Chain jumping off Chainring

[Jedi Mike]

I have a Gary Fisher Marlin that's 10+ years old. I bought a bash guard and removed the big and small chainrings as well as the front derailleur. I'm not using only my old middle chainring up front. I first attached the chainring backwards, but noticed this when the chain was jumping off while the bike was still on the stand. I took the crank off, unscrewed everything, and put it back on facing the right way.

Went for my first ride this morning and the chain kept jumping off the chainring, especially when going over bumps and regardless of the gear I was in.

I hadn't had this problem before installing the bash guard, so what might I have done wrong? Could tightening the chainring on backwards have caused this?

Thanks, Jedi Mike

[nfmisso]

Mike - put the front derailleur back on, use the limit screws to lock it in position, no cable, no shifter, your problem will go away.

Read the 1 by X information on the web, you will find that your situation is very common.

Putting the chain ring on backwards may actually help - BUT it sounds like yours is very worn. Changing to a single speed chain ring designed for 3/32" chains will help. Your current chain ring is designed to assist with shifting, you do not want it to shift at all.

Shortening the chain (follow Shimano's recommendation no RD, wrap around big rear and front ring + 1") will help to get the chain tension higher.

Is your RD original - if so the spring is probably tired, and a new RD would help a great deal. I would replace the cassette/freewheel, RD and chain ring at the same time.