Here we go again i hear you say! getting back to riding again after many years away from the sport. I am looking at the SCORPA range of bikes and have seen a few on this website, my biggest confusion is they all look very much alike only the colours change. would this be a user friendly bike for a ...

For those interested, we fitted the new rings and the standard bore is still within spec. Just waiting on tyres now so we can use it.

Gday, and further to the above, you will be lucky if you can get chrome rings to run in the nikasil bore. Cast rings will last anything up to about 15 minutes.
Don't Nikasil this bike.
Cheers,

Stork

Hmm might have to give up on the Nikasil from the sounds of it

I've found two sets of NOS ...

I've never seen a cast iron bore that was nikisil plated, as far as I know it is only done onto Aluminium. So to nikisil a TY175 barrel you would have to get all the cast iron bored out then have an aluminium sleeve made to take it back to standard bore before getting nikisiled. Could be a little ...

If/When a rebore is necessary I'll send the barrel away for nikisil coating along with a replacement piston & rings and they'll match it up.

David - can you show me the link to the genuine L-shape rings or do you know the part number I need for STD size? I did see some on the net but I couldn't ...

Dad bought a new TY175 in about 1978/79 - I'm pretty sure it was $1050.00 from the dealer including on-road costs (he used to ride it to work during the week, trials on the weekend).

Today in as-new, showroom condition I think it would be worth $5000-$6000. Unfortunately we sold it a few years back ...

Looks like you could be lucky with that sort of mileage.
Rings would have to be genuine Yamaha. If your rings are only just on max gap I'd just give it a good clean and stick it back together, use 32:1 oil ratio and it will probably go for quite a bit longer. When in the future it starts to get a ...

You realy need to get the the piston to bore clearence measured accurately as the eye isn't as good as a micrometer. If your Dad doesn't have the gear to measure it, take it to a engine shop and they should do it for you. What part of Aus are you in?
At 66mm it is still a stock bore and after 30 or ...

Dad says the top ring is an L-shape and is different to the lower ring.

The bore is measuring spot on 66mm with no lip or visable signs of wear.

The ring gap by the manual is right on the replacement mark for one ring and just past due on the other.

I figure it maybe safer to just get a piston ...

We want to change the rings on our TY175 but we are unsure if its been bored out or not and as such I am unsure which rings to order?

The barrel has .008 stamped on it. The piston doesn't have any numbers stamped on it (we polished the top of it to check).

Can someone advise what or how to measure ...