Secondary Clutch Spring vs. RPM

[pernikm]

96 ultra BB with 56 gram, polaris black white spring and Team secondary with red/black 140-240. It seems pull everything down low well, but at altitude, it pulls the RPM fine out of the hole but I lose 300 ish RPM at oh 40-50 track speed. If I went with the 140-260 spring would I find 300 rpm or should I take a gram off the primary weight tips...Seems like I have the recommended helix and they are pricey so I am hoping the increased Sec. spring tension helps a bit with the back shift too. Is this enough? If not what do you think about a little more rate on the primary. As odd as it seems I might be clutched a little light on belt tension because my rpm does bounce around a bit.

thanx

Karl

 

[wellfed777]

might be able to give you some tips but need more info like does it hold rpm under load (long climb) and hows your gearing the stiffer secondary spring will help with back shift but too stiff and it wont up shift good and will feel like it just stops pulling and if its ok at lower elivation but not up higher that could be lose in power due to the thiner air or its getting too rich?
give me more info on how when where

 

[pernikm]

no, it does not hold RPM under a long climb. I run 18/40 gearing. I am almost certainly losing power because of the thinner air and getting too rich. And you hit on the problem that I am wrestling with on the head. At the parking lot 6000 ft. I am running at least 1200 on the EGT's, but don't hold it open long enough and it seems like I am pretty hot in the mid range so I blip. When I get up around 9000 ft plus...I have seen my EGT's hold at 1200 as long as I am not plugged up with powder, pipe is out of the snow, and I am turning above 8100 rpm. The problem anything is wrong I fall off the pipe, drop to 7500 rpm and the EGT's drop to 1000. My plan was to make sure I run 8300 to 8700 rpm to stay on the pipe and then see if I can figure out my jetting. I am also wondering if my PSI mod blaster II pipes are too tight.

 

[wellfed777]

i see it will be hard to clutch perfectly with jetting in the mix
that being said there are some tests to try if you get out of the thottle in the climb and then back in it will it jump back to rpm ???
if not then a stiffer rear might help the back shift the problem is if you get to much weight in the primary it will pull the belt down in the secondary and it won't be able to back shift right

i found that out last time i rode i put 2g rivets in the tip of my mtx and i was lost it would'nt hit RPMs and it would also lose RPM in the climb
the rear spring could'nt compensate for the heavy weights
i usually try to test my peak RPM on the medows or trail to get an idea if i got the right weights then play with secondary on hills

ok a couple more thoughts if it only hits 8100 ever and you want 8300-8500 then i'd try taking a gram or two out and try that with a few tools you can mess with weights on the trail
also as to elevation changes i have the attcc altitude compensator and it works good if you change altitude alot just a thought
good luck

 

[HPJUNKIE]

Had a 800BB a few years back. At 6-7000' ran 54g w/ 140-300 in primary w/20/40 gear 144x2. As long as your helix is around 58-42.46 52g should work. If looking at rpm on factory tach target 86-8800, if running a Racepac,Digitron target 85-8600 with the PSI Modblasters. Ultras like to run @ 1250-1300* with probes approx 6" from piston, 1400*= oops!

 

[pernikm]

This seems close to what I got, you were running less weight but also less rate on your spring. You would not happen to remember what spring you had in the secondary?

thanx all good info!

Karl

 

[spring snow hero]

if you like the shift pattern, then don't screw with the spring, if you want to change the shift pattern and rpm, the spring can do both.

 

[RedRider]

what cam in the team??

 

[pernikm]

54-36 .46 ...I think...I rode today with an almond primary spring. It ran 8700 at 7000ft, and bounced around 8100 and 8500 at 9000+. I think I have to find religion and get my pilot jetting and my needle right. It loads up in the trees and never clears out. serious problems wiith the pipe plugging and I think I am injesting steam and /or exhaust.

 

[RedRider]

I would try your old polaris button clutch with a 34 cam.
I'm thinking that your 36 on the finish is too steep, if you have a 54-34 I would try that. As for your pri clutch try a black 140-310.

 

[pernikm]

The black white 140-320 is what I had. I tried the almond 140-330 and it did increase the rpm by about 200 at the truck, On the mountain 9700 ft it would pull 56g almond and 54 36 .46 with red black spring sometimes 8500 (racepak) but mostly 8300 but when it loaded up it was back to 7500 until I stopped let the pipes cool etc. Then back to 8300 or so until I went into the trees and it loaded up. I might try 54g or even 52. Any one know what pilot to use with ufo's. I have 340 mains, P6 nozzle and the stock needle in the middle clip. It feels about right at 7000 ft but at 9000 the egts can be as low as 1075. This thing seems super finicky with altitude and temp.