rms13

I have dropped my chain a few time in the past couple of months since I built it up. Most times I was somewhat cross chained and climbing so I'm sure there was user error.

Today I was at a stop sign in large chain ring/smallest cog and I put down a lot of force to take off from the stop and the chain came off the chain ring and fell to the oustide away from my frame. What would cause this? FD adjustment?

Retro Grouch 

Based upon what you've said and without seeing your bike I'm going to guess you need a high limit screw adjustment. Don't over do it. Probably 1/8 turn is all it needs.

RoadTire 

Start with the FD upper and lower limit screws - you will see two small ones close together. Might be marked "U" and "L." The upper is adjusted until you get a crisp shift to the large chainring, but not farther out. Small changes of a quarter turn are enough when you get close to perfect. Adjust the lower the same way, shifts w/o delay into the small chainring, but not any more than that.

I prefer takeing the pressure off the upper screw by shifting into to smaller chainring, then going a few turns in so that it won't shift up. Now start backing the screw out while spinning the crank until it shifts. Then back and forth with the shifting and screw, as RG said, even as small as 1/8 turn until it's just right. Test by shifting the RD into the largest cog (smallest gear as it were), proving to yourself the FD still shifts perfectly. Then onto the smallest cog in the RD and do it again.

After all of that, if you have shifting issues, start with barrel adjusters on the cables. Often the cables are too loose.

rms13

Thanks, I'll make adjust the limit screws and see how it goes

Andrew R Stewart 

I question the function of the der limit screws when not shifting and when the der cage is not already rubbing on the chain. The OP's situation was when starting up and not shifting. No claim of the cage having been moved (by the lever). So did the rider induce enough flex when powering away from the stop to bend the rings enough to cause so much chain angle to allow the chain to derail? Was the outer limit screw so off that the inner cage plate was almost but not quite rubbing when in the small cog/large ring so when the ring flexed to the inside the cage forced the chain off to the outside? If so then there would likely be rubbing in the large ring and middle cogs to, but no mention was made of this (and lack of info is not the same as the situation not existing). An interesting experiment would be to remove the ft der completely and see if the chain still derails under power. Andy.

Andrew R Stewart 

I should have mentioned that the Op might check that the BB and ring bolts are correctly adjusted/tight just in case other movements are going on. Andy.

rms13

Thanks. True , I was not touching the levers when the chain came off this time.