Spent 5 hours testing on Saturday. Got in ten runs. 500 foot track, clay for 60 feet then grass. Timeslip gave reaction time, 60 foot time, elapsed time and mph. Sled is a 97 Mach 1, 754 lbs. with driver. Motor makes 184 hp @ 10100 rpm. Geared at 19/46.

Went there with a given primary set up, hoping to pull rpms and then tune the cam.

Up front I ran a 310/460 spring, 12.9 grams in aluminium arms, with 145 ramps. In the back I started with a straight 47, to eliminate the variables with a compound cam until I got the front sorted out.

First pass was pretty good. 10050 out the end. Didn't see the rpm's out of the hole. (first pass, wanted to keep it straight). 60 foot time was poor. 1.54. Should 60 at 1.4-1.45. I left the front alone and tried some compounds.

Couldn't better the 60's all day. Past 60 feet it pulled like a #######. Nice flat rpms except out of the hole. It engaged at 5600 (no notches) When pinned it would bog for about 8-10 feet, climb rpm through the clay, then when it hit the grass it would pin 10100 and go like hell. I assume because the track was able to spin and unload the motor.

So I'm wondering-- too much pin wieght? Less pin and softer finish on spring? More pin and higher finish on spring? Engagement too low? Cam too compensate? By the way the two best passes were with the straight 47. Felt and looked like it was slipping in the primary. Not a lot of heat, but more than the secondary. All cams were installed with 21 lbs break away.

If someone wants to jump in I'll provide all the runs in detail for comparison. When I have more time. If I can get two tenth's I'm right there.

sht thats alot of gear. A few options come to mind, the 145 drops quick, a ramp like a cf1 is more graduale, a 47 isnt much helix but in theory if you wanted to keep the rpms high with the same preload maybe a 44/50 reverse loading it on top, (where the hell you gonna get something like that?) or how about testing at say 25lbs and seeing what the finish is like and possibly adjusting pin from there. I would try that first. What made you pick the other components? I coincidently just ordered a 310/460 spring yesterday totaly different project though. The other thing I`m thinking is maybe the carberation could be sharpened up maybe bump some timing advance too to try to make the motor itself crisper down low. Obviously if a motor runs to a peak at 10500 your gonna have some serious torque deficiantcies at 6000...

*cracks fingers*

Nice flat rpms except out of the hole. It engaged at 5600 (no notches) When pinned it would bog for about 8-10 feet, climb rpm through the clay,

What rpm does engine "Light up"?

So from your explanation, you are sitting there near engagment.
You pin the fuel.
Clutch engages
For a second or so the engine labors with loud bog at rpms above engagment but much below peak.
During this bog the engine rpm is increasing
Then "wham" the engine will accelerate and hit the peak...

...is this the events that are happening? If not, please describe in point form the events of when you pin the fuel to the engine hitting peak"

So I'm wondering-- too much pin wieght? Less pin and softer finish on spring? More pin and higher finish on spring? Engagement too low? Cam too compensate? By the way the two best passes were with the straight 47. Felt and looked like it was slipping in the primary.

...Felt and looked like it was slipping in the primary

Please explain your inspection...slipping in the primary
What made you conclude this?
If you are going to say what I think you are, then you may have found the cause of the problem.

I would like to see:
1 pic from the side of the sled at rest with you sitting on it. [Close up]
1 pic from the side of the sled at full throttle about 4 - 8 feet out from start line. [50 feet away or so..]

Want to know what your centershock spring setting is on.
Want to know what your rear torsion springs are set on.
Want to know if your rear/rear shock & centershock are revalvable.

pipes good and hot? pods or airbox, see if resticting the air with some 100mph tape helps the bog

Wow you guys are right on this. Good.

I picked the 145's because my two sets of 280's are both notched. My CF-1's are notched also. 310/460 for engagement and high rpm. Debated on 310-510 but wanted to concentrate on secondary. Tried 47, 50/44, 48/40, 46/40 and 53/47. with the 40 finish I had to add .8 grams per arm to get top rpms back down.

Added two pilot sizes also on the 9th run. Seemed to help a bit with crispness.

Joe , that's exactly what happens. Rpm's rise through the bog then bang, she hits the pipe and is gone like a mf'er. Belt residue and slightly warmer temps in the primary lead me to think it is slipping up front. Not a lot of heat in either clutch, but is warmer in the front.

Engine lights at 10000 to 10050.

Center shock full soft. Torsion springs full soft. ACM 2.5 turns out. Not revalvable. Seems to transfer and hook well. Sorry no pics. Forgot the digi cam.

Lots of heat in the pipes. Lots of timing advance as well. K&n's.

Seems like a lot of gear but it dosen't pull the motor up until around 470 feet. The sled is really strong past 60 feet.

...Rpm's rise through the bog then bang, she hits the pipe and is gone like a mf'er. Belt residue and slightly warmer temps in the primary lead me to think it is slipping up front. Not a lot of heat in either clutch, but is warmer in the front.

