Timing Key Tech - HCS Snowmobile Forums

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Old 12-03-2010, 03:27 PM   #1 (permalink)
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Default Timing Key Tech

When your on the quest for HP, timing keys always seam to come up in the conversation, You hear lots of talk saying they make HP and that you need higher octane fuel to run them buy not a lot of people know why.
A timing key simply advances your timing using a offset key in place of the straight cut key between the flywheel and crank. While looking at the motor from the right side the flywheel will be advanced clockwise causing your spark plugs to fire earlier, example: 2* timing key will advance the flywheel 2* clockwise and cause the plugs to fire 2* early. See Pic
But why does it make power?
Timing Theory:
On the compression stroke as the spark plug fires, It takes a few milliseconds for fuel to ignite and burn/expand and create enough pressure to push the piston down (making power) therefore if you were to set timing at 0* at top dead center (TDC), by the time the fuel ignited and expanded the piston would be half way down the bore and the motor wouldn't make any power. Stock F7 timing is set at 14* before top dead center (BTDC), This tells us that Cat/Suzuki engineers figured that it take 14* of crank rotation for 87 octane fuel to ignite/expand and get max pressure just after the piston passes top dead center (If ignites/expands to early, the fuel is expanding before or at TDC you get "spark knock" or detonation) Cat didn't max out the timing because of unknown variables like fuel quality and trail conditions. So when you add 2* of timing you move the point at which the fuel ignites and starts making max pressure closer to TDC making use of all the fuel and making max HP. 93 octane fuel burns slower than 87 so you can add even more timing making even more power.

If you donít mind running good fuel, Timing is your best friend.

(Timing key pic is from Nick on Arctic Chat)
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Last edited by CJ7Jeepoffroad; 03-03-2014 at 12:56 AM.
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Old 08-29-2019, 03:48 PM   #2 (permalink)
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Join Date: Mar 2009
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Current Sled(s): F7
Previous Sled(s): Formula 111, citation, kitty cat
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Age: 37
Riding Since: 1976
Default 17 zr8000

Have a stock 17 zr8000 and run premium fuel and looking to get rid of this little hesitation when starting off...really noticeable when breaking trail and tends to clear up after 10mph. I was told a timing key would make help but not sure which one to order. Any experience or help with this would be awesome
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Old 12-03-2019, 10:24 AM   #3 (permalink)
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Current Sled(s): 12 XF 1100 Turbo
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So you have been riding sleds since you were -7 years old?
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