Bicycle transmaission maximum torque

Hi, I am thinking of mounting a motor like this: 125CC FULLY AUTO ENGINE MOTOR ATV PIT BIKE ATC 70 XR 50 CRF 50 SDG on my GT LTS and running the power through a modified SBP jackshaft and a rear derraileur system. So, the chain would be a standard 8-speed and the cassete and derraileur Shimano xt. Does anyone have any experience with putting this much power through a standard bicycle transmission? The reason I am doing this is because I want my MB to be legal but still have a transmission. It seems to me that the things that would be the main problem would be the maximum force the chain could withstand, breaking the teeth off of the gears and ghost shifting under power. I've read around a little and haven't found anyone who has put this much power through a chain-derraileur system. So I could always just try it and see what happens...

Yes I am planning to use it on the street About legality, I spent around a month calling the DMV, WSP and talking to cops and everyone came up with a different answer. I also did a lot of reading here: Title 46 RCW: Motor vehicles and came to the conclusion that there is no law regarding gas powered mb's, just electric ones. So really, the most (legally speaking) they can do is impound it, which is not really a problem because I'll mostly be riding it on logging roads.

Also, I definitely made sure to beef up the other components on the LTS:

Front fork: Marzocchi Super Monster T Fork
Wheels: Modified 21" motorcycle wheels
Brakes:Hope Tech X2 Hydraulic Disc Brake at JensonUSA.com
Shock: FOX / Bike / Shocks / DHX Air 5.0
Motor mounts: Custom made out of plate steel similar to the SPB kit

I think the frame is up to the job as well, considering easyrider put a morini with similar power output on his: http://motorbicycling.com/f47/ezrs-full-suspension-summer-project-1286.html

I did some more researh and found that I could just use a Rohloff speedhub with a BMX chain, which could handle the torque (M55 use it on their high powered e-bike: M55 - Electric bikes with a torque figure of 50 nm compared to my 7 nm) but it would be way too expensive.

Yes, I've read that definition on the Washington State Patrol website. Trouble is, I just feel like i've been getting the run around by the gov't because everyone outside the DMV (i.e. the Washington State Patrol) say just get it registered as a moped. But I tried to get one of the mb's i'd built registered as a moped but they said they could not do it because it needed to have a VIN and the vehicle be deemed "made to be motorized" by a major manufacturer with a vehicle manufacturers license. So they said go to the Washington State Patrol for an inspection. Which said the could not inspect it because it is a moped, and I should get it registered as one. And so the loop continues. So basically that's why I'm going for a simple design with an automatic transmission and low levels of noise, so wherever I go there will be as little attention as possible given to me.
Also, according to wikipedia: Roller chain - Wikipedia, the free encyclopedia the maximum working load defined by ANSI for a bicycle chain (size 40) is 810 lbs. So, I guess if I hook an engine up to it with 5.16 ft/lbs of torque there is no way it could break? Also, according to this forum thread: Maximum Human Torque [Archive] - Bike Forums pro cyclists produce on average 80 ft/lbs of torque but over a very narrow rev range (which is why the horsepower figure is so low). So, according to this, an engine would actually be more gentle on the drivetrain than a human? Then again I do not have much experience with this and there is the question of the speed and vibrations produced by the engine.