Working out cam arms and springs on comet 108

[jonben8]

i have got a comet 108exp and wanted to know how to calibrate them i am running a 4 stroke engine with about 160 bhp and would like and engament rpm of about 4000rpm and shifting rpm of 7000rpm any help would be great

[LiveWire]

I suggest using a Heel Clicker setup with extra long shoulder bolts and extra washers with the black spring. The arms are adjustable in weight.

[jonben8]

where is the best place to buy these from

[Rat4020]

Call Thunder Products in Richmond MN ask for Von. ask him abought the heavy hitter clutch kit there # 320-597-2700 I have one in my Yamaha powered taz car

[LiveWire]

The heavy Hitter is just trying to get as close to the Heel Clicker without infringing on the Heel Clicker patent. The Heel Clicker adds weight outside the roller where the Heavy hitter just has a thick base on a standard shape arm.

Olav Aaen's clutch tuning handbook states that adding more weight and more spring load for a given tuned RPM will yeild a clutch that stays closer to the tuned RPM. This is backed up by mathematical proof. Standard clutch arms yield very little force on the rollers at low speeds. The springs have very little pre-load yielding low spring loads at low speeds. The Heel Clicker arms with the shoulder weight outside the roller significantly increase shift force off idle and at low speeds. The extra long springs that come with the kit create high spring load to balance out the shift force. The net result is a clutch that is far more sensitive off the line and up. The effect is felt on most engines, but is especially effective on any engine making significant low end torque. Instead of having a high engagement wasting that torque, ideal engagement ends up being lower. Properly tuned, the clutch will upshift as fast as the engine can handle. So even if the engine doesn't rev as fast as an engine with less torque, the driven clutch and wheels will be spooling up at a faster rate than the engine.

Installs I have done:
350 Odyssey gained 2 lengths in a 300 foot drag race
400 Pilot gained 3 lengths in a 300 foot drag race
3 cyl 1 liter powered buggy, I estimate 0-60 at about half the time. Top speed was increased by 8 mph. The stock shoulder bolts allow for 4.7 grams of added shoulder weight. I added 25 grams using longer bolts and more of heavier washers.

[diirk]

Is Heelclicker still in business? Do they make kits for all the Comets?

[s@ndm@n]

Originally Posted by diirk

Is Heelclicker still in business? Do they make kits for all the Comets?

how about Thunder Products - Performance carburetor and clutching for snowmobiles, motorcycles and ATVs. Eric?

[LiveWire]

Originally Posted by diirk

Is Heelclicker still in business? Do they make kits for all the Comets?

I ordered kits from them not that long ago. The same kits fit the 102 and 108. There are different base weights. The 4-pro has 4 arms, so is a different kit.

[diirk]

Good to know. I noticed their website was down. I used to be a dealer for them and was always a fan of their kits.

[450pumpkin]

I just installed a 108 exp on my mini rail with a blizzard 340 rotax. I don't have any torque down low so I need it to engage at a higher rpm (it's engaging @ 3300, bog city) Looks like I have the opposite problem, so I need lighter cam arms. It has a pretty stiff spring (green/yellow) so maybe just the arms? Can a 108 be dissassembled without special tools? It looks like the only danger is the spring pressure pushing on the cover, unless that is relieved enough when the 12 point bolts are loosened.

Thanks