jse Posted September 6, 2013 Report Share Posted September 6, 2013 I also run the Mikuni (with modifications) on my 85' TY350: Good little carb, works very well. Jon Quote Link to comment Share on other sites More sharing options...
chuckindenver Posted September 7, 2013 Report Share Posted September 7, 2013 the 250 and 350 motors are nothing alike, the only thing the have in common are the words Yamaha they mount different, as well. look at the back of the cases...make sure the its not broken out from hard use...most TY250s were rode hard. every 250 iv seen has had the rear case repaired. used to be a few after market goodies available in the UK...John Shirt did a lot of trick stuff on the 250s... he offered a tricked out 250 and very few 350s.. the carbs are poop..a newere upgrade is in order... Quote Link to comment Share on other sites More sharing options...
jontow Posted September 8, 2013 Author Report Share Posted September 8, 2013 Thanks for the pictures and info, folks! Extremely helpful. jse: is that a piece of radiator or fuel filler neck hose used as a spacer/intake tube for the carb? Here's another one, trying to identify what's original vs. what isn't on this bike: I have what is obviously a 44H frame and engine bottom end, but it looks like the cylinder/top end/much of the ignition/electronics are from a 38V, and the carb is cast-labelled as a 44J. Do the stamps I'm finding mean what I believe, or did they make a habit of using whatever model code parts they had / could get? Also, for what it's worth, it looks like I have (much of ) the 82nd 1984 TY250 from Canada, per the serial number and identification info I can find: neat, or at least I think so. Quote Link to comment Share on other sites More sharing options...
jse Posted September 8, 2013 Report Share Posted September 8, 2013 jse: is that a piece of radiator or fuel filler neck hose used as a spacer/intake tube for the carb? Jontow, That is fuel-proof reinforced tubing. What you can't see (except for the "ring") is the machined spigot extention I installed that fits down inside the tubing. Jon Quote Link to comment Share on other sites More sharing options...
axulsuv Posted September 8, 2013 Report Share Posted September 8, 2013 Jon , Nice detail work ....Make the carb fit the bike , not make the bike fit the carb ...! Glenn Quote Link to comment Share on other sites More sharing options...
jse Posted September 8, 2013 Report Share Posted September 8, 2013 Jon , Nice detail work ....Make the carb fit the bike , not make the bike fit the carb ...! Glenn Glenn, The extended spigot is so that the end of the carb spigot mates up against the special one-piece manifold/reed block. This way there is no "gap" inside the tubing between the end of the carb spigot and the beginning of the manifold spigot, which would form an "expansion chamber" of sorts inside the tubing. You want the cross section area of the intake from the needle jet to where the fuel/air column starts to expand into the area under the reeds to remain as uniform as possible. Any area variation will tend to degrade the air column "signal" at the needle jet orifice. The reason that flat slides work well and are so responsive is that the air column is not "split" around either side of the cylinderical slide (right at the area of the needle jet where it's most needed) but is concentrated over the needle jet, thereby vastly improving the pressure/vacuum "signal". Jon Quote Link to comment Share on other sites More sharing options...
axulsuv Posted September 8, 2013 Report Share Posted September 8, 2013 Trust me , I understand the principles of induction , you should've hit me up to ride my 'lightly' modified 240 @ the world round . Most folks come away with a 'OMG' look on their face ... But she'll still wheelie from below idle in third gear ( and no I didn't port the barrel I use , but I will duplicate it when I install a fresh forged twin ring piston and some new plating ...) Glenn 2 Quote Link to comment Share on other sites More sharing options...
htrdoug Posted September 8, 2013 Report Share Posted September 8, 2013 (edited) Trust me , I understand the principles of induction , you should've hit me up to ride my 'lightly' modified 240 @ the world round . Most folks come away with a 'OMG' look on their face ... But she'll still wheelie from below idle in third gear ( and no I didn't port the barrel I use , but I will duplicate it when I install a fresh forged twin ring piston and some new plating ...) Glenn We don't need no stinkin' reed valves! Valves are for toilets! My 240 totally ruined my TY350 for me,just couldn't get used to the different response One of these days I'll get around to doing the crank on my 309,it's like a nitro burning funny car in zap!(flywheel weight still installed too) Edited September 8, 2013 by htrdoug Quote Link to comment Share on other sites More sharing options...
