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Ty Twinshock Mods


taff
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Hey guys,

A mate of mine has a TY 175 twinshock & wants to do some mods. It has to stay twinshock so we can still ride in the vintage class. Has anyone out there changed stuff like foot peg positions, steering angles, length of swing arms etc?

I'm pretty new to vintage stuff (modifying them anyway) but any suggestions would be appreciated. He's already done the exhaust packing mod & taken off the auto oil feed to gain a few more bhp.

Thanks

Taff

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I have a TY250 that I have had for a while and the best thing I ever did to it was put a new set of shocks on it. I got a set of Falcons and never knew how poorly my bike rode until I put them on. They are expensive but the best mod you can do. Heck, my old shocks were stock which means they were 30 years old so you know a new set makes a difference. Other than new IRC tires and a Mikuni carburator, my bike is pretty stock. Very reliable and is capable of getting through, over and up things that are beyond my abilities. IMHO the TY dosn't need much fiddeling with. Enjoy it. I sold my modern bike to spend the money on my TY and a TL125 I have. I will get a Montesa 315 soon but I am enjoying the old bikes just as much.

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Useful mods for the TY175 are:

Use Sammy Miller footpegs. They are a tiny bit lower and further back but the best thing is that they are much larger, providing a much more comfortable ride and better leverage for turns.

I will repeat what the previous respondent suggested. Falcon Classic shocks transform wonderfully the way both the TY175 and TY250 handle. Mine have 40 lb springs which are a tad soft for the 83kg rider.

Don't make the swingarm longer unless you want to go desert racing.

Again retain the standard fork tube location unless desert racing. About 20mm of tube extending through the top clamp is ideal for trials and trail riding.

The front end from the TY250 twinshock (larger diameter fork tubes and clamps) fits straight in the TY175 headstock if the rider is exceptionally heavy or picky about fork flex. I find the standard forks to be a bit soft for very heavy landings even with 15wt oil. Increasing the fork spring preload upsets the steering a bit in floaty turns and doesn't have much effect on bottoming anyway. I don't know of alternate springs that are any good. I have tried single rate springs from a TM125 Suzuki set up to provide the same static sag but with a higher spring rate but the standard TY springs were so much better in turns I went back to standard springs.

There are aftermarket springs available for the TY250 from B&J Racing in the USA. These work very well in the TY250 forks compared with the standard Yamaha TY250 springs.

If you are serious about improving the steering, buy a Mini Majesty frame for the TY175 running gear from Craig Mawlam in the UK. They were made in 1982 and have superior chassis geometry. If you steepen the steering on a Yamaha frame, you may have to redo the exhaust to keep clearance for the front mudguard.

The motor can be increased in capacity for more grunt to 205cc with a larger cylinder sleeve. Breathing may be compromised by this ie it may not rev as high as the standard Ty175.

Increasing the compression ratio slightly from standard improves pulling power also but requires careful fuel selection and meticulous spark timing maintenance.

David Lahey (TY175B fan)

Australia

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I installed Boyesen reeds. My main concern was to avoid sucking the stock stainless units and causing many many $$$ of damage. I also fabricated a 1/4" spacer from aluminum sheeting. It worked fine, however the engine also showed signs of extreme wear in other areas. The engine rebuild is in the final stages and I hope to be up and running in a week or so.

I too have the Sammy Miller footpegs, very good investment, however they could still be about an inch lower for my tastes. I also picked up some used handlebar clamps to use as a riser/spacer to raise the handlebars to a more comfortable level for me. With the footpegs being a bit high I felt bent over all the time.

I bought my bike with a set of Betor shocks installed. I'm sure they're superior to the stock units although they needed to be rebuilt. I fitted new o rings and replaced the fluid, will have to see when the bike is up and running. If the TY becomes my perminant trials machine, a set of Falcons from B&J will be one of the first items to be purchased. Then a Sammy Miller tank seat unit to replace the ugly dented up stock tank.

My bike was also fitted with the IRC tire. I would say that the single most effective mod would be to fit a modern tire to the bike, there is no comparison between today's modern tire technolgy and that of year's past.

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I extended a swingarm a few years back on a 74 TY250. I had been riding with a fellow who had a Honda Reflex and the rear end seemed to work real well on it, so I extended the swing arm and repositioned the top shock mount trying to get the same angle as the Reflex. Also had to go to a Reflex shock as it's a lot longer for that long distance on that laid down positioning. It actually worked pretty awesome when I got it done. I doubt it would be legal in the serious vintage competition though as it had too much rear suspension. I rode it in the local club till I finally upgraded to a TY350. I've never seen it again since I sold it. Wonder what ever happened to it?

I've put new rear shocks and new fork springs on the TY250 I have now, but have kept the dimensions otherwise stock. It works pretty good too.

post-12-1074406553.jpg

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  • 2 weeks later...

Ok, the bike is back together and running very good. The biggest difference I can feel is the high position of the footpegs when compared to the GasGas. I'm bent over and the CG feels very high. After studying several photos of different trials bikes it seems that the most successful models have the pegs positioned along a line connecting the axels. I'm seriously considering building new peg mounting plates to lower them (and lower the brake peddle). Has anybody else done this? Results? BTW these are the Sammy Miller pegs.

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  • 1 month later...

Eric the Sammy Miller pegs lower them anyways? Or do you want them even Lower? Thanks for your replies guys. We've got the Sammy Miller pegs & the Falcon shocks on order. Let you know in a month how it worked out.

Taff

Edited by Taff
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