alan_nc

Power washer is one thought.... I usually end up with my motor at least half submerged in every Trial I ride. I change the primary and gear oil after each one. Alan

Feetup, Yes the band around the flywheel is what I'm talking about. Did not know that. My other bike does not have a steel (I guess) band around the flywheel. Both bikes had been used for motocross before I got them - that was the big thing around here 20/30 years ago. Guess the first bike had it removed to try and improve throttle response. The guy I bought the bike from said - "its a strange bike, the first two gears are useless". I just looked on the 'Speed n Sport' (Yamaha parts list) and it does show the flywheel with the band. Doesn't even show it as a separate part number. I don't think I have ever seen the correct flywheel show up on ebay. Thanks for the info - Don't you just love this site and all the information you can get. Alan

Picked up another 74 TY250 this past week. Guy about 1/2 hour from my house had it at a fairly reasonable price. Runs fine, had been used for motocross. I have been going through everything. Changed fork oil, took MX tires off and put Trials on, took the lights off (they actually worked), took the Preston Petty fender off the front. Pulled the flywheel side cover off and the flywheel has a large weight attached. I know they used to be used quite a bit but had never seen one on a TY. The bike has a beautiful slow idle and actually accelerates very well. Also has a larger rear sprocket than my other TY (haven't counted the teeth yet). Oh, and it has the lightest clutch pull of any non-hydraulic clutch I have ever seen (all springs are still installed). So would you leave the weighted flywheel in or take the weight off? I will be riding the bike in vintage Trials. Please.... any other comments appreciated. Alan

Tony/Feetup, Have you ever used ATF? The 10/30 just seemed to stiff and I couldn't easily find straight 10 weight oil. My understanding is that ATF is just about 10 weight. Oh, I also use it in all of my primary's. Alan

Mike, Couple of questions: You said you went to the 1st oversized on the piston (was the cylinder scored?). I would check all the tolerances as you take things apart. Check the end play of the crank. Once you have the cases split, go ahead and replace seals. I just pulled my 74 TY250 apart (ring broke and broke ring land on the piston), cylinder was perfect and still well within spec. I replaced the crank bearings, including the crank pin and bearing, and the seals. Note: Get the part numbers for the parts you are going to buy off the web listings. Check the big on-line Yamaha boat suppliers. They can get the same parts and I have found them to be 30 to 60 percent cheaper than the motorcycle suppliers. Good luck..... take your time. Alan

An update: Re-assembled the crank yesterday. New bearing and pin (same rod). Put pin in one half first. Then put bearing, shims, rod on and used a square to line up halves as best I could. Pressed 2nd side on pin 1/16 to 1/8" then put it in a lathe we had set up ahead of time. I was about .060 thou out the first time. Used lead hammer and after about 6 or 7 "adjustments" I had it +- about .0005. From then on I would press it in about 1/8" take it out and measure....repeat. Actually once I started it didn't move much at all. Just a note: I started with a 5 ton manual press. Gave up and went to a 15 ton hydraulic, Worked much better and I was able to press much more carefully. I had taken all of the measurements before I took it apart and I actually have it closer now than when I started. The proof will be when I start her up. Alan

Steve, You are correct. It makes them easier to replace and doesn't subject them to the heat and grease of the inside of the engine. I have mine mounted on the frame up by the coil - under the gas tank. Alan

Group, Update: Replaced the condenser, plug, points. Set timing to 2.5mm. Started 1st kick (cold). Didn't have a chance to ride any as it's raining buckets here. Hopefully I can get out tomorrow some. Thanks to everyone. Alan

Well it's been between 20 and 40 degrees (f) for the past couple of months, but I have had the problem at 0 degrees and 85 degrees. This bike has just never been a 1st kick starter. Will replace the points and set the timing this weekend, then report back. Alan

Dave, You are correct - but that still leaves me with a two or three kick start when hot. I don't know how your cousin did it this past weekend - he must have kick the Mont 10 times every start. Feetupfun, You see my problem. I'm wupppped about half way through. I get so tired it is killing my scores. Group, Do you set the timing 'by the book' or do you change it slightly? Thanks for the replies. Alan

