Invader vs. Liquifire!

[rminier]

 I toss this out there just for some fun discussion.
 Back in the day...Kawasaki was negotiating the supply of engines for John Deere....fan cooled Trailfires, Sportfires, liquid cooled Liquifires, etc.....at about the same time they were busy at work developing the soon to be introduced Intruder and Invader....in the fall of 1977....with the newly unveiled 78 models....the 1st "exclusively" designed, in house sleds.
 My experience with Sno Jets is curious.....Yamaha provided the engines for Sno Jet through the early and mid 70s...up until Kawasaki bought up Sno Jet.
 Yamaha did not share their "Auto-Lube" oil injection with Sno Jet....they remained pre-mix.
 Yamaha retained the "marketing advantage" of their oil injection technology exclusive to the Yamaha brand....even though it took a few years to drag some of the other manufacturers to recognize the advantages and reliability of oil injection.
 I wonder if Kawasaki wasn't confronted with a similar dilemma. They certainly didn't want to hand over to John Deere a liquid cooled motor that could kick the rear end of the soon to be released Invader.
 So, the Liquifire received a Kawi engine with a slightly reduced compression ratio.
 Lest you think otherwise, my respect for the Deere sled division is huge.
They publicized a concern for the quality of gasoline at the time, and it's effect on reliability...and a slightly reduced compression ratio that was more forgiving of gas quality..
 An absolutely true, viable concern.
 I just have to wonder if there wasn't more going on....if we could be privy to what was going on at the time.
 Kawi could not have been anxious to hand over a new water burnin' 440 to Deere that might have the "smoke under the hood" that the new Invader had.
 Just wondering what all took place back in the day....

[gixxer6]

There's more to it than a simple compression ratio change.  The Invader heads have a small diameter combustion area, the Deere heads have a larger area.  There's a design advantage to the Invader heads.  Ski-Doo did the same thing with there 1998 and 1999 High Output version of the 670 twins.  Among other things, the HO motors had the same design combustion area as the Invader, and the non-HO motors were similar to the Deere heads.  My 99 MXZ 670 HO had a sticker that read "Premium Fuel Only", where the non-HO's did not. 

IMO, Kawi did this to give the Invader an advantage.   

[Lloyd (ljm)]

There were more differences than just the heads. The Liquifire's used different rings than the Invader. The base timing is different and the jetting in the carbs is different.

 I'm not sure of all the how's and why's there are difference's. From what I understand the changes were required by Deere.

 The Sportfire engine is the same as a 440 Drifter engine and a Spitfire engine is the same as a Drifter f/a engine.

[rminier]

 Wow, that is a big difference in combustion chamber!

[JDmatt]

Just a theory with no facts to back it up- I've been told that Kawasaki Japan (making the engines) and Kawasaki USA (making the sleds) were fairly independent with the exception of the funding.  The USA sled division was more or less doing their own thing.  So Kawasaki Japan probably didn't care about the competition as much as they cared about selling as many engines as possible.  Deere built 9000+ 1980 Liquifires, almost 14,000 units total over the 4 years, plus all the other models.  I don't know what Kawasaki's production numbers were but I'm guessing not as many.

[jimvw57]

I believe the JD sleds weighed less

[gixxer6]

Just a theory with no facts to back it up- I've been told that Kawasaki Japan (making the engines) and Kawasaki USA (making the sleds) were fairly independent with the exception of the funding.  The USA sled division was more or less doing their own thing.  So Kawasaki Japan probably didn't care about the competition as much as they cared about selling as many engines as possible.  Deere built 9000+ 1980 Liquifires, almost 14,000 units total over the 4 years, plus all the other models.  I don't know what Kawasaki's production numbers were but I'm guessing not as many.

I think your theory is right.  I think Kawasaki USA was mostly a re-branded Sno-Jet.  I seem a similar situation today, the current Yamaha chassis' are made by Arctic Cat. 

I remember seeing some production numbers posted somewhere, but I was unable to find them.  I'm guessing they were close to the same.