I wish I could hear the first 100' of a run.
From my experiences, you just mentioning belt residue is characteristic revealing a nearly individual problem.
Im willing to guess that you are far below the rpm the engine comes on the pipe[s].

Can you:
1] Do a belt deflection check?
2] Do an exersize to find the pipe?

Here is a page out of my clutch kit manuals...
*Sled bogging out of hole and then 'wakes up'???
Tightening the secondary is not a remedy, this detail will:
*'Influence' how quick [time in seconds] your engine will 'Flash' thru the clutches to its peak rpm.
*Adjust the top end mph going across finish line.

How bout doing an experiment?
You must drop the belt in the secondary to deliberate make the engine bog and labor.
With an old belt installed, push open the secondary to let the belt drop in it.
So now you can see when the primary engages the belt will ride up at a higher shift ratio.
This here is to make the engine run below where the pipe comes on.
Put the hood back down and do your test.

With the engine running, Poise on your sled like you are at the start line of a race.
Sit there with your sled running at engagement.
Look at the tach and DO NOT take your eyes off of the needle.
Pin the gas and watch the needle while listening to the engine...

The Action:
The engine labors and bogs...the engine increases rpm slowly to a certain rpm, then 'WHAMMO' your engine comes on the pipe and barks to flash to its peak rpm, right?
***You are looking for the rpm where the engine lites up***

Pin the gas..
Watch the tach...
When the engine wakes up outta the bog, what rpm did the tach read?
Write it down.....

Shut the sled off, pop the hood and drop the belt in the secondary again.
Now on the second time you perform this exersize, you MUST let off the throttle at the rpm the engine climbs on the pipe.

For lack of better numbers this is good scenario...

Example:
You engage at 4000, you pin the gas, the engine bogs from 4000 to 4400 then 'Lites up'
Once the sled lites up, you can let off the gas.
Shut the sled off, pop the hood and drop the belt in the secondary again.

Do again...

You engage at 4000, you pin the gas, the engine bogs from 4000 to 4400 then 'Lites up'
Once the sled lites up, you can let off the gas.
Shut the sled off, pop the hood and drop the belt in the secondary again.

Do again...
You engage at 4000, you pin the gas, the engine bogs from 4000 to 4400 then ''Lites up''
Once the sled lites up, you can let off the gas.
Shut the sled off, pop the hood and drop the belt in the secondary again.

...Now you have a good average on the whereabouts you need to engage the engine to let it 'Climb onto into the pipe'

*Let a friend do the same exercise, but firstly do not tell your friend what rpm the sled 'Lites Up'.
Ask your friend what rpm this event happened at.
With your trial runs it seemed to lite up around 4400.
Your friend comes back after a few attempts and also says around 4400 or so...

It looks like you are engaging approx 400 rpm 'Below The Pipe'.
Solution...Increase engagement 400 rpm by whatever means.

Results should be:
You engage at 4400, you pin the gas, the engine 'Lites up' upon the gas flipper hitting the bar. There is no more bog.

There is a belt deflection procedure I give out also to guys who are doing this...if you like. :)

What you are doing here is step by step eliminating variables that should never bother you again. When you continue to troubleshoot your sled these are issues that you can brush off.

I took this pic on purpose.
I am doing clutching on a 700 OM hill climber.
Im doing the test to find the pipe[s] here.
Notice Im not taking my eyes off the tach and my runs are less than 50 feet.
I stop the sled, flip open the hood, reset the belt in the secondary and perform the test again.
This engine here bogs at <4200. It comes onto the pipe real hard at slightly more than 4200.

http://pic4.picturetrail.com/VOL52/486172/1703322/28024007.jpg

Joe &#39;sounds like a good test. The only problem is finding a spot to do it. Have a couple of places in mind. Will let you know. Worst case I race in two weeks. Don&#39;t like to pay $40 per pass but I may not have a choice. It certainly sounds like this could be the problem. Thanks.

*looks left...*

"psst!! ! !...Hey,..."

*looks right.....*

"....try the neighbor&#39;s front yard when after they go to work.
...yeah,...that&#39;s the ticket! :devil: "

Here is another thing I noticed at the track. Marked my primary with a marker as well as the cam ramps to check for full shift. After every pass, the primary had a ring of rubber about 5/8th&#39;s of an inch from the top. However the marker was gone and the cam ramp wiped to the bottom. Thought it might of been from the return to the pits but there&#39;s no way it would get that high at low rpm&#39;s.

Thinking back, I did notice my tach would blink about half track then come back on. I&#39;ve got it set to flash at 10150. (digitron) So now I&#39;m thinking that it&#39;s running out of gear as it fully shifts into overdrive and drops back to 1:1 for the rest of the run instead of pulling the motor up. Is this why it liked the straight cam and the compound&#39;s had little to no effect? Same result with all the cams. Geared at 19/46. Good mph as well.

Joe. Will you be going to the COSDRA race in the Sue the end of July?

