gives me some adjustment range for riding the mountains.

Soon as the kids are in bed the top is off the carb! Done! 20 minutes, 5 minutes on just about anything else, that carb is a bugger to get in and out of the boots. Rear out first, front in first, unscrew and remove the rear hose clamp before pulling the carb.

Sorry for the semi thread jack betachap.

Edited March 20, 2007 by ssiegmund

[the addict]

ssiegmund, I have removed the reed block spacer on my 06, this made a slight difference to pick up from low throttle openings for the better but not much. It has the big benifit though of making the carb a piece of p*** to take out and put back in , also swap the boot around so the standard air box end of the boot goes on the carb as its a larger opening. To put back on, put the air box end of the carb in first, push the carb towards the air box and the reed side will go straight in, real easy

[slapshot 3]

also swap the boot around so the standard air box end of the boot goes on the carb as its a larger opening.

I like that tip......give that a try later I think

[barrybaines]

Was one of the most helpful tips Betarev3 has given me! well cost me the least anyway

[ssiegmund]

Thanks Betarev3! I installed a reed spacer on my KTM 200, noticable difference in low-end torque. I'll give it a go with and without on the Beta and see what my seat dyno tells me. No doubt it would make R&R of the carb simple.

Have you experimented with after market reeds?

Has anyone ran an iCat, now iKat ignition amplifier on their trials bike? I had one given to me from an Australian distributor and installed it on the KTM, definately a noticable improvement in starting, and at very low rpm under load when searching for traction the motor was smoother and more resistant to stalling. Doesn't appear they've marketed to the trials community, which may be the best application for their product.

Betachap I hope you're taking notes! Thankfully the indirect hijack is delivering some very useful information.