Yamaha Enticer 250 Carb Change

2ooosrx said:
Here is the picture of my carb flange that you were asking about. We had to custom make an aluminum flange to account for the difference in mounting locations. Hope this helps. Also, we ran a 230 main and I believe a 32.5 pilot in the sled. I wouldn't exactly follow our pilot jet because we are running a UFO in our carb. Let me know if you have any other questions.



Thanks!! I'm running 220 main and 50 pilot - may need to fix that pilot. Tinkering away! Thanks Again!!
 

That is an interesting idea.....hmmmmmmmmmm....my ET340 could use some attention......
 
Would this be a VM or TM 36mm? Would you be able to provide the proper jet needle / needle jet combination to do this set up? Any and all help greatly appreciated!
 
Can some one post the numbers they are using for the throttle valve,jet needle,needle valve,needle jet,main jet and pilot jet only want to do this once any info would be great. just don't want to blow it up.
 
Just did this swap today on a 79 Enticer 250. I used a brand new Mikuni 34mm, followed the advice on a 220 Main and 50 Pilot jet to replace the stock jets. I installed the single outlet mikuni fuel pump, and blocked off the oil injection line by simply putting a screw into the stock hose. I took the linkage rod right off the oil injector as well.

Here are some pointers and good info for anybody thinking about doing this.
Parts:
Mikuni VM34mm carb
Mikuni single outlet fuel pump
Universal throttle cable
Carb flange
1/4 inch fuel line/vacuum line
2-1/4 inch pod filter (or velocity stack if you are racing it i guess)

The carb flange center to center stud spacing is something like 2-1/4 inches. The closest I could come up with to match the 34mm carb was a 2-3/8 (VM34/200 was the mikuni number on mine). And something that nobody is mentioning on here is that after you slot the holes inward to make the flange fit... you lose your clearance to turn the 12mm nuts as you are tightening them. I decided to remove the studs and bolt the flange adapter from the flange side into the angled intake piece. This worked better because I used motion pro 8mm bolts with the smaller 10mm heads. Allen head 8mm bolts would work best.

The rest is pretty straight forward as far as installation. I didn't think the universal throttle cable was going to work... but it did. I think mine was an SPI cable. I also started out with the 220 main/50 pilot with a velocity stack that i picked up cheap cheap with the rest of the parts. It ran pretty good just like that and the plug had a good color to it. I pulled the carb off to check some things and it was obviously inhaling some random belt dust and goobers that old sleds accumulate. I decided to run a UNI pod filter after seeing that to keep any further junk out. At this point the sled would no longer run happily with the 50 pilot jet.... just way too rich with the pod filter vs. the stack. So the only jet I had to change it with was the 30 that the carb came with initially. Changed it and it ran good again... starts first pull every time.

I proceeded to plow through the 18 inches of fresh powder we just got with it for 10 minutes or so. Brought it in to check the plug and it had lightened up significantly. Like too light. Not white, but a light tan. So this is where I am at. I ordered some 35's and 40's to fiddle with. I think the 35 might be the ticket. Depending on what you are going to be doing with the sled, I think the 34mm carb is almost too big. Even with the jetting too lean or too rich, you have to keep it "on the pipe" to get any response out of it. This sled has 130PSI of compression too, so its not the engine that's holding it back. It was a fun project though, and that keihin carb can rot in hell. :WayCool:

-Adam

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Thanks moore. I got most of the parts for mine but forgot to buy a choke so now I have to wait a couple of days more. I bought the "choke conversion kit" in hopes to use with the stock choke cable. Gonna see how that turns out? Also the carb I have is a 32mm so we'll see how different it runs. Got a uni pod filter with it to keep all the grime out. I ordered a few different jets. I have a 50 pilot, 35 pilot and I believe a 40 pilot in the carb right now. Also have a 340, 330, 280, 260, and 240 main jets to tinker with. I am running a q-2 tube (needle jet) and 6dh8 needle. I'm gonna start rich on everything and just work my way lean but I figure probably 260 on the main, middle clip on the needle and 50 on the pilot till I get it right.
 
The carb I ordered came set up with the provisions for a cable operated choke. I used the stock cable and it worked fine. I think a 30mm would probably be a good all around carb. This sled is used to scoot around the woods by a farmer that does maple syrup, so its not seeing a lot of WOT by any means.
 
