Stubborn YTM225DX just does NOT want to run right (tried a ton of different stuff)

[mattb348]

I have a ytm225dx (1983 I think, but not sure - would have to check engine serial).

I have put a lot of time & effort into this thing, but it just wont run right. And I am now pretty much out of ideas.

Here is what I have done/checked:

Different magneto (the original one was failing anyways), new plug, cleaned entire carb, all the jets, etc. (and it is the correct carb - model number 29u). Air screw is adjusted to specification, it has all of the right jets in it, it has the right needle (brand new even), and it has the right slide too.

The gas tank was cleaned, and fuel flows just fine to the carb, and flows INTO the carb just fine too (and to the proper fuel level).

There are no air leaks that I could find (intook is good, connection to airbox is good). Fuel level is set perfectly (did the clear tube test, and adjusted the float until fuel level was perfect). Made sure choke was not stuck. Even tried running it on half and full choke. Also, the bike was tested at different fuel levels too... made no difference at all.

Timing is set perfectly, valve clearance is perfect. And I tried literally every needle clip position too.

Here is the wierd part: the bike runs good at idle speeds all the way up to about 1/4 throttle. Anything past 1/4 throttle runs like crap (skips/stutters, and wont go past about 5,000 RPM's or so...... almost like a rev limiter kicking on..... even though it doesn't have one). And if you go wide open, it runs better, and goes up to about 8,000 RPM's or so, then starts doing the same thing (skipping/stuttering). And the bike idles pretty good too.

The bike has good compression (about 125 PSI) the last time I checked, but I noticed that it smokes quite a bit. And it seems to have burned up a lot of oil too (it was pretty low on oil after being full, and it has no oil leaks). However, I don't think that the fact that it burns oil is related to how it is running like crap at 1/4 to 3/4 throttle (this seems like more of a needle issue, but it doesn't make sense, because it has the right needle, and the needle is brand new).

There are only a few things left that I can think of, but I don't think that they will fix it.

First of all, the head was something I bought used from ebay. But it had good compression, and I found nothing wrong with the head. However, I found it strange that when I took off the decompressor cover, it had "21V" as the model number. That is the model number from a YTM200.

Also, the needle jet may not be the right one; I can't read the number on it to find out, though. But I don't think it is the wrong one. And by needle jet, I mean the big jet that has holes in it, on the sides; the one that the main jet screws into.

Another thing is that it actually has a magneto from a YTM200. But if that was the issue, I don't see how it would run great at idle to 1/4 throttle (and decent at wide open throttle).

Lastly, it pretty much has a brand new piston and rings in it, and again, it had good compression too. But it DOES burn oil it seems. Perhaps the oil ring is bad/stuck? Or was put in wrong? The new piston/rings were put in like 15 or so years ago....... and then the bike sat for about 15 years.

What the heck is making it run crappy at 1/4 to 3/4 throttle? That is the throttle position range where the needle should be the biggest factor....... but it has the right needle, and the needle is brand new. And I tried all 5 clip positions.

What gives? Anyone have any ideas? I'm a computer nerd, not a master mechanic. I am pretty much out of ideas now... and I don't want to spend the time/effort/money on getting a new needle jet (the things with small holes in it, that the main jet screws into) if it isn't going to help (and on top of that, I think it probably has the right one in it, anyways).

Oya, I'm not sure if the base gasket is any good, but would it be possible for that to make it run like crap at 1/4 to 3/4 throttle only?

Thanks for any help. I'm about ready to send this thing off a cliff :)

[bcredneck]

the needle jet is the jeting from 1/4to 3/4 throttle and your bike runs like crapp from 1/4 to 3/4 throttle its probley the problem

[mattb348]

the needle jet is the jeting from 1/4to 3/4 throttle and your bike runs like crapp from 1/4 to 3/4 throttle its probley the problem

So you are saying that I should go through the trouble/hassle/cost of getting the needle jet? (Not the one that is literally a needle, but the one with small holes in it, that the main jet screws into)??

[200XMichigan]

If it is smoking real bad and burning oil you might have to put new rings in it. If it sat for 15 years and wasn't fogged the rings aren't that good. Especially if its got 125 psi, it not terribly low but its not up to spec either. Are you sure the jets got really clean?

[bcredneck]

200x got a good point thouse little holes fill up with crap easy

[mattb348]

200x got a good point thouse little holes fill up with crap easy

I cleaned them out good :(

Guess I can double check though. Maybe I missed some of the little holes. And maybe I didn't clean the big hole good enough. If I remember right, my jet cleaner didn't want to go through it very easy, which is probably should have, since that hole is probably bigger than the hole in the main jet I'm thinking.

