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Discussion Starter · #1 ·
I'm trying to help a friend diagnose a motor bogging issue. He changed a few clutching components in his 2016 T3 163" Summit. This is at sea level (below 4,000') Stock gearing (23/51) stock helix & spring.

He has 441 ramps, 16.6 # pins and a 160/380 spring in the primary. In deep dense snow he's getting a bog after engagement. It could be the start of the 441 is to shallow (not steep enough) or the spring too soft of a start. Pins may be too light for this altitude also.

He wants to stick with OEM ski-doo parts, so don't tell me to get a DJ kit. We know that works, but he wants to use only OEM parts. Don't ask why - he just has that stipulation.

The bog is only in deep snow, and I mean like 4' deep pow, it's not a plugged exhaust outlet either. It rips on the top end, so the finish spring and ramp angle are OK, it's the start that isn't correct.

Anyone have any thoughts or experience with this problem?

Question is, if the motor is bogging just after engagement, is because it's shifting up too fast or too slow? Does the shift need to be stalled and shift harder? Just wondering if the problem can be fixed with a different spring start force or pin weight without changing ramps? Is there a better ski-doo ramp than the 441 for low altitude. We really don't like the finish on the 413.
 

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WHat's his engagement RPM and what RPM is the bog? Prob just needing more power at that RPM in the deep snow, so a higher engagement maybe? But if the rollers are past engagement and into the meat of the ramp, then that might not help. I would aslo wonder if a sec spring starting force increase would make the shift start at a higher rpm, but still keep engagement RPM the same?
 

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What secondary helix is he running?

I think the Summits have a real soft ugly secondary spring. You might want to try a Green Green or just go straight to the Purple Purple.
 

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What secondary spring is in this? I would suggest the 303# finish in the secondary. Forces the primary to have a slightly higher engagement initially and has no effect on rpm at the top end as the helix angle manages this. A side benefit is lightning fast back shift.
 

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Secondary is all stock.

So is the consensus the engagement is not aggressive enough, not pushing on the lever arms hard enough? I'm really trying to understand what it is that's causing the bog. Do we need to stall the shift so the motor can build RPMs or the opposite?

The stiffer secondary spring would cause the primary to shift slower - push harder?

Looking for more answers about the cause and reason than the quick fix answer.

This bog only started after we changed the primary spring and pin weight.
 

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Why the change in primary spring and pin weight in the first place? Is there more to the story?
 

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What did you change from? And does different clickers change the bog? Don't worry about top end rpm with the clickers just test to see if different clicker position changes the bog. Could help tell where the rollers are on the ramp at time of bog

Sent from my iPhone while my Heli plays with the gophers
 

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If it has the factory blue secondary spring # 417127118 that has a lot to do with the bog with that ramp. put at least a 180-303 ski-doo grn/grn or even better a 230-303 ski-doo purple secondary spring in that. That will cure most of that I'm sure. If its correct rpm at w.o.t. and on/off throttle response is good and rpm recovery is quick and 8000 then leave the pinweight and finish pounds the same on the primary spring.
 

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Discussion Starter · #10 ·
We're going to try the stiffer secondary spring first, if that doesn't cure this then we'll try different ramps.
 

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Metalhead
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The sled in your location should have come with 438 ramps. If you say 441's are in there, someone put them in the primary clutch after the sled got uncrated.

OR

The sled if used at less than 4000 feet, high probability it come with 413 ramps - then someone stuffed 441s in after.

Question - Did your bud change to the 441's? (yes or no)?

If that's a negatory on the rampatory, then who did?

Question - this "bog"... Explain the events that happen please.

Buddy hits the throttle from dead stop start and the tach immediately hits 7600, then grinds its way to 7900~8000? engine tachs at 7700, then grinds its way to 7900~8000?, 7500, then grinds its way to 7900~8000?

Question - What is the engine speed doing when he pegs the throttle from a dead stop start?

Question - Is there an aftermarket exhaust system installed (from y-pipe to muffler)?

