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Discussion Starter #1
i have 2 78 srx 440 these are going to be my beater sleds as i just got a vmax 4 880 big bore are these sleds as bad as every body says i just put them together last winter late and only got to ride them for about 1/2 a day they seemed to run good for old sleds nothing like my vmax but good for old sleds is it the bottom end thats bad or the top end only or both these sleds only show about 3200 on odometer  
 

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Discussion Starter #2
also the sled has a sticker on it that says gas should be mixed at 15to1 this seems real heavy to me is there a better mix this thing fouls plugs like crazy but i dont want to sieze it up is 40to1 ok or maybe 32to1
 

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If I remember, the engines didn't really give problems until 80-81 when they ported them to big.  If you use a good synthetic with a good cold poar I would guess that you could mix around 24-32:1.  Just guessing.  
 

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Back in the early and mid 70's the oil to gas ratio used to be 20-1, mostly because of the oil used back then, I had a few sled of that era and used what was written on the oil container usually 40-1 all ran ok for me. My brother had an 80 SRX I think it was oil injection though  i can't remember. But I don't think u need a synthetic oil, just a good quality snowmobile oil mixed at 40-1 will do. Also those machines were top of the line back then and they flew with the best of them. I don't believe they were any more trouble then any of the rest of them. Yamaha always put out a pretty good product.
 

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Moved to vintage.....might be a better home for it
 

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The 78 SRX was the most detuned of all the Srx's. They made 78hp at 9000RPM. They are really nice looking sleds because they looked like the 77's except for the black center section of the hood. There are also other differences but too many to list. As for the oil. The oil quality back then compared to the oils of today is night and day. You can use any high quality oil of today and just follow the mix instructions for the oil. I have a bunch of 77's and run anywhere from 32:1 to 90:1 depending on what oil I am running and have never even scored a piston, ring, or cylinder.
 

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I bought an 81' SRX 440 as my first sled 5 years ago.  It had 2300 miles on it, ran it for 1.5 years(1000 miles) before the crank bearings went.  What a light fast piece of lightning that thing was.  I later found out that these sleds were all recalled in 81' and the buyer was given a choice of $2,200 to buy the sled back or keep the rocket.  These sleds made too much power for their own good and would often self destruct.
 

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I bought a 1978 about 1987 and that thing flew! Found out later it had a 1976 ssr factory motor in it.Out of the hole nothing would touch it.Put out 105 hp back in 1976, pretty good for a 440.
 

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Discussion Starter #10
i know my 79 will flat haul put my 78 and 79 side by side the 79 eats the 78 but the 78 is bone stock the 79 has aaen pipes and 81 srx butterfly carbs i like the butterfly carbs because the throttle responce is much better than the slide carbs i just love this little rocket you hit the gas and you can run with the best of todays sled you hit the power band and you will out run most of todays sleds unless you have riddin one you just dont have a clue how powerful these old beasts are and running amsoil syntheth oil i have yet to lose a ring or have any engine trouble at all i think i ride it more than any of my other sled and i have 8
 

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my brother and i pwn a 78 srx all done up by aaen perf, all ported polished and 44mm carbs,with the lake pipes. aaen says this machine made 107 hp! it is for sale also, has been painted yamaha blue
 

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Ya all the talk these days about the horsepower of all the new big sleds!! back in the 70's and early 80's they were making alot more horses with less cc's. So as far as i am concerned they have not made much progress in the engine area of the new sleds.
 

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srx nice sled back then hows about the merc snow twister. that was a fast sled out of the box. too bad merc stoped maken sleds
 

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I personally love the 78's and think they are they best looking pre-1984 sleds ever made..As far as performance yeah 78's were the most de-tuned coming off 77 which was a very strong 440 that year..remove the airbox, jet according and there is a mod for the stock pipes which makes it absolutly crazy fast--reliability goes up too! Im in Michigan and would be interested in them if your selling. Oh by the way everyone; any year 440 srx can make 90-95 horse @ 8900 with stock pipes and 36 round slides easily. 105 with Aaens and porting @ 10500
 
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