11 replies to this topic

[WIfarmer]

Ok, here we go. I have a 03 600HO (carb) that I have set up for boondocking. The sled works great (besides the crappy mileage). The one problem that has come up is odd backshifting. First off, here's my setup. Stock motor, 1.75" 121 track, no studs, down 2 teeth on the top sprocket, 5600 miles. Primary clutch has a different spring. Same ending rate as stock but engages a bit higher. Stock arms, pins, etc.... I don't remember the exact RPM, but once it hits it stays nice and steady. I wanna say 7600 but don't remember exaclty from last winter. W/ the big track I needed a bit more backshift. I still have the stock helix. Put in the green secondary spring which seems to be fairly popular. Helped some but not 100%. Went one step farther and put in the ultra stiff spring from I think a 800 highmark. What the sled will do, in powder or even a long pull down the lake, it'll pull super hard for the fist 30 seconds or so. Then out of nowhere it'll shift out and fall off the pipe. If I chop the throttle for a second or two so the clutches can backshift a bit, it'll hit proper RPM again and pull hard till once again it falls off the pipe. So, I've pretty much narrowed it down the the secondary shifting when it shouldn't be. One possibilty I've thought of is the big bushing in the secondary. If it's a bit worn and causing things to bind up can't be helping. Also the 3 little bushings in the secondary seem ok, but I'll replace them this year just for good measure. I don't really care about top speed, I just want the thing to stay in the meat of the power when held wide open in the powder. So I was thinking I perhaps need a different helix. I kinda know my way around clutches, but the one thing I always forget is which way I'd need to go in the helix angle to make quicker backshifting. Any help on my dilema would be great. Thanks for reading my life story here!!!!

[Dynamo^Joe]

I hope you dont mind me conveying my thoughts here. I always like everyone to have a little bit of fun the way I respond or request answers by trying to dissect "fact" from "opinion". When you separate the facts from information revealed, then you can calculate a next move. I get many emails from people about tuning their sled, I will plow thru their message and read it first looking for opinions "i think this, or I think that" or "could it be"....then I re-read the message looking for facts. "rpms loss" "this much rpms" "backshift was poor"....

A few things....
*You have increased track lug height.
*For various reasons added up; A rule of thumb is for every 1/4 inch lug increase you will lose approx 4 mph.

*If you have lost 8 mph due to this additional load then compensate for the load increase with lower drive gears.
*2 teeth is a great start.

WIfarmer:...it'll pull super hard for the fist 30 seconds or so.
Joe:...what track speed did you have by the 30 second mark? [you need to know this]

WIfarmer:...Then out of nowhere it'll shift out and fall off the pipe.
Joe:...what track speed did you have by the 30 second mark? [you need to know this]

WIfarmer:...If I chop the throttle for a second or two so the clutches can backshift a bit, it'll hit proper RPM again and pull hard till...
Joe:...where is "pull hard till" Where is "till" what track speed did you have by "till"

WIfarmer:...I've pretty much narrowed it down the the secondary shifting when it shouldn't be
Joe:...Great! This is why we are looking for answers to those particularly worded questions...

WIfarmer:...One possibilty I've thought of is the big bushing in the secondary. If it's a bit worn and causing things to bind up can't be helping
Joe:...What other possibilities are there? Belt? With the increased load you have on the clutches/belt are you grabbing the belt hard enough at the point of [it'll hit proper RPM again and pull hard till...]

No need to talk about: [discuss however neglecting...]
...the bushing because this is a difficult task...
...the secondary spring because you've already changed it and noted its advantage over others...
...the gearing, you already compensated for the increased load

What is left?
WIfarmer:...So I was thinking I perhaps need a different helix.
Joe:...It would be the easiest part to change in a new direction.

WIfarmer:...I always forget is which way I'd need to go in the helix angle to make quicker backshifting.

Review Principles
Angles regarding "Shift"
Angles less than 45 upshift slower "stall the upshift" "prolong the upshift"
Angles more than 45 upshift quicker "speeds up the shift

Angles regarding "Rpms"
Angles "less than" 45 provide more engine rpms" under w.o.t. application?
Angles "greater than" 45 provide less engine rpms" under w.o.t. application?

