250cc Maico Mikuni carb

Maicoman07
What is the best Mikuni carb to run in a 1981 250cc Maico 36mm or 38 mm ?
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indy_maico
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indy_maico 1/26/2019 8:50am
1/26/2019 8:50am
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
riv187
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riv187 1/26/2019 9:19am
1/26/2019 9:19am
I use a YZ465 38 on my 1980 Maico 440. After getting the intake hose/boot, it worked with minimal jetting fuss.
MaicoJC1
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MaicoJC1 1/26/2019 5:10pm
1/26/2019 5:10pm Edited Date/Time 1/26/2019 5:10pm
I'd run the 36.
Maicoman07 1/27/2019 5:34am
1/27/2019 5:34am
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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indy_maico
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indy_maico 1/28/2019 5:14am
1/28/2019 5:14am
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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bigmaico
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bigmaico 1/28/2019 6:36am
1/28/2019 6:36am
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 250 Magnum...
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.
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.
indy_maico
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indy_maico 1/28/2019 7:39am
1/28/2019 7:39am
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 in the...
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.
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?
bigmaico
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bigmaico 1/28/2019 12:12pm
1/28/2019 12:12pm
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 in the...
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.
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. Still think it is...
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?
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.
Maicoman07 1/28/2019 3:33pm
1/28/2019 3:33pm
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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