Secondary Spring Adjustments To Lower RPM - Snowmobile Forum: Your #1 Snowmobile Forum

kingston_rider · 11-07-2009, 05:54 PM

I have a 98 550 Panther, red primary spring, yellow secondary spring. I have just finished cleaning my clutches and replacing worn weights and bushing in the primary and buttons in the secondary. The last thing I am going to do before the snow flies is replace the belt. My question is, if I increase the pressure on the secondary clutch spring, will this lower my rpms at cruising speed? I noticed last year to maintain 55 mph I was revving around 6000 to 6500 rpms on a groomed trail, this seems a bit high to me? The sled has lots of bottom end and mid range power. The secondary spring is in the second hole from the left so there is lots of room to increase pressure. Will increasing the pressure lower rpms at cruising speed? Any help is appreciated.

**BC_Dan** · 11-07-2009, 06:39 PM

6000 to 6500 rpm for 55 mph seems pretty close to me for that sled. My Prowler 550 2-up is in that range...

Mrdman2442 · 11-08-2009, 01:01 AM

Sounds normal to me, when you pin the throttle the rpms should remain around 8000 as you accelerate. Increasing secondary spring pressure causes sled to downshift faster. Installing heavier primary weights will reduce overall engine speed but then you may not have the power you should.

kingston_rider · 11-08-2009, 07:03 AM

Will increasing pressure on the secondary spring reduce engine rpms for a given speed or increase them?

**RJ Gleason** · 11-08-2009, 10:31 AM

It will change the peak +/- 200 rpm depending on the hole that you use.
You want the engine to not peak over 8200 rpm and not less than 7800 rpm.
Otherwise, you begin to lose performance and efficiency of the drive.

A more effective change would be to go +1 on the top sprocket in the chain case.

kingston_rider · 11-08-2009, 05:25 PM

Quote:

Originally Posted by RJ Gleason

It will change the peak +/- 200 rpm depending on the hole that you use.
You want the engine to not peak over 8200 rpm and not less than 7800 rpm.
Otherwise, you begin to lose performance and efficiency of the drive.

A more effective change would be to go +1 on the top sprocket in the chain case.

Thanks RJ, I am trying to get a bit better mileage this year so looking at different options. If I go +1 on the top gear, will I need to change the chain or will it be ok?

**kccats** · 11-08-2009, 07:07 PM

Don't increase your top gear! You will loose MPG and acceleration! To increase the spring presure will decrease your overall RPM as well as midrange!

kingston_rider · 11-08-2009, 07:12 PM

Thanks, man finding the sweet spot on these twins is not easy, guess I will leave as is and see where the rpms are this winter at WOT and adjust secondary if needed then. I installed a new track, sliders, bearings etc. I adjusted the track tension for 1.25" at 15 pounds pressure (used a fishing scale to apply pressure lol). I spun it up and aligned the track for center, this was done on a fairly warm day. Will the track tighten up when it gets cold, should I adjust it looser or leave as is, seems tight to me.

**RJ Gleason** · 11-09-2009, 12:47 AM

I use the 10lb weight method.
Put a 10# dumbbell in the center of the track and adjust tension so that the drive lugs are just higher than the slides.

kingston_rider · 11-09-2009, 05:51 AM

Quote:

Originally Posted by RJ Gleason

I use the 10lb weight method.
Put a 10# dumbbell in the center of the track and adjust tension so that the drive lugs are just higher than the slides.

In that case I am likely way too tight, will take another look at it tonight, thks RJ.