Ty175 Modifications Advice Wanted!

[newtotrials]

I'm looking to modify my 1977 Yamaha TY175 to make it more suitable for my size and for trials competition. But before I spend a ton of money I thought I would ask those who have hopped up their bikes for some advice on what works and what doesn't. Thanks in advance for the help.

Maybe a bit of info would help. I'm 50 years old, 200 lbs and 6 feet tall. Fairly muscular and a longtime motocross and ice racer. I just started riding again this season after 12 years of no dirt bikes. I picked up the TY175 two months ago and have ridden 1 trials event, in which I competed in the Twinshock C line. I plan to ride C the rest of this season and then move up to B next season and hopefully A the following year.

The bike is bone stock with the exception of Renthal motocross handlebars and oil pump being removed. All I've done to it is drop the forks 17mm in the clamps and cranked up the preload on the rear shocks to their stiffest setting. Both of those changes made a big difference!

The modifications I am definitely going to do are put on 6" rise trials handlebars, new Michelin tires, and add a Sammy Miller front mudguard stay. I'm not planning to touch the engine, as it runs perfectly, but I may add a WES silencer down the road. Here's some of the other items I've considered and my questions about them:

Shocks - I am going with the Betors. I've read that it is best to go with 14" shocks and then drop the forks flush with the top of the triple clamps. However some say stick with 13.4" shocks and the forks lowered in the clamps. Your opinions? Also at 200 pounds I assume I should go with the 50 lb springs instead of the 40 pound?

Forks - If I go with 50 pound shock springs, should I stiffen up the forks? And are there stiffer fork springs available?

Footpegs - I've heard good and bad about the Sammy Miller footpeg kit, most notably that they actually cause the bike to shake its head at rocks. Is it a worthwhile upgrade or should I just widen the stock pegs? The SM peg kit is very expensive here in Canada and I can widen the pegs for free! Also, I've heard KX65 footpegs will fit in the stock mounts. Is this true or are there any other pegs which would fit?

Also considering a new Sammy Miller seat/tank kit, but I'm holding off to see if I can find a used one. Can anyone comment on the benefits of this set up? My stock seat and tank are in very good condition so I could easily stick with them.

Any other suggestions for modifications would be greatly appreciated. Thanks!

Here's a pic of the bike as it is now from my ride yesterday:

Edited June 16, 2009 by NewtoTrials

[kimpybugalugs]

Sammy Miller tail pipe, boyesen reeds, uniflow air filter and 27.5 pilot jet made a big difference to my TY175. More grunt especially off the bottom end - usefull if you have to climb straight after a tight turn. I am about 105kg (230+ lbs) and it pulls me around ok.

I got the bits secondhand so not too expensive.

High rise bars on mine and I like them, otherwise I'm bent double and the back is not as strong as it used to be.

I have concentrated on performance rather than looks so I would'nt go the SM tank and seat unit route - I did get just the SM seat cheap secondhand so that went on.

Suggest you look through this Yamaha forum as there's loads of stuff in here - AndyT recommendations have been spot on for me but I think a boost bottle is just that bit too radical.

You should also look at the TY Trials website they know their stuff and have provided me great service.

Enjoy your riding.

[mattylad]

Best mod you can make is to lengthen swing arm by between 1 and 2 inches combined with lower and rearward footrests.

Stops it rearing up as often.

Engine wise you can use a DT 175 cylinder for more power.

Otherwise a piston with larger reed intake holes such as Dt or IT 175 is also good. Wiseco It175 or prox Dt200r prox is probably better but depends on avaliability

The exhaust is very restrictive so make sure it flows

Airbox inlet cover open out as far as possible

Open reed cage stops outwards by a few mm

[feetupfun]

Hi Newtotrials

I'm also 50 and am 208lbs and 5'10" and have been riding my TY175 since 1976. I see you have already worked out that the forks are a bit soft. I tried many things over the years and was not happy with the forks till 5 years ago when I fitted TY250 twinshock forks. The slightly stiffer rate springs and reduced fork flex are a good improvement. If you want to try stiffer springs in the TY175 forks, those from a TM125 Suzuki will give you just that and there are probably other Jap dirt bikes of that same era that will have springs that will fit in the TY forks and be stiffer.

The swingarm lengthening as previously mentioned is a good thing. The standard wheelbase is so short that stability is quite poor and riding up steep stuff takes quite a bit of concentration - especially turning up a steep bit from a cross-camber.

The decision of what length shockies to get is really a personal one because it depends on if you are a stationary balance/hopping person, or a no-stop type rider. The extra clearance with the longer shocks helps with no-stop riding but stationary balance is worse.

The Betors come standard with damping that is a bit stiff for best performance on things like loose rocks. They are good value though if you are not after the best at any cost.

Theres nothing wrong with riding the bike with SM footpeg kits. They are a tiny bit lower and further back than standard. The overall width of the bike is increased and they are way more comfortable. The RH peg will need to be held up to use the standard kickstart lever.

Theres no performance benefit with a SM tank - they don't give a weight saving over the standard setup and may even be heavier. They are useful though because many standard steel tanks have been lost to rust. Lightweight aluminium tanks are available for lots of $$$.

Yes 50lb springs will be perfect you and yes it will upset the suspension balance a bit with the standard forks, but most people I ride with use this combination and love it all the same.

David

[newtotrials]

Wow! Ask, and ye shall receive...

Thanks very much guys for the excellent tips on TY175 mods. I can believe the level of knowledge and advice offered so far. It is greatly appreciated!

I believe the bike already has Boyesen reeds and a few other things done to the engine by the previous owner, who was a very experienced trials rider. He rebuilt the engine last winter to get his son into the sport but said son ended up declining so I picked up the bike . The motor runs like a dream and pulls from idle smoothly up to the top. Starts first kick every time and it will sit on the stand and idle all day at revs so low you would swear it was going to stall... but it won't. It runs so well I am almost scared to touch it LOL! The WES or SM silencer though sounds like a useful option.

I am definitely a no-stop rider so I may go with the longer shocks etc. We'll see about the forks. Soft forks actually don't bother me that much on this bike because the front wheel seems to spend a lot of time just skipping over the ground...

Swing arm lengthening is something I had not even considered... however I do have a friend who is a very good fabricator and could certainly do the job for a case of beer. Might be worth looking into as a winter project.

Thanks again and keep them coming!

Edited June 17, 2009 by NewtoTrials

[nelly1]

the kx65 pegs do fit you have to trim the bracket a little its the loop that the spring goes through and take the corner off it but they sit perfectly and have a lot of grip

i got the idea off you newtotrials so thanks mate