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No Flathead lake is not frozen over. I will update changes made when completed.
2003 Edge with SLP 903 Motor
- Thread starter nowready05
- Start date
903's do NOT use a stock SLP head, the heads and domes are totally different, you can NOT get pistons anymore for 903's, they were custom stroker ones made by weisco for those motors only, ( I bought the last 6 there were at SLP like 5 years ago) (long gone btw) the ignition and porting is also way different,(modded 440xcr/ducati set up)
i would not tear the motor down without the parts sitting there for it if I were you, its a great high HP RACE engine if you shim heads,make domes ect ect it will not run well at all
heres some pics of the last all NEW 903 I had before it was all sold off. they made over 200 hp in race trim btw
i would not tear the motor down without the parts sitting there for it if I were you, its a great high HP RACE engine if you shim heads,make domes ect ect it will not run well at all
heres some pics of the last all NEW 903 I had before it was all sold off. they made over 200 hp in race trim btw
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Bill, if that is you I did buy piston kits and a stator from you and I also looked at buying your sled when you had it for sale. I did find two more new piston kits about a year ago and paid $35/kit. I'm pretty well set with spare parts I think. I wish I had your motor knowledge Bill, you sure could tune this beast up and get it dialed in. Bill, I have Adam's sled.
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umm adam ran it on a mix of fuel as it did not have the super high compression race head on it, it has all the cool other parts, so all good there. it's still "high" compression compared to regular stuff tho, maybe try fattening up the main jet a couple sizes and see how much that helps it, and yeah there a bitc% to pull start
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Bill, I did try larger main jets sometime back when I had detonation occurring quite often at lower elevation. Helped a little maybe. I will check my notes at home and see what was removed and installed. I am going back to a 50/50 mix of premium/race fuel.
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cool , luckey for you to have the old owners knowledge
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After I bought the sled from the previous owner, I had the pipes removed and noticed light scoring on one of the piston skirts. The top end of this motor was rebuilt, Milennium Tech. took care of the cylinder and new pistons kits installed. Right now timing is 27 degrees at 4000 rpm. Jets removed from carb were 430 and a 440. Next larger jets installed. Compression was checked on 2/14 and was 150 psi in both cylinders. Stator assembly had a broken trigger coil and bracket and a new one was also installed on 2/14. That's about where I am right now with the motor. Just need to get it dialed in and running consistent from 3000 to 7000' elevation, which we normally ride. It's basically a rebuilt motor with just a few miles on it. Any thoughts on my next couple of steps.
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what exactly are you thinking? are you still on about lowering cranking pressure for easy starting or what?
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Yep, lower cranking pressure for easier starting. May need to address denotation also, but I need to run it more to see if the plugs still loosen up. Above all else it needs to be reliable.
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what way do you favor for getting the cranking pressure lower?
boost cylinders is reversable if you dont like it
re chamber your head?
i installed lots of compression release valves in 2 stroke motors over the years, using this method if you think you have a fine tuned well ballanced motor well sorted out absolutly nothing changes about your system except a bit of bleed down at start up. i guess if you know your motor does well with race gas keep feeding it that... why change because you must know their may be detonation on lesser fuel? made bad by cold or lower elevation ?
just so you know i install compression relese valves as a income suplement .
i wouldnt care about loosing a few horse power over a few thou thicker base gaskets as a economical try out test.
boost cylinders is reversable if you dont like it
re chamber your head?
i installed lots of compression release valves in 2 stroke motors over the years, using this method if you think you have a fine tuned well ballanced motor well sorted out absolutly nothing changes about your system except a bit of bleed down at start up. i guess if you know your motor does well with race gas keep feeding it that... why change because you must know their may be detonation on lesser fuel? made bad by cold or lower elevation ?
just so you know i install compression relese valves as a income suplement .
i wouldnt care about loosing a few horse power over a few thou thicker base gaskets as a economical try out test.
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What's going on with this project ? What did SLP tell you?
I run in my new motor at lower elevations with home built fat cheater cyl base gaskets then put genuine Polaris gaskets and went to the hills riding. My squish gap was .065 and got me 120 lbs comp at sea level and my Polaris gaskets got me to .048 squish gap and 152 lbs compression at sea level. Stock metal coated gaskets measured .016 , pulling the rip start their is a big difference
I run in my new motor at lower elevations with home built fat cheater cyl base gaskets then put genuine Polaris gaskets and went to the hills riding. My squish gap was .065 and got me 120 lbs comp at sea level and my Polaris gaskets got me to .048 squish gap and 152 lbs compression at sea level. Stock metal coated gaskets measured .016 , pulling the rip start their is a big difference
hard pull to start
Well, a simple way to make it start easier that's pretty crude,
Build a little jig to carry with you that you can hold ex. valves open:
drill down through exhaust valve caps to allow you to get a hold of end of plastic end on bellows. On Skidoo, 1/8" FNPT works, I use a "dresser" coupler as it is very thin. Other end of coupler extends through cap. Tap it out to 3/8" fine thread.
