Miatav8,MstrASE,A&P,F wrote:

I don't think I answered your question though.

Consider the extra weight to be like towing a trailer.

I will assume the bike weighs 380 lbs, requires 92 octane, and is tuned to carry two 180 lb people without detonation under most conditions.

The design weight (gross) would be 740 lbs.

The locost will be 1180 lbs which is 1.59 times the design weight, a 59% increase. If you decide to have a passenger later, with two people onboard, it would be 1360 lbs and 1.84 times the design weight, a 84% increase.

A single occupant in a 1000 lb locost is equivalent to two R1 riders towing a 440 lbs trailer.

Two occupants in a 1000 lb locost is equiv to two R1 riders towing a 620 lb trailer.

If the bike will not detonate at gross on less than 92 octane, then there is a buffer and the load can increase somewhat without detonation if 92 is used.

For a single occupant, a 1.59:1 gear reduction would keep the load on the engine the same as it was designed for at gross, 740 lbs.

For two occupants, the ratio would be 1.84:1.

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Now to figure out the other changes.

The tire change is decreasing the gear reduction and increasing the load, going from 24.48" to 25.04". Think of this like a wrench attached to the axle, where the wrench handle has been lengthened .28" (half the tire diameter increase). When the lever is increased, the leverage the ground has to resist the rotation of the axle increases.

The 2.41:1 chain system is replaced with a 3.70:1 diff, increasing the gear reduction and decreasing the load. This is a gear reduction increase of 1.29:1. What you really want is 1.59-1.84:1 IF the top speed is adequate, 92 octane is required stock, 92 octane is the highest octane you plan to use and there is little or no detonation buffer stock.

A 4.00:1 diff will give you 126 mph and keep loading close to stock. Durability of the bike drivetrain should be close to stock.

So this fella seems to know what he's talking about. I got the old 900RR out this spring, started hard, choke not working. But long story short, it started overheating, I wasn't going fast at all, in fact probably too slow and too high a gear and I'm thinking crappy gas started making it detonate (I should have noticed) and overheat. Problem went away after I got some new gas and added some octane boost to it. Now I'm worried a bit about my BEC!