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Discussion Starter · #1 ·
Please avoid the "why would you want to get better top end" discussion.

I am not quite at the, "I don't care how fast it is on the top" point in my life.

I still want to pull past everyone when we are blasting down the county roads.

Currently I have 04 F7efi std (with 1in. track, now about 7/8th's after 4k miles).

Clutching is stock. Engine has BMP pipe mod and 2.5 degree timing key. I run 6.5" shapers on stock skis.

Here are some of the options:

ODS clutch kit (ask Dan to tune it for midrange/top end).
taller gearing
10 tooth drivers on driveshaft
offset big wheel axle
BMP head mod

I just don't know which of these would give me the most top end ( more midrange would be cool too as long is doesn't take away the top end).

I would see 113 when it was stock. 118 after pipe mod/key (with increased pull in midrange). These are all on the speedo of course (not GPS'd).

I'm looking for 123-125 to give the Mach's a run.
 

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Gearing and clutching are the way to go...

I believe your sled came stock with 23-40 gearing. If you want to stick with the 9 tooth drivers step up to 24-39 gearing, then add some clutching to help hold your RPM's.
 

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Hey bigblock, when do you plan on doing these mods, now or before next season??? I am curious to see how you make out, because I want more top end too. Let me know what you decide to go with. What does the BMP head mod entail? Will the sled be reliable?? How much??? Thanks
 

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I see one problem with your set-up, the timing key and efi's don't get along so well. They are great for short runs but long wide open runs arent a good choice for an advanced timing key. I've read about this on a lot of different sites as well as a news letter from Black Magic. Try removing it and give it a wide open run. You may never put it back in again, this being on the efi only, carb sleds its o.k. Also, a lower wind shield will net you about 1 mph.
One more thing, on long wide open runs, draft the sled in front of you, it really works and it helps to have a friend "drafting you" if you know what I mean.
 

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Discussion Starter · #7 ·
<div class='quotetop'>QUOTE (tiggershark @ Mar 14 2007, 07:07 PM) <{POST_SNAPBACK}></div>
I see one problem with your set-up, the timing key and efi's don't get along so well. They are great for short runs but long wide open runs arent a good choice for an advanced timing key. I've read about this on a lot of different sites as well as a news letter from Black Magic. Try removing it and give it a wide open run. You may never put it back in again, this being on the efi only, carb sleds its o.k. Also, a lower wind shield will net you about 1 mph.
One more thing, on long wide open runs, draft the sled in front of you, it really works and it helps to have a friend "drafting you" if you know what I mean.[/b]
I have around 1200 miles on my 2.5 key without issue (4000 miles on sled total). I do alot of long WOT runs (at least 1 or 2 per ride to 110+). There are several railroad grades and long straight groomed county road stretches where we ride.

I did the pipe mod with the key, so I can't say if the key alone had an affect (good, bad, or otherwise). I doubt that you would be able to tell the difference with or without it, but it's kind of a PITA to replace, so I'm keeping it in there. I can say that for $200 there was a noticeable improvement in midrange response and top end. In addition, there seems to be an extra "kicK" at around 85mph that feels like the "pipe", so my guess is that the key is at least partly responsible for the midrange improvement. BMP has dyno sheets on their website (tuning an F7). They used the key, so that is what I used.

I like the lower windshield idea too. If I lowered the windshied and put on handgaurds do you think it would be a "wash".

Good discussion, thanks for the replies
 

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Discussion Starter · #8 ·
<div class='quotetop'>QUOTE (speedstang91 @ Mar 14 2007, 05:00 PM) <{POST_SNAPBACK}></div>
Hey bigblock, when do you plan on doing these mods, now or before next season??? I am curious to see how you make out, because I want more top end too. Let me know what you decide to go with. What does the BMP head mod entail? Will the sled be reliable?? How much??? Thanks[/b]
I am going to the U.P. one more time (leaving tomorrow), so the mod will happen over the summer/fall. Most of the riding this weekend will be trying to get lost in the Hiawatha swamps, riding 3 wheelers, cutting firewood, and drinking beers (god I can't wait).

There was a thread on here awhile back called something like "squish, how far can you go", which discussed what happens when you shave a head. Turns out you actually have to rechamber the heads to maintain the squich area but increase the compression ratio.

