TY175 Rings

[jacks1071]

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 and what numbers I am looking for to work out if its been over-sized and if so, by how much?

Also where do I find the parts?

Last question, what should we mix the oil at? I was thinking 80:1 with fully synthetic but being and older bike I'm not sure if it requires a richer oil ratio?

[David Lahey]

First off you will need to find out what type of piston is in it, because different pistons have different types of rings.
The other thing is to measure the bore accurately to know which size rings to get
Bore size is usually in steps of 0.25mm (0.010") above standard so if you can measure the bore above where the top ring reaches to, you can tell which oversize it is. To tell which type of piston will probably require taking the cylinder off.
Most people rebore when the rings get worn because new rings and piston in a new bore will last way longer without attention compared with new rings in an old bore. However some people really enjoy working on their bike and if that is you, then there is nothing wrong with just changing the rings (provided the bore is not worn).
If you can take the cylinder off and post up photos of the piston, it may be able to be identified by someone on the forum (there are many different brands of pistons made for the TY175)

[TriCub]

What david said for your first questions about the rings. I'd say if there are no markings on the piston top it could be a stock original piston but be carefull if you measure around the cylinder top to clean off the carbon first.
On the oil ratio have a look at this post from a while back.
viewtopic.php?f=16&t=6928

[pop]

with the oil ratios, I would do what the oil company recomends and ignore what the bike manufacturer says, someone used 20.1 of Belray MC1 and when it stopped runing, the inside of the motor looked like a tub of grease, and you should rejet the carb whenever you change oil brands or even ratios.

[jacks1071]

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 & ring kit even though the piston looks fine.

Are the ones on ebay acceptable or is there a known good source for these?

http://www.ebay.com.au/itm/YAMAHA-TY175 ... 3f0078fe49

[TriCub]

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 more years I would be surprised if it didn't need a rebore. However if it is still within specs the original Yamaha pistons had a top L ring so I would say that it is an original piston. One other thing you need to note is that with an L ring there is not ever much of a lip at the top of the cylinder as the ring comes almost to the top of the cylinder.

[jacks1071]

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 more years I would be surprised if it didn't need a rebore. However if it is still within specs the original Yamaha pistons had a top L ring so I would say that it is an original piston. One other thing you need to note is that with an L ring there is not ever much of a lip at the top of the cylinder as the ring comes almost to the top of the cylinder.

The bike still has the origional speedo on it mounted down on the fork leg, just over 2000kms - the condition of the bike tend to also match that sort of usage so I think there is a fair chance its an origional bore.

The the L rings available anywhere?

[TriCub]

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 bit rattly by a local aftermarket piston and get it bored to first oversize.
What does the motor sound like at the moment and what does it go like?
The Ebay piston on your pervious post is a bit of an unknown quality. It's not a brand I've seen before in Australia, I'd guess that it is made in China.

[jacks1071]

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 bit rattly by a local aftermarket piston and get it bored to first oversize.
What does the motor sound like at the moment and what does it go like?
The Ebay piston on your pervious post is a bit of an unknown quality. It's not a brand I've seen before in Australia, I'd guess that it is made in China.

Its reasonably quiet, the rubbers are missing between the cooling fins which probably account for some of the noise and it runs fine.

I've ordered this kit: http://www.ebay.com.au/itm/270590869065 ... 1423.l2649

When its due for a rebore I'll probably send it to get coated so it'll be right forever - not that we are going to ride it much but beacuse of that I want to be able to put fuel in and use it without any concerns.

Dad has a few days off work due to the rain and is giving it a tidy up, I've told him not to go nuts because I want to ride it!!

[David Lahey]

What is it are you getting coated when you get it rebored?
It would be a good idea to have the piston-to-bore clearance checked with your new eBay piston, and check the ring end-gap of the new rings in the least-worn section of the bore.
I have seen genuine Yamaha ring sets for Yamaha pistons with the L top ring from eBay sellers in the US.