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199B Mikuni Question

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Seem to remember somebody asking the other day about jetting for a VM28 Mikuni on a 199B but I cant find the post. I've got one fitted to one but runs like poo so just wondering if anybody knew a starting point for jetting the carb as it feels week. Don't have any spare Mikuni jets so will have to order and they aint cheap so just wondering what is the starting point on jets slide etc. Thanks

i mate it was me what was asking about the mikuni on a 199B. the jets are not that much few pound each put motocarb in your seach engin he as the jets and he is prity cheap. im leaving the bing on mine and puting a new slde and needel and new jets in it. before i buy anything esle. the bike is runing good but could do with some fine tuning. i like the 199A beter wish i hadnt sold it know i have spare motor for 199A but needs building. i ham looking for another 199A but id be after a deal with my 199B my 198A id nearly finished just took the wheels 2 be respoked.

  • Author

thanks for that but do you know what jets should be fitted to a Mikuni VM28 to use as a starting point ? Carb was supplied by Motocarb who was told what it was for but jetting is a mile out. I need to get it right which was why I asked. thanks

Hi OTF , when i had a 340 bully , i tried 2 28mm mukuni's , an old one i got from a auto-jumble , then a new one i got cheap .The old one ended up with a 130 main and 25 pilot , but the new one ended up with a 130 main and a 35 pilot .Both ran very very well , loads better than a crap worn out Bing . I seem to remember, i may of fitted a 250cc inlet manifold and rubber , the 250 rubber was a better fit on the mukuni carb .

Good luck

hi mr hewson ive just fited a mikuni to of my bults but the 199B as a bing on it ive just got new slide and jets but im thinking of a oko carb i may be having a biger airbox and the exhaust done as im keeping it know so should be alot beter.

  • Author

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Love to get one of those kickstarts. Thanks for the info Hewson. Why did you fit the fuel tap the other way round ?

Edited by old trials fanatic

Kickstarter came from Italy years ago , and having the fuel tap this way round , stop's it getting damaged if you fall off ;)

If you search the forum (Bultaco) I put the jet sizes on here from the OKO on my 340 some time ago. Must be pretty much the same for the 250

Hi Smelling 123 - Can't remember the exact number but I do know they are the same as Woody's 340 - that's where I got the info. I did try one size leaner on the pilot for a while but changed back. By the way belated cheers Woody :)

hi woody are the oko carbs beter than the mikuni? i dont know witch 1 to buy

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