Vacuum Carbs

[rok-the-boat]

I have an old bike with a CV carb and am wondering where I can get the replacement rubber boot thingy that is on top of the throttle slide - mine has holes in meaning I lose vacuum ... meaning the throttle slides don't rise up enough to get max power. Can anyone recommend a good parts shop in Auckland. Or should I go rummaging around wreckers? I imagine parts from other bikes with similar/same carbs would be the same. Any ideas welcome.

[rogson]

The rubber diaphragm is normally vulcanised to the slide and so the slide and diaphragm must be replaced as a unit. I recently priced OEM slides - they are expensive (over $250 each), so finding what you want at a wreckers is the way to go if possible.

An approach to going about this is described below. I haven't got around to trying it yet so I don't know if it works. Perhaps someone else could help (?), or you could try it and let me know.

Your carbs will be either Mikuni or Keihin, and there is a good chance they will have been fitted to other bikes (models and makes). Do a search on the web for the specs of other 4 stroke bikes of similar cylinder capacity (if yours is a 4 cylinder bike - then its 400/4 = 100cc) to see what carbs they have. Slides from different bikes with the same carbs should work in your carbs but the cut-away and the air-hole may be different. If you are replacing one slide then you could try filing/drilling to get it the same as the others. If you need to replace 2 or more then I would recommend you get a compete replacement set and redo the jetting if necessary to get them tuned for your bike.

[rok-the-boat]

Kinda thought of that. Was quoted almost $300 for one diaphram!

[Paul in NZ]

It's an utter pain in the arse eh! The cost of the carbs is often more than the whole bike is worth!!!

One trick is to dab a little rtv or rubber glue onto the splits. Does not last for ever but can often do the trick!

[Motu]

Econohonda does it for Honda's,but I don't know about other brands.They did both my XLV750 carbs - the diaphram is rolled onto the slide like a rivet,this is unrolled and a new diaphram fitted.He had a supply of warranty claim slides he took the diaphrams off.So it can be done,just a pity others aren't as motoivated as Malcolm is with Honda's.

[TwoSeven]

Exactly what bike is it - a kz400 ? Ltd nor standard ?

I think Kawa do a carb rebuild kit for the kz400 but dont think it contains draphragms, you may need to get a part number and order separate. The alternate is to get the carb number and contact keihen to find out what their real part number is and if they can say what other bikes it was used in.

[smokeyging]

I've had the same problem. i have tried a lot of things, i was put onto a guy that could make-up a Compound that is the same as the diaphragms but, that didn’t work too well neither.
Have a hunt around the wreckers and see if you can find another model carb that can fit on your bike? or at lest get one that can be made to fit. those bloody diaphragms are $330 or more each now.