Carburettor reassembly and problems

[Christian Raith]

http://xs11.com.au/Info/Mikuni_BS-CV_Carburetor_Rebuild_Tutorial.pdf

[Christian Raith]

[Jonesy :-)]

In the bowl(s) there is a jet that the brass tube on the carbys goes into when the bowl is assembled to the carby. I think this is a "starter jet" check that these 4 are all clear. I had a similar problem where bike would fire then stop straight away

[Colin]

I solved that problem. It was just that floats were sticking - shaking or tapping stopped the leaking.

Now I have a new problem. Giving the carbies a squirt of aerostart results in it starting beautifully but it won't pick up fuel beyond that. The tank is not fitted yet and I am running fuel in from a drum. There seems to be fuel in the bowls though. The breathers aren't connected to anything and there is no air filter currently.

Any suggestions are gratefully received.
Colin

[makzy]

If yours have brass floats then they are early carbs and should have replaceable needle seats, if they are hex shaped then you screw them out, later ones aren’t removable, you should invest in a set of carb rebuild kits with needles and seats, gaskets, 0 rings. I’m not sure if you can use the plastic floats in early carbs, someone else on here might know, search the other threads about carbies on here. It would also pay to get them ultrasonic cleaned first, after you’ve done all that if you want to send them to QLD I’ll assemble them and set them up for you gratis but you will need to have vacuum gauges to tune them once back on the bike.

[Colin]

Thanks for the advice. They are the brass float type. I will check for pin holes. The problem seems to be with at least one carbie of each bank of two as the leaks are all over.

I do have another set of carbies, I don't know what sort of floats though. Would the plastic ones be a better option?

When this is all done we can run it properly. So far, it has only run for as long as a spray of Aerostart lasts. At least it does run, so we must have done something right!

[makzy]

Yeah Jonesey is rite Collin, cleaning, rebuilding, and tuning must be done in a very meticulous way, when I bought my XS 15 yrs ago I almost burnt the ;(:/$! Thing, but you’ve got to learn what to do and how to do it, that’s what this forum is here for, search for carby and tuning threads on the forum and it’s all there, STEPTOE has videos, and like I said to someone just recently you will need a good set of vacuum gauges to get it rite after you’ve got everything else rite like getting the float straight  to start with then setting them at the right hight and so on, one thing I’ve found is if a PO has fu.:$? With the floats the pin mounts can become bent or twisted or bent which can make them stick and cause exactly what your saying! It’s probably a bit like brain surgery, follow the rules, it’s not hard, and you’ll get there and then you can tell everyone else how to do it with a big proud head on your shoulders.

[Jonesy :-)]

I think there are 2 types. one is an all metal needle and tip, the other is a rubber tipped needle where it seats, as far as I know they are interchangeable (I'm sure I'll be corrected on that one), my alloy top carbies are running the all metal type. Also check the float level pin that the float hinges off isn't bent, that can make them stick, also check you haven't got a pin holed float(if its the brass type) what you are experiencing is one of the XS achilles heel PITA problems.

[Colin]

We just recently overhauled the carbies and the bike is nearly all done. However, the bowls overfill and fuel runs everywhere - out the breathers etc. I can't work out why.
When blowing through the supply line and wiggling the float they seem to cut off OK. Are there different models of needle valves? Could I have bought the wrong ones?