Hitchcocks Forum

Hi, had a problem with the 500 racer, it would run OK then at the next meeting it would only run on choke. I tried everything, jets ,fuel flow float height etc. Finally after stripping the mikcarb and comparing with the spare I found the problem. Comparing the float needles, the original had seized the little pin plunger. Checking with a transparent float bowl I found a 4mm difference in fuel level. A very small item easily missed. Vince

That's worth knowing Vince. BTW where did you manage to find a transparent float bowl?

I had this exact problem recently on an early 90's Kawasaki. I was lucky it didn't self-immolate, the fuel had overspilled into the airbox and had clearly been on fire at some point then put itself out judging by the charred hole in the plastic.



The flooding/sticking happened more than once too, despite having freed them off and ultrasonically cleaned them. Then someone on a forum pointed out that it was a "pre ethanol" bike and the problem was almost certainly corrosion of the alloy plunger causing it to stick, changed the needle valves out for "new" ones. Didn't happen again after that.



So, something else to consider. How old is the valve and is it ethanol proof?

Vince makes an interesting point about viewing fuel level which I had never thought about - and in reply to presto's query I guess any polythene container cut down and held in place would suffice, depth nor seal won't matter as it is the surface height above fuel that matters and we don't need to run engine etc to check this.... I'll be giving it a go! A little plastic bowl with mm's scratched on it would be a useful checking device.

The easy/usual way to check the fuel level on a carb equipped with a float bowl drain is to attach a piece of clear tubing to the drain, bend it up alongside the carb body so the top is higher than the float bowl flange (fasten it up with a cable tie/rubber band) and crack the drain screw open. The fuel level in the tube is the same as the level in the float bowl. Fuel height is usually quoted as mm below the flange on the carb body.

p, I fail to see how any old plastic bowl can serve as a float chamber to check fuel level unless you can fit a needle valve and suitable needle seat and the original float? What is there otherwise to stop fuel flow?

The float assembly and needle valve are attached to the carb body. The float bowl is just that, a bowl full of fuel held on by 4 set screws.

Ah yes! You're quite right!! I was thinking of AMAL Concentrics - which are quite different. Apologies!

I am still trying to picture a 500 racer with a Mikcarb. Sorry, I'll get my coat ...

REgards, Mark