1984 Ty250 Mono Revival: Few Questions, Parts Source In Usa?

[jontow]

Boy, this sure is an ongoing saga of me being stumped by this bike

It started today, ran a bit, then died again, started back up after unplugging the dodgy kill switch and a few kicks, but was running ragged. I got it back to the garage and later installed a new kill switch: it started up and was running ragged the same way as back in the woods: would sometimes keep running if I revved it a bit, but wanted to die at every opportunity, and backfired a bit. Later tonight (after my kids went to bed, of course), I started doing some right leg exercise on it again and it coughed a few times then *big backfire* and it opened up the silencer again, similar to the picture above.

Plug reads fairly rich (black and sooty, not oily anymore), but will spark readily if I clean it up. As a bonus, for the brief moment it ran, I confirmed that my headlight works as is! Lot of good the headlight's doing at the moment.

I couldn't find any numbering on the jets when I had them pulled, but I suppose the jetting could be wrong. Usually everything I get here is jetted too lean, I'm at about +750ft over sea level. Is it possible the stock jetting (if indeed it is that) would be that far off?

[lineaway]

Since chasing all these symptoms have you tried changing to fresh fuel? Bad fuel can make a bike run just like this!

[jontow]

That was the first thing I did with the bike when I unloaded it, pull the tank, drain it, pull the carb, drain and clean it thoroughly, and refill with fresh 91 octane ethanol free gas mixed at ~55:1 with the same 2T oil I run in my injected 70s kawasaki F7 & KE125.

I have been battling with a small drip-leak out of what I can figure is the overflow tube: it comes out of the very bottom of the carb. The leak acts as though the float is adjusted incorrectly or the inlet valve is leaking. Does it even when the fuel cock is turned off, and takes quite a while to build up enough fuel in the bowl: usually a few hours.

I've replaced the inlet jet/seat with a brand new sealed one, even though the old one was good and clean and showed no depression on the rubber cone tip. I've adjusted the float everywhere from barely running fuel into the bowl at all (taking MINUTES to fill) all the way to the other end of the spectrum, just to test. It seems to do it no matter what, although is more pronounced with the float adjusted somewhere between "properly" and "too high". I've put a piece of clear tube on it and checked, the level it reads is not even to the seam on the bowl. The tube is, I believe, the one that has an internal tube that runs up into the carb more like a vent, and then back down and out, vs. just being a hole near the top for gas to run out if you tip the bike over. Because of this drip leak, I've exchanged the fuel completely now over the last few weeks, and haven't really found much change in the matter.

I've now tried with the needle clip position at #3 and all the way up on the needle (presumably to lean it out, if memory serves me). The bike came to me with it at #3, dead in the middle of the selections.

I'm starting to lean toward just tossing the cash at a mikuni flat slide and getting it adapted onto the bike, but I really don't have a lot of cash to spend, and so have been trying to make due with tossing very little cash and more time at the OEM carb. It wasn't clear/obvious that someone drilled out the jets, but I guess its possible: its an old bike with an unknown history. I'm struggling to understand why it's fouling plugs like it is, even when I adjust it as lean as I can with what's available.

Do I have it correct that the brass adjustment screw on this bike is an AIR screw, located on the air side of the slide, and so therefor backing it out makes the mixture more lean?

[jontow]

After leaving the clear tube on the overflow (confirmed that it is indeed an overflow, per the manual) for a few hours, it DID read slightly over the bowl seam, so I popped it apart again, and theres a little factory cast notch by that upward pipe mentioned prior, which allows gas over the seam directly down into the overflow. So I adjusted the float to close a little earlier, got the bike running and cleaned it out a bit, rode it around the yard a few times; it was running better than the last time, but still not great: it eventually started loading up again, so I shut it off and brought it back inside. Mind you, I've also still got the blown up silencer on it, and it would occasionally belch a little smoke. I'm wondering if its simply not able to rid itself of as much of the exhaust gas as needed to get a clean charge in the cylinder, due to blockage? I didn't burn out the expansion chamber, but am thinking now maybe I should have. The bike ACTS like its running lean at times, but the plug never shows it.

[guy53]

That was the first thing I did with the bike when I unloaded it, pull the tank, drain it, pull the carb, drain and clean it thoroughly, and refill with fresh 91 octane ethanol free gas mixed at ~55:1 with the same 2T oil I run in my '' injected 70s kawasaki F7 & KE125 '' Did you use injection oïl for your premix ? If so what oïl do you use ??

