YTM200E cutting out at full throttle under load

[dz]

Well, where do I begin. I found my YTM200e under somebody's deck, been there for years and years. Entire fuel system jammed up. Cleaned petcock, flushed gas tank with new gas, put on a newer working carburetor, put in a new air filter and changed the oil. Engine fired right up without a hiccup, let it warm up and got the oil flowing, ran extremely well with no smoke. Rode it around my yard for a bit, with the intention of changing the oil and rear fluid once warmed up and moved around a bit. After about 20 minutes there was a little cough from the carburetor and she sputtered and died. Started her back up and all seemed well, but an increasing problem arouse. Under load approaching full throttle the bike would severely sputter and if more throttle is applied the bike just dies like it lost spark or its will to live. If you cut back on the throttle she comes to life. I've tried adjusting/re-cleaing the carburetor to no avail. I took the fuel cap off, no difference. I disconnected the fuel line from the carburetor to check fuel flow, it flows freely and fine. I disconnected both the key switch and handlebar stop switch thinking it may be electrical with no change. I changed the spark plug coil with no change. I changed the spark plug with no change. I sprayed contact cleaner around the carburetor intake looking for an air leak, but no change. Anybody else have this type of problem before? Why all of a sudden would it hiccup and run crappy now? Could I be looking at a CDI or trigger coil problem? Any help would be greatly appreciated, really looking foreword to taking her out on the trail.

[muthey]

I have ran into this a couple of times, one the main needle is moving in the slide, or two your bowl isn't filling fast enough, which means the float level is wrong, or it is flooding out into your air filter and motor, which in turn the o-ring that goes to the float needle seat is shot or the float needle itself is shot, I know it sounds like a lot but it all mainly boils down to the carb, check the main jet for debris, a hair in there can give you some issues as well.

[dz]

Well, I've tried another needle/slide combo with the same result. It doesn't seem to be flooding, no gas in air box and no black smoke. It rev's up fine no load, but under load it just dies.

[dz]

Forgot to mention the main jet is clear, I can hold it up to some light and see through it.

[muthey]

take a piece of wire and go through all of the holes at the back end of the carb there was a guy on here that had debris in them that kept cutting out his throttle from it

[code-blue]

I had this problem with my 1985 225DR, my float bowl wasn't filling up fast enough under WOT, it would sputter and almost die unless I backed off. Try setting the float level. Good luck.

[dz]

code-blue,
whats weird about the problem is that it was running perfectly fine for 20 minutes with the current setup. It just kinda backfired through the carb. and then developed this problem. I'm still wondering about an air leak. When I moved the main needle up to run richer it seemed to run a little better.

[muthey]

have you tried a new spark plug possibly a hotter one as well, I know you said it's not smoking, but have you tried a compression test yet? On top of all that what is the actual part number on the carb you put on? it does make a difference, it can be found on the top of the intake mounting face, might have the wrong jets in it?

[dz]

Well, here is an update and hopefully someone could chime in. I've tried another known working CDI with the same results. I've tried another spark plug boot with the same results. I've tried yet another spark plug with the same results. I hooked up an auxiliary gas tank with different fuel with the same results. I've looked at the timing and it's spot on. I've installed a new carburetor intake boot and new o-rings with the same results. I've re-cleaned the carb. with the same results. After all that its still sputtering past 1/2 throttle. I know it's screaming main jet but after all I've done I don't think it can be. I tried re-adjusting the carb. raising the needle all the way and lowering the needle all the way with the same results (although I looked at the exhaust and no matter which direction I move the needle the exhaust is smoking black like it's burning rich while it's sputtering or it's losing spark). It starts right up when cold with no hesitation up to 1/2 throttle even under load. It did not have this problem when I first intsalled the carb. and ran fine for almost a half hour with no problem at all. Could this be a sign of a weak pickup coil that picks up the flywheel magnets? I really don't know what else to try, valves are adjusted properly too. Running out of ideas. Any help would be appreciated.

[dz]

Also, while I had the carb. apart I installed a new o-ring that goes into the needle pickup tube, and that didn't change anything either.

[muthey]

run it for awhile and check your oil I am starting to wounder about your valve seals as well, even with properly adjusted valve, bad seals will cause it to smoke. so many possibilities check your pickup coil then after that you might have to open the top end even as much as I hate to say it, but something is just not working right. But check the coil first as that is alot easier to check then the top end. After that all I can say is there is a starter jet in the bowl of the carb make sure that is clean and that your choke is working properly and has the right o-ring. would be awesome if it was just something with the choke so double check and double check, before tearing into a motor. The one thing that concerns me the most is the backfire through the carb as you described it.

[tri again]

Sounds like you did the carb to death altho,
I've done the same carb a couple times and found a
clog on the 3rd time through.
Very frustrating for sure.
Just because the jets are clear or new doesn't mean the internal passages are clear.

Blow thru them under water with a piece of fuel line and look for bubbles.
Heck, I've even boiled a few of mine in water with vinegar and lemon juice.
Amazing where crud can hide.

Is there any chance the exhaust plugged itself somehow?
Baffle came loose?
Is the compression good?
valve hanging open?

Try nipping the last tiny bit of the plug wire so the cap has some new wire to bite into.
Free and fast and I've seen that cause days of headaches.
or take the cap off altogether and use a piece of copper wire.

Signal breakdown?
Check all your frame and wiring grounds, esp coil to frame mount.

It may be failing at the higher revs simply because of a weak connection.

I even had an air filter that looked NEW but was plugged with the finest dust on the planet and would NOT pass air.

..and finally, here's my fav chart, but prob has nothing to do
with your issue.

Good luck.
You'll get it.

[El Camexican]

Sounds like something is cutting off air. Bad valve seals won't make it do what its doing, DON'T open the engine!. Make sure your air box isn't full of water from the last wash and that there isn't something obstructing the air filter or anything else air tract related. Too much oil in the filter can do this as well.

[dz]

Camexican, It's a brand new air filter and I even removed the air filter and it did not change anything. I've never been able to wash it because after I got it running it only ran for 20 minutes or so so it really didn't get dirty.

Drjoe171, I've isoltaed everything except what was needed to make it run with the same results. I've disconnected everything and looked at every connection, every connection was clean. I even tried jiggling the wire harness with it running and that didn't change anything either. Today I am going to look at what color the spark is, I forgot to do that yesterday and probably make a video of what it is doing so you guys can see what I am talking about. I had my buddy looking at the spark while I was cranking it over and he said it looked orange which could signify a problem. Exhaust is pretty much free flowing at this point, the baffle end was rusted pretty bad and on the first start after I put it all back together it pretty much just blew out.

Muthey, It's not blue smoke it black smoke when it starts coughing. It sounds like somebody is turning the kill switch on and off real fast, not bogging down like too little or too much fuel.

[muthey]

ok I'm starting to think it is electrical, and not fuel related at all. You can check the pickup coil with out tearing into the motor, the repair manual has instructions in it, and can you see any spot where the wiring might have been repaired or replaced at any time, ie: lots of black tape. There should be a fuse in the wiring it make look good but for the price just replace it anyways, have had far too many that were old and looked good actually turn out to be my culprit. And like drjoe said go through all the grounds again take a piece of sand paper or emery paper to them all to ensure a clean connection. Have you opened up your kill/light switch to see if there is anything in there that could be messed up that might start moving under higher vibrations? Lift tank and unplug keyed ignition, and start it see if that is the culprit, maybe there is a loose connection in there wiring is a real pain at times but not hopless