Hello all! I believe this is my first formal post here. I've known about this site for a while, but finally getting around to posting here as I've recently made a career change that allows me more time to play with all of my toys
When I was just a young buck, my dad bought a 340 invader and went through the sled in the late 1990s. I rode the shit out of that thing as a kid in the early-mid 2000's. Went to college in 2010, and got too busy with college/work/marriage etc to ever touch my favorite hobby (working on and riding vintage stuff, especially kawi snowmobiles). So the sled sat for a number of years, and eventually a lesser appreciative family member got a hold of the sled and blew it up (without knowing it). When I started re-collecting my families old sleds, I found my dad's old 340 quite literally buried behind a barn. Drug it out and thought I could get it going. After cleaning the carbs, checking spark etc, found the compression to be 80 PSI stator side and 100 PSI.... RIP.
decided I would put the time and money into rebuilding it, more for fun, learning and nostalgia than anything. What an undertaking that was. Found some very useful information here about removing the flywheel (thank god). Took me a full 10 days to get it off lol.
Finding top end parts was surprisingly difficult. I spent quite a while trying to find 0.5 mm over bored pistons, but I couldn't find anywhere that made them, so I had to order 60.0mm and figure out a different application for the cylinders. Al's Snowmobile salvage ended up having a pair of them, and they were labeled as identical. When I got them, the stock tickets said they were both good condition 60.0mm, but one of them had "Bored 0.010 over" written on it in marker.... soooo took it to an engine shop, and sure enough i had one 60.0mm cylinder and one 60.5mm cylinder. I ended up being able to hone the cylinder that had 100 PSI compression (the other one was scored too badly), and hone the one that wasn't bored over to the upper tolerance in the repair manual. So now I have a scored cylinder and a brand new sleeved cylinder thats 0.01) over
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Either way, put her back together... after a few hours, a 6 pack and some seriously busted knuckles.... I'm actually dumbfounded that it's working! I've never rebuild a motor before, and there was enough crap that went wrong on this rebuild that I thought for sure it would be screwed (Still holding my breath to ensure the crank doesn't explode after how rough I had to be with it to get the flywheel off).
Fresh top end with 145/150 PSI compression stator & clutch side respectively, Fresh crank seals so LOTS of suction, and gobs of assembly and 2 stroke oil.... and I have a fresh 340 Invader!
I only took it about 2 miles because unfortunately the new windsheild wasn't here, the snow was waaayyy to soft and it was too warm out to break it in. Couldn't keep it cool easily and didn't want to risk messing something up, so it's sitting in my yard waiting to be broken in.
If you want a laugh... He'res a video of initial start up.... I'd say I got enough oil in the case/cylinders
https://www.instagram.com/p/BsOVdamA9HC/Any ways, just wanted to share that my dad's old 340 invader (and the rest of our family's sleds" are being resurrected and enjoyed!
I do have one question though. It seems that crank seals are a VERY big deal for these 2 stroke motors. We have an easy way to test if the cylinder holds pressure well (compression test), but I can't find any guidelines for testing vacuum. Does any one have experience with this? I'm planning on getting a vaccum gauge to put onto the fuel pump vacuum line and test this with my freshly rebuilt 340, and then I'll test the rest of my sleds. but what should one be shooting for to tell if crank seals are ok?