Intake Manifold Porting YTM 200/225

[El Camexican]

I doubt many folks spend a lot of time hot rodding these things, but in the event that someone wants a little more out of their Yamaha 4 strokes here’s something I picked up messing with mine.

The head on the 200 and 225 is identical. The carb on the 200K is a tiny little thing with round spigots on both ends. It looks like it would fit well on a chainsaw. The 200L came with a small carb as well, but it has an o-ringed flanged spigot that bolts to the intake manifold. The 225 came with a much larger carb. 29mm I believe, but the I.D. of the exit spigot is 31mm.

So at this point you may be wondering why they made the carb so much larger to suit the same head which by the way has an intake port opening of about 24mm. I don’t have an answer for that, but the K and L model intake manifolds are uniformly 25mm from end to end whereas the intake for the 225 starts at 29mm and tapers down to 25mm where it bolts to the head.


In my quest to get a little more out of my 12hp wheelie maker I bought a carburetor and manifold for a 225 and hogged out the manifold to be 30mm all the way to the head which is the same size the head port now is also. As terrible as the port looks in the photo I swear it’s smooth


When I was bolting everything up It seems the carb didn’t want to match up to the air box tube very well. I managed to get it to line up, but it never felt right. Ran like a raped ape for a few hours and then started backfiring when I’d chop the throttle. Couldn’t figure it out until I pulled the carb to put a richer pilot in it and found this.


Turns out the mount angle was out enough that the thinner wall of the ported intake couldn’t take the stress. I threw in an unmodified 225 manifold and it has held up for a couple years, but the power felt down a bit. So last night I finally got around to measuring and matching a flanged 200L manifold to suit the carb and head. I can’t wait to try it out!

[Jmoozy27]

Interesting, my 85ern has a 22mm carb. Not sure about the id of the intake but I would definitely like a little more pep out of it. It has a DG rcm, and I have some spare mains but I never changed anything because plug chop was spot on. Maybe the small carb was to blame for that.

[El Camexican]

Interesting, my 85ern has a 22mm carb. Not sure about the id of the intake but I would definitely like a little more pep out of it. It has a DG rcm, and I have some spare mains but I never changed anything because plug chop was spot on. Maybe the small carb was to blame for that.

Your trike came with the same manifold mine now has, V24 (was V21), far right in the first photo. The 225 part is a U29. Putting a 225 carb on yours should complement the pipe, it will bolt right up to your manifold, but without opening up the ports I doubt it would make a huge difference.

I'll need to start from scratch on my jetting now. I don't have a lot of brass for that carb. Found out the other day that I ordered the wrong style of pilots for it, so I hope what few I do have works.

How long do you have to leave your choke on before it will idle on it's own?

[jakep53]

I have a ytm 225 dr and when I got it it would idle forever but bog out and die as soon as I touch the throttle so I put a carby off of a yfm 200 which Im guessing is the same carb as the 3 wheeler my 225 runs so much better but....some days it has so much more power the plug is always brown so im sure its jetted correct but I don't understand why it will not run with stock jets and carb..but runs better with smaller jets?

[ironchop]

I love this kind of thread...keep it up

[El Camexican]

I have a ytm 225 dr and when I got it it would idle forever but bog out and die as soon as I touch the throttle so I put a carby off of a yfm 200 which Im guessing is the same carb as the 3 wheeler my 225 runs so much better but....some days it has so much more power the plug is always brown so im sure its jetted correct but I don't understand why it will not run with stock jets and carb..but runs better with smaller jets?

That can be a bunch of reasons. If something runs better on cold days it's likely because it's jetted rich. Unfortunately if your trike did run better on warm days because the jetting was spot on you wouldn't feel it because the lack of air density would lower the power level the engine could make. Dying when you touch the throttle is usually an indication of a plugged pilot circuit, or the fuel screw (your carb does not have an air screw) is closed, or almost closed.

I will confess that my original YTM 200 carb ended up in a parts box. I spent a bunch of money rebuilding it and never got it to run properly. It was 27 years old and had a zillion hours of use on it. I am content to believe that the slide bore simply wore out. I saw that happen on a set of 33mm smoothbores once, the owner replaced almost everything and never got them to work the way they once did. I'm no carb expect, but I'm good enough with math to know when I'm on my way to spending more than a new carb is worth.

As far as I know all the 225's came with a larger carb than any 200, so if max. performance is your goal you may want to get a new U29 carb. They are proprietary, so I can't give you a Mikuni #, but I'm sure there is a compatible unit available. If you do go the U29 route make sure you order the correct pilot jets for it. There are 2 that are almost identical, but the tips are available in 2.0mm and 2.5 mm. The Yamaha carb uses the 2.0mm tip X 28mm long .

[Jmoozy27]

15-20 seconds

[El Camexican]

15-20 seconds

Sounds about right for a warm weather area. Mine was so rich at one point I could start it without the choke at 70 degrees. Back up North with the old carb and cool weather it could run on the choke even when warm.

[jolson185]

Mine starts on the first or second pull at -22 with no choke. Idles forever. Same at 70 degrees. No power difference. Too rich .

[Six Stroke]

I'm curious, have you tried any other camshafts with the hogged intake? The 200/225 atv engines, BW/TW200 engines, and TTR230 engines are all the same platform, yet all three groups have different cam part numbers.

[Trike_crazy]

I've been looking for a larger carb and intake replacement myself and noticed that the tt225 has the same head as the ytm 200/225. So one would think that the carb and intake would be a bolt on deal other then the airbox to carb boot. I would just throw a pod style filter on it and be done. The carb I have been looking at is the 86/87 TT225


This is what I've been looking at. Its a larger bore so it surely would offer better performance than stock?

[czac]

Just to add to the info on this thread.... One of my DX's (the 1984) has a Timber wolf 250 carb on it and it runs great. it looks a little different because the gas line goes in differently but the innards, choke and such are the same as are the flange mount and air box tube end size.

Also when buying the Pilot jets for these trikes... there are two different sizes that look the same as ElCamexican stated in one of his posts above... I have found that one easy way to tell the difference from a photo is that the larger one (that wont work in these carbs) has a small groove / ring around the body of it, you can see the difference in the two in this pic off the Niche cycle parts . com web site.
the one on the left is the correct jet for the Yamaha 225's, the one on the right is too big but notice the tell tale ring... you can also see the size difference when they are side by side.



Another thing. use the part numbers below the jet in the above pic to find them on Ebay. if you put a -25 on the end of the number you will get a #25 or a -30 will pull up a #30 and so on... not sure if these numbers relate to the Jetsrus site or the Mikuni site but they work fine on ebay lol