Yamaha Enticer 250 Carb Change

Both answers..

Inlet Vlave is the main fule shutoff.

Next..

If you bought a motorcycle carb it wil have 3.5 inlet hole which is for gravity feed. You need a 1.5 inlet needle.

Air Jet..is used for that final air mixture as the fuel enters throat. Best deal is just to remove it or put the #2 in..

I always took it out. The racing snowcross carbs have it out as stock and I bet the Yamaha 2/ MX bikes don't have it in either.
 
The-Hoss! said:
Before doing all those changes. Have you tried bypassing the fuel shutoff on the side of the fuel tank?
Mine gave me the same scenario. I bypassed the shutoff valve
& it fired right up.
Let me know how you make out
Hoss
Orangeville, Ontario
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Thanks Hoss, We checked the valve, and it flowed gas when we tested it without a hose. I appreciate the suggestion.




RJH said:
Both answers..

Inlet Vlave is the main fule shutoff.

Next..

If you bought a motorcycle carb it wil have 3.5 inlet hole which is for gravity feed. You need a 1.5 inlet needle.

Air Jet..is used for that final air mixture as the fuel enters throat. Best deal is just to remove it or put the #2 in..

I always took it out. The racing snowcross carbs have it out as stock and I bet the Yamaha 2/ MX bikes don't have it in either.
Click to expand...


Thanks kindly for the information, I was exactly looking for that. I'll try removing the air jet to see what happens. I also notice there is a slight richness bog at low throttle. Don't get me wrong, it idles good, and runs great - fast, but it's "pick up and go" isn't as snappy as it used to be. But once it gets going, its fast.


Crazy_Axe said:
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
Click to expand...

How did this work out for you in the end? Did you get the parts? Did it clean up the low end bog? Im running the following,
Main Jet: 220
Pilot Jet: 30
Air Jet: 0.5
Needle Jet: 159 Q-2
Jet Needle: 6DH2
Throttle Slide: 2.5

Thanks!
 
ALso - Put a little pressure to the fuel tank by blowing into the fuel line vent tube (not with an air compressor-and be carefull!!)- had to do it to our old 80' ET250 years ago and i now have yet another 80' 250 that needed the same thing to get the fuel "primed" to the carb. they seem to do that after they sit for long periods of time - you'll be suprised !!

** With Stock carburetor of course.

just remembering from way back when....hope it helps!!
 
MSASRX said:
ALso - Put a little pressure to the fuel tank by blowing into the fuel line vent tube (not with an air compressor-and be carefull!!)- had to do it to our old 80' ET250 years ago and i now have yet another 80' 250 that needed the same thing to get the fuel "primed" to the carb. they seem to do that after they sit for long periods of time - you'll be suprised !!

** With Stock carburetor of course.

just remembering from way back when....hope it helps!!
Click to expand...


LOL, too late now! Although I appreciate everyones suggestions, I've already converted the et250 to a vm34. I managed to find a 6DH4 needle at my parts supplies in town here - get this - for free. O-0 tube has been ordered... hopefully that fixes the slight low end laziness.

One thing to mention to anyone reading this, wanting to convert their et250 to a VM34, make sure you get the "ANGLED FILTER" NOT THE STRAIGHT ONE! The clutch interferes with the filter when it's fully opened, therefore, if you don't make a bracket, like someone did in this thread, the straight filter will get chewed by the secondary clutch.

Will keep you all posted once i get the O-0 needle jet.
 
stanage said:
LOL, too late now! Although I appreciate everyones suggestions, I've already converted the et250 to a vm34. I managed to find a 6DH4 needle at my parts supplies in town here - get this - for free. O-0 tube has been ordered... hopefully that fixes the slight low end laziness.

One thing to mention to anyone reading this, wanting to convert their et250 to a VM34, make sure you get the "ANGLED FILTER" NOT THE STRAIGHT ONE! The clutch interferes with the filter when it's fully opened, therefore, if you don't make a bracket, like someone did in this thread, the straight filter will get chewed by the secondary clutch.

Will keep you all posted once i get the O-0 needle jet.
Click to expand...


Finally got the 6DH4 needle and 159 O-0 needle jet. The sled is lightning fast, and picks up both skiis when the accelerator is pressed. Needle clip is in the middle, might try raising or lowering it to see if it changes anything, but otherwise it's all done, and it rocks pretty hard! :2strokes:
 
Toss the Kehin, Toss the oil injection- ETC 250 ET is a new sled.

