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Discussion Starter · #1 ·
Hi all, found out about this list at SnowmobileWorld.com, and thought I'd head over for more specific advice on sled stuff...

Have essentially spent my way into a "FrankenMach", a 94 MXZ chassis with a 779 triple, and 97 suspension (moved up to a 136 x 1 1/4" paddle w/extensions to minimize getting the beast stuck). In talking around about triples in general, I think I may have had too big a hard-on for a triple and should maybe have put in a 670 instead of a 779, but that's what turned up first, and right now there's too much money under the bridge to go in a different direction...

Anyway, after having the "rebuilt, good shape" motor I purchased from an area dealer re-rebuilt (formerly pto .030, mag .040, center stock, now all .060), I still seem to have issues with spark and fouling. When I got the motor there were 9s in it, and up these would make it run a wee bit hot. Put 10s in, and that solved the hot problem. However, the 10s seem to foul out fast (fortunately, not quite as fast as the previously crapped-out top end ate 9s)...to be honest, I haven't checked the jetting (2.2/2.5 Turbo Dodges are more my bag, but I'm working on my 2-stroke repertoire), so there could be issues there, but beyond that, I have been told that a lazy stator could cause similar problems. Last weekend I had it cut out on two occasions after fairly spirited romps across my buddy's lake. Started all right afterward, but 6 days and 5 riding minutes later, the plugs were fouled enough to keep it from a mild slope up from the lake to the cottage. In light of this behaviour, I'm not exactly confident enough to put a trail pass on it yet. Looking for opinions and, with the luck I have been having with this thing, probably a stator for a 779 as well. Should I find one, will an 809 stator fit? Could I use 809 specs to test/diagnose the 779 stator?

Also, I'm running Amsoil, and have collected 3 spare stock jugs and pistons "just in case", but am wondering if anything else can be done to try to "blam-proof" this thing...

Thanks
 

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Mötorhead said:
Hi all, found out about this list at SnowmobileWorld.com, and thought I'd head over for more specific advice on sled stuff...

Have essentially spent my way into a "FrankenMach", a 94 MXZ chassis with a 779 triple, and 97 suspension (moved up to a 136 x 1 1/4" paddle w/extensions to minimize getting the beast stuck). In talking around about triples in general, I think I may have had too big a hard-on for a triple and should maybe have put in a 670 instead of a 779, but that's what turned up first, and right now there's too much money under the bridge to go in a different direction...

Anyway, after having the "rebuilt, good shape" motor I purchased from an area dealer re-rebuilt (formerly pto .030, mag .040, center stock, now all .060), I still seem to have issues with spark and fouling. When I got the motor there were 9s in it, and up these would make it run a wee bit hot. Put 10s in, and that solved the hot problem. However, the 10s seem to foul out fast (fortunately, not quite as fast as the previously crapped-out top end ate 9s)...to be honest, I haven't checked the jetting (2.2/2.5 Turbo Dodges are more my bag, but I'm working on my 2-stroke repertoire), so there could be issues there, but beyond that, I have been told that a lazy stator could cause similar problems. Last weekend I had it cut out on two occasions after fairly spirited romps across my buddy's lake. Started all right afterward, but 6 days and 5 riding minutes later, the plugs were fouled enough to keep it from a mild slope up from the lake to the cottage. In light of this behaviour, I'm not exactly confident enough to put a trail pass on it yet. Looking for opinions and, with the luck I have been having with this thing, probably a stator for a 779 as well. Should I find one, will an 809 stator fit? Could I use 809 specs to test/diagnose the 779 stator?

Also, I'm running Amsoil, and have collected 3 spare stock jugs and pistons "just in case", but am wondering if anything else can be done to try to "blam-proof" this thing...

Thanks
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Hey man never second guess yourself on a 780. it's twice the motor than the 670 will ever be, if you can handle the gas bill.

I can take one of these motors apart with my eyes closed and have delt with every problem that you can have with these motors (there are alot), so you better get used to working on your own. The biggest thing with these motors is tuning, they have to be constantly tuned because there are so many things on a triple that can go wrong..

For fouling plugs this is the list that I would follow:

1. make sure your using the right plugs.
2. gap plugs correctly
3. check stator and coils with an ohm meter
4. make sure proper grade of oil is used (these motors burn way cleaner with synthetic and if thats too expensive, use Shell injection oil(works well with 780)
5. use high octane gas (have to with 780, 92 octane or greater)
6. check timing(not with light but be locating TDC on mag side then set timing 2.18mm before TDC and aligning marks on flyweel and mark on trigger coil)
this is inside the recoil starter. these motors were known to jump timing be shearing off the woodridge key that keeps the flywheel inline with the crank.
this is espicialy true for sleds with no electric start.

If key is sheared, timing light will still show that motor is on timing.

7. check jetting is not to rich, ski-doo has changed recomended jetting for 780.
contact local dealer
8. check needle valve is seating properly, and set float height.

If this dosen't solve your problem, provide with more information about the symptoms and i'll give you more ideas.

This is the best motor you'll ever own when it's working right.

P.S. get a shop manual from ski-doo, you'll need it.

GO BIG OR GO HOME , TRIPLES RULE !!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!
 

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My 809 was fouling plugs at WOT. During a process of elimination someone noticed that a little smoke was coming from one of the Raves. I open one and the bellows were in pretty bad shape, one had poped off. Put new ones on and voila, problem solved. At the same time, I found out why I couldn't catch my buddies MXZ 800 anymore.
 

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REman stator better than the original $125.00 Todd 1-260-833-2536 or 316-2839.
 

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Discussion Starter · #5 ·
Thanks for the tips 1meanmach, that is a lot of good info to check out. I'll be testing the stator this weekend far as I know, as long as a FSM for the 97 809 will do (got one from a friend, and all the suspension stuff was relevant)...can I take as granted that the electrical testing steps/readings in it would apply to the 779 as well? I'm going to try a fresh set of plugs this weekend, with a 5'er of Sunoco 94 and some octane boost to help colour the plugs. Hopefully I'll be able to check the carbs' setup before that, but not sure with work. As for oil, I did run one quart of Shell Injection oil through it last year, but had since added 4 quarts of Amsoil.

After paging through the FSM, looks like I'll have to get myself a good dial indicator for timing checks, but I've been wanting one for a while. I'll post up when I get back and let you know how thing turned out.

thanks muchly
 
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