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There must be more to this story. Anyone have any info???

A stock 03 F7 had 92 ft-lbs of torque. The newer EFIs with ECU tweaking, timing advanced and fuel pressure regulated were 100 ft-lbs.

The Apex engine has 77 ft-lbs of torque and after the gear reduction has 95 ft-lbs at the primary clutch shaft. The 800 REV has 96 ft-lbs and the 800R XP has 100 ft-lbs.

Yamaha probably was the one that came up with the 4 stroke specs for snow cross. They were the same ones that started this in Motocross. It was easier in Motocross since the other manufacturers (Honda, Kawasaki and Suzuki) all had similar engines. In this case the other 3 manufacturers may...

The reason for the switch to 3 cylinders is to reduce engine width and max RPM more than the overall weight. The 3 cylinder engine is over 2 inches narrower than the 4 cylinder. With the stroke only 8mm longer on the 3 cylinder, the overall heights are almost identical. To increase the...

The CR9EKs are now standard on the R1 street bikes. Yamaha even mentions the dual electrode plugs in their product description of new features.

The 9.7 to 1 is the ideal NOS to fuel ratio by weight or mass. Those ratios (or those approaching that ideal number) can be used when combined with good monitoring equipment (good fuel also) for racing purposes and will produce more horsepower. Most companies that supply NOS kits to the public...

The amount of fuel used in a modern 4 stroke engine is 0.5 lbs. per horsepower per hour. The ideal air fuel ratio using normal air is 14.7 to 1. When using NOS, the ideal NOS to fuel ratio is 9.7 to 1. Most commercial tuners shoot for 5.5 to 6.0 to 1 to stay on the safe side. So if you...

The formula for calculating nos usage is: Time in seconds =(Tank size of NOS in lbs.) divided by (0.0008 multiplied by the horsepower increase) Here is an example: 2.5 lb. bottle 90 horsepower Time in seconds = 2.5/(0.0008 X 90) = 34.7 seconds Hope this helps.

Here is a link to snowmobile journalist Jerry Bassett's blog on the REV and FX Nytro along with the rest of the Yamahas. Scroll down and read. I know it is just another journalist's view so take it for what it is worth. http://snowmobilia.blogspot.com/

The magic number for starting most any fuel injected vehicle is -30 f. Most will have trouble starting at this temp or below if left out long enough without a coolant heater. The fuel you have in the tank also makes a difference at those temps. This is why you were asked the question about...

The Apex GT/ER gets beat bad out of the hole by an Attack and never catches it in a race that long. Put a 23 top gear and clutch in the Apex GT and it will win by even greater distances. A better race would have been an Apex RTX (lower gearing than GT) against the Nytro FX.

There is something really wrong with this race. The Nytro FX has only 12 less horsepower (138 vs 150 actual dyno numbers) and Yamaha says weighs wet 70 pounds less than the Apex GT. The race is 600 meters (~2000 ft.) and the Nytro can not reach a top speed of roughly 100 MPH. The huge lead...

Good luck. The Asian motorcycle manufacturers do not leave much on the table without adding very large dollars. This increase in horsepower may come at the expense of other portions of the power curve.

Good trick. You have found a gear reduction that is 100% efficient. You will find the crankshaft horsepower higher than the clutch output shaft. Probably 3 to 4 horsepower.

The biggest gain in the wet weight was from reducing the fuel tank by 3 gallons.

The sled had a SkiDoo SC-4 rear skid for the race. I wonder if more rear skid changes are coming.

Here is pic. May be a preview.

Re: What is the center to center distance '06 APEX front sho 419 mm

Mike You did not adjust cam timing back to stock after adding additional head gaskets if I remember your original post. I assume they are advanced by that amount (0.034") in your current setup. Did you adjust cam timing on any of your tests. There should be additional gains with cam and...