Piston Rings

[delvey91]

Hi all,

Im rebuilding a DT 125 engine at the moment. The problem is ive got a new piston and i dont seem to be able to get the top ring to sit properly, Bottom one went in fine but the top dosent want to go in! Tried them the other way round but no difference! There both located correctly in relation to the little pins.

Also the kit also came with a small springy ring whats this for??
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2016 Honda Africa Twin
2006 KTM 200 EXC

[MaybeGuy]

Did the rings come with the piston?
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Blue_SV650S wrote: it was a sh1te wheelie, but it proves that he can get it up in 3rd and can do angles. In summery, mattsprattuk is a gobby little sh1tebag, dopehead tw4t, but sadly for all of us, he probably isn't THAT full of sh1te!!
Kickstart wrote: Hi I tend to agree with Matt. All the best Keith

[delvey91]

Yep they came with the piston, its a genuine yamaha kit
____________________
2016 Honda Africa Twin
2006 KTM 200 EXC

[MaybeGuy]

definately a dt piston? Small springy one sounds like an oil scraper ring found on 4 strokes.
Any pics?
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Blue_SV650S wrote: it was a sh1te wheelie, but it proves that he can get it up in 3rd and can do angles. In summery, mattsprattuk is a gobby little sh1tebag, dopehead tw4t, but sadly for all of us, he probably isn't THAT full of sh1te!!
Kickstart wrote: Hi I tend to agree with Matt. All the best Keith

[Blue_SV650S]

[delvey91]

Hmm tried fliping them and got the top to squeeze in but its deffo to stiff, the bottom one is ideal i think?

Pics:

https://i280.photobucket.com/albums/kk193/delvey91/DSC01823.jpg

Springy one:

https://i280.photobucket.com/albums/kk193/delvey91/DSC01824.jpg
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2016 Honda Africa Twin
2006 KTM 200 EXC

[Blue_SV650S]

[.....]

I had the exact same problem with a diddy PW50 piston. Never did get the top piston to seat properly so ended up using the original top ring. Far from ideal but it was an old bike for kids so didn't really care too much.

I did measure both sets of new rings with some (crap) vernier calipers and they appeared to be the same size.

The very thin ring sits behind one of the other rings, probably the bottom ring.

[ms51ves3]

The expander ring sits underneath the bottom ring, but it's up to you whether you use it or not. Some people leave them out, some fit them. Have a Google

EDIT: I just had a Google and found nothing. I read it in A Graham Bell's 2 stroke tuning book though so if anyone has that they could quote from it.

[oldbiker]

Top ring is tapered about 7 degrees I think, but the taper is only on the top face of the ring.

The top ring is usually quite stiff.

Also the top of the piston is machined a little narrower than the rest of the piston, so the ring being too big may just be an illusion.

As others have said the expander ring goes with the bottom ring.
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It`s all powerfull white mans magic
https://i897.photobucket.com/albums/ac178/tzrsteve/album%201/035.jpg

[delvey91]

Cheers for the help guys, got it all sorted today. Yeh after a bit more swapping and turning it fitted like a glove in there! And it started first kick! Im well chuffed first rebuild ive done and it works
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2016 Honda Africa Twin
2006 KTM 200 EXC