F7 Radar Run Question - Snowmobile World : Your #1 Snowmobile Forum

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post #1 of 9 (permalink) Old 01-16-2005, 04:52 PM Thread Starter
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went to a radar run yesterday and had a very hard time going over 100 mph, the sled is a 2003 f7 lowered with a speed track and a 500 ft ecu box , the track was in pretty bad shape, but the thing that gets me is i ran 8 times and every time i got 100 mph, and i made many changes, my first run the sled was running at 8200 rpms so i added 3 grams of weight to the primary to bring the rpms down, next run still ran 100 mph, i made 3 helix changes, and added 6 grams of weight to get the rpms right but that did not matter still ran 100mph on the radar gun, I think the problem is my gearing it just does not make sense i am runnig 23/40 for gears. thanks any help would be great
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post #2 of 9 (permalink) Old 01-16-2005, 07:17 PM
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Well i would say that the track could have something to do with it..not getting enough traction..how much rpm's did you drop from 8200.. i think 8200 is to high.
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post #3 of 9 (permalink) Old 01-16-2005, 07:33 PM Thread Starter
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got the rpms down to about 7650
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post #4 of 9 (permalink) Old 01-16-2005, 09:23 PM
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The 500' box with a 2.2 key has its hp at 7700(150.9) so your rpm's should be good, you would think that it would pull harder than that..must be the conditions..
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post #5 of 9 (permalink) Old 01-20-2005, 09:53 AM
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Sounds like a traction probleme to me.....you can have 200hp , but if you can`t get to the ground.....

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post #6 of 9 (permalink) Old 01-21-2005, 08:49 PM
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was talking to a tech guy last year at a race about the speeds of the f-7.(stock class)
he said on average they were running right around 105mph. in a 1000ft. (ice track) just going by what i was told.
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post #7 of 9 (permalink) Old 01-22-2005, 01:48 AM
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You might want to try a stock ECU. The 500' box is for short drags right? You should use race gas when you advance engine timing in a sled that is used in a sustained full throttle high load application.
Detonation will kill top end power and speed in a long full throttle run, thats what often happens when timing is advanced or compression is increased.
I prefer stock timing, stiff primary spring [D+D Black], heavy full tip weight's [70gr],53deg helix, red 4th hole, or a green 2nd hole in my 03 F7, load engine down to 7600-7700rpm.
23/40 with the stock 10tooth drivers should be good for 120mph.
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post #8 of 9 (permalink) Old 01-22-2005, 08:44 AM
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Most F7's run 98-104mph, depending on rider weight and traction.

A 250lb rider will go 98mph, a 160lb rider 104mph. If they have 100% hook.

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post #9 of 9 (permalink) Old 01-22-2005, 08:45 AM
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i went to a sanctioned radar run 3 weeks ago and the ave fcat was running 95-104mph there was one that ran 110 but he was quite modded.

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