Freestyle Port timing for rec ski??

Wiseguy92

Wiseguy92

Location
Saginaw MI
I'm new to the rec ski game. I have a lot of expirerenced with two strokes in high performance snowmobile racing and was wondering if the port timing of the exhaust and transfers would be similar? We run more rpm's and have better exhaust pipes but power is power. What are some of the numbers guys shoot for when porting cyls? 202 degrees on exhaust and 185 on transfers? Any help would be much appreciated!
mike
 
kevbo

kevbo

Location
dfw
Wiseguy92 said:
I'm new to the rec ski game. I have a lot of expirerenced with two strokes in high performance snowmobile racing and was wondering if the port timing of the exhaust and transfers would be similar? We run more rpm's and have better exhaust pipes but power is power. What are some of the numbers guys shoot for when porting cyls? 202 degrees on exhaust and 185 on transfers? Any help would be much appreciated!
mike
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There is an almost direct trade-off between response and power as the ports are raised, all else equal. Small engines burning pump gas need low ports for any throttle response. Larger engines, especially with high compression and programable ignitions can have good response with very high ports and make a lot of power. The actual porting spec depends largely on the tuners ability, some guys can make high port engines work but most can't.
 
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waxhead

wannabe backflipper
Location
gold coast
No one is going to give away there port timing specs online. It like asking a nascar team what camshaft they are running. but between 185 and 195 exhaust and 120 to 130 transfers will port you in the ball park
 
Wiseguy92

Wiseguy92

Location
Saginaw MI
Im working with a 66e motor with the 66v cyls in a carbon ROK. Its big bored to 87mmm. I have been running the stock yammi electronics but just installed a msd total loss tonight. I shot the timing and it was around 14 degrees in stock fashion. Knowing twostrokes, I know that is very mild for static timing and maybe why the motor dosent seem to make great power. I have 46 full specs, waterdog dry pipe and the motor compression ratio is up there where it shoud be. It seems to me the motor shoud make more power than it dose. Stock timing and stock 66v cyls are the only pieces of the puzzle left keeping the power down that I can see.
I will run it this week with the timing where it shoud be and see if thats what it needed. If not Im going after the cyls. Thaks for the Info guys......
 
Matt_E

Matt_E

steals hub caps from cars
Site Supporter
Location
at peace
Well about that stock ignition: that motor was built for pretty heavy sitdowns with equally heavy fatass riders who cannot be bothered to buy anything but the cheapest, lowest octane marina gas possible, and then go wide f'n open all day long. That engine has to last through the warranty period (and then the PV's drop, lol).

That's why that motor has that ignition timing and pretty low compression (in stock form)
 
Wiseguy92

Wiseguy92

Location
Saginaw MI
Copy that Matt E! It seems like all the parts are there to rip but its just not. Even with the timing in the ball park, the exhaust ports are sooooo small, I wonder if it will breathe fire no mater what you bolt on to it. I have a bad to the bone engine guy that will do what ever I want him to, but our expierence is mainly in snomobile engines. I just dont want to set it up like a sled motor that spins 9200 rpms when these motors spin far lower. I like the power valves. They give you more room to be greedy with the port size while getting 10 degrees back with the blade.
 
Matt_E

Matt_E

steals hub caps from cars
Site Supporter
Location
at peace
TheBuzzard said:
the hard facts are............ those motors are just turds and not designed for bottom end performance. no sitdown motor is designed for bottom end.
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The XS1200 is a 66E platform. Though the only thing that it uses are the cases.
 
E

egbrig

I ran a 66e that I ported, with twin pipes, msd t/l in a blaster. Whats funny is at the time it was considered "race ported". Now those same port duration numbers are used in many freestyle builds. Its about making the power and getting to that power band using the pump as the transmission. BTW, a couple of pounds of the extra weight in the crank is because of the larger bearings used on the crank.
 
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Waterdawg Kustomz

Waterdawg Kustomz

RIP NATION
Location
Pac NW
Deck the cylinders .080 and recut the domes, set squish clearance at .065 with .010 run out. Set the power valve cap almost all the way out. I have a great timing curve for you......send me an email. Oh, and hang the f#$k on, makes awesome bottom end. Hope this helps.
 
Nuklear6

Nuklear6

I Dream 10' Surf!
Location
Bordentown, NJ by week / Brigantine, NJ by weekend
Stock 66e crank is 27.4 lbs on my scale. Stock 701 just a little over 19. That's a huge different add to that the availability of a 701 based crack that's 2 lbs lighter then stock.... I do realize not all of that is rotating mass but still alot of weight to over come. But then again the 66e is a 10 mm Stroker vs 701 and has good bore spacing.?.?.
 
Wiseguy92

Wiseguy92

Location
Saginaw MI
I believe in the potential of the 66e. A 10 mil stroker over a 701 stock stroke has big potential with a stock crank. I have learned a few lessons with regard to rotating mass over the years and two strokes and sometimes things aren't as they seem. Tks again for everyone's input!
Mike
 
augustaf

augustaf

Location
central florida
Waterdawg Kustomz said:
Deck the cylinders .080 and recut the domes, set squish clearance at .065 with .010 run out. Set the power valve cap almost all the way out. I have a great timing curve for you......send me an email. Oh, and hang the f#$k on, makes awesome bottom end. Hope this helps.
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The Dawg has spoken! Listen to him, he has quite a bit of experience with this engine.
 
TheBuzzard

TheBuzzard

Location
the jetski grave yard
i'm not buying it. its going to take a lot more than that to get desireable bottom end power out of those gp800 motors. we are not competitors and we aint exactly buddies either, he's in the dawg house as far as i'm concerned :)=
 
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waxhead

wannabe backflipper
Location
gold coast
Pulling the port timing down 2mm is going to make a huge difference to the engine. You may or may not like waterdawg but i wouldnt discount the information he just gave you.
I havent measured up one of these recently so I dont know the timing off the top of my head but its a simple calculation if some one knows the stock timing and rid length to figure out what you would end up with.
 
TheBuzzard

TheBuzzard

Location
the jetski grave yard
i like him as long as we are on the phone. not so much if he's behind me............. AKA sending me something i'm kind of anxious to get......
 
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