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WIfarmer:...If I chop the throttle for a second or two so the clutches can backshift a bit, it'll hit proper RPM again and pull hard till...
Joe:...where is "pull hard till" Where is "till" what track speed did you have by "till"

What helix angle were you utilizing at that moment in time [along the shift curve] ?
Now we need to know "what helix do you have in your sled?"
We'll be able to calculate what angle that could be causing a problem and go from there....

[WIfarmer]

All right, I'll answer your questions the best I can. Here we go!!

W/ the bigger track height I can top out just over 90. W/ the stock track I could top 100 on occasion so your right on. The 2 teeth make it get there easier but didn't really loose anything. Also it pulls out of the hole MUCH harder. I also figured the gearing would help reduce belt temp a bit.

Pulls super hard up to about 60 or so than tapers off a bit. On the lake it'll do that, then pull good to about 80, then just kinda keep going till 90 or so (this is before the clutch falls on it's face.)

Track speed when it fall on it's face is generally 70ish, unless in deep powder where it's much lower. It'll do the exact same thing on a long pull down the lake as it will on a long pull in the powder. I'm 99% sure it's not engine realted also. Still have good compression and the thing runs great. Not fuel delivery.

When I chop the throttle to allow the clutches to come back I'm not exatly sure what speed it is. One thing I've done in the fields is lock the track for a second (at 70ish mind you). Then when you get off the brake I can hear the secondary "spool up?" (is that the right way to say it?). Then bag the throttle and I'm off. Seems like it needs a bit to get the sheaves back together.

I've tried 3 different belts w/ pretty much the same results. Also have cleaned both clutches inside and out, and lightly sanded the faces. It helps a little here and there but nothing really solves the problem. BUT, have not replaced ANY of the clutch bushing. The arms and rollers are nice and free.

Ya, I know I've neglected the bushing. I'm ordering a new one tonight.

Helix is nice and easy to replace. Good way to go A-B-A-B testing. And yes, I get stupid every summer and forget which way to go for what.

Should be the stock helix in the sled which I THINK is a dual angle. Im thinking maybe bushing, but mostly the second angle of the helix is where the fix is at. When the secondary can stay in it's first half of the ramps it works wonderfully. Seems when the secondary gets over that hump (I'm assuming when it gets to the second angle) that everything falls appart. Like it's good good good then it snaps all the way open. Jab the brakes or slow to get it back to the first half of the helix and life is good agian.

Also, if anyone can give me some good tips, I have full acess to our hayfields, so testing / fixing can start right now. None of this waiting for the snow to fly bull!!!!

[f7eater]

All right, I'll answer your questions the best I can. Here we go!!

W/ the bigger track height I can top out just over 90. W/ the stock track I could top 100 on occasion so your right on. The 2 teeth make it get there easier but didn't really loose anything. Also it pulls out of the hole MUCH harder. I also figured the gearing would help reduce belt temp a bit.

Pulls super hard up to about 60 or so than tapers off a bit. On the lake it'll do that, then pull good to about 80, then just kinda keep going till 90 or so (this is before the clutch falls on it's face.)

Track speed when it fall on it's face is generally 70ish, unless in deep powder where it's much lower. It'll do the exact same thing on a long pull down the lake as it will on a long pull in the powder. I'm 99% sure it's not engine realted also. Still have good compression and the thing runs great. Not fuel delivery.

When I chop the throttle to allow the clutches to come back I'm not exatly sure what speed it is. One thing I've done in the fields is lock the track for a second (at 70ish mind you). Then when you get off the brake I can hear the secondary "spool up?" (is that the right way to say it?). Then bag the throttle and I'm off. Seems like it needs a bit to get the sheaves back together.

I've tried 3 different belts w/ pretty much the same results. Also have cleaned both clutches inside and out, and lightly sanded the faces. It helps a little here and there but nothing really solves the problem. BUT, have not replaced ANY of the clutch bushing. The arms and rollers are nice and free.

Ya, I know I've neglected the bushing. I'm ordering a new one tonight.

Helix is nice and easy to replace. Good way to go A-B-A-B testing. And yes, I get stupid every summer and forget which way to go for what.

Should be the stock helix in the sled which I THINK is a dual angle. Im thinking maybe bushing, but mostly the second angle of the helix is where the fix is at. When the secondary can stay in it's first half of the ramps it works wonderfully. Seems when the secondary gets over that hump (I'm assuming when it gets to the second angle) that everything falls appart. Like it's good good good then it snaps all the way open. Jab the brakes or slow to get it back to the first half of the helix and life is good agian.