[bcredneck]

i use guitar string very carfully

[beets442]

Some of the new carb kits are not right for these carbs, especially Keister. I use everything but the jet and needle. Jets and needles don't wear out unless you stick things in them. I would put your old jet and needle back in and see if that works. Inline fuel filter wouldn't hurt either....Beets

[200XMichigan]

If you let them soak for a while then blast them out with aerosol carb cleaner and an air comp if you have one, that will get them good and clean. If you have to put anything in them I use copper wire.

[mattb348]

Some of the new carb kits are not right for these carbs, especially Keister. I use everything but the jet and needle. Jets and needles don't wear out unless you stick things in them. I would put your old jet and needle back in and see if that works. Inline fuel filter wouldn't hurt either....Beets

It actually does have the OEM jets in it. I don't trust jet kits much either :)

I put a brand new jet needle in it, but it was genuine yamaha (stupid thing cost $40 after tax, just for the needle!!).

The rest of the jets are OEM, and are the right number. However, I can't read the number on the stupid needle jet, but I am pretty sure that it is OEM. At least I HOPE it is.

And I do have an inline fuel filter :)

[bcredneck]

i dont think a 200 head on a 225 is helping the issue

[beets442]

Was wondering is the throttle slide guided one way only? I've put the slide in backwards(on other carbs) accidently that will make it idle and run at WOT only...

[mattb348]

Was wondering is the throttle slide guided one way only? I've put the slide in backwards(on other carbs) accidently that will make it idle and run at WOT only...

The slide can only go in one way :(

[mattb348]

i dont think a 200 head on a 225 is helping the issue

I don't know if it has a ytm200 head. It may just have the valve cover from a 200.

Also, I think that the head is exactly the same for a 1983 ytm200 and a ytm225dx. I know that they have the same exact head gasket for some reason.

[bcredneck]

check the numbers they are made from the same cast and will fit on each other but the ports and valves are bigger on a 225 just like with xr 75 80 and 100 the parts are intechangeable but if you put a part from a 75 on a 100 it will run like crap

[mattb348]

check the numbers they are made from the same cast and will fit on each other but the ports and valves are bigger on a 225 just like with xr 75 80 and 100 the parts are intechangeable but if you put a part from a 75 on a 100 it will run like crap

I feel like an idiot, but where can I check the numbers of the head? (OTHER than on the removable valve cover)

[Kevo225dx]

make sure the needle can't move inside the air valve. there is a spring-clip that is supposed to be on top of the e-clip to hold the needle in position in the air valve. if the clip isn't tight, the needle will "float" and screw up your mixture.

[mattb348]

make sure the needle can't move inside the air valve. there is a spring-clip that is supposed to be on top of the e-clip to hold the needle in position in the air valve. if the clip isn't tight, the needle will "float" and screw up your mixture.

The e-clip, spring clip, and spring is there. I tested, and the needle can't move.

[bcredneck]

i dnout know where the numbers are on that head some motors have them under the head cover some hondas have numbers on the bottom air fin but if your head comes with a 200 part it most likely is a 200 iv tryed puting a 75 head on a 80 and it ran like crap and thats only a 5 cc diff

[bcredneck]

if the cam came with the head its differnt to

[bcredneck]

haveing a 200 magnioto is ok but if youve done electical work grab a timing light and test it

[mattb348]

i dnout know where the numbers are on that head some motors have them under the head cover some hondas have numbers on the bottom air fin but if your head comes with a 200 part it most likely is a 200 iv tryed puting a 75 head on a 80 and it ran like crap and thats only a 5 cc diff

I think it does in fact have a ytm225dx head, but I couldn't find the numbers.

It said 21v on the valve cover, which made me think that it may be a ytm200 head. However, after fixing the clutch adjust assembly, I was surprised to find that it also said "21v" on the secondary clutch, inside the case.

I'm starting to think that some of the parts are labeled 21v, and maybe this is normal.

Now before people start saying its probably a ytm200, it is definitely NOT. The engine serial starts with 29u, the carb says 29u, and the intake from the carb to engine says 29u. That, and it is shaft drive, and also says 225dx on the fenders or something, if I rember right.

BTW I'm really starting to think the problem is that it has the wrong needle jet in it.

I took the carb apart again, and could not find anything wrong with it anywhere, nothing clogged, no air leaks, no bad orings, etc. And ALL of the jets are the correct numbers (needle, main jet, slow jet, throttle slide cutaway).

The needle jet is fine too.. but it doesn't even have a number on it. I cleaned the needle jet up real good (the outside), and I swear it has no number! It is supposed to have "N8" on it. So I'm guessing someone put the wrong needle jet in it.

Also, I am pretty sure the bike is running WAY to rich at 1/4 to 3/4 throttle. It is "crackling" and will sometimes backfire when you let off, after having it at like 1/2 throttle.

But what really makes me think that it is way rich, is the fact that if you turn the gas off, and hold it at 1/2 to 3/4 throttle, it will crackle and sputter, and only run at like 5,000 RPMs or so, but once it has almost drained the bowl (and is starting to run out of fuel), it will actually start running GOOD, and rev up to like 8,000+ RPM's, then die about 3 seconds later (once it completely drains the bowl).

