Invader problems

[440RX]

Any thoughts on why this happened? New seals & crank  bearings. Used pistons and cylinders with new rings. Only about 5 miles on and this happened at mid throttle. Stock jetting ,oil pump tested and pumping as per spec. I have 4 other used cylinders that came with 2 separate invaders  and all 4 have the same issue on exhaust side .

[Dandb7]

Do you have scrape marks on 3-4 ''sides'' of the piston...? Because it looks like a  ''cold seizure''.......did you warm up the sled long enough before heading out...? And did you hold throttle midway without varying throttle position...?

[Tory944]

  That would be my guess too...  we all have our own riding styles/technique, but warming up the engine is a must.  The 80' 4/6 engine (especially) had problems with cold seizure and for that reason Kawasaki updated their pistons with a skirt "coating".  Also, check your oil pump for adequate flow from idle to WOT.  I am probably the only Kawi guy who does this, but I also mix 70:1 syn in the tank for precaution.  Just preference.

Warm up for at least on minute or until coolant temp is up.      Tory

[Tory944]

Sorry, re read your post and saw that your pump checked out fine.

[Dandb7]

Tory, glad to see i'm not the only one pre-mixing my tanks also....i do a 100:1 in each tankfull as a precaution..!

With my Ceptor, when the temp is warm to the hand in the trunk box floor, that tells me the coolant has gained enough temperature, has made it around the whole coolant system and  that pistons and cylinders have expanded proprely......which means it's time to let her loose...  :-)

PS We are in the deep freeze here...... :-(     but sleds like it ....   :-)

[440RX]

thought I had here warmed up good. I constantly was varying throttle position with very short burps at wot. mostly was mid throttle . marks just on the 2 sides (between exhaust port and transfers) Plugs look nice both dark tan.   I also received the following post on another site:
(Apparently the update was never done on that sled, kawi had a problem from the start, with no bypass in the cooling system thermostat, as you take off the cly. heats up and expands along with the piston but then the thermostat opens up and a rush of ice cold anti freeze shrinks up the cly. and sticks the expanded piston, kawi's fix was back then a bypass built into thermostat housing but back then the quick fix (until kawi got us the parts) was to drill a 1/4 hole in the thermostat itself so some anti freeze is always circulating, I will look thru my books to find the bulletin, if I find it I will post it or just do the fix with the drill bit it worked)  . 

[Tory944]

I've heard the same thing, but have never performed the modification.  I run the same engine in my J/D Liquifires and haven't had the problems you've experienced.  I dunno...  I've seen plenty of "cold seizure" cyl markings.  It sounds like you've covered all bases w/warm up etc., so I really don't know what to tell you.  Check your ring end gaps?  I'd consider running a bit wider end gaps?  FYI...  I don't run cheap oil.  You get what you pay for.  I use Klotz R50 in the tank (Castor base) with the Techniplate inj. in the oil resevoir.  No problems and I have four Liquid Kawi engines running hard right now.   

[Interceptor398]

Long story short---go easy until the temp gage says warm??

[440RX]

I must have the update ?

[Boomologist]

I agree that this appears to be a cold seizure.
Also, running pre-mix can cause a slightly lean condition because some of the gas flowing through the carb has been replaced by the oil.

[Tory944]

  I've read many books on performance two stroke tuning and "yes" running a premix may lead to a "slightly" lean condition, but IMO as a general rule more oil "within reason" has been proved to actually gain horsepower on the dyno.  We all do what we feel is beneficial and it the case of oil ...  I do what works for me.    Can of worms.

[Tory944]

  An air leak will also cause piston scuffing, but generally I've seen this happen on the intake side of the piston....  like a intake leak (boot) or seal leak (sucking in air).

[Boomologist]

I agree that some oil can generate a little more power but I believe this is the result of being slightly lean on gas. The best performance I got from a 440 was caused by a slightly leaky crank seal causing a lean condition, just before the piston melted down.
For years I ran a little pre-mix and didn't seem to cause any harm. I constantly was playing with jetting to get the best out of the engine because of elevation changes going up the mountain and I did run EGT's.
Sure miss riding!

Just added this. Hope it helps:
http://gothotrocks.com/kawasakitemp/piston.htm

[kawhead]

imo  lean burn...running a stock airbox?i'd like to see that thermostat bulletin

[Tory944]

Just for conversation sake...     A. Graham Bell "Two Stroke Performance Tuning" is a great book.  He talks about oil types, mixtures, etc.  Very good read!  I am one of those type of guys who has to "read  it to believe it".   I 've heard some pretty crazy (and scary) advice and opinions over the years and this guy explains his results scientifically and through testing very well.  I will warn you...   this isn't your wife's romance novel!!  LOL