In Depth Mikuni

Here is what they look like




Take the top off and this is what is inside. Same as the Hitachi the slide has the diaphragm and the needle assembly however the needle is held in place by spring pressure. Here is the needle assembly also. If you need to shim the needle you must add the shims between the E clip and the plastic stop.




Pilot screw is as shown. remove, clean, inspect. turn in to soft seat and back out two turns for initial set




Next comes the slide track. It is held in place by “safety torx”. You have to get these bits to remove them.


They are made of soft metal and tend to strip and break easily. Be prepared to drill an tap to clean it up. Once you have the slide track out you will find two o-rings that dry rot over time.




The main emulsion tube slides out the top after the jet is unscrewed and is slotted so it only goes back one way.




Open the bottom and pull the float pin releasing the float and needle. Shake the float and listen for fluid. If you hear fluid, replace the float or repair. Remove the needle seat and clean the fine mesh screen under the seat.




Clean drains and emulsion jet. Use a torch tip cleaner to clean the bowl jet tube as there is a small jet at the bottom. If you make this hole bigger you will run very rich with the choke.





An extra system on some Mikuni is the “Coast Enrichment System”
Coast enricher is located on the side of the carb. Both carb’s have one. On some of the older carbs the enricher is a separate piece. It is possible to disable this so you do not have to fool with it any more.




The enricher can be disabled by removing the Diaphragm spring. This will seat the needle against the seat–retainer closing of the excess air to the pilot slot


 This is a break down of the parts in the order they are removed.
Actuator spring slides over the end of the needle which slides through the retainer. It contacts the diaphragm with the stiff diaphragm spring at the end





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© Michael Tullock