Guess I better get a needle jet :(

[bcredneck]

if you whan to test it tie a thin wire around the main jet and have a little sticking in to the main jet and run it thats how i see if i want to go leaner

[Macs]

check the numbers they are made from the same cast and will fit on each other but the ports and valves are bigger on a 225 just like with xr 75 80 and 100 the parts are intechangeable but if you put a part from a 75 on a 100 it will run like crap

The heads are the exact same including cam, valves, springes, gaskets, cover ........ The whole assembly is the same. They also share the same part numbers.

I know you are new here bcredneck but please do not give out false information. It will cause a member to start chasing his tail, which has happened in this post. If you dont know, then don't answer.

Matt, it sounds like something is a bit funky in the carb. Honestly though, it is almost impossible to diagnosis over the internet. I would start by pulling it back apart, cleaning it again, inspect it, check every part and put it back to factory settings.

[bcredneck]

i realy dont think your smarter than sevice honda i have the book for honda xr 75 -100 and ive do alot of work on them
ive had to use my 75 head on my 80 cause the valve bent it ran like total crap till i got a valve

[mattb348]

The heads are the exact same including cam, valves, springes, gaskets, cover ........ The whole assembly is the same. They also share the same part numbers.

I know you are new here bcredneck but please do not give out false information. It will cause a member to start chasing his tail, which has happened in this post. If you dont know, then don't answer.

Matt, it sounds like something is a bit funky in the carb. Honestly though, it is almost impossible to diagnosis over the internet. I would start by pulling it back apart, cleaning it again, inspect it, check every part and put it back to factory settings.

Wow, I can't thank you enough. I am very glad that you cleared that up.

I just found a great deal on a complete carb for a 225dx, so I can just try swapping the carbs out now, once I buy it. First I will try the needle jet, and if that doesn't work, I will just change the whole carb :)

[Mr.Jake]

make sure the float is in correctly, the flat part faces down. its screwed up a few ppl in the past!

[mattb348]

make sure the float is in correctly, the flat part faces down. its screwed up a few ppl in the past!

Yea, I learned all about that when I put it in upside down once, and noticed no fuel would flow into the bowl at all :)

I never did that again :)

[MTS]

Do the yamaha's run a similar Advance set up to the honda's? Possible the springs for the Weights are getting "hung up" in Worn out holes...And not Coming out till you put a Real hard/lean load on the motor..?? Might want to Check with a Light over the RPM range to see if it is Advancein Properly....Seems odd the needle would Cause that Much problems on a little 225,,, Unless its WAY far off...Imo..Could pull the air-filter off in the shop to See how it likes to run a bit leaner too....I couldn't find a 225 Manual...but if the 200 Is quite similar...This might help you http://72.52.143.80/~trikes/Manuals/ATC%20manuals/YamYTM200ServiceManual.pdf

[bcredneck]

the reson why i told him to check his head is because he said some of the parts that came with it had numbers from a 200 and of corce it makes a difference ive tested with my xrs before and mac the cams on my xrs are totaly different dont even think honda or yamaha would just boar out a motor and not change head parts
http://www.3wheelerworld.com/attachment.php?attachmentid=113860&d=1294939729

[mattb348]

the reson why i told him to check his head is because he said some of the parts that came with it had numbers from a 200 and of corce it makes a difference ive tested with my xrs before and mac the cams on my xrs are totaly different dont even think honda or yamaha would just boar out a motor and not change head parts
http://www.3wheelerworld.com/attachment.php?attachmentid=113860&d=1294939729

We are talking about a yamaha though.

Also, I am pretty sure that the ytm200 and ytm225 have the same diameter bore, but the 225 has a longer stroke.

Like I said, the ytm200 head gasket also fits the ytm225. It says that right on the package (of the head gasket).

Weird, I know...

Also, unless for some reason someone happened to switch out a bunch of parts (like the secondary clutch etc.), the ytm200 and the ytm225 really DO share part numbers.

[Macs]

the reson why i told him to check his head is because he said some of the parts that came with it had numbers from a 200 and of corce it makes a difference ive tested with my xrs before and mac the cams on my xrs are totaly different dont even think honda or yamaha would just boar out a motor and not change head parts
http://www.3wheelerworld.com/attachment.php?attachmentid=113860&d=1294939729


I can't believe you are arguing this. We are talking about a yamagata and the part numbers, specs, everything is the exact same thing on a top end. Do me a favor, call yamaha and argue with them. I understand they are different for the xr's but am unsure what that has to do with it.

[mattb348]

LOL, I love your sig Macs (all of it). TOO Funny!

BTW I'm also a 1981 heh heh. I'm only 2 years older than my trike :)