Author Topic: Family Heirloom; 340 invader engine rebuild  (Read 79 times)

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Worldawg

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Family Heirloom; 340 invader engine rebuild
« on: January 09, 2019, 01:23:34 PM »
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  >:(.

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  ;D
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?
1979 Invader 340
1979 Invader 440
1981 Invader 440
1980 Drifter 340 F/A
1978 Intruder 440
1980 Drifter 340 F/A
1980 Drifter 440
Someday a 1982 Interceptor 550 :^)

gixxer6

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Re: Family Heirloom; 340 invader engine rebuild
« Reply #1 on: January 09, 2019, 02:31:25 PM »
Welcome to the site!  Great story! 

In the future if you need parts, this forum is a great resource...many of us have lots of extra parts. 

I never bother to test the crank seals, if they are more than 10 years old or you are unsure, just replace them. 

Worldawg

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Re: Family Heirloom; 340 invader engine rebuild
« Reply #2 on: January 09, 2019, 02:43:41 PM »
I never bother to test the crank seals, if they are more than 10 years old or you are unsure, just replace them.

Oh man, I hear you there. The reason I'm asking is I was actually looking at a new[er] Bearcat 440 fan that I could take on trail rides in case I need to haul fuel, food, tow a broken sled etc.
"Oh ya, brand new top end so she should be good for another 3,000 miles at least!"... except it wouldn't idle, despite the pilots being clean as a whistle.

After that I got to thinking, in the future if I'm buying sleds, how do I make sure I know if the crank seals have life in them or not? Logic says that one SHOULD be able to measure vacuum and have a criteria for it, but I can't find any literature on it. Just a questions for the curious :)
1979 Invader 340
1979 Invader 440
1981 Invader 440
1980 Drifter 340 F/A
1978 Intruder 440
1980 Drifter 340 F/A
1980 Drifter 440
Someday a 1982 Interceptor 550 :^)

rminier

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Re: Family Heirloom; 340 invader engine rebuild
« Reply #3 on: January 09, 2019, 05:07:08 PM »
 Welcome and congrats on the progress you have made already!   8)
Here is a good thread to read from a respected individual that markets a kit to test an engine for air leaks:
https://vintagesleds.com/bs/index.php/topic,191761.0.html

 You can make your own by cutting up a tire inner tube and using that as a gasket between the exhaust y pipe and the cylinders, and doing the same thing on the intake side by removing the rubber carb boots and placing the inner tube gasket between them and the cylinders....then you have to rig up a hose with a low pressure gauge to shoot compressed air into the impulse fitting on the crankcase....where the tube that goes to the fuel pump ordinarily connects. Shoot 5 to 7 psi of air into the engine and close a valve on your air hose and watch to see if it holds pressure for 1 or 2 minutes.
 This do-it yourself-method does not allow you to check the air tightness of the rubber carb boots......they deserve a close check to make sure there are no cracks in the rubber and you have them sealed to the engine very well.
 1 more thing that really works to check the PTO end (clutch) seal is to get the engine running at a steady idle and spray starting fluid (ether) or carb cleaner behind the drive clutch toward the end of the crankshaft....if that seal is leaking, you will know it immediately because the engine RPM's will speed up when the spray gets sucked into the engine through the leaking seal. The MAG side of the engine has so much stuff in the way, this doesn't work very well on that end.

 Our motto on here.....if you don't know the condition of the crank seals.....change them.... ;)
 
75 SnoJet Astro SS, 79 Kawasaki Invader 440 (two of them), 81 Scorpion Sidewinder, 82 Blizzard 9500, 83 Yamaha Vmax 540, 97 MXZ 670....and holding...for now.

Worldawg

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Re: Family Heirloom; 340 invader engine rebuild
« Reply #4 on: January 09, 2019, 05:34:08 PM »
Welcome and congrats on the progress you have made already!   8)
Here is a good thread to read from a respected individual that markets a kit to test an engine for air leaks:
https://vintagesleds.com/bs/index.php/topic,191761.0.html

 You can make your own by cutting up a tire inner tube and using that as a gasket between the exhaust y pipe and the cylinders, and doing the same thing on the intake side by removing the rubber carb boots and placing the inner tube gasket between them and the cylinders....then you have to rig up a hose with a low pressure gauge to shoot compressed air into the impulse fitting on the crankcase....where the tube that goes to the fuel pump ordinarily connects. Shoot 5 to 7 psi of air into the engine and close a valve on your air hose and watch to see if it holds pressure for 1 or 2 minutes.
 This do-it yourself-method does not allow you to check the air tightness of the rubber carb boots......they deserve a close check to make sure there are no cracks in the rubber and you have them sealed to the engine very well.
 1 more thing that really works to check the PTO end (clutch) seal is to get the engine running at a steady idle and spray starting fluid (ether) or carb cleaner behind the drive clutch toward the end of the crankshaft....if that seal is leaking, you will know it immediately because the engine RPM's will speed up when the spray gets sucked into the engine through the leaking seal. The MAG side of the engine has so much stuff in the way, this doesn't work very well on that end.

