TY175 swingarm lengthening

[David Lahey]

Had some workshop fun last weekend - just another page in the endless "fiddling with my TY175" story

[Reinald]

Hi Dave,
Is this due to other frame modifications or just for stability up hill?

[David Lahey]

The standard TY175 frame is short and has slow steering. I find the standard combination is pretty good except for uphill turns. The first set of frame mods made the steering lighter in turns so is a bit easier to control when going very slowly with a lot of load on the front. It also moved the bars forwards, which improved the ergonomics but uphill turns were still tricky. The motor mods made the motor much more snappy which exaggerated the instability in uphill turns. The swingarm mod has put noticably more weight on the front end and it now turns uphill much better. The steering is still nice and light even when loaded. The swingarm lenthening has also softened the rear suspension a bit, due to the increased wheel travel.
I rode the modified TY175/205 back to back today with the 250 Majesty and the handling and steering is very similar, but the TY175/205 is lighter-feeling overall.

[Reinald]

Was this the bike that you cut a piece out of the frame to shorten the "backbone"?
If you can get to handle like the Majesty then that would be worth the mods.

[David Lahey]

Ah yes - from a man who has ridden the Majesty. The TY175 might now handle like the Majesty, but what more do I have to do to it to make it handle like an SWM TL320 hey??
The frame mod was to lengthen the top tube frame tube. That moved the bars forward and steepened the head angle.
I've just put a better story and more photos on the Trials Central Yamaha forum by request
David

[Tee-Why]

Nice productive work David, I always enjoy the reasoning behind the mods too. I know how much thought it is before one cuts and welds, measure twice-cut once is the plan. As with the final results, it can be a bit of budge with something else to alleviate like the brake rod items etc. (from experience with making a lift kit for a 4x4, there was another added task attached with each step!)

I have been looking at my own TY175 for similar reasons, more power has made the front end plow in tight turns. So far I have managed to keep the bottom end tractable enough. I made new footpegs plates fitted new wider footpegs lower, not back. This lowered the rider weight without loading the rear any further, and less tendency to feel poor on uphills. But I want to weight the forks by moving the controls forward to load the front end with bar offsets. This will basically mean no frame mods. But the rear springs are standard length, and could really be the longer ones to achieve a bit more forward bias. As always, never finished looking outside of the box for improvements!

[Guy53]

Super nice job on the swingarm. My question is not on that job but on the front end, I finaly laid my and on a ty250A frame that I intend to torture, I will lay shock mount '' A LA Majesty '' try to raise the motor an inch but what realy interest me is to play around with the fork rake, it seem's to me that I should '' close '' the angle. Did you ever tried and if so what was the result?

Guy

[David Lahey]

I like the standard steering angle on the TY250 twinshock so have not tried changing it. I have fiddled with a TY250 frame though, to raise the motor by shortening the frame uprights.
Raising the motor by relocating the shock mounts does give more ground clearance under the motor but also raises the bike's centre of gravity. The first Majestys were made using modified Yamaha frames that had the frame uprights shortened, as well as relocating the top shock mount to soften the action of the rear end.
If you raise the bike by raising the rear end you will get a steeper steering angle without having to do frame cuts.

[Guy53]

That was my first intention but I tought it would alter the overall balance of the byke. Footrest mod made such an improvement ( 1 3/8 inch lower and back ) my idea was that increasing the lenght of the shock more than 340 mm would pin down the front end without giving me quicker steering.

[Greg Harding]

Hi Everyone,

Interesting, I assume all of you realize that there are purists who only beleive in concourse del elegance and the manufacturer got it perfect in every way!

Thankfully most people are more realistic, ever since the beginning of time we have been improving things and why not?

All of the modifications discussed here could have been acheived in that era and I have no problem with them at all.

Personally, (hypothetically speaking) A 35mm longer swingarm with axle slots 10mm lower mounted to a standard frame improves the overall handling. What about the chain hitting the swingarm pivot you say? Good question, 60 tooth sprocket and 340mm between centres shock absorbers gives enough squat under power. Plus more ground clearance and steering which is both responsive and stable. Yes it does raise the centre of gravity a little but the improvements in the way it puts down power up hill makes it worth it. Always more than a couple of things to consider.

David and Chippy, maybe this will distract your attention away from my heavy duty tie down points?