I think the thread ended with me supposed to be asking BMP what they do to the head specifically (maybe they'll chime in here, but prolly not).

I will ask them before I send in my head though.

My reasoning on the head mod is that I already have the timing key, so I am already running premium fuel. I know that when you increase the compression you have to increase the octane to avoid detonation.

Whatever I decide, I'll be posting the result here for sure. If you do the same, we'll both benefit (and maybe others too).

Happy rippin'.
 

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<div class='quotetop'>QUOTE (bigblock2stroke @ Mar 14 2007, 07:29 AM) <{POST_SNAPBACK}></div>
Please avoid the "why would you want to get better top end" discussion.

I am not quite at the, "I don't care how fast it is on the top" point in my life.

I still want to pull past everyone when we are blasting down the county roads.

Currently I have 04 F7efi std (with 1in. track, now about 7/8th's after 4k miles).

Clutching is stock. Engine has BMP pipe mod and 2.5 degree timing key. I run 6.5" shapers on stock skis.

Here are some of the options:

ODS clutch kit (ask Dan to tune it for midrange/top end).
taller gearing
10 tooth drivers on driveshaft
offset big wheel axle
BMP head mod

I just don't know which of these would give me the most top end ( more midrange would be cool too as long is doesn't take away the top end).

I would see 113 when it was stock. 118 after pipe mod/key (with increased pull in midrange). These are all on the speedo of course (not GPS'd).

I'm looking for 123-125 to give the Mach's a run.[/b]
add HP then gear up. even as you are now you can gear up a bit you will likely lose nothing bottom end as you will have less track spin.
 

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I think to 04 already has 24-39s. I'd just get an 03 driveshaft with 10 tooth drivers already on it, and try it with out the key.
 

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leave the key in it. have you ever seen a f7 thats modified with out a key? iv have a 2.5 key in mine for 1000miles and it been fine. just run premium.
 

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Discussion Starter · #12 ·
<div class='quotetop'>QUOTE (maxi426 @ Mar 18 2007, 09:01 AM) <{POST_SNAPBACK}></div>
I think to 04 already has 24-39s. I'd just get an 03 driveshaft with 10 tooth drivers already on it, and try it with out the key.[/b]

Really?

So my 04 has 8 tooth and an 03 has 10 tooth?

I am a little clueless about driveshaft mods. I have heard about going to 10 tooth cogs on the driveshaft, but I thought I would have to buy the cogs from an afetermarket company and press them onto my driveshaft.

Can anyone confirm the driveshaft thing between the 03's and 04's? Seems like the best bang for buck would be a used driveshaft from an 03F7. Would I have to change anything else to make it work?

I can confirm the 24/39 gearing in a stock 04F7.

This would also prolly explain why my friends 03 would always pull on my 04 slightly no matter what and he's 25lbs heavier. That of course was before the pipe mod and key.

Now its the other way around.
 

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04s have 9 tooth drivers:

24-39 was stock for standards / 23-40 was stock for Sno Pros in '04. (I assumed you had a sno pro)

If you look at the gearing chart: CLICKY
You will see that:

24-39 w/ 9 tooths = ~119 (w/ 15% overdrive)
22-41 (stock '03) w/ 10 tooth = ~ 118 (w/ 15% overdrive)

Your buddy pulling you on top has nothing to do with gearing.

W/ 10 tooth drivers maybe try 25-38??? ~ 126 (w/ 15% overdrive)
 

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The stock gearing on a 99 ZR 700 was 24/39. I still own one.
For some extra top end, cut some slits in your hyfaxes for snow packed lube, put your springs on the softest settings( to lower the whole sled)and reduce track tension and remove that timing key! Its for short drag racing not for wide open runs on an efi sled. The 87 octane and a regular keyed sled will run better at wide open runs than the other way. I own 2 F7 efi's and I'll never put a timing key in them.
Some say the larger intake flange will help, I dont agree with that either. I'll bet you run just as fast w/o the timing as you do w/ it and save 20 cents per gallon while doing it. This is just my opinion.......................tigger
 

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hey big block, i would skip the clutch kit cause if your going to do some more modding than your probably going to want to tweek the clutching. i was running the same setup your running now but with a fuel reducer also. i checked the sqiush and then had .010 taken of just to get to the factory spec of .059 i know that made a difference cause it pulled more rpms and i had to reclutch after that. it was over revving and no matter how i adjusted the secondary spring i couldnt get the r's down. i had to add morre weight. i wouldnt pay for an aftermaket head either. take the money from the head and clutch and get that baby ported. that will give youu most seat of the pant ejoyment for your buck.
 

