Detonation or??

[Jayski]

Hey guys, Hears the situation.

Dropped a piston in my last Kawi 800..

Rebuilt my motor 6-8 tanks of trouble free riding..

Yesterday my new bendix buggured up so i removed the front case, and flywheel. After doing so i noticed that my front seal was swinging in the air.

Split my motor, Found my Brand new Hotrod Crank's bearing to be missing a small bit of metal, and to have walked pushing the seal out.

Removed bores and found my pistons to look like this,
Rear seams to look really good ( left ) front no to good

Close up of front piston

Engine specs,
1mm oversize
New plugs nearly every ride. 8's
190-200 PSI
Standed head, Slightly milled with Squish adjusted
98 octain fuel,
twin 48's running ritch.
Advent T3 timing
Standed base gaskit, i was told that my motor was slightly nocking, Not burning fuel at low rev's so a thicker base gaskit was needed, No idea if this is true... Rear looks Good, front looks as above.


Any idea's guys???


Hotrod cranks seam to have tiwan junk bearings..
Currently in the process of trying talk with there sales rep, this shouldn't happen..

 

[Matt_E]

If the front crankseal was out, you would have had an air leak on the front cylinder.
Maybe that has something to do with how your piston looks.

 

[Jayski]

Yes BUT the seal had not been out 4 that long.. Not long enough to Fek a piston like that..

And the hole front case is jst another chamber as it's a sealed unit with no water inside...

 

[kevbo]

The front cylinder on a kawasaki 750-800 is usually the hot one, unlike the other brands. You simply found the limit of whatever fuel you were using. The jetting may have been too hot and/or the spark was too early. Compression at 190 is certainly a lot for pump gas if you do any full throttle runs. When you fix it make sure the timing is stock and richen up the carbs.

 

[2XLR8]

Is that epoxy on the bottom of the case? I would also check the timing with a strobe light just to make sure it is what you think you should have. Does not look like you have good luck since your new bendix also went out.

 

[Jayski]

Hey guys, i have big jets and the ski wasn't running lean wat so eva, im just thinking it was 2 much comp for pump gas also, but in saying that the rear was perfect..


I have my advent d7 set to curve 2 witch is perfect for my application.


I might lower my comp down to 170-180 and go from there..
Brand new bendix went, But it was a cheap gold 1, now i have gone for a silver OEM with a warrenty.

So hop4ly i have some luck, my list piston come out the bottom of the case, the epoxy or metal mend is to block pin holes in the welds, it's just incase..