Yamaha Enticer 250 Carb Change

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igottajob2

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Hi- I have a 1980 Yamaha Enitcer 250 and I am sick of the stock carb. It likes to decide when it wants to work and I want something more reliable. So I went to a grass drag and talked to a guy with a racing vintage enticer. He showed me what he had done and told me to put a 38mm mikuni slide carb on it. So I went and got one. I have several questions with this carb switch. One what do I do with the oil injection ports after I disconnect it? What do I do with the line coming from the crankcase? Do I use that line as the fuel pump or do I buy a fuel pump? Do I need to rejet the carb? If so do I use the jets from my stock carb? Anything else I need to know and any help at all with this would be great. Thanks! -Jake
 
I know that you will need a fuel pump for sure and will need jet it appropriately. As to the rest of your questions, I am eagerly awaiting some responses. There are tons of threads out there talking about what a POS this Kehin is and barely any talking about how to replace it. I have rebuilt the Kehin on my 79 ET250 twice so far and it still is not right. I have followed all of the advice with regards to fuel level bolt adjustment, pulse lines, etc. etc. It was running pretty good last night now nothin unless I prime it. Please Please Please, somebody post a step by step about a carb swap to a bowl type carb. I will even pay for the info if necessary. On the flipside, is there a direct bolt in replacement for the Kehin??? Thanks,

Phil
Priest River, ID
 
I haven't actually done this swap, but did look into it a bit. The line from the crankcase will drive your new fuel pump (pulse) which you will need to add. You can either fab a bracket and cable stop and then use a split cable for the oil pump. Or you can pre-mix oil with the gas and not use the oil pump. Or you could leave it all on there and just leave the arm fixed in one position.

I have actually been considering putting a single Mikuni butterfly off a Phazer 485 on it. Maybe cut the rack and use the oil cable from the carb. I haven't checked to see if it will fit or not.
 
A 36 mm would be best for a 250..and that is on the big side…

The line from the engine connects to pump..that pumps fuel to the engine.

If you bought a motorcycle carb ..it will have a 3.5 +/- inlet needle designed for gravity feed. To use a pump..it needs a 1.5 +/- inlet needle.

Mix gas oil..you have no chance with a scab setup…to get it right.

Depends on what carb you bought VM, TM. TMX or TMXx . They all have different tuning applications…

If it is a fixed emulsion tube..you may be in trouble. The tube is designed for the specific engine it was designed for. If you have a VM or TM..you have a chance…
 
I have a 38mm, at least that is what I'm told. How do I find out the carb size? Here are some pictures. Take a look and let me know if this will work. I spent $40 on this carb and I want to use it if I can. If it will but I have to re jet it what jets do I have to get? Can I use the same ones from my old carb? I need to get this done before the snow flies. I am sick of it not starting all the time so any help from anyone would amazing. Once this is done it should gun dependably for years to come. Thanks!
 
measure the I.D. of the hole in the carb that goes into the engine..that is the size.

What you have is a VM carb.

1st..check the inlet valve..it needs to be a 1.5.

Then..go online to a mikuni site..and look for the stock settings..buy those parts to start.

make sure you get the low speed circuit clean...squirt carb cleaner thru to test...
 
Yes, the needle valve is what RJH is referring too. It needs to be the type that works with a pump which is the 1.5. The needle valve can be changed, so I would check what you have. Anyone who sees a lot of carbs can tell you by looking at it.

The emulsion tube is the brass (hopefully) tube that the needle drops down into. The top of it can be seen in the bore of the carb when the slide is raised. The visible portion usually has half of the tube cutout. If you do not have this, you may a bleeder type emulsion tube which is no good for 2-stroke sleds in my opinion. It can be removed after taking the main jet out. It should be brass and have a stamping on it such as 224 AA-5. This part must be closely matched together with the needle and the engine that is feeding. These 2 together largely control the mid-range and mid throttle position mixture where a typical snowmobile engine spends a lot of time (unless strictly drag racing).
 
I do have a emulsion tube. It looks to me that it is the kind that will work with a fuel pump. There are pictures above also but if you need more let me know. According to some websites I have visited the needle valve is a 1.5. If this is all correct then what do I do about jetting? Is that the last hurtle I have before I can out this thing and on see if it will run right?
 
Yah I see the primary style tube in one of the pics. You need to pull the parts and identify them.

Pilot Jet
Needle
Slide
Needle Jet - Emulsion Tube
Main Jet
Needle Valve (inlet)

Post which parts you have. I question whether the 38 will work well with the single lunger, but maybe we can give you a starting point.

Also make sure the air jet and both passageways are clear - One comes out behind the slide and the other under the slide. These are connected to the pilot jet and the air jet.

And measure the needle valve, just because it is a VM38 doesn't mean that it has a 1.5 in it. Also you have no idea what someone might have swapped in there.
 
i did this exact thing to my 1980 enticer 250 this summer. i measured the carb mounting studs on the cylinder and ordered a mikuni carb boot close to my measurement. i did have to slightly enlarge the mounting holes. i used a mikuni 38mm roundlide. it starts so much easier now, but i stll have to get it jetted right. i also bought a universal throttle cable and had to file some material off the throttle block so it would let the carb close all the way.

i let a guy ride it that races a full mod polaris 600 and it surprised him!!!
 
The needle valve measures 2.5 inches end to end. I am sure I have all the parts but I am unable to clean it at the moment. Would it help if I posted more pictures of it?
 
I feel the 34 is a better match. You always need to use the right jets (within a few sizes). It is possible that the carb already has the jets you need in it when you get it, but not likely.
 
I believe we are running a 34 on our 250 and it runs extremely well. I cant remember the exact jets in it but I do believe the mains are ~230. If you run the 38mm, it will be up in the 400 range for the main jet.
 
We have had great luck with the 34mm on our 250 (Actually won at eagle river last year) and have raced against guys running the 38's. One thing you must remember is that everything has to be pushed through that stock exhaust pipe eventually. I would personally run the 34 due to the better throttle response.
 
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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