Knocking off the cob webs (finally)

[Solohunt01]

Afternoon KawasakiTrax! long time lurker of the forum, newly minted member.  Finally getting serious about the restoration of my 78(?) Invader 440 that I have had since I was a kid.  It hasn't run in 10+ years and never really ran well for me before it sat.  I don't know anything about the history of it and I'm not very experienced with snowmobiles but I am an experienced ATV mechanic and ready to learn.  What I have found so far - it has a JD Comet 102C primary which I have read is a common swap for the early kawi's.  The exhaust is "stock looking" - factory 2 into 1 muffler with a downward discharge and the engine shows no outward signs of modification.  So you can imagine my surprise when I compression tested it and found 175/170psi PTO/MAG !! I'm guessing shaved heads? The carbs are stock looking 36's but I see some blocked off ports and the airbox is missing.  Last time it ran "well", my memory says it would knock on 80mph with my 12 year old self doing my best impression of a flag in the bed of a pickup off the bars.   

I have found the fuel and oil line schematics on the site which I plan to use to replace all the lines with new, and hopefully find the sources for the few blocked off ports in the process.  I am gathering gaskets and seals to go through the engine and carbs and I am sure I will end up needing some bushings, bearings, bogey wheels, etc.
- what is a good parts source for these sleds? 
- do I need to seek out something more than 93 from the pump if it's making 175psi?  maybe run a colder plug?
- any reliable way to date the sled? I don't have a clue what model year it is, just my memory of a manufacturing date on the back of the tunnel that I can no longer read.

The history - I live in West-Central Indiana where snowmobiles get ridden once a year for about 3 days at best.  According to the odometer the sled only has 691mi on it!  The sled came out of a neighbor's yard circa 2008 on the basis of "if you can start it, you can have it".  What 12 year old, budding gearhead can turn that down!?  It ran "okay" winter number 1 but I didn't have a foggy clue what I was doing and it's condition deteriorated over the next few years until it ended up sitting.  I'm tired of seeing it sit and I'm 10x the mechanic now that I was last time I touched the sled so it's time to get serious about the "restoration".  Looking forward to learning from the best and further exploring the forum in the coming weeks!  Keep up the good work on here, what a great resource for keeping the old Kawi's on the trail and out of the barn 

[Interceptor398]

Welcome to the site!! Last picture shows the primer hose plugged off,  not uncommon as the plunger primers are prone to leaking.  A 78 440 Invader carbs will be 36/60.  What is the number stamped on the right foot area of the tunnel?  This will tell us what sled you have.

[mswyka]

Love the imagery of the flag in the pickup.  175 psi is higher than I have ever seen.  Do you have a manual?  If not, I have a copy of the 1980 manual that I can send you if you shoot me a PM with your email.

[gixxer6]

Welcome to the site! 

Yeah, 175 is high.  Although I have heard the 78's were a little different.  Maybe they had higher CR heads?  I would start by checking the squish before you tear into the motor.  I'm not sure if you'll need more than premium fuel for that.  I have a motor built for race fuel and one for premium fuel, I can get compression readings from each to get an idea.  I believe stock usually run around 130ish psi (depending on the gauge and condition of the motor). 

Dennis Kirk is good, as is https://newbreedparts.com/.  You can post a wanted ad in the classified section on here as well, there's plenty of good used parts out there.  Finding an airbox and replacing the crank seals is a good start. 

[sprocket]

You could change out the carbs and run some 38mm or 40mm just jet it and add air filters no need for the air box. I would also put in a new fuel pump & a primer. Get yourself new carb boots and eliminate those plastic spacers.
180 psi would run c16 Sunoco race fuel If you plan on driving it the engine will get warmer faster. Check and see if there is a thermostat 160 degrees any higher than that you will loose power. I would check the squish, then freshen up the engine

[Solohunt01]

Thanks guys, I knew I was in the right spot!
Invader - I pressure washed the tunnel and found more numbers pictured below. 

mswyka - PM on the way

Gixxer - Thanks for the tip.  ya, 110-130 is what I was expecting to find (though I was prepared to see 50 haha).  I'm familiar with the theory of checking squish but not the practice.  best to check at the cylinder wall or near the spark plug? (seems easier to do near the plug).  I know I have seen threads on it in passing, I'll have to do some poking around. 

Sprocket - new boots are already on the way, experience tells me it's worth the ~$50.  I've been (unsuccessfully) trying to find a rebuild kit for the pump.  I didn't think to grab a primer, good call.  I may put pods on the stock 36's just to get it running, then look into getting an airbox or some bigger carbs. 

[gixxer6]

To check the squish:  I use plumbers solder, bend it to an "L" shape, insert in the spark plug hole inline with the wrist pin, turn the engine over until you feel it squish the solder, then measure with calipers.  Check each side of the each cylinder (2 measurements per cylinder). 

Careful with some of the aftermarket carb boots, they are cheap and tend to warp and leak.  This can cause catastrophic failure.  Same goes for running the stock power jet carbs without an airbox.  You need to re-jet them or it'll run lean. 

[Interceptor398]

SS440-A2 is 1979 and the motor should be TA440A-B201.  The right side foot area of the tunnel will also be stamped.

[Solohunt01]

Parts are rolling in and the engine is out a degreased, waiting on the workbench for a free evening.  The engine numbers checks out with Interceptor398's numbers and mswyka's owners manual was much apprecieated. 

Here's my current conundrum.  I measured squish on this motor and I have more questions than answers.  *at the thinnest point* the squish checks out for a lightly hotroded motor as per numbers I found while perusing this forum and other 2-stroke sources, .070-.073".  The problem is, the squish band is not only not parallel, it's non-parallel the wrong way.  .070" occurs near piston center while clearance "at the wall" is .012-.015" wider on all 4 measurements (.080-.083").  To clarify: no, it's not a lip at the end of the solder from the edge of the piston.  It is a progressive change across the squish band.  My understanding of squish tells me this is backwards - clearance should grow towards the center if not parallel to encourage turbulence at the plug.  I am beginning to wonder if someone raised the compression by installing domed pistons in this motor?  There is a lot of carbon build up (the motor ran on premix for a long time before 12 year old me learned about oil injection  ) which I can see accounting for some variation in the squish measurements and maybe tightening it up from the desired .075" to .070" but not .015" worth, only in the middle of the pistons...   Obviously this isn't "ideal" as far as 2-cycle engine theory but my question is - am I shooting myself in the foot putting this motor back together as-is?  I know for fact the sled ran on 87 octane up to this point and the squish testers didn't show any signs of detonation in the pistons domes or head surfaces. 

This is probably in the manual, but I'll ask while I'm on here in case I don't find it.  What would be stock jetting for a 78 440 Invader? 

If you made it to the end of this post, thanks for listening haha.   

[Interceptor398]

I have done a few heads and have a tool to match the chamber to the piston.  Price is very reasonable. 

[Solohunt01]

Thanks Interceptor.  Provided the rest of the motor/sled turns out to be worth saving, I may be send some parts your way

[gixxer6]

Interceptor398 has done several sets of heads for me, including the custom ones on the Intimidator, great work with excellent results.  However, I wouldn't recommend starting with heads that have already been modified.  Without measuring the cc of them, you don't know what your starting point is.  If it were me, I'd source another set of uncut stock heads, either run them as is, or send them to 398 to have them cut properly. 

I've never seen pistons with larger domes installed in an Invader, but that doesn't mean it's impossible.  I think it'd be unlikely.