alan_nc Posted March 12, 2009 Report Share Posted March 12, 2009 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 Quote Link to comment Share on other sites More sharing options...
feetupfun Posted March 13, 2009 Report Share Posted March 13, 2009 Standard they have a steel band fitted to the OD of the magneto flywheel. Are you saying that yours has a weight fitted to the face of the magneto flywheel as well as the band on the OD? Quote Link to comment Share on other sites More sharing options...
dave dix Posted March 13, 2009 Report Share Posted March 13, 2009 I would leave it weighted as the weight helps bottom end running Dave Quote Link to comment Share on other sites More sharing options...
alan_nc Posted March 13, 2009 Author Report Share Posted March 13, 2009 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 Quote Link to comment Share on other sites More sharing options...
feetupfun Posted March 13, 2009 Report Share Posted March 13, 2009 Alan, the B, C and D model flywheels have an even bigger external steel band on them than the A model. I've ridden them with and without the band and find that while they are quite zippy with no band fitted, you need to have a very quick clutch hand to avoid stalling when riding serious dry rock sections. I have ended up with steel bands that are about 2/3 the size of the B,C and D model bands (or 3/4 the size of the A model band) on my B and D model motors. David Quote Link to comment Share on other sites More sharing options...
tony283 Posted March 13, 2009 Report Share Posted March 13, 2009 Alan, The bigger flywheels are much better for those of us that never use the clutch, allowing the motor to rumble on at idle without stalling. Re the gears and sprockets check to see what chain you are running. Normal set up was 13T and 53T with the 428 but is better with a 12T front. 11T is just too low. If you have the 520 chain then 12T and 42T seems about perfect. Tony Quote Link to comment Share on other sites More sharing options...
dave dix Posted March 13, 2009 Report Share Posted March 13, 2009 I actually use 11/53 with a 428 chain and i like the extra low gearing as it enables me to use higher gears which will spread the load away from the lower gears Dave Quote Link to comment Share on other sites More sharing options...
jessie wallace Posted March 23, 2009 Report Share Posted March 23, 2009 Back when these bikes were new, we added an additional brass flywheel weight to the smaller factory steel band. Flywheel in the freezer, brass weight in the oven; it'd slide right on. It had a huge effect on the preformance, but this was in the days before good rubber and you needed every bit of help you could get. Quote Link to comment Share on other sites More sharing options...
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