Polaris 726, 727, 797

[Mopar21277]

Hey gang, I'm trying to get my head around everything with the special SnoX race engines like the 726, 727 and 797. Please educated me here; as best as I can tell, these 3 use an 85mm bore with the 726 & 727 using the stock 64mm stroke and the 797 uses a 70mm stroke.

Interestingly enough, the new 600 race engine uses a 70mm stroke and the 800 CFI is 85x70. I'm a bit ingnorant on how "stroke" a motor; is it simply installing longer connecting rods to go from the 64 to 70 mm stroke? Is it a completely different crankshaft, with taller journals? Does an engine with a 70mm stroke use taller cylinders than a 64mm stroke engine?

What exact components did these race engines use? 800 Big Block crank with the small block cases heavily machined out? Cylinders? Can the 600 small block cylinders be overbored from 77.25mm to 85mm and re-nikasiled? I'm wondering if the 800 CFI components can be fitted to the 600 VES and HO cases; that would be one smokin setup...

 

[sled_guy]

The 726 and 797 are built on the "old" small block, pre 2006. They use custom cylinders and the 726 uses the stock 600 crank, the 797 used a stoked crank with those same cylinders.

The 727 is based off the new small block with the bigger reed cages. It uses the same cylinder castings at the 726, SLP either bought or licensed the castings. I don't know that there is actually any difference between the 727 and 726 jugs, I think it's a "round up" sort of thing.

You can put the 800 CFI top end on a new 600 race motor and get an 800 out of it that is carberated. I know 3 guys that have done just that.

I have a brand new 726 motor still in the crate with extra pistons that I've never run. I should get busy and sell it I guess.

sled_guy

 

[Mopar21277]

Thanks sled guy for the info; to me there would be a market out there for bigger bore, carbureted engines, particularly with the CFI mapping b.s. Particularly if you can pick up an '07 600 for $4500 and add in $2000-2500 for parts and machining.

If the 600HO could be massaged to accept the 600R/800 CFI crank and cylinders, then this would be a doable project. If memory serves, the retail on the 600R/800 crank is like $850 and the monoblock cylinder is like $580.

Is the longer stroke acheived by longer connecting rods or are the crank journals different too? I wonder how many 797's were built over the years and what are their availability?

 

[sled_guy]

It takes a lot of work to put the 800 crank in the 600 CFI cases... lots of grinding.

I know a couple of guys that have put the 800 cyinders on the 600R bottom end to make a carbed 800.

sled_guy

 

[Mopar21277]

Sled guy, do you know what the guys who put the 800 monoblock on the 600R engine are running for the ignition setup and are they running them in the race chassis or consumer chassis?

 

[JET FUEL]

Gary(RMKRIDER) did that to his 600r motor. As far as ignition I think he is still running the stock racer cdi with a timing box so he can use it in the mountains.

I have a 797 and one of the difference's is between some of the newer kits is the powervalve bellows housings. also the piston sizes are a tiny bit smaller from the older ones, i had mine re nic'd to run the newer pistons, so I guess mine is technically a 795 ish?
I also did a new head to match the pistons.

The new pistons came in a slp727 box.

My motor is built on the 600 ves case, I have a buddy that moved his crank and cylinders over to a H.O. case from his ves case, not really sure the time and cost was worth it for him, but to each his own.

The story I got was SLP built these kits for polaris race team and polaris built their new motors based off these kits and slp got to keep the castings.

It a good story even if it isn't true.

 

[Angermangement890]

Gary(RMKRIDER) did that to his 600r motor. As far as ignition I think he is still running the stock racer cdi with a timing box so he can use it in the mountains.

I have a 797 and one of the difference's is between some of the newer kits is the powervalve bellows housings. also the piston sizes are a tiny bit smaller from the older ones, i had mine re nic'd to run the newer pistons, so I guess mine is technically a 795 ish?
I also did a new head to match the pistons.

The new pistons came in a slp727 box.

My motor is built on the 600 ves case, I have a buddy that moved his crank and cylinders over to a H.O. case from his ves case, not really sure the time and cost was worth it for him, but to each his own.

The story I got was SLP built these kits for polaris race team and polaris built their new motors based off these kits and slp got to keep the castings.

It a good story even if it isn't true.

My info on the race engines was Polaris cast the cylinders and built the engines in house, once they were satisfied with the package, they had SLP build the engines/pipes to the specs provided. Once the change was made to 600cc sno cross engines, Polaris sold the casting rights for the cylinders to SLP. SLP made a few porting changes (pump gas friendly) and have renamed them the 727.

Most of the guys using the 70mm stroke bottom end out of the 08+ IQR are running the stock ignition as it allows you to rev 8400+ which the engines seem to lilke.

If I remember properly, you will not be able to wedge the CFI 800 crank into the 600 HO case, as the Mag ends are different tapers and utilize different width bearings.

Carls cycle has 70mm stroke cranks for the 600 HO case that they developed for the 860.

 

[JET FUEL]

My info on the race engines was Polaris cast the cylinders and built the engines in house, once they were satisfied with the package, they had SLP build the engines/pipes to the specs provided. Once the change was made to 600cc sno cross engines, Polaris sold the casting rights for the cylinders to SLP. SLP made a few porting changes (pump gas friendly) and have renamed them the 727.

Most of the guys using the 70mm stroke bottom end out of the 08+ IQR are running the stock ignition as it allows you to rev 8400+ which the engines seem to lilke.

If I remember properly, you will not be able to wedge the CFI 800 crank into the 600 HO case, as the Mag ends are different tapers and utilize different width bearings.

Carls cycle has 70mm stroke cranks for the 600 HO case that they developed for the 860.

Who know what the real story is, but you can buy the older pistons from slp, so I would assume slp had their fingers in the original motors.

 

[sled_guy]

Sled guy, do you know what the guys who put the 800 monoblock on the 600R engine are running for the ignition setup and are they running them in the race chassis or consumer chassis?

I don't. I just know some people have done it. I assume they are running the 600R ignition. I'm pretty sure they are in the race chassis.

sled_guy

 

[CraigBondy]

Good day fellow 2 strokers.. 726 Pistons eh.. I'm looking for some replacement pistons and rings for my 2001 726. The Number on top is B00J2 9373 and they are 84.85mm.

Also does anyone know if it's possible to convert this engine to run 92 pump gas, or 100LL, or at the very least 110/92 50/50 mix at 1000'

The 110/92 almost works, but currently I pretty well need pure 110 to keep it from going 30mph without throttle. The domes installed have one number and thats 26. Im hopping there is an available set of domes for this thing that will make it a little less detonation prone, while running cheaper fuel. But somehow I have a feeling this will requier some custom parts?? Any help would be much appreciated, and pistons would be a god-send.

Much thanks

 

[Roadwarrior102]

Running SLP 727 heads on an 01 726 will let you run 50\50 pump gas\110 or less at sea level, above 5000 ft pump gas is good by it self. You will want to run less timing advance. I run the SLP head and Pro-X 600 ignition on my 726 and have had great performance.

 

[pura vida]

i had a carl's cycle 726/7 that i ran on pump gas at sea level. i believe they (carl's) recommend running a mix with some race but i never had any issue. i just always made sure to run good, fresh gas and check for detonation. i currently run a carl's 797 in an iq chassis that i also run on straight pump gas without issue. although i carry a couple gallons of race or some good octane boost just in case the gas i buy isn't quite up to snuff. the 797 is definitely more on the edge than the 727. both very impressive motors. i run both with single pipes. with twins you must run some race. i'd call carl's. they should be able to set you up. fwiw.

pv