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74 srx sno-pro

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74 srx sno-pro

Postby jake_arcticcat » September 23rd, 2006, 8:52 pm

Does anyone have any info on these sleds. I was reading the new snowgoer it says only 3 were sleds and 6 engines were made. Anyone no of any pics or specs on them. Just wondering, thanks
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74 srx sno-pro

Postby ZR800XC » September 24th, 2006, 4:01 am

There were 4 built...One was built for each Ed Schubitzke and Lynn Trapp, one was meant as a back-up sled. When the Chaparral team quit, they picked up Larry Omans and he raced the spare. The 4th was built from spare parts after Lynn crashed his. Supposedly there were only 6 engines built, but I gotta believe they had spares and R&D engines???? The whole sled was built of Aluminum and Magnesium. They only used steel where it was an absolute must. They also did very well taking over half of the 440 Sno Pro wins in 74...

For some pix of the 74 Yammis, and a whole bunch of other cool sleds of Sno Pro get yourself a copy of "Best of Sno Pro '73-78" from [url=http://www.teshio.com/vsm.htm]http://www.teshio.com/vsm.htm[/url]


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74 srx sno-pro

Postby sled_king » September 28th, 2006, 3:33 pm

i just read the article in snow goer Canada by Hal Armstrong on the '74 Yamaha SRX 440's. awesome article!
when the sleds were first built, they never met the 250lb weight limit, yamaha had to add weight to the sled to get them up to 250 lbs. the titanium cleats broke alot, they switched them to steel as required. one thing i never new about the '74 yamaha srx snowpro was that it had a one piece forged crankshaft...
the motor made roughly 115 hp.
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74 srx sno-pro

Postby AHood » September 29th, 2006, 6:13 am

[quote=sled_king]i just read the article in snow goer Canada by Hal Armstrong on the '74 Yamaha SRX 440's. awesome article!
when the sleds were first built, they never met the 250lb weight limit, yamaha had to add weight to the sled to get them up to 250 lbs. the titanium cleats broke alot, they switched them to steel as required. one thing i never new about the '74 yamaha srx snowpro was that it had a one piece forged crankshaft...
the motor made roughly 115 hp.[/quote]

wow one piece forged crankshaft?? how is that possible it would have to be like the outboard motors and use split race roller cages on the rods and all the crank bearings. the two piece cap screw rods are far more prone to failure than a single piece conventional rod and are far heavier. i was under the inpression that those motors were based off the GPX motor like the later liquid GPX'
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74 srx sno-pro

Postby sled_king » September 29th, 2006, 3:40 pm

it is possible. yamaha did it.
it was expensive but they did it.
each '74 yamaha srx snopro cost $20k to build. that was unheard of back then.
the motor was piston port, crome bore, liquid cooled with aditional cooling fins on the outsides of the fuel transfer ports. there was no motor plate. the motor mounts were on the lower sides of the motor for a real low cg. they rev'd them 7500-8000rpm
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74 srx sno-pro

Postby AHood » September 29th, 2006, 7:53 pm

[quote=sled_king]it is possible. yamaha did it.
it was expensive but they did it.
each '74 yamaha srx snopro cost $20k to build. that was unheard of back then.
the motor was piston port, crome bore, liquid cooled with aditional cooling fins on the outsides of the fuel transfer ports. there was no motor plate. the motor mounts were on the lower sides of the motor for a real low cg. they rev'd them 7500-8000rpm[/quote]

i find it hard to believe that they could make 115 Hp at an unheard of low rpm like 7500-8000. even today to make 115 hp from a 440 twin piston port motor you will have to rev it to 10,000+. im not trying to debate anyone i rather find this very interesting as im a big fan of the yamaha engines.
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74 srx sno-pro

Postby ZR800XC » October 1st, 2006, 1:24 pm

Gordy Muetz, the crew chief, claimed at one time the motors ran close to 9,000RPM They were definately the strongest running 440s in 74. They would dominate the other 440s until they would have a breakage.

There is alot of speculation and rumor about the engines as I'm sure Yammi kept close tabs on them, and surely they were destroyed or stashed far away at the end of the season. But I'm doubting they were 115hp. The 78 SSR didn't even accomplish that.

I've seen pix of the engine...it's unlike any other engine, liquid or F/A. It doesn't even really resemble any other Yammi engine of the time, or later, for that matter.


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74 srx sno-pro

Postby sled_king » October 1st, 2006, 3:05 pm

the '78 Yamaha SSR 440 was low on power. in fact,it had less power than the '77 srx. Hal stated in his article the '74 yamaha srx 440 motors made between 112-116hp. new cylinders arrived half way through the season, which were 3 or 4 hp more than the original cylinders. i am sure they were experimenting with pipe set up also.
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74 srx sno-pro

Postby AHood » October 2nd, 2006, 6:11 am

[quote=ZR800XC]Gordy Muetz, the crew chief, claimed at one time the motors ran close to 9,000RPM They were definately the strongest running 440s in 74. They would dominate the other 440s until they would have a breakage.

There is alot of speculation and rumor about the engines as I'm sure Yammi kept close tabs on them, and surely they were destroyed or stashed far away at the end of the season. But I'm doubting they were 115hp. The 78 SSR didn't even accomplish that.

I've seen pix of the engine...it's unlike any other engine, liquid or F/A. It doesn't even really resemble any other Yammi engine of the time, or later, for that matter.[/quote]


so was the 74 engine and or cylinders totally different from the later GPX liquid motors some times called pdc when did those start 75? from pics ive seen the heads or head rather (its mono right) look similar between the 74 srx and the 75 pdc aka liquid GPX
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74 srx sno-pro

Postby ZR800XC » October 3rd, 2006, 12:59 pm

I don't know for sure...I do believe the 75 engines were basically GPX bottoms with a top end based on the 74 engines. Then changed to the "SRX" engine in 76.

If the 74 engine was 115hp, it was quite a feat. Getting a rotary valve triple exhaust port Rotax to 115 I think is prety good. With 120-125 being excellent and taking alot of experience and knowledge. And this is by todays standards. Alot of these numbers are achieved by manipulating data...Doing a cold pull with a hot pipes and leand jetting in the dyno room doesn't simulate real world results.


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