Also, if anyone can give me some good tips, I have full acess to our hayfields, so testing / fixing can start right now. None of this waiting for the snow to fly bull!!!!

stock helix is 47/44 you may want to try an angle like 47/40 or something like that, but this can get expensive at over 100 bucks a pop, and you would be better off in the long run to just get DJ's kit and live happily ever after. the 03 600 is notorious for running way rich in the mid range and this could be contributing to your problems and also giving you horrible gas milage, you may want to drop the needle for a crisper mid range.

[WIfarmer]

I've read way too many posts on the fuel mileage thing. I'm sure the 1.75" fan that I' swinging around isn't helping. As for jetting, seems like everyone is split between it works great and it burns down. I also don't wanna be jetting on the trail. If I have to loose a little snap to be lazy I'm fine w/ that. I do think that I might play w/ the needle a bit around home just to see how it feels though.

[f7eater]

I've read way too many posts on the fuel mileage thing. I'm sure the 1.75" fan that I' swinging around isn't helping. As for jetting, seems like everyone is split between it works great and it burns down. I also don't wanna be jetting on the trail. If I have to loose a little snap to be lazy I'm fine w/ that. I do think that I might play w/ the needle a bit around home just to see how it feels though.

my 440 will swing the 1.75 all day. i would look other places than the track. do yourself a favor and get either dj or cudneys kit. either one will put a smile on your face.

[Dynamo^Joe]

To show how I think about clutching discussions - I have taken the paragraph and separated into 2 details. Facts and Opinions far below...

Facts
03 600HO boondocker
Stock motor
1.75"x 121
no studs
down 2 teeth
pri spring - 200/320
600 @ 8000 rpms
stock helix. [47/44]
secondary spring - 225/300


Comments:
5600 miles.
Works great
Odd backshifting.
It'll pull super hard for the fist 30 seconds or so. Then rpms fall off.
Chop the throttle it'll hit proper RPM again, pull hard then falls off.
I don't really care about top speed, I just want the thing to stay in the meat of the power when held wide open in the powder.

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Knowing what helix you have, you can figure out what angle you were using at that point in time along the shift curve, the angle used where you found the upshift stalled or came to equilibrium.

WIfarmer:...and pull hard till...

From experience when I find a sled will stall at a certain angle first you determine if the stall is from angle being too big or being too small.
In this case the stall is from being too big. Monitoring secondary temperature will let you know that the belt is not being grabbed hard enough.
If the temperature is high - Then the belt is slipping excessively in the secondary - Temperature will increase - Upshift is stalled. "equilibrium"
So to grab the belt harder then can lower helix angle.
From experience make a calibration change large enough value that you'll be able to measure a difference and have repeatability.
So at 70mph then make a big enough difference like lowering the angle value 2 degrees.

In the drawing you see the 47/44 angle being used and 70mph is equilibrium.
What helix angle would provide a 2 degree lower value at 70mph?
Looks like a 47/40 will do. The difference is about 7% lower value.
In the exact same test place, the same run on the same grass, basically your test laboratory; I have no doubt that you'll be able to add around 7% more mph than previous.
If you had 70mph at stall
Then 70 * 1.07 = 74.9mph
I don't doubt you'll be able to pull off another 5 mph which may not seem like much but if there was an equivalent sled beside you to race, you'll continue to pull away while the former sled stalls at 70mph, you will gain and gain and gain until you let off the throttle or the load of the ground increases against the sled.

---------------------------------------------------------

Ok lets look back at what we used to make an educated guess of what calibration change can be applied...

Look at the Facts above and look at the Opinions below.

My question is; Can you use the opinions below to calculate what calibration change can be applied...
---------------------------------------------------------
Opinions
The sled works great (besides the crappy mileage).
The one problem that has come up is odd backshifting.
I don't remember the exact RPM, but once it hits it stays nice and steady. I wanna say 7600 but don't remember exaclty from last winter.
W/ the big track I needed a bit more backshift.
So, I've pretty much narrowed it down the the secondary shifting when it shouldn't be.
One possibilty I've thought of is the big bushing in the secondary.
If it's a bit worn and causing things to bind up can't be helping.
Also the 3 little bushings in the secondary seem ok, but I'll replace them this year just for good measure.
So I was thinking I perhaps need a different helix.
I kinda know my way around clutches, but the one thing I always forget is which way I'd need to go in the helix angle to make quicker backshifting.

