shooter308

I talked with my brother who talked with my step brother that used to ride the TY, and he said that the bike runs crappy when you sit on the seat, but it runs normal when you stand up and ride. So with that said, it seems as though the seat pan when compressed is blocking all the air flow coming to the air filter. I did notice that it seemed to rev up better when I had it in the shop, and I was not sitting on it, but I thought that it was my imagination. The air box is on the bike and the new air filter is in the proper position. Is there supposed to be something on the bottom of the seat pan that will keep it from squishing down and suffocating the air filter's air flow?

I completely disassembled the carb again and soaked it all in SeaFoam overnight and then hit it all with the air compressor to blow out all the ports, passages, and jets. Both jets are clean, needle and seat are clean, float height is set to factory specs. I did notice that my header exhaust pipe is cracked in the first bend after it leaves the cylinder head, but that shouldn't cause this issue I wouldn't think. Air filter is new, and airbox is clean and unrestricted. Carb has been cleaned and needle clip is in the 3rd slot, factory jets, emulsion tube is clean, and idle mixture screw set at 1 turn out from seated Exhaust is not plugged up and it runs the same with or without the muffler on it Compression test is 120 # on a cold motor Spark is a healthy blue color when grounding the plug on the head I sprayed carb clean while I had the bike running to find an air leak, but nothing evident happened to change the rpm of the motor while it was idling fine It starts on the first or second kick with the choke on. While it is idling, if I pull the choke to full choke, it will kill the motor. My Dad said this bike had lots of power when he test rode it once before I bought it from him. The only thing I can think of now is checking the crank seals behind the stator? Any other ideas? I could really use the help to get this bike running great before the fall weather kicks in and it gets too cold for my wife to practice on this bike. Thanks.

Thanks Bird!

I ran a compression check and the motor cold has 120 #. I've checked the spark plug and it is chocolate brownish/black in color and it produces a nice healthy blue spark, and the air filter is brand new. I've taken the carb apart twice now to clean it because when I got it from my dad it had some old gas in the tank. It has a 146 main and 38 pilot jet in it, and I live at 1900' elevation, and the float is set to 22mm. I took the carb apart and blew out the jets, ports, and orifices with my air compressor. The reeds look normal and intact even though I didn't take the reed cage off the bike. The throttle slide opens all the way up under full throttle and closes normally when the twist throttle is returned to idle position. The bike starts up on the first or second kick and idles great, but when I give it throttle, it doesn't want to accelerate very much at all, like it doesn't have the fuel to produce power. My dad said when he rode it before I bought it from him, it had lots of power, but it did sit for a few months in between him riding it and me buying it from him. I'm to the point of buying a different carb for it, but which is best - a VM26 round slide, or a PK27, or? Anyone have any starting points for jetting a VM26 carb for a TY350?

Is that with the plunger on the needle fully depressed? Thank you very much for the help!

Does anyone have the OEM carb float specs that they can post? I don't have a service manual for my TY350 yet, and I think the carb float is too high causing it to to dump too much fuel. Thanks.

I looked at the rear shock and I didn't see a remote rezzy, then I ran the VIN; 1985 YAMAHA TY350 -------------------------------------------------------------------------------- VIN:JYA46Y005FA00XXXX World region:Asia Manufactured in:Japan Year:1985 Make:Yamaha Model:TY350 Body style:Trail Drive type:RWD Cylinders:1 Cylinders I feel I still got a great buy for a great running TY350 for $350.

That is great info to know. I'll look when I get home from work to see what it looks like. I'll take some pics and upload them so you can see what I'm working with. I just ordered a brand new clutch lever as the one on it is partially broke off but it still works. Thanks.

He knew the bike needed to have the stator and points cleaned again, that is why I sold it to him for $200. He knew I was buying a TY350 so it's all good between us.

I just sold my 74 TY 250 to a friend because I was tired of always having to clean the points and stator to get the coil to produce a spark, but I did buy a either 85 or 86 TY 350 from my dad. It has gold rims, new tires, new rear fender, etc. Is there a VIN decoder that I can use to figure out which year it is? It runs good but I have to mod a FMF silencer onto the exhaust pipe. The head pipe has a hairline crack in it in the chamber area and I was wondering if I could mig weld it carefully? The headpipe looks like an aftermarket one because it definitely doesn't look like the stock pipe I've seen in photos on the web. Also, the bike didn't come with a headlight assembly on it, and I was wondering if I could use a square style headlight from a Yamaha TT or IT 80's motorcycle? I'd like to install a side stand on the bike and was wondering if a Yamaha TT side stand would be an easy swap? Anyone else retrofit a headlight from another bike onto their TY350? Thanks, Doug

Thanks for the reply Alan. I'll take a look at it this afternoon and see if I can see what the lever needs for tweaking. I do know that the lever is moving the choke plunger up and down depending upon which way you're moving it, but like you said maybe it's bent a little and just not holding the plunger up to engage the choke.