jontow Posted September 9, 2013 Author Report Share Posted September 9, 2013 (edited) Well, slightly new turn of events tonight: my known dodgy exhaust decided to share a look at its dirty underwear when I was kicking it over after making more carb adjustments. Good bit of backfire and *poof* the seam split. Damage done, I decided to see if I could pull it apart the rest of the way and clean it out, not being sure if I'd be able to reassemble or not. It's mostly an unwelded pinch seam around the outside edge, with just a few welds, so I cut them and found a lot of pieces rattling, some oil/mud plugged packing, and a lot of carbon. Not sure if I have the cash on hand to get new packing on the way, but it looks like I will at least have a good shot at reassembly. There's been a lot of dirty oil dripping out of a leak in the bottom of it since I got it, and it's been running rich when it's been running at all, so I'm not surprised it finally lit up a bit. Edited September 9, 2013 by jontow Quote Link to comment Share on other sites More sharing options...
jse Posted September 9, 2013 Report Share Posted September 9, 2013 My 240 totally ruined my TY350 for me,just couldn't get used to the different response The stock TY350's throttle response is akin to a sheep with asthma........ Jon Quote Link to comment Share on other sites More sharing options...
lineaway Posted September 11, 2013 Report Share Posted September 11, 2013 Oh, another note, because my exhaust has seen better days. I've noticed a few TY250/350 pictures around with an aftermarket silencer of some sort, just a small round polished aluminum/stainless can type. Does anyone have any info on this, or shall I just measure and start digging? Since it seems to be a separate expansion chamber / silencer, the silencer shouldn't have a great effect on how well the engine runs, correct? Mostly just an effect on the noise output. That was probably the answer spark arrestor model. Which has not been available for years. Quote Link to comment Share on other sites More sharing options...
lineaway Posted September 11, 2013 Report Share Posted September 11, 2013 the 250 and 350 motors are nothing alike, the only thing the have in common are the words Yamaha they mount different, as well. look at the back of the cases...make sure the its not broken out from hard use...most TY250s were rode hard. every 250 iv seen has had the rear case repaired. used to be a few after market goodies available in the UK...John Shirt did a lot of trick stuff on the 250s... he offered a tricked out 250 and very few 350s.. the carbs are poop..a newere upgrade is in order... Chuck, the `84 250 vs `85 350 used the same crankcases. Do you really think Yamaha built a whole new bike just for the USA? Just a bigger cylinder and a few odds and ends. Most parts that started with 38v were interchangeable, the 46y were mainly 350 parts or later UK bikes. 1 Quote Link to comment Share on other sites More sharing options...
motovita Posted September 11, 2013 Report Share Posted September 11, 2013 The O ring asked about in the original question is a common replacement part that should be available from any Yamaha dealer. It fits a million different models and many dealers will have it in stock. I just pulled a box of TY350 parts out of my barn. I haven't sorted through it yet. I saw kick and shift levers, many gaskets, clutch cable, and some suspension linkage parts, brake shoes, all N.O.S. If anyone needs anything like that let me know and I'll see what I've got. Quote Link to comment Share on other sites More sharing options...
jontow Posted September 22, 2013 Author Report Share Posted September 22, 2013 Well, to continue the twists and turns of my TY mono adventures, exhaust system is back together and leaking only very little now. I took the opportunity to clean up a previous owner's work and weld the expansion chamber mount back on. I also sourced some cheap ignition coils that seem to work to fire the bike. However, I can't keep consistant spark! At times its a nice fat happy spark, sometimes its sputtering off the side of the plug, etc. When it's running, it's running really well, but all of a sudden it'll just die, not even sputter, just die. Usually when I'm on top of something, or far enough away that pushing is annoying! At some point, previous owner swapped in a 38V CDI, I think, and maybe the connector wasn't the same 3 pin plastic barrel deal as this bike, because they had cut the wires and crimp spliced + heatshrunk it back together. Because I was curious, and I'm running out of good options, I cut it open last night and soldered+heatshrunk it back together instead. It seemed to help, along with a freshly cleaned plug, but erratic spark is still with me. Again, the coils measure out to spec per the online manual I dug up, but CDIs are usually not something easy to test. Any ideas whether a dodgy CDI would do this? Or other ideas? I wish I had a known good CDI with the 3 pin plastic barrel plug to test with, but they're harder to come across than gold nuggets. Does anyone have any ideas what other CDIs might work on the bike? Sorry: a lot of questions in one post, but the theme is simple: I want to ride! Thanks all. Quote Link to comment Share on other sites More sharing options...
jontow Posted September 22, 2013 Author Report Share Posted September 22, 2013 Crossing my fingers, here, but on recommendation of this thread: http://www.trialscentral.com/forums/topic/34488-ty250-mono-starting/ I went ahead and cut off the male/female ends of the 3 pin connector and crimped on some butt splices to test. I just rode for 30 minutes straight (longest yet!) and had an absolute blast. It got dark, and I still don't have my headlight wired up: I believe its a 6VDC bulb in it, and I believe I'll need a 6VAC bulb, and I should probably acquire a switch! Now maybe it'll start again tomorrow Quote Link to comment Share on other sites More sharing options...
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