Hi: I just found this forum and this thread:
I thought I would share some stuff on a project I finished this morning, not really bragging, it took way too long, started this fall, My grandson got a pretty minty looking ET 250 to drag race and ride two winters ago, well it nearly drove my son and I over the bend, would not run right, one time would start-- next time not, sometimes ran great. went racing in Earl Grey last Feb., couldn't get it to start, missed his class. took it home started right up and Grandson rode all over. My son took apart kehin cleaned , set fuel level replace pulse line , all these things a feat to do if you have ever worked on ET with oil injection. Anyways he brought it to me this past fall. well about that time I stuck my finger in a meat grinder so never got at it. Xmas came and family was home but worked on Son's thunder jet. So yesterday I said that's it ET will be fixed. Took off kehin carb, thought about it and tossed it. . Tried to see if seals were leaking couldn't even see PTO seal because of oil pump, couldn't get recoil off without taking off oil injection tank, pulled engine, thought about oil injection-- took off oil tank-- tossed, took off oil pump-- tossed, now we are getting some where , PTO oil seal shown in pic below. So problem solved-- well not completely, the ET has a filter in the fuel tank on the fuel outlet fitting, you can't even get to this till you remove the oil tank. Well filter had never been changed in ET's life and, had collapsed from suction as was full of yellow varnish and other stuff-- tossed filter. Now mounted on oil tank is a fuel shutoff in main fuel line with a toggle switch on dash. Be dammed if this wasn't seized only about half way open, cable moved but fuel shutoff did not. --tossed this. Went to my good used parts, selected a pretty good looking 34 mm carb, Cleaned and good used parts in it , mounted a nice cleaned used single fuel pump (off a sno jet) gotta be a good one. new choke and throttle cable, took a wee bit of throttle block mod to get it to idle and open full . Here are jets and parts I ended up using in carb. Started out too rich, didn't really have much to go by, Yamaha never used a micky on their little single.
Main jet--220 -- think it's still a bit rich.
Needle jet--159 05
Needle 6DH7 have it in three, may need to go up one.
Piolet 30-- seems to idle good and throttle response is good
1.5 inlet
2.5 slide,
Anyways pleased with how it turned out, hope this post can help someone thinking about doing the same thing. ET starts with one pull in shop. left it outside overnite took two pulls with choke, and goes faster than Grampa wants to go anymore . If anybody has any tips, comments or questions please do reply. Feel a little bad about tossing kehin, don't think there was any thing wrong with it. Cheers Jack

PTO seal--rotted right out in oil pump housing

405385694.jpg


Tossed parts

405385690.jpg


Made bracket and mounted fuel pump on fuel tank where oil tank had mounted.

405385692.jpg


close up

405385693.jpg


out on the snow

405385700.jpg
;)
 
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those seals are the root cause of alot of poor running sleds. I just rebuilt a spare ET340 motor that needed new seals - it'll be dumped into an ET300 chasis....then i'll rebuild the 300 motor and keep as a spare - I suspect the 300 motor needs new seals as well, but will get'em either way.

Long Live the ET250.
 
I've got an '80 et-250 I've swapped in a 34mm VM mikuni. It came with the keihin but I killed it trying to set it up so I swapped a 26mm VM in originally but wasnt happy with how it ran but it kept the power down which was good for the kids. I just put the 34mm on this year and have been tinkering with the jetting. I came across this thread and referred to it often to get my jetting dialed in so I will contribute what I've come up with so far that seems to be working best so far.

Pilot: 30
Needle: 6dp1 on 3rd clip
Tube: O-0 (thanks to this thread)
Slide: 1.5 filed to about a 2.0 cut away
Main: 220
Compression cold: 120psi
Compression hot: 116psi
Premix 40:1 w/87 octane
Altitude: about 2000'
Temp: about -10c, just below freezing
The plug is McDonald's coffee cup brown. No sign of black. I think there's still a lil tweaking room left, if I find it ill be sure to post more.

This is pretty good so far. I ran the 6dh4 needle like in this thread but I was a lil lean on the bottom clip still so I put the 6dp1 which has a way steeper taper. I started on the top clip and it seems to work best in the middle clip. I've ran a 210 main, bumped to a 220 and notice an improvement. I will try a 230 next. I also ran a 3.0 cut away but the 1.5 I ground cleaned up some of the bottom end bog I was getting with the 3.0. I think some of that bog is from my timing too advanced. I had the engine apart and put the stator plate in with some extra advance when I reassembled.