I have a 74 TY 250 that runs fine, but the choke plunger will not stay in the up position when I push the choke lever down to start it when it's cold. Does anybody have a fix for why the choke will not stay engaged to start it? Thanks, Doug

You can just get a 4 pin molex to sata power connector cable. Any computer shop should have one or you can get one off of Ebay for cheap.

If the oil pump doesn't work any longer and a person just pre mixes the gas can a different throttle cable be used from a different model of bike i.e. the DT or MX bike? Thanks.

I'm in NE Oregon and I've searched Ebay quite frequently for the complete throttle cable assy, but I still haven't seen a good one for sale on there lately.

I'm looking for a throttle cable assembly (from the carb top to the adjuster nut at the twist throttle) and the carburetor spring for the carb slide of my friend's 74 ty 250. Where is the best place to find these parts? Do these parts interchange with any other yamaha model? Thanks, Doug

I see a single engine kill switch on his website. Did the TY 250's have a combo switch (headlight/engine kill switch) from the factory? There isn't a headlight switch on my Ty250 just a regular 2 stroke motocross style kill switch that somebody else put on there. Thanks, Doug

I have a 74 TY 250 that doesn't have a headlight/engine kill switch on it. Therefore, I do not have a working headlight or tail light. Does anybody here know where I can locate a combo switch or if one from a different model of yamaha will work on it? Thanks, Doug

I got it figured out. I don't have a manual for the bike yet, but I cleaned the points up really nice, and then adjusted them to where they would at least open up. Then I adjusted them to .015" and re-gapped the spark plug to .022" and it has a nice healthy blue spark to it now. It seems to run really good now, so I'll be teaching my wife how to ride a motorcycle again.....

Okay, I've got the flywheel off and I'm gonna clean the points. How do I gap the points? I can spin the flywheel around, but I cannot see the points open and close. At what point should the flywheel be for the points to open up? Thank you very much for all of your help. Doug

I was just wondering if anybody here on the forum has tried to convert the TY points ignition over to electronic via parts from another yamaha bike i.e. DT, IT, etc.? I was just wondering if it could be done any cheaper than say the $410 kit from bjracing.com?

Thanks for the info Tony..... So if I read your post correctly, I can check the points gap and clean them without taking off the flywheel? That would be nice to be able to at least get it running while I wait for the new tune up kit to show up that I ordered. Thanks again, Doug

I figured I'd check the points, but I have to wait to get a flywheel puller first. What is the gap on the points for these old bikes? When my best friend had the bike, he sold it to our mutual friend and gave him the title to the bike, a Yamaha service manual, and a flywheel puller. But since he passed away last fall, his wife doesn't know where they are...... Looks like I'll be selling the custom water cooled gaming desktop pc I just built to afford to buy the electronic ignition from bjracing.com......

Hello, My name is Doug and I live in NE Oregon. I've been riding motorcycles and atv's since I was 9 yrs old which is a long time ago since I'm 43 now....lol I got my first trials bike (74 Yamaha TY 250) from a friend last fall when he passed away. I plan on keeping it and possibly restoring it in the near future. It's complete except for the headlight switch assy and a speedometer. As soon as I get spark to the new spark plug I plan on teaching my wife the basics of motorcycle riding so she can get her motorcycles license. I hope to make lots of new friends here on the forum and maybe someday meet some of you to ride together. Doug

Oops.....Sorry I guess I should've mentioned that stuff also. I put a brand new NGK B7ES spark plug in it. I put a brand new mix of 32:1 Castor 927 pre-mix into the tank as it was bone dry when I got it. I would think that the spark plug and fuel mix should be good to go now, just no spark. The factory automatic-oiler is non-functional, so I just pre-mix the fuel with a ratio rite bottle - I have an 85 Honda atc250R so it's easy to just make enough mix for both. Was there a common problem with the factory coils on the TY bikes going out? What would cause a weak spark and plug fouling? My wife wants to learn how to ride a motorcycle again (she hasn't been on a dirt bike in over 10 yrs) so she can get her motorcycle license. I figured that you can't get much better balance control than from a trials bike, so I want to get this bike running ASAP. Thanks, Doug