out for a sunday thrash and BANG.

[two-stroke-brit]

Well i wasn't expecting this .
10 miles from home temp gauge @ normal.
turn of the interstate too early , no worries i just whipped it up the next on ramp and SEEEEEEIZE.
Back wheel locks up,clutch in , coast to a stop. FUDGE.
Call wifey (good lass) brings the trailer and home we go.

now home and plugs out (one was loose) but both covered in Ali .
peer in the hole and i can see the con rod smiling back at me on one side.

so before i tear it apart anything i should check .

i am a bit stumped by this as i did due diligence with dyno testing and all looked good.
if it was only one cylinder i would say massive air leak but both plugs are same condition.
BUGGER
T I A Mark

[Hooligan]

SHITTY! Sorry to hear it. Hopefully your crank will be OK.

You are in for a complete strip down and internal cleaning. When my RZ went, it didn't even hole the piston and there was still bits of aluminum down in the cases.

Its kind of odd that both pistons went at the same time. Wonder if you had an air leak where the cases join? If it were one crank seal or the other, only one piston should go lean.

[silverstrom]

Certainly sounds lean. Could be a case leak, or a compression issue, fuel octane issue, or just riding hard and overheating the cylinders, which wouldn't necessarily be obvious with the temp gauge.

How loose was your plug?

This might help http://www.thetuningworks.co.uk/assets/ ... gnosis.pdf" onclick="window.open(this.href);return false;

[two-stroke-brit]

How loose was your plug?

This might help http://www.thetuningworks.co.uk/assets/ ... gnosis.pdf" onclick="window.open(this.href);return false;

thanks for the piston diagnosis.

as to the plug it was a couple of turns loose.

[Hooligan]

This kind of thing is why I run an EGT on my LC and will be running an EGT on my RZ. The ca $400 of the EGT is less than the cost of melting pistons and damaging bores.

[2smoke]

I was worried when you said this:

there is a small annoying stutter/surge when on half throttle, when ridding at slow speed on steady throttle ,but i think this is caused by the carbs being out of sync

I think your pilot jets were too small. I know the UFO sellers say to use smaller ones but.........
I would also look at the installation of the O-ring head for leaks.
I know it didn't overheat, but is the coolant level in the bottle the same as before or lower?

[two-stroke-brit]

the coolant level was the same.
the ufo peps say half the pilot which would have been #11.25 but the smallest i could get was a #15.
and the dyno guy said i could reduce the pilot 1 size if i was looking to be spot on .
but i though a little fat cant hurt.

but i think before i take the top end off i will do a leak down test to see if i can find a air leak.

then it will be the joy of a complete strip and rebuild.
as the old saying goes "it was running great until it didnt"
thanks everyone.

[JonW]

Bummer, sorry to hear this Mark.

[Arrow]

Sorry to hear this Mark. The loose sparkplug would be of concern to me.

[Hooligan]

The thing I don't get is how a fault or issue on one side could cause both sides to seize?

[two-stroke-brit]

The thing I don't get is how a fault or issue on one side could cause both sides to seize?

yep me too .. i will post up the gory pics when i open it up.

probably over the Christmas break

[75RD350rider]

Damn.... Sorry to hear that...

[silverstrom]

The thing I don't get is how a fault or issue on one side could cause both sides to seize?

Because both sides are still connected. Any air leak on one side will affect the other side. The labyrinth seal is only there to deter fluid migration between cylinders. It does nothing to stop pressure, which is why when you pressure test the cases you only use one cylinder. So, if that loose spark plug was allowing air to enter and/or escape the cylinder you have the potential to lean out both sides, especially when you no longer have compression due to a loose plug.

That explanation is exactly why I asked how loose the plug was.

[two-stroke-brit]

the strange thing about that. is i think the side with the loose plug was not the most damaged but will know for sure when i take the head off.
if the crank is toast might be "Hybrid time"
cheers mark.

[two-stroke-brit]

well i did the leakdown test and it holds 6 lb for 6 mins.
so it must of been the loose plug massivelyleaning both cylinders out to destruction.
so i can build em i just cant maintain em.
(schoolboy error costing many hundreds $$$$$)
feel like a right tit now.

oh well,out it comes and on with the surgery.

thanks all,
mark