 Our motto on here.....if you don't know the condition of the crank seals.....change them.... ;)

I've heard of utilizing the starting fluid method before. Never tried it though.

Out of curiosity, that seems like a lot of farting around - Why can't you just hook up a vacuum gauge to said impulse fitting? I mean if it were to work the same fashion as a compression tester, you would test your "peak vacuum", just like you test the "peak pressure" of the cylinder during compression testing. this to me seems like a much more simple solution, and may give much less messy results when trying to figure out if seals are good or not. You absoultely could block off the exhaust and intake and pressure it up to 5 PSI and just see how long it lasts, but I feel like that impulse line would be so much simpler. There's gotta be something I'm missing or some one would have done it by now haha

That being said, I'm 100% sold on the "if you aren't sure about crank seals, change them" argument I think most guys REALLY underestimate how important they are. My big thing is I want to be able to check this on future sleds to make sure I know how much work I'm getting into for what I'm paying for ;)
1979 Invader 340
1979 Invader 440
1981 Invader 440
1980 Drifter 340 F/A
1978 Intruder 440
1980 Drifter 340 F/A
1980 Drifter 440
Someday a 1982 Interceptor 550 :^)

Interceptor398

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Re: Family Heirloom; 340 invader engine rebuild
« Reply #5 on: January 09, 2019, 08:52:32 PM »
Great story and work!!

jimvw57

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Re: Family Heirloom; 340 invader engine rebuild
« Reply #6 on: January 10, 2019, 06:18:05 AM »
Testing crank seals will tell you the condition of them at the time of the test. NOT after arming up the motor or when it is running at traveling speed. I would just replace then every time you buy a sled. I worked on a sled for quite a while because the crank seals were replaced by the original owner. after messing with it, I found the seals were not put in correctly and were torn. Brand new seals on a dry crankshaft equals torn seals!!

Checkmarks

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Re: Family Heirloom; 340 invader engine rebuild
« Reply #7 on: January 14, 2019, 01:59:55 PM »
My little take on crank seals

The crank seal does both pressure and vacuum (pulse if you will), this is why the fuel pump, pumps.  If you have a bad crank seal (old crank seal), pressurize and determine yup its good.  Start up the sled, warm up and then press the fun button to the bar that old seal tears and you takes out your piston and cylinder.  Think of the pressure pulse in the crank case.  Under pressure it may hold pressure, conversely under vacuum it may hold vacuum, but in transition it may have a leak.  It may tell you absolute the crank seals are bad but a pressure or vacuum system will not tell you if the seals are good (flexibility of 40 year old rubber parts).  Apply to tires on a race car 40 year old tires! Not with me or my family in the car!

Cost analysis Old sled goes to the trash because it cost too much to repair!  Additional bonus if you have a 4/6 or 8 port motor  Crank seals $15!  4/6 piston $100 if you can find it.  550 cylinder or piston, good luck.

Not a tough call at all!  It takes 2 hours to change them, you don't even need to take off the heads, cylinders or pistons!  The time spent is cleaning the dirty old sled oils out of the pan and junk off the motor. 

Why not as a young friend might say "Just send it".  It will cost you your ride.

Not to accost anyone; the pleasure of an exceptional horse out rounding up cattle or a snowmobile between your legs when the snow is too deep for horses is priceless.  And hopefully we all learn

Worldawg

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Re: Family Heirloom; 340 invader engine rebuild
« Reply #8 on: January 14, 2019, 02:07:15 PM »

Under pressure it may hold pressure, conversely under vacuum it may hold vacuum, but in transition it may have a leak.  It may tell you absolute the crank seals are bad but a pressure or vacuum system will not tell you if the seals are good (flexibility of 40 year old rubber parts). 


Bingo. That's what I was looking for. I knew there had to be a reason you couldn't just test it like that. That pressure transitory period make sense. That being said... I wonder if one could test them using a pressure swing device.....

Once again, I am in no way looking to "cheap out" on putting in crank seals. they're so cheap and so likely the weak link that it just doesn't make sense not to. That being said, I find it hard to believe and one can change them out in two hours... it took FOREVER to get that motor apart lol.
1979 Invader 340
1979 Invader 440
1981 Invader 440
1980 Drifter 340 F/A
1978 Intruder 440
1980 Drifter 340 F/A
1980 Drifter 440
Someday a 1982 Interceptor 550 :^)