Sticky Mikuni

photoguy_43420 · Oct 31, 2009

I have a 73 Commando that seems to have a sticky slide, its has a Mikuni carb on it. The strange thing about it is that when its not running the slide snaps right back when its under power about a quater turn on the throtle then its seem to stick for just a few seconds when you let of on it. I have lubed the cable and throtle and every thing seems fine any tips on fixing this?

Thanks,
Guy

Cookie · Oct 31, 2009

Does it have a fiberglass tank??

photoguy_43420 · Oct 31, 2009

No it has a steel tank.

splatt · Oct 31, 2009

Not uncommon, try adding a Amal spring inside the Mikuni spring,it doesn't make the throttle to heavy but just check the slide still goes all the way up you may have to shorten the spring.

MEHAVEY · Oct 31, 2009

Also throw some SeaFoam & MMO into the gas and see if that doesn't loosen things up.

photoguy_43420 · Nov 1, 2009

I will give it a try.

Thanks,
Guy

bpatton · Nov 1, 2009

Guy,

The amount of force on the slide is pretty high when the slide is shutting on de-acceleration, so it makes sense that you would notice the problem then and not when the motor is just sitting. Mikunis don't wear out as fast as Amals, but they do wear out, and when they do weird tuning and sticky slides are what shows up. Are you using a 45deg cable adjuster at the carb? Is it a 34 or 36? The 36 is a taller carb and sometimes there's not enough room for the best routing. I had a throttle cable break a strand last spring that showed up like what you're describing, but it got much worse in a hurry.

MEHAVEY · Nov 1, 2009

+1 for bpatton's coment above.

I would also offer that whatever else MMO does (or doesn't do), it does lubricate the moving/interface parts in the carburetors. For AMALs with like-metal slides & bodies, that's absolutely critical. Even with (aluminum slide?) Mikuni's it guards against uneven wear/galling along the huge wear surfaces of the slide/body.

The effects of today's gas mixes are brutal otherwise.

photoguy_43420 · Nov 3, 2009

Its a 34mm I do not have a 45deg cable adjusteron it. I know what Sea foam is but what is MMO? Could you take raw Sea Foam and just wipe it on the Slide?

Thanks,
Guy

batrider · Nov 3, 2009

Splatt has it right. Definitely needs the Amal spring along with the Mikuni spring.

Russ

SteveMinning · Nov 3, 2009

I ended up adding an Amal spring to mine too. Works great.

MEHAVEY · Nov 3, 2009

MMO - Marvel Mystery Oil.

Find it in any auto store in the oil additives section and use about 1 oz/2.5 gallons gas (which is fortuitously about the capacity of Roadster tank fillup).

While greater spring force never hurts, the "sticking" part needs to be resolved.
Carb body warp is one thing, but fouled/galled surfaces can be addressed relatively quickly.

MMO wil immediately deposit a thin lube layer/probably stop any sticking not caused by warped carb barrels.
The SeaFoam will gradually clean up/keep clean any varnish within a tankful (or two).

Sticky Mikuni

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