250cc Maico Mikuni carb

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1/26/2019 5:23 AM

What is the best Mikuni carb to run in a 1981 250cc Maico 36mm or 38 mm ?

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1/26/2019 8:50 AM

I'm putting a 38 on my 1980 440. Some people say a 36 is better on that, so I'd think you'd be better off with a 36 on a 250

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“If I remember how this worked, you’d put a side on, and then you’d go and have something to eat, and then you’d put another side on.” … Mick Jagger

1/26/2019 9:19 AM

I use a YZ465 38 on my 1980 Maico 440. After getting the intake hose/boot, it worked with minimal jetting fuss.

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1/26/2019 5:10 PM
Edited Date/Time: 1/26/2019 5:10 PM

I'd run the 36.

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Earn it!

1/27/2019 5:34 AM

Thanks for the replies Bought a 250cc engine and it came with a brand new 38mm Mikuni Tried it on the bike and it was ok on the first 1/8th of the throttle then it was drowning with fuel with the 380 main jet it came with Was recommended that I try a 330 main It was still drowning with fuel that it stalled going up a gentle hill Gave up with it and tried it on my 490cc and it was perfect after altering the pilot jet 1 size so the carb was for a 490 Anyway going to a couple of bike jumble sales in the next few weeks so will look for one if you think the 38mm will not work

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1/28/2019 5:14 AM

I looked back into my old archives and found a Dirt Bike magazine article with Paul Krause doing a Mikuni conversion on a 1978 250 Magnum (same engine as the '81 mega 2)

They tried 34, 36 and 38 and decided that the 36mm worked best.
They used a 36 off a Yamaha IT250, but changed everything out.

Here are the specs.

Pilot jet 25
Slide cutaway 2.0
Needle 6F15
Main jet 300

Should be a good starting point for you.

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“If I remember how this worked, you’d put a side on, and then you’d go and have something to eat, and then you’d put another side on.” … Mick Jagger

1/28/2019 6:36 AM

indy_maico wrote:

I looked back into my old archives and found a Dirt Bike magazine article with Paul Krause doing a Mikuni conversion on a 1978 ...more

Indy,

I think you forgot that the 81 Maico 250 was the first year for the reedvlave.

Might make a little bit of difference in the jetting.

I’ve also seen a few 81 Maico 250 with a Kehine (sp) 36mm , don’t know much about that setup.

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00' BMW K1200 RS
83' Maico 490 ( The Project bike)
81' Maico 490- FOR SALE
03' KTM 525 SX (In ICU)
14.5 KTM 450 Fe- FOR SALE

1/28/2019 7:39 AM

bigmaico wrote:

Indy,

I think you forgot that the 81 Maico 250 was the first year for the reedvlave.

Might make a little bit of difference ...more

You're right! I was thinking that the 82 Alpha was when they converted the 250 to reed valves. Thanks for the correction. Still think it is a good starting point, though. What do you think?

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“If I remember how this worked, you’d put a side on, and then you’d go and have something to eat, and then you’d put another side on.” … Mick Jagger

1/28/2019 12:12 PM

indy_maico wrote:

I looked back into my old archives and found a Dirt Bike magazine article with Paul Krause doing a Mikuni conversion on a 1978 ...more

bigmaico wrote:

Indy,

I think you forgot that the 81 Maico 250 was the first year for the reedvlave.

Might make a little bit of difference ...more

indy_maico wrote:

You're right! I was thinking that the 82 Alpha was when they converted the 250 to reed valves. Thanks for the correction. ...more

I'm not a Mikuni guy, more in tune with the Bing's

But it should be a good starting point, Or the OP can check any of the Vintage Maico group sites & get more info.

You might be able to call sudco & get jetting information also.

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00' BMW K1200 RS
83' Maico 490 ( The Project bike)
81' Maico 490- FOR SALE
03' KTM 525 SX (In ICU)
14.5 KTM 450 Fe- FOR SALE

1/28/2019 3:33 PM

40 minutes after my last post yesterday I was in the kitchen sink cupboard looking for something when I noticed a Bing carb away at the back of it Was surprized to say the least Thought it must have came off a 490 as it did not have a choke on it Put on my specs and read the numbers on it and it was a 38mm one I have not got a clue how I acquired it as no bike I have had in the past ever used that model of 54/38/107 Took the jets and slide off the one on the bike fitted it to the new one put it on bike and fired up first kick and is running fine It sure made my day!

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