I know some people upgrade their TY175s from a 428 chain, as someone who has had zero problems with the little chain I'm wondering just how much stronger is the bigger one?

A 520 is about 25 % stronger than a 428 but comparing the tensile strengths of the chain is not that useful. You can look up minimum tensile strengths in engineering tables but this would not tell you everything. All decent chain is stronger than the minimum but some are much stronger and more hardwearing than others. All other things being equal a 428 chain will wear slightly faster than a 520 because there are more links to wear in a given length. A 428 chain is smoother running and lighter. A 428 chain will stand over 2 tonne which is far more than a TY 175 will put on it. Best thing you can do for a trials chain is an oiler dripping bio degradable gear oil onto it and spay it with WD 40 or similar after washing the bike.

I ran a 428 chains on a 120kg bsa for many years (plus 80++kg rider)  More than capable, and lighter as stated above.

Edited August 30, 20223 yr by b40rt

Thanks Like the upgrade to 250 mono forks I suspected it was more of a want than a need, but it's good to know the reasons!

 You can buy high strength 428 racing chain that probably exceeds the strength of low grade 520. Look up manufacturers specs online.

 And TY mono forks are an ENORMOUS improvement over TY175 forks.

Edited August 30, 20223 yr by motovita

I'll take your word for it over the forks, I have Magials progressive springs in mine and TBH now I've got the oil right I can't tell the difference between them and the forks on my ST2.5, so I don't feel the need to upgrade

4 hours ago, turbofurball said:

I'll take your word for it over the forks, I have Magials progressive springs in mine and TBH now I've got the oil right I can't tell the difference between them and the forks on my ST2.5, so I don't feel the need to upgrade

I run a 428 chain on my TY250 twinshock with no problems - it is how it came out of the factory. Mick Andrews was very frank with Yamaha about the TY range,got his own way over most of the design. Looking at how little needs doing to a TY compared to other brands of the time I think he and Yamaha did a very good job. There was a time a while back when it was popular to fit mono forks onto the twinshock TY's, then most went back to the originals as they felt the leading axle of the mono ones spoilt the steering. The progressive springs are the way to go as you already have.

Edited August 30, 20223 yr by jon v8

23 hours ago, turbofurball said:

I'll take your word for it over the forks, I have Magials progressive springs in mine and TBH now I've got the oil right I can't tell the difference between them and the forks on my ST2.5, so I don't feel the need to upgrade

 As long as they work for you that's all that matters. Personally I'm not a fan of putting non period correct parts on vintage bikes so i wouldn't do it either.