MC28 Piston & Ring problem.

**Mon Feb 23, 2009 7:53 am » Post: #1 » Download Post**

Hi Gents,

Just received my piston, OE Honda parts ordered via Tyga Performance.
The top ring groove is thinner than the lower groove however the rings supplied are both the same thickness.

Are the grooves supposed to be of different thickness?
Have I been supplied the incorrect rings?

Thanks in advance.

**Mon Feb 23, 2009 8:57 am » Post: #2 » Download Post**

Have you read this website's rebuild notes, in workshop section?

http://www.nsr-world.com/workshop/rebuild/page-4.htm

(note - pic linked from within this site).
_________________
Rich
MC21 Track Bike / RS250 NF5 'Spencer', NX5 'Cadalora' & NXA 'Aoyama' / RS500 / Two Brothers Racing RC30

**Mon Feb 23, 2009 9:12 am » Post: #3 » Download Post**

Yes, but I never received a keystone shaped ring.
Both rings are identical.

The keystone shape of the top groove, is it noticeably keystone? mine looks flat like the bottom ring groove.
I stuck an used ring(in spec), from a single ring piston in and it fitted perfect.

Will recheck it now and take some photos to share here.

Thanks.

**Mon Feb 23, 2009 9:29 am » Post: #4 » Download Post**

Part numbers for the rings are correct. 13010-KV3-305

Piston is 13103-KV3-830

**Mon Feb 23, 2009 9:41 am » Post: #5 » Download Post**

The rings are pretty similar, takes a close look to get the right one.
If you bought the rings under that P/N, they come as a correct set of 2 from Honda. Worth another look.
_________________
Rich
MC21 Track Bike / RS250 NF5 'Spencer', NX5 'Cadalora' & NXA 'Aoyama' / RS500 / Two Brothers Racing RC30

**Mon Feb 23, 2009 9:49 am » Post: #6 » Download Post**

I checked both, and tried them too.
Neither fit, this is a Tyga top end rebuild kit. They forgot to ship the one top end kit with the order, so when that arrives this week I will check and compare.

What is odd is that the piston, according to the web site parts list should be a 13104-KV3-830 - D piston. A is 13101, B is 13102 so I assume this is a C?

**Mon Feb 23, 2009 9:52 am » Post: #7 » Download Post**

In each genuine Honda box there is one of each type of ring. Make sure you not only have the top ring for the top groove but they are also the right way around.

Ring markings always face up.
_________________
If I have to take the carbs off once more...

**Mon Feb 23, 2009 9:57 am » Post: #8 » Download Post**

Marks are correct. Box was sealed but assure you these rings are identical.
I'll measure and take a photo along with the vernier, micrometer even, just to show you. Or come back red faced. Smile

Going to the garage to play with bikes, will posts pics later.

**Mon Feb 23, 2009 10:30 am » Post: #9 » Download Post**

2 minutes later micrometer in hand and my face starts to turn a little pink...then red.
I was checking the ring using the outer edge which of course will not work in a tapered groove.
Thanks for baring with me while I got a bit bent out of shape, but that is what this forum is for.

Yours in piston ring fitment,
RedFaced.
Smile

**Mon Feb 23, 2009 10:33 am » Post: #10 » Download Post**

Nothing beats a bit of back peddling hey?

'least you know where you went wrong though.
_________________
If I have to take the carbs off once more...

**Mon Feb 23, 2009 11:01 am » Post: #11 » Download Post**

Your not on your own RaceFan, first time I was fitting rings I thought 'what the heck??!!'. Hope she runs well when back together.
_________________
Rich
MC21 Track Bike / RS250 NF5 'Spencer', NX5 'Cadalora' & NXA 'Aoyama' / RS500 / Two Brothers Racing RC30

**Mon Feb 23, 2009 6:13 pm » Post: #12 » Download Post**

Yeah, it's not uncommon to hear about this, and when you aren't familiar with them it's not so easy to see any difference with the naked eye.

Do a couple of rebuilds though, and you can soon spot the keystone ring a mile off.
_________________
Andy.
NSR-WORLD.COM

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**Sat Mar 14, 2009 7:34 pm » Post: #13 » Download Post**

Too bad I didn't find this thread earlier...I did the same thing and mistook the top and bottom rings.

The bad part is, I ruined a new piston because I ended up jamming the ring into grove and cant get it out.

Some one should update the Rebuild walkthrough in the Workshop. It's pretty clear that the rings have a "this way up", but not too clear that while both rings in the package might look the same, they're NOT!

For first time rebuilders...you SHOULD be able to hand compress BOTH top and bottom rings. If the TOP rings doesn't compress you have the wrong ring in the grove. DONT USE A PISTON RING COMPRESSOR!

Cost me a new piston to figure that out... Sad

**Sat Mar 14, 2009 8:27 pm » Post: #14 » Download Post**

The question is who is stupid enough to use a ring compressor on a ring which doesn't compress into the ring grove by hand anyway?

I mean, that takes quite a bit of force doesn't it?!
_________________
If I have to take the carbs off once more...

**Sat Mar 14, 2009 9:18 pm » Post: #15 » Download Post**

Sorry, I have to agree... there has to be an element of common sense, else I wouldn't even suggest attempting the rebuild in the first place!

I'm afraid I can't think of any reason why a ring compressor would even be necessary on a 250. Confused

_________________
Andy.
NSR-WORLD.COM

Please keep all responses to Forum posts on the Forum so that others may benefit.

Please DO NOT PM me for technical advice. My time is precious, and you will probably receive a faster response on the Forum anyway.

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