james n Posted October 13, 2014 Report Share Posted October 13, 2014 Hi all In July I had a piston failure and since have rebuilt the top and bottom end of the ty 250a. Now i feel the clutch is slipping when going down hills. The clutch does not slip at all under hard acceleration. I was using atf fluid after the rebuild and noticed a small amount of slipping going downhill so I switch to honda gear saver trans fluid. The clutch would slip on acceleration until it got really warmed up about an hour, so I went back to atf fluid and it only seems to slip going down hills. This doesnt make sense to me. Hopefully somebody can help me out before I tear back into the clutch. I have two more trials coming up soon . James Quote Link to comment Share on other sites More sharing options...
zerorev3rev4 Posted October 13, 2014 Report Share Posted October 13, 2014 never heard of a clutch slipping downhill ,, why not use your brakes more than the engine braking long engine braking on a 2 stroke is not good as theres little lubrication at high rpm which can cause a seizure Quote Link to comment Share on other sites More sharing options...
feetupfun Posted October 13, 2014 Report Share Posted October 13, 2014 The best test for clutch slip is acceleration in top gear It is extremely unusual for a clutch to slip when the engine is working as a brake, because there is much less torque being transmitted by the clutch in a given gear when the engine is used as a brake, compared to when you are accelerating Quote Link to comment Share on other sites More sharing options...
james n Posted October 14, 2014 Author Report Share Posted October 14, 2014 When I say going downhill I talking about a small slope where you just coast down with no brakes. The bike did not do this before I rebuilt it maybe I put something in wrong.The bike runs alot better and pulls a lot harder. I am able now to use 2nd & 3rd gear going up long steep uphills where as before it would have been 1st maybe 2nd gear.I am not even sure its the clutch slipping its like when the engine is working as a brake the rear wheel over rides the braking action. Quote Link to comment Share on other sites More sharing options...
guy53 Posted October 14, 2014 Report Share Posted October 14, 2014 Do I get this right. The clutch slip going downhill : the motor does not pick up rev but the speed increase ? Guy Quote Link to comment Share on other sites More sharing options...
james n Posted October 14, 2014 Author Report Share Posted October 14, 2014 The slip is only momentary then it goes a little farther and may or may not do it again . Someting I noticed when putting the clutch back in was the differance between my clutch and the yamaha parts diagram for a ty 250a. In the parts diagram it shows clutch plate #1 ref. #4 qty 1 then friction plate ref# 5 qty 7 then clutch 2 ref# 6 qty 7 then pressure plate #1 ref # 7 qty 1. On my clutch there was only 6 clutch plates ref #2 which means the pressure plate was against a friction plate.I looked at a parts diagram from a 1976 and it was like my clutch in as much as the pressure plate was against a friction plate, so I thought it might be right. Another differance was my clutch does not have the the spring , belleville ref #12 in the parts diagram,I thought thats really strange but it worked before. I wondered maybe I lost it but I was very carefull when disassembled the motor. Has anyone ever had a clutch that didnt match the yamaha parts diagram for a ty 250a. Quote Link to comment Share on other sites More sharing options...
james n Posted October 15, 2014 Author Report Share Posted October 15, 2014 Clutch slip solved,I hope. A couple of the answer from this post questioned clutch slipping going downhill ,so I started wondering what else could it be. I took the bike for a ride and started to watch the chain when it sliped I noticed the tensioner jumped hard every time it appeared to me to slip.I tighten the chain a little more then I normaly do , and no more downhill slipping. I just started running an o-ring chain in july hopeing to get more life from the chain and sprockets, theres lot of mud and hills in n.w. pa u.s.a.and I seemed to be wearing regular chain and sprocket out quickly so I tried the o-ring. I am running a 10 frt & 50 rear sprocket and could tell right away that the o-ring chain wasnt happy going around that 10 tooth front sprocket. anyhow dont really know what was happening but tighten the chain fixed it. Thanks to every buddy that replyed and made me start looking at other things beside what I had stuck in my head. james Quote Link to comment Share on other sites More sharing options...
james n Posted October 16, 2014 Author Report Share Posted October 16, 2014 Two other things: 1) Has anyone noticed the difference between my clutch (described in earlier post) & the Yamaha TY250a parts diagram? 2) I am not sure if this applies to all Yamahas, but the Honda Gear Saver Lubricant did not work with my Yamaha - it caused my clutch to slip until it got really hot. Now I am using ATF & it works fine but I am probably going to put Silkoline gear oil back in it since that is what I have always used. Thanks, James Quote Link to comment Share on other sites More sharing options...
jon v8 Posted October 16, 2014 Report Share Posted October 16, 2014 My TY250 didn't like ATF in the gearbox,now I'm using MTF94 which is a Land Rover manual transmission fluid,works very well.(Guess what I do for a living....) Quote Link to comment Share on other sites More sharing options...
guy53 Posted October 16, 2014 Report Share Posted October 16, 2014 10W30 for me Guy Quote Link to comment Share on other sites More sharing options...
lineaway Posted October 17, 2014 Report Share Posted October 17, 2014 Sounds to me like the rear tire is going into a skid or slide going downhill. Beware tightening the chain too tight as you can break parts. An O-ring can be a great investment, but totally wrong on a bike that is designed to go slow. It robs what little power the ty makes. Push it around your block once without the motor running! Quote Link to comment Share on other sites More sharing options...
tony283 Posted October 17, 2014 Report Share Posted October 17, 2014 Your main problem would seem to be the chain and sprocket set up and nothing to do with the clutch. The original set up was 13 front and 53 rear with a 428 chain. The ideal for modern day events is 12 front and 53 rear. Any smaller on the front and it will bite into the swinging arm and clack as it tries to follow the front causing the chain tensioner to bounce. Tony 2 Quote Link to comment Share on other sites More sharing options...
james n Posted October 17, 2014 Author Report Share Posted October 17, 2014 I think you are right Tony, the only place I have found that has sprockets for a ty 250a is sunstar. I was wondering where you can get a 53 tooth rear sprocket. Lineaway my ty seems to have plenty of power, it preforms better now the ever before because of the rebuild. even before the rebuild I didnt notice a power differance when I put the o-ring chain on. ps I put a wossner piston in it because it was the only piston maker that had one available. So far I very pleased with the wossner piston. Quote Link to comment Share on other sites More sharing options...
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