Hey Krusty who did your motor work for you? Looks like u got some pretty good number out of er, i should be testing with my 700 improver in about 2 weeks, mine dynoed out at 183hp.

A rotax guy here in Peterborough Ontario. Harrison Performance. Excellent machinist. Greg at Jaws sent the specs with his pipes. First pull on the wheel we hit it. Yours a CK3?

KRUSTY]...Here is another thing I noticed at the track. Marked my primary with a marker as well as the cam ramps to check for full shift.

I like to look at the path on the helix. I clean the path every run if I can and check how much the secondary opens. Many guys with my kit come back to me and say that their mph is down, then I get them to check the mark and tell me the distance it is from the bottom. They give me the measurement and I just say to add a little more weight like sanding a .7g setscrew in 1/2 and install. Usually turns out fine.

KRUSTY]...After every pass, the primary had a ring of rubber about 5/8th&#39;s of an inch from the top.

I find this one always a toughie to solve. Can come from misalignment and/or the belt slipping in the secondary causing excessive heat.

KRUSTY]...However the marker was gone and the cam ramp wiped to the bottom. Thought it might of been from the return to the pits but there&#39;s no way it would get that high at low rpm&#39;s.

If button wiped the mark off the helix, then it was because of the clutch shifted open. The sliding sheave moved towards the chassis almost its full distance.
Have to keep this in mind that the sheave only opens towards the chassis about 1.3" inches. So to go from 0mph to peak mph that is not much travel of the sheave. How many mph could the sled go faster/slower with 1/8th inch movement?....In your case up to a possible 8mph loss/gain.

KRUSTY]...Thinking back, I did notice my tach would blink about half track then come back on. I&#39;ve got it set to flash at 10150. (digitron)

ooOOoh...that&#39;s a neat function. I wonder why of the overrev then. The primary is not upshifting momentarily. Add slight more flyweight to make the primary push harder?

So are you saying that you are running at 10250 at 1/2 track and the engine is bouncing around that rpm while going down past the 1/2 track to the end?
Im not too clear on the event that is happening.

KRUSTY]...So now I&#39;m thinking that it&#39;s running out of gear as it fully shifts into overdrive and drops back to 1:1 for the rest of the run instead of pulling the motor up.

What is this term "pulling the motor up"? Do you mean the engine all of a sudden climbing in rpm?
If the engine is at peak and stays at that rpm, the secondary is in OD, then falls back "backshifts" like you say, the sled theoretically should slow down and lose mph.
If the engine loses rpm, but shifts up from 1:1 into overdrive the speed should stay the same. "proportioning"
Im foggy on your explanation.

KRUSTY]...Is this why it liked the straight cam and the compound&#39;s had little to no effect?

Hmm...well in my opinion say you used the straight helix [47] and were using compound angles with a spread of only 4 degrees like a 47-44 or a 50-46 or whatnot, I dont think there will be much of a change to measure. What were the prog angle helix&#39;s you used to compare to?

KRUSTY]...Joe. Will you be going to the COSDRA race in the Sue the end of July?

No! Getting laid off in the end of July. Taking my sled to the U.S. to get on the dyno. "hopefully"

Sorry, maybe I was a little unclear with my explaination. The marker on the primary and secondary cam was wiped clean, so obviously it fully shifted out at one point. It looks like it tops out and then drops back down the 5/8th&#39;s of an inch. The tach hits 10250 only for tenths of a second then drops back to 10050-10100. I&#39;m wondering if this is when it downshifts and won&#39;t climb back in to overdrive. When I say &#39;pull the motor up&#39; I mean when the sled fully shifts out and uses the full gear ratio increasing rpm a couple hundred in the last 20-30 feet. Does that make any sense?

I wonder what the theoretical mph is for that combo at .83:1 and 1:1. The race book only has a chart for 44 bottom gear. I&#39;m running 46.

KRUSTY]......The tach hits 10250 only for tenths of a second then drops back to 10050-10100.

Remember this way back when...

http://www.snowmobileworld.com/forum/index...ic=21118&st=135 (http://www.snowmobileworld.com/forum/index.php?showtopic=21118&st=135)
Because i added more flyweight my rpms ended up falling off peak and I would go several hundred rpms below.
I compensated with a 47-41 helix.
I could sustain the rpms for hundreds of feet farther.
I kept losing rpms at top end.
I compensated again with a 47-37 helix and went hundreds of feet farther than the 47/41 and had higher mph.

Yup mine is a ck3 chassis, so what are your 500ft times so far then?

5.6-5.7 @ 87-90 mph. Up here a 5.5 is pretty competitive.

I got my engine back this past weekend so i will let u know how it goes krusty, wont have any e/t&#39;s til our first race in end of july, hoping to hit 5.40 on the first pull and then once the suspension is dialed in i hope to be down low in 5.30&#39;s, i have a rock solid clutch setup i just need to dial in the chassis.

Care to share?

Thats some pretty tight info krusty, pm or email me and we&#39;ll talk about the setup.