Joey
 

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Discussion Starter · #12 ·
It came with the 413's in it stock (low Alt) set-up. We tried the 441's because the had read/heard/felt they would do better on the top end. He told me it bogs at engagement. He also thinks the 16.6# pin weight doesn't let the pipe build heat and that may be part of the cause of the bog.

I'm 800 miles away and haven't seen the sled run. I'm heading home tomorrow and will get it figured out for him, I was just looking for some input from people that have experience the same symptoms or knew why we were getting the bog or as he called it "flat spot" at engagement.
 

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Metalhead
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Howdy...I did email you eh Mon 28/12/2015 11:29 PM

Anyhoo...

3 inch track or with a 2.5" then converting to 3inch from the 441's, the engine will come in low speed.

Example 2.5 and hit throttle, engine speed goes to 7800 and quickly climb to 7900 or 7900 and quickly to 8000.

Change track out to 3" and now see laboring engine speed. Engine tachs at 7500~7600 and eventually grinds its way to 7900~8000.

It is the harder and more efficient engagement with the ground those 3" paddle tracks have that can cause the engine speed to "grunt" up to 7900, taking a bit too long.

This is why BRP apply a 438 ramp to overcome the 3" track.

Either the 438 ramps or my mountain 415/441 ramps.

Hope that helps

Joey

Tire Automotive tire Font Auto part Rim

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Chain of events in slow motion.
Idle speed 1100 rpms. Operator presses throttle, engine speed increases.

When the engine speed has built up to create enough centrifugal force to overcome only the start force of the primary spring
· this is engagement speed (3800)

When the engine speed has built up to create enough centrifugal force to overcome the start force of the primary spring and start force of the secondary spring, the belt will start shifting out and the clutch ratio will change.
· This is called the "low speed ratio" and not to be confused with "shift-out-point."

When the engine is at rated speed (peak power engine speed) 7900~7950 rpms
· This is called the "shift-out-point."

Here we go; smash throttle from engagement speed...
· Engagement speed (3800), then engine speeds up quickly to low ratio speed (5500)[441] engine accelerates to "shift-out-point" 7900 (how much engine torque is at 5500?)

· Engagement speed (3800), then engine speeds up quickly to low ratio speed (5900)[438] engine accelerates to "shift-out-point" 7900 (how much engine torque is at 5900?)

· Engagement speed (3800), then engine speeds up quickly to low ratio speed (6300)[DJ ramp] engine accelerates to "shift-out-point" 7900 (how much engine torque is at 6300?)

Font Bicycle part Wood Composite material Auto part

With the less aggressive ramp off the bottom end, it will allow the engine to get to a higher speed, with a bit more power to "hit" and start to pull and at the same time allow the engine to more quickly climb to 7900 without bogging.

Using a less aggressive ramp angle will allow you to maintain a lower primary clutch engagement speed but build needed engine speed to increase power to overcome a bigger load.

The difference in engine torque between an example 5500 and 5900 rpms could be enough of an increase to successfully let the engine grind its way, quickly to 7900~8000
 

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Metalhead
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It came with the 413's in it stock (low Alt) set-up. We tried the 441's because the had read/heard/felt they would do better on the top end. He told me it bogs at engagement. He also thinks the 16.6# pin weight doesn't let the pipe build heat and that may be part of the cause of the bog.

I'm 800 miles away and haven't seen the sled run. I'm heading home tomorrow and will get it figured out for him, I was just looking for some input from people that have experience the same symptoms or knew why we were getting the bog or as he called it "flat spot" at engagement.
If the engine is coming in low like taching at say 7600 and grinding its way to 7900 without having "pipe surge" then the engine is warming up the exhaust pipe plenty.

I say there is no pipe heat problem. Just too aggressive of load problem off bottom end.
 

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How did you make out ID? Did you get him ripping again?
 

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Discussion Starter · #17 ·
My sled is ripping strong this year, I love the set up, 50 lds lighter, solid clutch kit from Bronco at Hot Rod Sled Shop, his custom cut ramps and helix are spot on. No flat spots, hesitation or RPM Fade.
 

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