spokerider

Well the source coil came in from Japan [ they are still available unlike the cdi units ] and I installed today. The spark at the plug is now a nice fat, blue spark, just what I was hoping for! The bike went on the first kick, so, it appears that the problem is solved. Now, I'll see if the improved spark has any effect on the rich-fouling spark plug problem with the next ride out. Would be nice if that problem was corrected too!

Never have done this to a Yamaha, but did use lye / H20 on a Cta 348 exhaust.........worked somewhat.......used a propane torch to burn out the residue........also worked........ended up cutting into the silencer with a cut-off tool, repacking with glass pack and welding it up again. Time and effort wise, the latter method was most efficient / effective. So if you weld........

Stork, Thank you for the informative explanation on what a source coil does, what has exactly broken down with mine [ causing the low resistance ] and the effects of the dysfunctional coil on the running of the bike. I now understand it. I have ordered a new source coil from the local Yam dealer and it's coming right from Japan, no less........ just have to hurry up and wait for it to arrive..... The spark plug cap is the original piece. It appears that it IS a resistor cap. I bought a NGK non-resistor cap today, and was going to install thinking " more juice at the plug" is a good thing. Would you recommend against that idea? May damage to the CDI result with a non-resistor cap? Thanks, Spoke......

Thanks for sharing your knowledge you two guys, it's helped me get a better understanding of the problem I'm trying to solve. I found an online manual for the TY 350 [ specs should be the same as a TY 250 mono ] and have read the electircal section on troubleshooting a no-spark situation. It has also provided the resistance specs for the electrical components, and I have just finnished the step-by-step testing with a multimeter. Here are some specs from the manual and my test results: Source coil leads spec 240 ohms +/- 10% Mine tested at 157.4 ohms. Pickup coil leads spec 4.0 ohms +/- 10% Mine tested 4.1 ohms. Ignition coil primary resistance specs 1.0 ohms +/- 15% Mine tested 1.1 ohms. Ignition coil secondary resistance specs 5.9K ohms +/- 15% Mine tested 5.9K without the plug cap on the high tension lead and 11.6K with the plug cap on [ not sure if the plug cap reading is significantly high?? ] So it seems that the source coil is low resistance..........would this be the cause of the weak spark? Just what is the "source coil"? I haven't been able to remove the flywheel yet as I don't have the Yam specific flywheel puller tool. Thanks.

I'm trying to sort through a spark problem on the 84 TY 250 mono.... 1] Had the bike 4 weeks now, two rides on it, and a bunch of time working on wheels, carb, etc. When I got it, it started on the 3rd or 4th kick. It ain't like that now. 2] Noticed it's getting harder and harder to start, each time I try to.....needs more kicks. Had a plug fouling [ over rich gas ] problem which didn't help. Eventually it needed a new plug just to start it when cold, a lightly used plug would not spark. 3] Went for a ride today, as usual, was a bugger to start. With a brand new plug it ran however. Then I tried crossing a river that looked 1.5 ft deep [ was last week ] ......wrong, it was deeper....much. Got swept over a drop off and submerged the bike. 2 hrs drying it out etc, and with a new plug it ran again. No problems for the 4 miles back to the truck. 4] Back home, doing the oil changes to get the H20 out, and even with a new plug it won't start. I can *barely* see a faint spark when I shade the plug tip from daylight.....even then it's tough to see. When I hold the plug and my hand is the ground, the shock I get is very anemic. Ever since I got the bike I thought the spark was very small and weak.... 5] The coil to frame ground looked fine, but I cleaned it up anyway. Wires all seem fine and intact around the coil and that other little electronic "gizmo" just up front of the coil. Haven't checked the wires coming from the magneto yet. Tried to unscrew the high tension lead from the coil to check for appropriate resistance, but I don't think it unscrews? 6] Does this sound like a coil problem / fix? Other? My stihl chainsaw just quit the other day......it needs a new coil.......grrrr. These two strokes are making me mental. 7] Thanks for your insight.

Does anyone know what the rear shock sag should be on a 1984 TY 250 mono? My 220 lbs [ rider and gear ] gets alot of sag, about 50% of shock travel. The shock only has reboud adjustment and no sag adjustmet. Did yamaha offer heavier springs for these bikes as an option? Thanks.