However you hook up, the effect is the same, you open exhaust valves to lower compression for easier starting.
I do this with big motors that have high compression on the dyno here at sea level. Sure saves on recoils and on the hand!!!!!!!!!!!
Good luck!!!!
Well, a simple way to make it start easier that's pretty crude,
Build a little jig to carry with you that you can hold ex. valves open:
drill down through exhaust valve caps to allow you to get a hold of end of plastic end on bellows. On Skidoo, 1/8" FNPT works, I use a "dresser" coupler as it is very thin. Other end of coupler extends through cap. Tap it out to 3/8" fine thread.
However you hook up, the effect is the same, you open exhaust valves to lower compression for easier starting.
I do this with big motors that have high compression on the dyno here at sea level. Sure saves on recoils and on the hand!!!!!!!!!!!
Good luck!!!!
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That's slick how much would you think it would drop lbs of compression on the 903 ?
starting
Unfamiliar with the build. On other motors seen 20#'s drop depending of course on your valve config. etc. Your hand will tell you for sure when you pull the rope!!!!
Unfamiliar with the build. On other motors seen 20#'s drop depending of course on your valve config. etc. Your hand will tell you for sure when you pull the rope!!!!
Starting
I have to apologize. I've been busy and really didn't think this problem you have through.
Hard starting:
You have a couple of choices. They're both going to change the way the motor runs on the very bottom end only.
To lower cylinder pressure for starting, cutting exhaust valve further back will work but not my preferred way as when wide open doesn't fit flush on top of
your nice ported exhaust port . It will work, just disturbs flow .
The other way I have not done on an older Polaris. On the Skidoos I put a spacer inside the bellows that physically stops the valve from going down all the way, but, valve still fits flush on top @ WFO.
You can play around with different lengths on the spacers to get it where you want.
Note:
You are going to notice it might be more "marbly" on the bottom end as this obviously changed your port timing at the bottom only. The engine will want to " 4 stroke " to a higher and higher rpm as you raise the valve up under light throttle no load. It's a trade off cruising on the trail but man do they ever start easier!!! You will be amazed how little you might have to go.
Good luck>>>>>
I have to apologize. I've been busy and really didn't think this problem you have through.
Hard starting:
You have a couple of choices. They're both going to change the way the motor runs on the very bottom end only.
To lower cylinder pressure for starting, cutting exhaust valve further back will work but not my preferred way as when wide open doesn't fit flush on top of
your nice ported exhaust port . It will work, just disturbs flow .
The other way I have not done on an older Polaris. On the Skidoos I put a spacer inside the bellows that physically stops the valve from going down all the way, but, valve still fits flush on top @ WFO.
You can play around with different lengths on the spacers to get it where you want.
Note:
You are going to notice it might be more "marbly" on the bottom end as this obviously changed your port timing at the bottom only. The engine will want to " 4 stroke " to a higher and higher rpm as you raise the valve up under light throttle no load. It's a trade off cruising on the trail but man do they ever start easier!!! You will be amazed how little you might have to go.
Good luck>>>>>
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Interesting thought on lifting the power valves off their seats to make less cranking pressure, but what about detonation? I assume that's what's loosening the spark plugs.?
Just a guess but wouldn't rechambering the head to increase chamber volume make the motor be less prone to detonation also reducing cranking pressure at start up time? I guess that's kind of like putting in thicker base gaskets like I said earlier and thats kind of crude n wrecks performance all up?
Just a guess but wouldn't rechambering the head to increase chamber volume make the motor be less prone to detonation also reducing cranking pressure at start up time? I guess that's kind of like putting in thicker base gaskets like I said earlier and thats kind of crude n wrecks performance all up?
Detonation
Detonation = bad design or going cheap on fuel for the compression. Operating parameters would have been for an elevation that matched with a given fuel also obviously.
As I said earlier, you can chase it forever or just do it right and blueprint the motor to see what it needs / wants.
Sweat equity is way cheaper than parts and a lot more satisfying.
Detonation = bad design or going cheap on fuel for the compression. Operating parameters would have been for an elevation that matched with a given fuel also obviously.
As I said earlier, you can chase it forever or just do it right and blueprint the motor to see what it needs / wants.
Sweat equity is way cheaper than parts and a lot more satisfying.
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