New M7 Clutches Low RPMs

[Blueside]

So I managed to pick up a 05 M7 EFI 162" pretty cheap a few weeks ago, was in a hurry when I bought it and didn't go through the clutches very well.

Anyway long story short, when I got it home there was a bad roller on the primary and the secondary looked like someone was trying to spread the sheaves with a pry bar.

Starting fresh.
I picked up a "upgraded" primary (AC new part) and BD 10.4 sheaves, after reading what seems like endless information on here regarding set-ups I bought a new Orange M8 Spring with BD High Temp Rollers and the BD deflection nut. For the primary I went with the Gold AC Spring and 70g weights, with an M8 belt.
Seems to be stock, except a MBRP Can, I've heard stock is the way to go, I'll have a look and see if I can get one.

Was riding at about 3400' last weekend and RPMs topped out at about 7400. I think I should be around 7800RPM? It held RPM well on pulls up hills but seem like it was hitting a limiter at WOT (like a wah-wah-wah) sound. Just wondering if this sounds like a simple case of dropping weight 66-68ish? My next trip will be out to Mcbride (hopefully we get some more snow) 6000-7000 I believe should I drop even more?

Also, I read somewhere that these motors rather a lower octane fuel, any truth to this??

Also completely unrelated but are there many differences M7-M8 chassis wise? can I put a 08-09 M8 engine in this or is heavy modification required, I'd rather buy a used engine rather than a BB as hopefully I could keep the Electronic reverse from a newer engine.

Thanks you guys are always so helpful!

 

[Rixster]

Yeah the m7 liked 88 octane. 70 is way to heavy IMO. I would bet you need to be more in the 62-65 range. and yes, as you gain elevation you need to lose weight in order to keep you rpm.

 

[manlye]

I have 67.5 on a 900bb at 10-12k 70 is way to heavy


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[arctic2009]

So I managed to pick up a 05 M7 EFI 162" pretty cheap a few weeks ago, was in a hurry when I bought it and didn't go through the clutches very well.

Anyway long story short, when I got it home there was a bad roller on the primary and the secondary looked like someone was trying to spread the sheaves with a pry bar.

Starting fresh.
I picked up a "upgraded" primary (AC new part) and BD 10.4 sheaves, after reading what seems like endless information on here regarding set-ups I bought a new Orange M8 Spring with BD High Temp Rollers and the BD deflection nut. For the primary I went with the Gold AC Spring and 70g weights, with an M8 belt.
Seems to be stock, except a MBRP Can, I've heard stock is the way to go, I'll have a look and see if I can get one.

Was riding at about 3400' last weekend and RPMs topped out at about 7400. I think I should be around 7800RPM? It held RPM well on pulls up hills but seem like it was hitting a limiter at WOT (like a wah-wah-wah) sound. Just wondering if this sounds like a simple case of dropping weight 66-68ish? My next trip will be out to Mcbride (hopefully we get some more snow) 6000-7000 I believe should I drop even more?

Also, I read somewhere that these motors rather a lower octane fuel, any truth to this??

Also completely unrelated but are there many differences M7-M8 chassis wise? can I put a 08-09 M8 engine in this or is heavy modification required, I'd rather buy a used engine rather than a BB as hopefully I could keep the Electronic reverse from a newer engine.

Thanks you guys are always so helpful!

08-09 engine will not fit without some modification.. not worth it imo. just buy a big bore kit if more power is what you are looking for.


Try swapping out the Arctic Cat gold spring for the Polaris straight gold spring. It has a lower start rate but the same finish rate as the cat yellow white spring (which is stock for an M7) 70 gram weights are recommended for 3-6k feet but your cat gold spring is a little light on finish rate which could be your problem with not getting proper R's. If you would rather stick with the cat gold, drop a few grams and go from there.

 

[Blueside]

Thanks guys. I'll be Trying out some adjustable weights next week

 

[diggerdown]

Throw a shim about 1/8" thick in the spring cup before spending more on weights. That should give you 2 to 300 R's. Cost nothing to try. Don't shim so high you don't have enough cup left to keep the spring retained.

 

[pano-dude]

I use 68 gram weights, pulls 7900-8000 up to 8000', after that it needs less weight, maybe 66.

all stock 700-162

 

[Cat00]

Im Running cat 0range Black spring and 66g weights holding 7800-8000 rpm all day on my m7

 

[Blueside]

I went with a 65. Ran great but a trenching monster now!
Read some pretty informative posts on rear skid setup, so I guess I'll start there