TZR125 2RK Top end Rebuild

[binge]

Okay the Pit locked up on me again today. Seems the engines really tired and on its way out.

I got home, Stripped it down. And heres the result.


https://img.photobucket.com/albums/v358/binge/Photo0568.jpg

https://img.photobucket.com/albums/v358/binge/Photo0569.jpg

https://img.photobucket.com/albums/v358/binge/Photo0570.jpg

https://img.photobucket.com/albums/v358/binge/Photo0571.jpg

https://img.photobucket.com/albums/v358/binge/Photo0567.jpg



I'm no pro. But I can see for myself that the barrel and piston are scored quite bad.

Whats my best option. AFAIK these are an Iron Lined bore? I've been told it can be re-bored and I can fit a new oversized piston?

Is it worth considering a big bore kit?


What do the people of BCF suggest?





Ben

[Blau Zedong]

Just get it rebored and sling a new piston and little end in it. But you do need to find out why it seized first.
____________________
18:54:48 Rob Fzs: jews don't give away stuff for free

18:54:59 Rob Fzs: unless its their clothes/ hair/ golden teeth

[binge]

I think the reason it has seized is because the crank seals have gone.
It's been sucking in gearbox oil, Oiling up the plug. I've been thinking its running rich so fitted a smaller jet.

Kept going leaner until the plug was burning right.

But it was then running very lean on petrol/air but still appeared to be running okay due to the oil from the gearbox.

Mild heat seizures have caused the scoring.


BUT the lack of power since the day I got it running suggests its always been down on compression?




Anyway, I've dropped the cylinder off at a local engine machinists in Newington. He is going to measure the current bore and get back to me with what size piston I need to get. Then he can re-bore it to the perfect size for the new piston.

I'll get it built back up with the new carb and crank seals. And run it with a closed powervalve for the time being until its all run in and set up.

Then I'll get the powervalve servo up and running and go from there.





Ben

[dlatch]

barrel will need replating ben i think.
its only the later 3mb barrels that are not plated.

but its definatley goosed no wonder it was so boggy

[Kickstart]

Hi

The 2RH lists oversize pistons in the Yamaha parts list and thing the 2RK is pretty much the same. Fairly certain they do not use plated bores.

That piston doesn't look that bad to me (still knackered, but seen far worse from a simple single seizure). Almost looks like there is more debris on the barrel. Possible it has seized in the past and someone has just lobbed in a new piston?

All the best

Keith
____________________
Traxpics, track day and racing photographs - Bimota Forum - Bike performance / thrust graphs for choosing gearing

[binge]

Well its a very tight bore. The piston sticks if I push it into the barrel by hand.

It does look like its seized in the past and its had a rebuild on the cheap. The previous owner (Not Gaz, Before Gaz) was a bit of a numpty. He said it had been rebuilt 200 miles before Gaz bought it. Clearly not rebuilt properly.


I've been told I can re-bore the cylinder. I've dropped it off at a local machine shop, The guys gonna measure it, Get back to me, Then I can buy an oversize piston, Take it to him, He can machine the barrel to a perfect fit and I can get on with this rebuild!




Ben