So I put the 35 pilot in today and it was super blubbery down low, and I had to turn the idle all the way in to get it to work. Too much fuel. Just threw the 30 back in it and its crisp again. Looking at the chart that dyslexic posted maybe I am worrying about nothing as far as it being lean. Anybody else think that the "normal" color that they show on the second link looks too lean for a 2 stroke??? I usually like to see a cardboard brown or a little darker.

Anybody have a quick and dirty way to know which way to go with the main jet? It runs good past 1/2 throttle, not blubbery like its overly rich. I'm wondering if I should bump the main to get a touch more color on the plug.

*Edit- I'm running the 220 main as suggested btw.
 
moorepowersports said:
Anybody else think that the "normal" color that they show on the second link looks too lean for a 2 stroke??? I usually like to see a cardboard brown or a little darker.

I agree it does look lean in the "optimum operating region" picture. If you scroll down there's some more pictures to compare to.

So I started on my sled today and come to find out the f(*&@#*($ing choke is an odd sized thread so the new mikuni choke kit I got, doesn't fit (too small but the plunger fits good) I tried to force the keihin choke in it and it started to strip the threads out so I dunno I might have to tap it bigger, screw a bolt in, drill it, and tap it to the mikuni choke size. That's like the absolute last thing I want to do but I want to get this thing running before the snow melts!
 
Here is what I'm working with. I threw a fresh plug in it and gave it a whomping around the yard here. I keep expecting it to sink the the deep powder, but it keeps on chugging. This thing really goes when you open it up! I know, I know... its blurry. My cell phone camera has no kind of macro setting that I know of. The left is a new plug, the center is with the 30pilot/220main, and the right is with the 35/220.

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I was getting a ton of smoke with the 35 pilot, and all it did was smoke and not move with the 50 pilot. I believe I'm on the right track now.
 
The middle plug looks pretty good from what I can see.. You do have to keep in mind that if the temp drops, the air gets more dense and you need to run a bit more rich. If you are trying to set your jetting and leave it, you might want to find a way to run a TAD richer than the 30/220 combo. Maybe even try shimming the needle or moving it up one notch with the 30/220 setup? You can always move it back if it's too rich
 
Crazy Axe said:
The middle plug looks pretty good from what I can see.. You do have to keep in mind that if the temp drops, the air gets more dense and you need to run a bit more rich. If you are trying to set your jetting and leave it, you might want to find a way to run a TAD richer than the 30/220 combo. Maybe even try shimming the needle or moving it up one notch with the 30/220 setup? You can always move it back if it's too rich


Middle Plug Looks real good. If I recall, as the outside temp goes up then it will run richer - if it gets colder then it runs leaner. Is that right?
 
DYsLeXiC said:
as the outside temp goes up then it will run richer - if it gets colder then it runs leaner.

Exactly.. The air is less dense the warmer it is and vice versa. So since he's running 220/30 combo right now, if the temp drops 30* (hypothetical number) from where he jetted today, then he might want to run the 220/35 or maybe a 230/35 (or whatever satisfies the proper air/fuel mixture) Also air is less dense at higher elevation so you would use smaller jetting in that case as well. Humidity can also play a factor in getting proper mixture and I believe it is higher humidity, more dense but not certain on that one.
 
So i finally got all my parts together and got it put together. It starts but it's running RICH with 35 pilot and 240 main. I've been doing some calling around trying to find a place local to pick up a 30 and 25 pilot and a 230 main but most of the places around here the service guys seem like they have no idea wtf I am talking about. Also, I'm going to end up needing a mikuni specific choke cable. The stock one works, but there's not enough throw in it to open the enrichment passage fully. Obviously it's not an issue right now since I'm running so rich right now.
 
So I took it to my "mentor"'s place and he/we came to the conclusion that I need a leaner needle and needle jet. We swapped out a P-2 tube and 6DH4 needle from one of his other sleds and it ran a LOT better.. Going to order a O-0 tube and 6DH4 needle here pretty soon and she should be about done. Got 8" of fresh snow today so as long as it doesn't get too warm and melt off I should be having a LITTLE bit of fun before the year is over!
 


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