Group, Need some suggestions: I ride a Model 92 Sherpa T in Trials. Totally stock bike, points, AMAL carb. Great bike, runs fine, rebuilt about a year ago. Plenty of power, very good throttle response. My problem: It isn't now, and never has been a "first kick start". 5 to 7 kicks when cold and usually 2 or 3 when warm. This is a real pain in Trials where you have to start the bike about 30 times in an afternoon. Any suggestions to improve starting. I don't even care if I loose a little power. Thanks in advance. Alan

I have a lathe available and plan to chuck it on the bearing surface and check runout with a dial indicator. Does anyone have any idea what the runout would be on the tip end (flywheel side) if I chuck on the clutch end? Well, I guess, what would allowable runout be on one bearing journal if I chuck on the other? Thanks for the help - I think I have the idea...... proceed sloooooowly. Alan

JSE, Thanks, that will help. Do you have anything special you do to align the halves of the crank prior or during assembly? I have a good press (used to take it apart), that will press it together fine, but what do you do to maintain the shaft alignment? Alan

Split my TY250 crank (bearings were bad). Marked it good for re-assembly but would really like to have any suggestions on "Tricks" to ease the re-assembly process. I'm still concerned about getting it aligned correctly. Thanks in advance. Alan

Group, Along with several "errors" I noted that he lists it as having a 4 speed transmission. He states that the serial number of the engine makes it a 1960 - I know of no 1960 Bantams that had 4 speed transmissions, and it's my understanding that a 4 speed will not fit in the 1960 cases. Unless the transmission gearing has be altered drastically that rear sprocket is not going to work for Trials (note the one on my bike). He states that it is 'street legal'. Well my experience is that if you make a Bantam ,Trials ready ,you are not going to be riding it on the street. Mine has a top speed of between 25 and 30 mph. I just hope that whoever buys it understands what he is getting. Alan

Interesting, I competed on a '59 Bantam for a couple of years. I finally gave up as they really don't make a very good Trials bike - even after much altering. Someone has taken quite a bit of time working on this one. It seems to suggest that the Factory had something to do with it .... I really doubt it. I would say that it's a "one-off" that someone built to try riding Trials. Would be fun to try it out.... but sure not worth very much. Here is mine:

Dave, Was hoping to have everything sitting ready to go back together when I started. Do you happen to know the number(s) of the two crank seals. I have the Yamaha numbers, but not the Seal Company numbers. Alan

Thanks guys, Does anyone have a source for the seals? Found the bearings on ebay but am striking out on the seals. I know Speed and Sport have them but I'm a cheapskate...... $36 for two seals seems a bit much. Alan

Well I had a wonderful weekend of riding but about 5 minutes before loading her back on the truck I seem to have blown a crank seal. Lot of bottom end noise for awhile and now the carb won't settle on an idle - guess air is getting past the seal on the flywheel side. Will get bearings and seals this week and start in. Have never split the cases on a TY250....... please...... anything I should watch out for ...... any suggestions? Thanks in advance. Alan

Tony, If AHRMA would switch to peer scoring you would need a lot less folks to put on an event. I would rather have someone who knows/understands Trials score me than some random person who walks in off the street. Just my .02 Alan

Go to Britbike.com and look under the forums section. There is a specific section about stickers/decals. Here is what I have used:

Mine were painted black when I got the bike. I used paint remover to take it off. I kind of like the weathered look, but then mine is a rider not a show bike. (that sort of came off wrong - I'm just not into the looks of a bike.) Alan

Just went through the same thing. Used a DT250 piston. You do have to grind the skirts to clear the crank but everything else is fine. I found one on Ebay for a very good price with rings, clips, pin included. I also replaced the small end bearing while I was in there. I was surprised at how much harder it was to kick over after replacing the parts. Alan

axulsuv, That looks like it would work, how do you mount it on the bike? Alan

Thanks to everyone for the responses: I'm riding modern trials on a '74 TY250 - this is the only local club that I have a chance to ride with. They have hydraulic clutches that can be pulled (and held) with one finger all day. My clutch works fine (for a '74 TY250) but I'm trying to make a silk purse out of a sows ear. No.... I can't afford, and don't really want a modern bike. Not only do we NOT have a "NO STOP" rule, we usually have several sections that you can't negotiate without stopping. I don't know about you guys but I just want to be able to ride a Trial every weekend. Thanks to everyone for the suggestions. I will put all to use (including trying the bike with 2 clutch springs removed). Alan