garyo Posted March 25, 2016 Report Share Posted March 25, 2016 Hi, i am using my ty 125 on the road, what would the best combo sprockets be? Currently it had a 17/37 combo, and wont go more than 40 mph and combletelly flat, can manage to get into 5th gear but not in 6th. Quote Link to comment Share on other sites More sharing options...
collyolly Posted March 26, 2016 Report Share Posted March 26, 2016 If it cannot pull the higher gears there is no point changing it for faster roadwork, suggest you get a bigger bike or one more suitable for your needs. Don't kill a classic, it was not designed for the road. Quote Link to comment Share on other sites More sharing options...
2stroke4stroke Posted March 26, 2016 Report Share Posted March 26, 2016 (edited) As you have discovered, the bike is grossly overgeared with 12, I think, being the standard front size (not sure about the rear). It's a wonder you can use it in trials going (if you do). I don't know why it would have been changed so drastically. I assume still on the 420 chain? I seem to recall someone trying one tooth up from standard in the day but can't recall how satisfactory that was in terms of trials use. You could always work out the overall ratio in each gear then choose sprockets to match what you know the bike will pull. I'm sure you can get the necessary info to do this from the net. Edited March 26, 2016 by 2stroke4stroke Quote Link to comment Share on other sites More sharing options...
garyo Posted March 26, 2016 Author Report Share Posted March 26, 2016 Hi, the 125 was designed for road usage, this bike still has all the bits on it from factory, bat box, indicators etc. I have just checked the haynes manual and bizzarley it states a 17t/37t combo. So i must have other issues preventing from pulling and bogging down, throttle response in 5 gear from half to full throttle is nothing just an induction noise I assume i have a blocked exhasust? I am thinking first to try a 15t front sprocket and assume this will let the engine rev harder in 5th gear? Or go for a 13t? The standard ty175 sprockets are 13t/51t Quote Link to comment Share on other sites More sharing options...
spen Posted March 26, 2016 Report Share Posted March 26, 2016 Check air filter and exhaust for cleanliness. Make sure your brakes aren't binding. Quote Link to comment Share on other sites More sharing options...
dpyam Posted March 26, 2016 Report Share Posted March 26, 2016 (edited) If it has still got all the "road" bits fitted it sounds like a rarity to treasure - enjoy ownership! My TY175 is road legal but realistically a TY is designed for slow, low-revving off-road riding, but with some lights fitted, allows use on-road. I wouldn't use my TY for commuting or anything - it would kill it - a trail bike (like a Yam DT) would be a better bet for that - a good excuse to own 2 bikes! The steep fork angle on a TY, plus off-road tyres, makes it unstable over 40 compared to a road or trail bike. There are road legal classic "enduro" bikes around as well (e.g. Yam IT175) but again they're very off-road focussed. You don't say what the history of the bike is but before trying more sprocket variations make sure the bike is running as its best: new spark plug check timing check carb jets and settings are set to standard (if the rest of the bike is) clean the air filter check exhaust is not blocked brakes not binding tyre pressures etc Having said that, a 17 front sounds very over-geared. Edited March 26, 2016 by dpyam Quote Link to comment Share on other sites More sharing options...
dpyam Posted March 26, 2016 Report Share Posted March 26, 2016 Another thought - I don't know what the 125 is geared like but my 175 is basically 1,2,3 and 4 are "crawler" gears for off-road, with a jump to 5 and 6 for road use (max cruising around 40mph). Maybe someone thought that with a 17T front you would end up with 4 "road" gears, and 5 and 6 are only usable down steep hills? Quote Link to comment Share on other sites More sharing options...
2stroke4stroke Posted March 26, 2016 Report Share Posted March 26, 2016 The 125 silencer was a bit more restrictive than that on the 175 and could be choked. Find a road in the middle of nowhere and try running without it? Quote Link to comment Share on other sites More sharing options...
garyo Posted March 27, 2016 Author Report Share Posted March 27, 2016 Thanks, yes the bike has all the original bits on it and never trialed. I have done the crank seal, inc the shaft o ring, stripped and cleaned carb, fuel tap, this was grotty, points, and condenser, they were sparking like a sparkler, now no arching, new plug, seems to get quite oilly wet, checked the oil pump and set this to book, but i suppose if you open the throttle and its not pulling then all you are doing is pumping excess oil into the pot thats not getting burnt. Brakes not binding. I put caustick on the end pipe, it is still the original big black silencer, will try and find a ty 175 1 to try on it. Could the rest of the exhaust be blocked? Ordered a 13t sprocket to see what it does. I also found in the yamaha parts book for the 125, they list a 15t/45t combo on the sprockets, so 2 conflicting sets, would of thought this combo would be better than the haynes quoted set detailed above. So a 13/37 would put it somewere close to a 15/45 allowing 1 on the front is equivelent to 3 on the rear? Quote Link to comment Share on other sites More sharing options...
dpyam Posted March 27, 2016 Report Share Posted March 27, 2016 So it may well be there's nothing wrong with your bike other than the front sprocket is way too big. A change of one tooth at the front is usually quite noticeable so you will be see a huge difference with a 13T - with chain tension too. For reference, I can pull away happily in 3rd and 1st and 2nd are a bit pointless on the road. I bet if I had a 17T front then 5th and 6th would become pointless - you can't win them all........ :-) Quote Link to comment Share on other sites More sharing options...
garyo Posted March 27, 2016 Author Report Share Posted March 27, 2016 Yep, the 13 is on order, will try it then if needed step up a tooth, i will be happy if i can get some rpm on 5th to stop the 2t just pouring in. Currently 1 to 4 is like a road bike, so if i can get 2 to 5 would be better. The bike is only going to be ran about 5 to 10 miles per week,a if im lucky min would be 2 miles. Friday night to bike night 1 mile away, and if nice to airfield on a sat or sun 4 miles away. I have an aeroplane that I spend my time mostly with at w/ends, hence no trials riding. I will prob restore the bike over the next winter then decide on what to do with it. I have a 1974 fizzy that I fully restored, but only do about 100 miles a year on. Quote Link to comment Share on other sites More sharing options...
garyo Posted March 30, 2016 Author Report Share Posted March 30, 2016 Fitted the 13t tonight, had 2 remove 2 links from the chain, so I now have 13/37 2.85 to 1 I must say it has totally transformed the bike, 1 an2 are quite low, 3 is ok, 4 and 5 are what I wanted and 6 will still pull. I blasted it down the rd and got to 60 in no time, it was still pulling but a bend was approaching so slowed up and turned around and went back home. The stock is 15/45 which ends up at 3.00 to 1 so close to this and would be spot on. Will invest in a new chain n sprocket set later in the year as other jobs to sort on it, but over all quite chuffed Quote Link to comment Share on other sites More sharing options...
feetupfun Posted March 31, 2016 Report Share Posted March 31, 2016 The (very high) standard gearing on the TY125 may have been chosen to help meet noise level standards rather than be ideal for road performance. It was common practice in the 1970s Quote Link to comment Share on other sites More sharing options...
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