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i run just a 2 deg key on my '05 f7 efi ext and i found it cleaned up bottom end throttle response. btw i just run 87 octane that is suppose to be around 10% ethanol mix. i also leave the fuel connector connected on the sled. with it unplugged it just smokes more and uses ALOT more fuel. not necessary. i dont have my engine modded any other way though. i just have a custom can on and thats it.
 

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Discussion Starter · #17 ·
<div class='quotetop'>QUOTE (sledsearcher @ Mar 21 2007, 03:32 PM) <{POST_SNAPBACK}></div>
04s have 9 tooth drivers:

24-39 was stock for standards / 23-40 was stock for Sno Pros in '04. (I assumed you had a sno pro)

If you look at the gearing chart: CLICKY
You will see that:

24-39 w/ 9 tooths = ~119 (w/ 15% overdrive)
22-41 (stock '03) w/ 10 tooth = ~ 118 (w/ 15% overdrive)

Your buddy pulling you on top has nothing to do with gearing.

W/ 10 tooth drivers maybe try 25-38??? ~ 126 (w/ 15% overdrive)[/b]
So, you'd go to the 25-38 because just putting the 10tooth drivers on would be too much?

Thanks for the link to the gearing chart. Your calculations seem right on. 2 different people have seen 118 on the sled as it sits right now.

I already have the "ported" hyfax and the springs are as soft as I can go with the standard suspension (bottoms on big hits a little).

As posted earlier, I think (and BMP thinks too according to their dyno charts) the key helps the response, I have over 1000 miles on it with the 2.5 key, its a PITA to change, and I will have to run premium after the mods anyway.

Is there an accepted reason why the 03's were fastest (why he would pull on my before the mods)? I know there was a lot of talk why and I thought the general consensus was that the ECM's were calibrated differently. I personally think the oil pump and fuel pressure settings would more than make up for the difference if I actually got off my lazy can to tune them.
 

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Discussion Starter · #18 ·
<div class='quotetop'>QUOTE (f7ben @ Mar 21 2007, 10:50 PM) <{POST_SNAPBACK}></div>
hey big block, i would skip the clutch kit cause if your going to do some more modding than your probably going to want to tweek the clutching. i was running the same setup your running now but with a fuel reducer also. i checked the sqiush and then had .010 taken of just to get to the factory spec of .059 i know that made a difference cause it pulled more rpms and i had to reclutch after that. it was over revving and no matter how i adjusted the secondary spring i couldnt get the r's down. i had to add morre weight. i wouldnt pay for an aftermaket head either. take the money from the head and clutch and get that baby ported. that will give youu most seat of the pant ejoyment for your buck.[/b]

I will prolly skip the clutch kit for now. I wish I knew enough about clutching to tune it myself (add some weight to the primary, steeper helix angle in the secondary, the whole spring influence in both clutches, etc), but I don't think I have the patience.

So you checked the squish and your spec was too high (as in .07 or something) and so you just straight milled 10 thou off to get to the factory spec of 0.59?

If so, that would be way cheaper/easier than the head mod.

So, $300 for the CK, and $189 for the head mod doesn't save me enough money for the $700 port job (with new rings/gaskets).

I might as well put the F8 kit on it at that point and be done with it, but I've been down that road and I would rather bite the bullet on a leftover XF1.

In the end, for now, I think I'll do the driveshaft first (cheapest) and see how it runs. If it takes too much away from the low/mid to the point that I have to "wait" for it to come up on the pipe when going corner to corner, then I'll gear it back down a little.

Again, this is a great thread for me. Thanks for all the replies.
 

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I may be able to help you in the 10 tooth driver department! Pretty cheap too! I'm in the process of buying a 1.7" track and 9 tooth drivers with axle....so I could sell you my entire drive shaft with drivers already presses on.....

PM me if your interested!
 
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