I'm still experiencing a loss of power when climbing a hill but the 220 main and 6dp1 needle have cleaned that up a fair amount. On the flat it runs out clean and nice lots of power. If I feather the throttle down and back up on the "hill climb" it clears up and zings along again. I think some of this might also be contributed to the timing having too much advance. We will see.

I'm running the secondary with zero preload. Climbing the hill it's barely shifted out, belt has maybe 1/4" drop down the sheaves. I get full engagement on the primary, the secondary doesn't quite shift out all the way but I haven't been able to find a long and smooth enough run to hold er open for a good duration. Otherwise the shift feels good, you can feel the secondary start to shift out after the primary has fully engaged. I had the secondary spring with maybe 60 degrees of twist before (rotated the helix one tooth over past straight up). And it didn't shift out as nice as is it does now, back shift was way better tho. Less preload means easier shift out on the secondary and less back shift. When I had it cranked up it would back shift (gear down on decel) a lot better but it didn't go as good in the deep. When I decel is with the spring straight up (0 degree twist) I can feel the secondary staying shifted out when I give it throttle again, but a couple blips of the throttle shifts it back in if I need it to.

I know a lot of that isn't pertinent to the carb but I thought I'd add it all in there for future reference for anyone tinkering on a 250 that comes across this thread in a google search like I did.

I also drilled the spot welds out on the steering post bracket and bolted some flat bar and gussets down to relocate the bracket forward a couple inches, maybe about 3"-4" I haven't measured. I can just squeak the helix and spring out on the secondary. The carb clears just fine and lots of room left for removal.
 
I recently did a carb swap on a 1979 250 Enticer. Used a Mikuni VM34 with jetting as listed above. Works great, the only problem I am having is the original (chrome) thumb throttle does not pull the throttle valve all the way up so I can get a wide open throttle position. The sled is all original in appearance, and near mint condition and I didn't want to change the original thumb throttle, I like that original look. I did grind the thumb throttle a bit and reformed it some but it cannot be reformed enough to achieve what I want. Anyone have any success with this or any ideas how to get a fully open position on the throttle? I also reconnected the oil injection by using a split throttle cable and connecting it to the oil pump rod which I have not seen anyone do before.
Awesome little sled. yammieET.JPG
 
I have ran into this issue many times when switching from the butterfly carb to a round slide on our vintage yamahas. What I do is cut the lever and add metal to it making it longer with more throw. you need access to a welder to achieve this. you can also cut a slit in both sides of the lever, stretch it and fill the void with weld. a little grinding and polishing and a shot of clear enamel or black paint gives it a oe look.
 
DJSOPA said:
I have ran into this issue many times when switching from the butterfly carb to a round slide on our vintage yamahas. What I do is cut the lever and add metal to it making it longer with more throw. you need access to a welder to achieve this. you can also cut a slit in both sides of the lever, stretch it and fill the void with weld. a little grinding and polishing and a shot of clear enamel or black paint gives it a oe look.
Click to expand...

Thanks for the tip. I do have a Mig welder and Tig welder option. I will try that. Makes perfect sense.
Thanks!
 
If you go back to page 7 there are 2 pics of how the stock throttle levers were cut out to achieve full operation of the Mikuni....it worked well on mine.
 
Thanks, I ground my throttle lever that way and my cable is adjusted properly but I'm still only getting about 75-80% throttle. Sled works as good at 75% throttle with new Mikuni setup as it ever did with that old Keihin. Just trying to make it even better. Thanks for the tip.
 
Hi I recently did a carb swap on my 79 ET250 to a VM34 Mikuni and have run into some issues in getting it to start on its own and idle. The carb came with a 330 main jet but i changed it out to a 220 main jet. I can start it by spraying some fuel into carb and then it will run but once I throttle down it dies. My specs are:
Main jet - 220
Pilot - 30
Needle jet - 159 Q-0
Jet needle - 6DH3
Throttle - 2.5
Main air - 2.0
Needle - 1.5

I am at 2800 feet elevation. Any suggestions on changes or what I can do? I removed the oil injection and added a single fuel pump, and bought a choke conversion kit. How do you get your choke to seat properly? I think the throw off my original choke cable is too long and will not allow the choke to work properly.
 
I'm trying to do the same conversion but I'm not too sure on what the cut away is supposed to be. I see guys using 2.5 slide. Is that the cut away? Sorry if this is a dumb question.
 
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