[WIfarmer]

Wow, all kinds of good information already. One thing I want to be clear of is that I care 0% about total top speed. I just want it to be very responsive no matter how long of a pull through the powder or from corner to corner. If I could get it to top out at 80 but pull my shoulders out of the socket through the whole range would be killer!! I like a nice hard hit.

I know a 440 will pull the big track. That's not the point. I'm after the idea that I KNOW my engine can do it. Just that there's one piece of the puzzle that's messing it up and I would like to remedy it. Also, I don't want to buy a canned clutch kit. That takes ALL of the perosnal satisfaction out of it. I'll experiment all day long. They way I see it, ya can't learn a thing by buying a box full of parts. I'm sure their kits work great, but I want to learn how and why.

[f7eater]

Wow, all kinds of good information already. One thing I want to be clear of is that I care 0% about total top speed. I just want it to be very responsive no matter how long of a pull through the powder or from corner to corner. If I could get it to top out at 80 but pull my shoulders out of the socket through the whole range would be killer!! I like a nice hard hit.

I know a 440 will pull the big track. That's not the point. I'm after the idea that I KNOW my engine can do it. Just that there's one piece of the puzzle that's messing it up and I would like to remedy it. Also, I don't want to buy a canned clutch kit. That takes ALL of the perosnal satisfaction out of it. I'll experiment all day long. They way I see it, ya can't learn a thing by buying a box full of parts. I'm sure their kits work great, but I want to learn how and why.

thats great that you want to learn about clutching, and there is a lot of satisfaction in finding what works for your sled and your riding style. i'm sure you are already aware, but be prepared to spend some $ and a lot of time before you find what you like.

[WIfarmer]

Totally aware and prepared. This is half the fun of the sport!! And i dun gits ta meat all kinds uh smrt people like yalllls!!!

[WIfarmer]

So if you read back a few posts, you'll be able to see the clutching issues I'm trying to sort out. W/ some advice from Dynamo Joe and others I decided to try out a different helix. So, here's how my testing went last night. The conditions are 70 deg air temp, 1/4 mile hayfield that has been cut. We've had some rain the last few days so the field is very moist but not muddy. This results in HUGE friction on the skis. I have not gone through the sled from last season yet so it has my crappy clutching (stock primary except spring has a bit higher engagement), secondary w/ Highmark spring (I think 230 lbs) and stock helix, -2 teeth top sprocket, and 1.75" track w/ no studs. Motor is stock but fresh. Also, both clutches are still dirty, the belt has plenty miles on it, and it's running old gas from last season. For sure not ideal conditions for all out speed!!! Anyhow, took it out as is w/ the stock 47/44 helix and it did just as expected. Pulled hard to about 60 and then 100% just fell on it's face (upshifted too fast and fell off the power). This is exactly what it would do last season in the powder, or on long pulls with 2 riders. So I got my hands on a 47/40 helix per Joe's recommendation. All I can say is wow, I love my sled again!! Whack the throttle wide open and it would go right to 7800 rpm and never waiver at all. (still w/ 230 secondary spring). Would pull very hard to 85ish at which point I was letting off because the sled was starting to float and dart a bit. I think it probably had another 5 in it, which is pretty darn good considering the field and air temp conditions. Did 4 passes all w/ the exact same results. VERY VERY HAPPY!!! So then back to the shed and I put the green 180 lb spring in. Almost the exact results. RPM was good. The only difference is that w/ this spring when I'd get some G force pushing the sled into the ground, the additional friction would pull at the motor some. It would recover VERY quickly but you could tell it was happening. Not a big deal but also not the flawless performance of the 230 spring. I know this is different than powder or a nice long lake, but so far the clutching advice I've gotten was spot on!!!! Next up is to put all new bushing and buttons in the secondary, clean both clutches, and go for some new gas. Then I can do a little more hayfield playing while I wait for the snow to fly!! Thanks for all the help guys!!!! If there's any other combinations you'd like to try, and if I have the parts, I'll gladly try to work it into my schedule. If I can find everything, I should have the stock primary spring, 3 secondary springs (135, 180, 230lbs I think), stock top gear, and 47/44 47/40 helix's. I guess one last question. What RPM should I be shooting for, and how accurate do the stock tach's seem to be??

[marc_brown98]

8000-8100 rpms for a stock 600ho..