Guy

[jontow]

guy53: I'm running QuickSilver multi-use 2 cycle oil, claims marine, but pictures power equipment and motorcycles and ATVs as well.

http://www.quicksilver-products.com/water/outboard/lubricants/

^-- that

[bestrcpilot]

Is the chrome on the slide and showing brass. Is the bore for the slide in the carb showing any Rough spots or Groves in it? I could not get my ty250 mono running right until a carb change. Like your's it would foul plugs and just run like crap. One time it would seem lean next it would run rich. But before buying a new carb burn out the exhaust. Does it run Differently when it gets finally warmed up? Is the coil getting a good ground? Rust on the mounting lug for the coil can give you fits.

[jontow]

Burned out the expansion chamber today on lunch break.. made a heck of a stink, and got a fair bit of ash out, so I at least accomplished something.

Ignition coil is new, behavior is the same with an old and new coil. Right now, after cleaning the exhaust, all I'm getting out of it is a bit of afterfire (backfire out of the exhaust), rather than any actual *running*. When it DID run, it did change some after it warmed up, usually getting more blubbery and acting even more rich. The slide doesn't show any brass that I can find, and seems to fit well in its confines.

I just wheeled out my TW200 and used its battery to power an inductive timing light with the lead clipped around the TY250's plug wire. Firing plenty often, by my estimate. Lighting up the driveway like crazy!

[guy53]

I don't know about burning a TY mono exhaust, there not like the twinshock, they are the '' paked '' kind I did not do it on my 250 because of that.

Guy

[jontow]

Sounds like I might've done myself more harm than good, just there, then. Live and learn, I guess.

[bestrcpilot]

Check the reeds. make sure they are seating good on the reed block. No light showing between the reeds and the Reed block when held up to a light.A broken or non sealing reeds will make it run rich and down on power. I do not think you could have done any harm burning out the exhaust. I did mine and never any harm done.

[jontow]

Took a quick picture of this so everyone can see what I'm talking about.

This is with the fuel cock OFF, and the bike sitting overnight. It seems to me that no matter where I put the float, this is what happens. Thats a lot of extra gas, and its at the bore of the carb.. meaning its probably flowing right into the cylinder. Argh.

Again, new fuel inlet valve/seat/gasket. Leaking fuel cock should contribute to this, but if the float/inlet valve are doing their job, this should be prevented, no? It does seem to take a while to get to this point, though, so I'm not sure how much it affects the bike while its running. It'll certainly make it hard to start the next day!

[tony27]

Take your floats out & put them in a container of hot water, sounds almost like they are leaking, the hot water will cause the air inside them to expand & force out any fuel etc causing a fizzing effect & the float should also sink.

If the carb is filling up when the tap is off then you need to put a rebuild kit in the tap as it must be leaking

Edited September 26, 2013 by tony27

[guy53]

Have you tried to run the bike with the tap half or 3/4 close?

Guy

[jontow]

This evening I had a few minutes to tinker, so I pulled the fuel cock apart, confirmed: its not really an 'o-ring' exactly that seals it, but more of a rubber band. It was a little chewed up on the back side where it squished in, so I trimmed off a bit of the excess, cleaned the corrosion and general garbage out of the bore of it and put it back together: no obvious leaks, yet.

I also took the opportunity to tear into the carb, take a few pictures, and look at the slide and floats in a bit more detail. The slide *DOES* have some brass showing, but its in little strips along the bottom edge, not along the vertical axis. I tried to get pictures of this, but my phone flash won't cooperate, and I just get a bit of a reflection. The floats do not leak, confirmed with the hot water test, which I was already fairly certain of, simply by shaking them close to my ear prior and hearing no sloshing.

Took another opportunity to try bending in a different place on the float frame itself. This time, I bent the little ears where the inlet needle rests back close to the rest of the frame, and bent the 'wings' on the float itself, trying to get them roughly even. Nowhere have I found particular instruction on what you bend. I may have gone a little too far, as I suspect fuel level will be slightly low, but the inlet needle now has a much more positive open/closed action. This combined with the fuel cock changes may at least prove to me that something changed. I hooked my overflow tube back up and will leave it like this with the bowl full and the fuel cock off, as I've done previously.

For those interested, here's a quick gallery of the carb pictures I took: http://bd.zenbsd.net/~jontow/phone/trials/ty250/carb/

I hadn't found any such teardown pictures anywhere in the past, so maybe these will come in handy for someone.

Also:

Couldn't read the numbers on the main jet very well, looks like it might've read "5 44" or similar on one side, and a symbol on the other. The pilot jet says pretty clearly "48".

Per the manual (online one) for the TY350, the jets are supposed to be a main #145 and pilot #37 -- I'm not sure what to say about the main, but the pilot sure is a lot higher flow than factory spec. Anyone know a source for these jets?

Edited September 27, 2013 by jontow