MIKUNI 25mm CARBIE MANUAL.

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mudjimba

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I was just thinking, are 25mm mikuni carbs even a genuine product? Im pretty sure the Mikuni VM series only comes in vm20, vm22, vm24, vm26... u get the point. I have a "Mikuni 25mm carb" and it doesn't even have normal mikuni jets, my main jet is a big long sucker that rungs all the way through.

Bloody Chinese, i tell you.
 

bmracing

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hi guys im having a bit of a problem with my bm racing 110, when i get it started up it splutters and has loss of power and backfires,when i get the biting point it slowly tuggs away and when i release the clutch fully it cuts out (not stalling it) i seem to have a decent enough spark i really dont have a clue what it could be:( and the exhaust gets really hat very quick.

i would apriate it if you could get back to me on this, cheers p.s i bought this 2nd hand and think that it has a stock carbby on it. :S
 

mudjimba

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First thing, replace your spark plug. I would recomend a NGK plug. There is a converter on there website, just type in the code on yours, and it will tell you which one to buy.

Now with one of the main ingreadients out of the way, you will want to clean out your carby. Its easy. unscrew the the fitting on your air filter so you can slide it off. theres 2 screws the hold it onto the manifold, just grab an 8mm spanner or socket and take em out. Then unscrew the cab on the top and take out the slide. Then when you have it apart, theres 2-4 screws on the bottem you can take out to take it apart. There a big float and 2 jets, which a ong skinny cylinder things. Unscrew them and give them a blow out, make sure therenot blocked up. And pour some fuel around the carby to wash it out, just try not to get it on the rubber gasget. *You need this place dirt free*. Put it all back together the way you found it. You mightwant to try and wash out your air filter to, just make sure its 100 dry before it goes back on. If theres any dirt oil or water inside the bowl, it will black the jets from suck up fuel, therefor make your bike choke and stutter.

Theres 2 screws on the side, one is the revs and one is the air/fuel ratio. The rev screw is the one clossest to the sentre of the cylinder that ones fine. Screw the other one in untill its firm, but dont tighten it. Then unscrew it 360 degrees, then a ferther 90 degrees. This will be around the right mixture you want to run, but u can change it within the 90 degree mark in most cases to make it run better.

You also may want to pull the tap off your fuel tank and flush it out, just dont reck the threads on any holes. And if you have a fuel filter, you should replace it if its old.

Check the condition of your coil, which is the plug the goes onto the sparkplug, all the way up to the big cylinder part with 2 wires attached to it. Make sure its in good condition and not melted or split.

Its also worth checking your Valve clearence. They may have hammered them selfs in. Any motorbike mechanic can do this easily, and you can do it your self if you know how, although the internet lacks good guide about it for mini 4 stroke engines.
 

jaime

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does anyone know whats wrong with my mates bike????
It runs all good but then the bowl will fill up and keep filling causing him to lose alot of fuel????
Its got us stumped whats wrong with it ay....
Oh its on a AGB-29......
this happened to me it turned out to be the overflow control it was caused by a grain of sand stopping the needle in the float from closing hence the fuel from the tank kept on flowing into the carb till it filled up to the overflow and just leaked out.
to fix this you take out the four screws and get the float out by taking the float pin out and then pull the needle out and clean it aswell as the seat that it sits in
 

SSR70cc

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I just bought a 25mm Mikuni before I found this forum. It don't work on a
72cc Ducar motor. Going to put my original carb back on and see how it goes.

*by the way the MIXTURE screw is under the carby you need to take it off to adjust it*
 

[email protected]

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The screw you want is directly under the venturi (big opening, or throat) screw in is leaner, out is richer.
 

dylanatomik70

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the only way I can get my 70cc ducar to run is put the small throat manifold back on but it defeats the purpose. It wont run with big diameter mnifold that matches mikuni
 

Gecko

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Sounds like, you may have a sticky needle in the float bowl.
Take the bowl off, turn your fuel tap on.
Lift the float gently with your finger till the needle is just closed.
Fuel should stop running before you have to squash the little spring in the needle.
If not, new needle and seat.
 

[email protected]

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hey guys. i think i got a 25mm or 26mm mikuni carby and when i start my bike when its cold it never wants to idle. my dad has adjusted it but it just doesnt want to idle. i have to rev it to keep it going. once the engine is warm though it idles fine, probably a little bit to high. would anyone know what the problem is. Also how to fix it. help would be very appreciated.
 

pickles09

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hey guys
me cuzins bike was runnin like poo and it always worked good for a minute then turned too poo the reason being that wen he revved the bike hard the butterfly clip was pushed down putting the choke on and makeing it runn like shit so just thought id let yas no that if ur carbie is running like shit that is another thing to check with your carbie.

TO FIX:
pull the choke lever off and there is a litle metal clip that holds the choke lever on bent that in a litle bit to make the choke lever tighter


This will fix your problem
 

adr125pro

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dont need a picture jus get carb/choke cleaner take yur carb of nd apart nd spray it with the cleaner scrub with a tooth brush nd take a peice of copper wiring nd scrape the inside of yur jets then put bak together make sure to dry it tho nd do not let the rubber gaskets get the cleaner on them
 

pbk

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yer mate easier said then done for someone doing it there first time though there is a video on this site oh how to clean it, made by a member of this site too
 

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