Yamaha Enticer 250 Carb Change

igottajob2 said:
Good to know. so if I buy a brad new carb from Dennis Kirk( a Mikuni 34mm) do you think I will be able to run it like it comes from them and it will work? How did you go about mounting the carb? Did you get a carb flange? How is your acceleration and top end performance?
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It should be a bolt on and go from them except for the jetting which will more than likely need to be changed. I have our jets written down in a notebook to get you in the ball park. I believe we had a carb flange laying around the shop that we used but as long as the stock one can clamp the slightly smaller diameter, the stock one should work out for you. Our 250 the way it is set up is very responsive and quick off the line and will top out near 64 - 66 I believe we measured last year which is very fast for a "Stock" 250 single. The picture below is ~40ft off the starting line at the eagle river finals for the single 340 fan class...we are 950



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That is awesome. Your 250 is a lot like mine. Same year it looks like. The response and speed your talking about is the kind of speed I use to get when the stock carb was in it's prime. The 250's will surprise you at how fast they can be. No one believes me when I tell them. If you could tell me what jets to get that would be extremely helpful. That way I can get them from Dennis Kirk the same time I pick up the carb and fuel pump and be done with it. Thanks for your help with this. Any other suggestions?
 
i had to buy a carb flange. the stock carb on mine bolted onto the engine, no way to clamp it otherwise on mine. i measured the center distance of the studs on the cylinder and found a flange in dennis kirk that was close. i did have to slot the holes for it to fit right. the carb sits very close to the secondary clutch. i made a bracket to push/pull the carb over a bit so it wouldnt touch.
 
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igottajob2 said:
Sounds good. did you know which one you got at all? What the size was? Also what jets did you put in it or change from the stock 34mm?
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the flange i used was Dennis Kirk Part #: 18850 i believe. i jetted for summer so my jetting wont be any good for winter. i would start rich and work your way leaner by checking your plug color and wash.
 
igottajob2 said:
Is a smaller jet leaner or is a bigger one? I am clueless when it come to jets.
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the bigger the number on the jet=richer, more fuel. the smaller the number=leaner, less fuel. its always best to start out to rich and work your way lean.
 
Ok good to know. These are the specifications for the carb I think I might buy new.
SPECIFICATIONS:
Spigot OD: 40 mm
Bell OD: 58 mm
Main Jet: 330
Pilot Jet: 30
Air Jet: 0.5
Needle Jet: 159 Q-2
Jet Needle: 6DH2
Throttle Slide: 2.5
Choke Type: Cable

How does that jetting sound? Will it work well?
I'm sorry for all the questions and I do appreciate your help.

The carb flange was 36mm to a 38mm. Does that seem big or will it snug up?
 
thats the 34mm carb, it should snug up. its really not that big of difference. im gonna say it will run with that jetting but i would check your plugs and wash. the jetting that comes with it isnt going to be perfect for your sled.
 
Thats what I have - the 34mm from Dennis Kirk; it fires up no problem. I now have to hookup nice new fuel lines and go with it - will rejet in the winter.
 
I would appreciate some follow up on this thread. This is what i have gleamed from it.
To replace a stock carb (using Dennis Kirk Parts):
Purchase a Mikuni 34mm (Part # 1655)
Purchase a Mikuni flang adapter (Part #18850)
Jet correctly (size 220) 2ooosrx can you size this for sure?

Replace straight gas with premix
using a fuel pump (part # 1609) to increase fuel flow

Miss anything?

I read on other threads you should probably remove the cog that drives the oil pump from the clutch housing to preventing seizing.
 
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woodland said:
I would appreciate some follow up on this thread. This is what i have gleamed from it.
To replace a stock carb (using Dennis Kirk Parts):
Purchase a Mikuni 34mm (Part # 1655)
Purchase a Mikuni flang adapter (Part #18850)
Jet correctly (size 220) 2ooosrx can you size this for sure?

Replace straight gas with premix
using a fuel pump (part # 1609) to increase fuel flow

Miss anything?
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Think you nailed it. Get an air filter while your ordering too. I'm at 3500 ft, so I need to go even smaller on the Jetting...in the process of doing that now.

Hey 2000SRX, would you have a snapshot of your engine with the carb on?

Thanks, Great thread.
 
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Hey DYsLeXiC,
Will you post your jet size when you figure it out? Also what air filter are you running? (easier to match jets)
 
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I might start working on our 250 either tomorrow or friday so I will have to get back with you on the pictures. As far as the main jet, it was a 220 or 230 depending on the temperature for OUR 250. Keep in mind that this jetting is for a motor nowhere near stock.
 
2ooosrx said:
I might start working on our 250 either tomorrow or friday so I will have to get back with you on the pictures. As far as the main jet, it was a 220 or 230 depending on the temperature for OUR 250. Keep in mind that this jetting is for a motor nowhere near stock.
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Thanks - it gives me a baseline to work with. Your at about 600ft above sea level and I'm 3500ft - I currently have mine at 220 as well and it starts no sweat, but boggy - if its not the jets then I may have a leak somewhere.

Were hitting -29C here today and I may not have the fortitude to go in this cold....I picked up a 200, 195 and a 185 main jet yesterday. I did change my pilot and 1.5 turns out on the air screw - it starts two pulls every time and idles forever.

My nephew's ET300 has a main jet of 200 and runs great. Now that I think about it, I should look at my ET340.
 
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woodland said:
Hey DYsLeXiC,
Will you post your jet size when you figure it out? Also what air filter are you running? (easier to match jets)
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Will do - I'm running a UNI Filter off Dennis Kirk. I think it was this one. It has an angle on it to help angle it out of the way of the steering column.

UNI Pod Filter
Dennis Kirk Part #: 305783
Manufacturer Part #: UP4229SA
 
I'm in the minneapolis,mn area. It's at about 900 or a little above sea level in most areas I am riding at. What jetting should I use? I got the stock 34mm Mikuni. Also I used my original carb flange and then hooked a Polaris boot up to it. You can get it from Dennis Kirk. So I used my angled carb flange and hooked up a rubber boot to it that would fit the mikuni. But any advice on jetting would be nice.
 
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.

 
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