Any interest in an ET250 Mikuni swap howto?

C

Crazy Axe

New member
Joined
Dec 16, 2010
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42
Location
Burton, MI
I should be getting my parts Monday.. Was thinking about putting together a howto regarding swapping the keihin out for mikuni. I would take pics and write up a fairly detailed instruction on what is needed, why, and how to put it all together.. Would any of you guys like to see something like that on here? I figure it would cut down on some of the "Can I do this to my enticer?" questions and whatnot.. Maybe mods could make it sticky if I write it up well enough? ;)!
 

Yea maybe.....i'll let you know soon - in the middle of trying to rebuild the stock keihin...
 
That would be great Crazy Axe Maybe we could add it to the Tech pages ;)!

Hows the weather there in Bur-tuckey, :Moon: jk neighbor, suppose to get 2-4 tonight!
 
Sno-Xr said:
suppose to get 2-4 tonight!
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:letitsnow haha seriously we need more!!

I didn't realize there was anyone from this forum so close to me also didn't realize there is a "tech section"
I should be spending hours and hours reading over there! :jump:
 
MSASRX said:
Yea maybe.....i'll let you know soon - in the middle of trying to rebuild the stock keihin...
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Let us know how that works out.. That would also be some good info for those of us who want to keep it original. Like finding a rebuild kit that fits it and variations between the keihin models. I'm pretty sure I read there are two different models they used on these year sleds but that's as far as I know about it.
 
will be lots of interest in the how to as i have seen at least 4 threads on guys wanting/doing it to the et250s this season alone.
 
I would definately be interested in seeing how you do this, I'ved been trying to do this swap but can't get it to run right.
 
akdoorider said:
I would definately be interested in seeing how you do this, I'ved been trying to do this swap but can't get it to run right.
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Do you need help with tuning the carb? What size carb and what specs on pilot/tube/needle/fuel inlet/main/slide are you running? How is it not running right? Won't start? Won't idle? Bogs? Dies?
 
Crazy Axe said:
Do you need help with tuning the carb? What size carb and what specs on pilot/tube/needle/fuel inlet/main/slide are you running? How is it not running right? Won't start? Won't idle? Bogs? Dies?
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I was trying with a tmx 34mm carb off a mxzx 440 just using the stock needle with a 45 pilot and 290 main using a single outlet fuel pump. Sled will start but will just bog and eventually die. I think I'm going to try and find a 34mm round slide carb and try that out. Also running a unifilter.

What carb specs to you reccomend for a 34mm roundslide carb and do you know of any type of snowmobile that it would be good to get a 34mm carb from?

let me know, any info would be awesome.
 
Being the new owner of an old 250 I would be very interested in this swap.
Especially with the step by step details
 
akdoorider said:
I was trying with a tmx 34mm carb off a mxzx 440 just using the stock needle with a 45 pilot and 290 main using a single outlet fuel pump. Sled will start but will just bog and eventually die. I think I'm going to try and find a 34mm round slide carb and try that out. Also running a unifilter.

What carb specs to you reccomend for a 34mm roundslide carb and do you know of any type of snowmobile that it would be good to get a 34mm carb from?

let me know, any info would be awesome.
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You could probably get the TMX to run but you may need to run a lesser slide like 2.0 or 2.5. The needle looks like a 5 series so it should be shorter and start running more fuel sooner, which is good as the TMX is supposed to allow more flow. It just sounds like you need to experiment with your tuning. Maybe run the needle higher 1 clip at a time and see if you can get it to keep from dying. The only way to know what it needs is to experiment with it.
As for the round-slide setup. You will be okay with just about any 34mm but you are still going to have to do some tuning..
http://www.psep.biz/store/mikuni_carburetor_part.htm this is a very good site to get jets from they are 3 and some change for mains.. much better than DK if you need to buy a few. But I would try running more rich first, and then if nothing works go back to the first setup and work your way lean.

I will try to include as much as I can about tuning the carb but I'm not that experienced with it. It will be more of a "Here are the parts you need and this is how you swap it" and if anyone who is a little better with the carb tuning wants to chime in, good. If not, I will try to involve as much info as I can.

Also, this might be a good read for you: http://www.mikuni.com/pdf/vmmanual.pdf
 
BTW the carb I got for this project, I bought on ebay for roughly $30 shipped. It WAS missing some parts so I had to get a hold of some stuff to get it complete but no biggie. I did have a problem with it being advertised as a 34 and actually being a 32 but it should still run good (might even have a little more low-end grunt with the smaller)
You have to think of it this way tho.. Most snowmobiles are at LEAST twin cylinder now.. Being you are swapping onto a 250, find a snowmobile that is twice that displacement with two carbs. Any 500 will be close. However, the amount of compression, the spark plug, the way the fuel burns in the cylinder, the efficiency of the exhaust leaving the cylinder, all that stuff is going to be different. So you will need to tune accordingly.
 
...still waiting to get my choke, jets, and retainer plate for the carb before I start writing this up


EDIT: Snowpocalypse '11 and PSEP just sent out my parts today :o| :o| :o|
(I ordered Friday) Oh well at least I can get my buddies polaris out and maybe blow that one up too haha :letitsnow
 
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The guy I bought my 250 from did this conversion. Wish I knew what all of the parts are from. It starts in a couple pulls, idles all day long, and runs high 40's with my 10 year old on it.
 
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