I took the fouled plug to my local bike mechanic.........he said running very rich and it's not fouled from oil, but gas. Having done that, I raised the needle in the TK carb up one notch, so it'll be a tad leaner. Also tried leaning the slow air screw a little too. The needle was in the middle position, is now clipped in second notch from top. The mechanic says these carbs never were really good even when new....... What setting are you running your TK carbs? Can you even get different jets for these carbs? I'll fart around with this TK for a while longer..........

I've been looking a little for a newer rear shock, one that has the remote resevoir, but have not seen any around on ebay, etc... Did Yamaha offer different spring options on the 84's to match different riders weights? The damping is great on the oem shock, I was just hoping for a stiffer spring. Even a spring from a different bike might work. Dunno what weight the bue spring that I have is rated for. Just wondering if anyone else has experimented with different shock spring weights.

I removed the condenser wire from the points and just tucked the pig-tail end of the wire up out of the way, leaving the condenser in place on the stator. Wired a new condenser under the tank next to the coil on the 348. Seems to work.

I just got some NJB shocks for my Cota 348........yup, all the way from the UK. In Motion Trials shipped fast, but UPS tried to mail them all of the way back to the UK after they sat in their warehouse in my city no less, for 8 days. Nobody attempted delivery, nobody from UPS tried to contact me to inform me that the parcel was in, they just sat there. Couldn't get a straight answer from anybody when ased why. Was I p****d! Grrrrrrr. After complaining to UPS via phone calls x 4 days, I got them to turn the parcel around and ship back to me. UPS.......what a joke. I hear that Falcon are great shocks, and prolly worth the wait. Just don't get shipped by UPS , or you may never see'em, lol.

I took the 1984 TY 250 mono [ new to me ] out for a ride after stripping and cleaning the carb. I seemed to run great [ with the TY carb ] and pulled strong on the run. I had ridden some fast logging roads in 4th and 5th gear, then went to a single-track trail up a mountain. An hour into the ride I turned around to come back, and began picking my way down the rough single track in 2nd and 3rd gear using engine compression to slow the decent. 10 minutes later, the engine quit and would not restart, so, out with the spark plug and it looked to be very black. A new plug and I was good to go.....engine started easily and away I went. The black fouling on the plug *felt* on the oily side, but was not shiny / wet looking, nor was it dry / fluffy looking. Now, I'm wondering, is this oil fouled or rich-gas fouled? I'm using Amsol synthetic oil at a 50:1 ratio. Plug is a NGK BP6ES. Exhaust system has been cleaned out by previous owner, and I have the air filter well oiled with air filter oil. Jetting in the TK carb is factory as far as I know....... Will a TY foul the plug [normally] when using engine compression and running slow down a steep hill for 10 minutes? How many spare plugs you guys taking on a ride? Hummm....I'm thinking I'll be needing three, lol. In fairness, this was my first ride with the bike. Next, a question about the mono shock. The 84 shock does not appear to have any adjustment for preload to the spring in which to set sag. There is an air valve on the top of the shock that slows rebound when I add air, but that's it. Mine has a blue colored shock spring. Can a heavier spring be obtained and put on? Perhaps from a different model Yamaha?? I need a stiffer spring as the stock one is too soft with too much sag. Other than that, the bike was a blast to ride!

Yeah, I'm definitly going to use it, wobble or not. I had to the bike shop for a new tire and the mechanic said that the nipples were too corroded to start twisting = breaking. Ain't going to be doing any high-speed stunts in any case......

Yes, it probably IS easier to just buy new, but, I really do not like discarding things that are perfectly good, with the *cost factor* being a secondary reason. Just my humble nature I suppose........ Yup, I use solvent to soak the tip in and wire brush followed by compressed air.

My 84 Yam TY 250 mono has Z spokes with the gold colored rims. There is some lateral runout of about 7mm over 30 deg of the front wheel. How are these wheels for truing? I've never tried truing a Z spoke wheel before. Also, is there a wheel from another bike......newer perhaps, or from another model of Yamaha or other make that would work on the ty 250? Wondering if replacing the whole wheel is any option at all? Cheers.

Ah yes, it worked! Not so sure I could do it again, but, all of the twists and turns I did added up to it slipping into place. Thanks again for the tip!