Evo Carb Issues

[bruces670]

Hi after cleaning out my carb several times I'm still getting the dreaded dribbling problems,I've checked the float height and from what I can tell it seems ok but a bit tricky to measure,also I may have inadvertently moved the air mixture screw how crucial is this and will it cause engine wear damage? Can you send the carb to lampkins for any kind of modifications?

[outlaw dave]

Why don't you just call John Lampkin - They are easy to adjust.

[bruces670]

Yea that's tomorrows job mate,just after measuring the float height I can't see a problem with it

[0007]

Adjusting float height will never solve it because its not the cause

If you dribble is because the needle is not sealing

Maybe you need a new needle but a gob of toothpaste and a Q tip will clean, lap and polish the seat

(Outlaw Dave trick)

That is #1 likely cause if your problems, give it a try before anything else

[copemech]

The Kiehin carb has a built in dribble device called an overflow tube which enters the bowl and exits at the bottom. Fuel sloshing will allways dribble out and you cannot prevent this untill you block it off or run the hose up and over the carb which defeats its purpose anyway.!

If you have other running problems, then may be related to float levels, god knows where yours is set, but otherwise, capping off the dribble tube will fix that!

Edited April 15, 2013 by copemech

[bruces670]

Ok thanks guys I will try that I'm guessing the toothpaste acts as a grinding paste to reseat the needle but where does the q tip come into it?

[overdale]

Check the float height as per the pinned Keihin carb item on Beta forums, don't turn it completely upside down as it gives a false height.

It could be that there's a score mark on the valve or seat allowing fuel to leak past, carefully inspect, you can always try 0007s trick, also check that the seat is tight in the carb body.

Don't worry about the airscrew position, you should always remove it and the spring when cleaning the carb to blow through the air side of the pilot air system. For a start, count the number of turns to screw it in until it lightly seats. Then remove it fully, watch for the spring to come out.

Remove the pilot jet (screwdriver) and blow through where you have removed the pilot jet, air comes out a hole at the air inlet side of the carb and the airscrew hole, blow both ways to ensure clear. Put jet, pilot airscrew and spring back in to the same setting as before, right in then say 1.5 turns out. Most EVOs run at between 1.5 - 2 turns out from fully in. If it is in too far it runs rich at the bottom, just ease it out 1/4 turn at a time til it picks up cleanly, but keeping to around the setting mentioned.

Hope that helps

[bruces670]

That's great thank you how do you know of its running rich at the bottom?

[deadwood]

Hi after cleaning out my carb several times I'm still getting the dreaded dribbling problems,I've checked the float height and from what I can tell it seems ok but a bit tricky to measure,also I may have inadvertently moved the air mixture screw how crucial is this and will it cause engine wear damage? Can you send the carb to lampkins for any kind of modifications?

Bruce weve had around 6 or seven evo,s with the keihin carb , only had one which had a slight problem overflowing , 1 remove carb and clean ,2 remove floats with the silver pin ,, it just slides out , when you remove the floats you will see that the needle is attatched to a little tang , with a thin piece of shaped wire, 3 take youre q tip , or cotton bud and carefully add a blob of toothpaste a give it a spin in the recess where the float needle sits, this helps to clean this area and gets a good seal, 4 as you look in the floatbowl youll see the brass over flow tube sticking up at an angle you can buy a tiny little stopper which reduces the diameter of this , it is a push in fit , this is available from gary or Richard at beta uk,, This little stopper vastly reduces any overflow from the carb as it sloshes about,, THE MIXTURE screw is not a static setting warmup the engine thoroughly and start with the screw around 1 full turn out from fully in and adjust until you get the best response ,, this can be anything from 1 turn to 2 , each engine is different , hope this helps Bruce,,

[bruces670]

That's great guys Gunna have a go tonight thanks a lot for your help

[bruces670]

I had a small brass pipe drop out the carb when reassembling today I think it sits in the bottom of where the main jet went and protrudes into the main inlet area of the carb,can anybody confirm this??

[0007]

Is it your emulsion tube?, bunch of tiny holes in it and a hood on top where it's exposed in the Venturi

If so it goes in from the top and the main jet screws into it holding it in place

[bruces670]

That sounds like it sticks out but can't see any holes in it

[overdale]

That bit that dropped out is the needle jet, it is like a top hat shaped piece of brass and is held in place in the body by the needle jet holder.

Put it back in the bore where you took the needle jet holder pt 35 out, with the smaller diameter going in first then it sits on it's shoulder and just protrudes into the air bore of the carb body. Then refit the needle jet holder. This jet sometimes falls out when you turn the carb over with the needle jet holder removed, so always take care. The bike hardly runs if that part is missing!!

It is part 34 -Needle jet on the Keihin PWK28 parts list.

Hope that helps.

Edited April 18, 2013 by overdale

[bruces670]

That's spot on mate exactly what I needed,had been searching the net for a decent exploded diagram,thanks very muchly