Mikuni carb

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FastFred

FastFred

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Just fitting a Mikuni 34mm carb kit from Motocarb in the UK. Have put a Amal carb spring inside the mikuni spring but it still hangs on the cable (i.e slide sticking). The carb cable has a 90 degree entry, I may straighten it a bit to say 60degrees?Any tips please.
 
Is this a new Mikuni? If so, the slide is unlikely to be sticking, however remove the carb, and take off the cap and spring(s). Gently push the slide up and down in the body. It should rise and fall smoothly. If yours does that, the "sticking" is most likely to be in the cable or twistgrip. There should be no need to have a 2nd spring in a Mikuni.

Mick
 
Fred,

I made the same double-spring mistake with my Mikuni last year; turned out to be a slighty bent cable. As Mick said, the original spring is more than adequate to snap the throttle back when released. When you are about to remove the extra spring and test the slide, remove the fuel tank as well. Test the slide, then replace the original spring and test the throttle response with the cable unconstrained. If the response is still mushy, the problem is in the cable or throttle. If the response is crisp, the cable had been bent under the tank. Carefully replace the tank while continuing to test the throttle to insure a smooth cable path; it doesn't take much of a bend to affect the throttle feel. There is enough room above my Mikuni to bring the cable in vertically, and to avoid an angled entry.
 
FastFred said:
Just fitting a Mikuni 34mm carb kit from Motocarb in the UK. Have put a Amal carb spring inside the mikuni spring but it still hangs on the cable (i.e slide sticking). The carb cable has a 90 degree entry, I may straighten it a bit to say 60degrees?Any tips please.
Click to expand...

I put a 34mm Mikuni on my 72 750 and I didn't need to bend the cable 90 degrees. It has a MAP manifold.
I did put an Amal spring inside the Mikuni's however as the throttle stuck open once while at full throttle. Only went down after I used kill switch to slow her down

http://i924.photobucket.com/albums/ad82 ... CF8671.jpg
 
Get used to it,if new try taking it back, I have had to fit a mk2 amal spring, and the mk1 spring, the mk2 spring is thicker than the mikuni one, still stick in the cold and damp.
 
splatt said:
Get used to it,if new try taking it back, I have had to fit a mk2 amal spring, and the mk1 spring, the mk2 spring is thicker than the mikuni one, still stick in the cold and damp.
Click to expand...

The only time mine will stick, or seems to, is when it is wet or damp. The first time it happened was in August going on holiday in the pouring rain, I had only gone 3/4 miles when I noticed there seemed to be a reluctance for the revs to drop when I shut the throttle. Rather than take the chance, as I was going to be riding on single track roads, I turned back and changed bikes. Has anybody an idea why it does it in the wet and damp?
 
rick in seattle said:
Fred,

I made the same double-spring mistake with my Mikuni last year; turned out to be a slighty bent cable. As Mick said, the original spring is more than adequate to snap the throttle back when released.

Yes it is, worked every time on the shop floor, halfway along a 50km straight the slide started rising by itself, accelerating faster up the road, sort of gave me the impression that the spring isn't stong enough, got so pissed with it over winter I even contemplated a set of FCR's, it will do 1000km on a fine day without a problem,about 10 in the wet.
Click to expand...
 
Is it strange that Mikunis work perfectly well on millions and millions of Japanese and other bikes yet when used on Nortons all kind of skullduggery arises to thwart their performance and to force one to consider switching back to the Amals? Is it like a human transplant recipient's body rejecting a newer, much healthier organ because it does not come from a related compatible source? :twisted:
 
dorteerts said:
Is it strange that Mikunis work perfectly well on millions and millions of Japanese and other bikes yet when used on Nortons all kind of skullduggery arises to thwart their performance and to force one to consider switching back to the Amals
Click to expand...

agree!
Personally, I am a huge fan of properly set up Mikunis. I've never had a problem with the slides or springs in any of them - ever.
I have a couple of sets of Amals in a box under my workbench. I'm pretty sure I won't put them back on any of my bikes.
(not one that I would want to ride regularly anyways).
 
Thanks but yes I know it's not the slide sticking, it's the cable. I did have the same problem on my old Commando when I fitted one. I will make a straight entry into the carb I think. Cheers.
 
My new Mikuni flat-slide (TM34) came with a 90-degree adaptor for the top of the carb that allows a smooth bend of your cable as it enters the top of the carb. They may be available from Sudco as a separate item?
 
FWIW I had an issue awhile back with a bent needle dragging on the needle jet causing a hesitation in the slide return. Not visible to the eye but evident on a flat.
 
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