Kawasaki Sportsbike Riders Club - Australia - Online Forum

Me and my mate just got our lisences, and we both just got our bikes. I got my ZZR 250 and he bought a Honda NSR 150. Its a 01' Model with 30,000 km's, he has only had it for 2 days, and its already out of action!

He blew a hole in his piston! We took the piston out ourselves with another of our mates dad's who is a mechanic, but it must be extremmely disapointing to see his beleoved NSR in peices in his backyard!!!

Should be fixed by friday, costing about $300 for the new parts.

tell him to buy a kwaka

Bu all in all very unlucky

Top end rebuilds are part of the 2 stroke thing instead of changing oil you change piston and rings and if properly looked after they are good fun.

yeah thats not good... Sell his bike to Froggy and yeap get him on a Kwaka....

You might suggest to your mate that he check the jetting too. 2strokes don't normally hole a piston unless something else is wrong like running too lean.
Hate for him to drop 300 bucks and have it hole the new piston too.

balanse wrote:You might suggest to your mate that he check the jetting too. 2strokes don't normally hole a piston unless something else is wrong like running too lean.
Hate for him to drop 300 bucks and have it hole the new piston too.

Yeh... we thought it may have been a spark plug problem but we took the head gasket into the shop and it was the right plug. So we are now thinking it may be a fuel problem? Perhaps a problem in the automatic oil mix?

When we took the piston out, the inside of the block had some scorching damage, but it looks like its just slowly worn over time, as well as the hole in the piston - it seems like it was gradual.

Lets just hope when we replace it it lasts another 30,000 km's and 5 years!

RobertR wrote:we thought it may have been a spark plug problem but we took the head gasket into the shop and it was the right plug. So we are now thinking it may be a fuel problem? Perhaps a problem in the automatic oil mix?

Rather than something being wrong with it and causing it to fail, if it's made it to 30,000km on its original piston before it went poot, it's nothing short of a miracle.

You don't show a pic of the other side of the bike. Is the expansion chamber stock? If not, chances are the carb hasn't been jetted to match and it's caused the bike to run lean... and when strokers run lean, they burn holes in their pistons.

I-K wrote:

RobertR wrote:we thought it may have been a spark plug problem but we took the head gasket into the shop and it was the right plug. So we are now thinking it may be a fuel problem? Perhaps a problem in the automatic oil mix?

Rather than something being wrong with it and causing it to fail, if it's made it to 30,000km on its original piston before it went poot, it's nothing short of a miracle.

You don't show a pic of the other side of the bike. Is the expansion chamber stock? If not, chances are the carb hasn't been jetted to match and it's caused the bike to run lean... and when strokers run lean, they burn holes in their pistons.

Had a sports exauhst put on not long ago... dont know if that would have been a factor.

the good thing about 2 strokes, just whack another piston in it.

so does the ZZR beat the 150 ?

hoffy wrote:so does the ZZR beat the 150 ?

I don't think the ZZR250 can beat the SP at low speed, maybe at higher speed.

RobertR wrote:Had a sports exauhst put on not long ago... dont know if that would have been a factor.

I reiterate...

I-K wrote:Is the expansion chamber stock? If not, chances are the carb hasn't been jetted to match and it's caused the bike to run lean... and when strokers run lean, they burn holes in their pistons.

Find out what the stock jetting for an NSR150 is, then pull the carb off and yank the float bowl off, so you can see if the jets are stock... I have a box of glazed doughnuts that says they are.

Changing the pipe on a two-stroke without changing the jetting is asking for a hole in the piston.

As a rule of thumb when you change the stock pipes on a two smoker you go up 3 sizes on the main jet and do a plug chop on the first run it should be a bit rich which is ok also increase the auto lube to accommodate the richer mixture.
After initial run in if it's bogging down or the plug indicates it's running rich re jet until the plug colour is correct its all trial and error but your better running a little on the rich side to avoid holing the piston
If its got 30k on the speedo and on the original piston and bore you will need to rebore it to an oversize piston be careful who you get to do the job as tolerances have to be correct or it shortens the piston life

too stroke = too bad

No way a ZZR 250 can beat a NSR in any way shape or form.
EXCEPT that it IS a Honda of course....
mmmmm.... chrome spannie

RG wrote:

hoffy wrote:so does the ZZR beat the 150 ?

I don't think the ZZR250 can beat the SP at low speed, maybe at higher speed.

He gets much more initial speed but once I hit my higher gears he has no chance of keeping up