Bicycle Mechanics - problems with single speed conversion freewheel

so i recently converted my 12-speed road bike to a singlespeed and kept the freewheel on for various reasons. i have yet to get spacers for the rear so i kept the old gears on it, but the chainline is ~98% straight. anyway, now sometimes when i walk the bike, i notice that the cranks turn, and sometimes, it doesn't. this happens both when the bike is moving forward or backward. is this supposed to happen? i'm a newb to all this bike stuff. the bike appears to work fine otherwise; i.e., i can ride it and coasting isn't a problem. my guess is that the chain's rubbing on something it's not supposed to.

i released the rear wheel once to clean the frame, but i'm pretty sure the chain is back on correctly.

thanks for any advice.

ps, i did try to search the forums for an answer, but the only keywords i could come up with were: pedals, singlespeed, cranks, etc. and that didn't help narrow my search any.

It's normal when moving forward.
However, the crank should always turn when you roll the bike backwards.

It sounds like maybe the freewheel has some gunk in it, so that it has enough resistance that it will turn if you walk it forward, but not enough to actually bind it up if you're riding on it.

This happens to old freewheels quite a bit, I've noticed...

The easiest thing to do is take off the freewheel and spray some WD-40 in the back, until it loosens up and doesn't bind anymore.

does this happen w/ "regular" 12 speed bikes too? i may never have noticed the turning before, but i wanna say it didn't do this until after the conversion.

as to the gunk on the freewheel, thx for the advice and i'll try our your suggestion soon.

most importantly, does this pose any safety threat in the immediate future?

does this happen w/ "regular" 12 speed bikes too? i may never have noticed the turning before, but i wanna say it didn't do this until after the conversion.
So lemme get this straight, it still has a 6 speed freewheel on it, but you're only using one cog?

This happens with normal freewheels too, yes. You may not have noticed it before, or maybe now you are using one of the larger cogs, and that cog has more mechanical advantage with respect to the chainrings: if the freewheel was only "slightly" gunked up, it might have enough resistance to turn the chainrings on a larger cog than on a smalelr cog.



as to the gunk on the freewheel, thx for the advice and i'll try our your suggestion soon.
most importantly, does this pose any safety threat in the immediate future?
I don't think it's dangerous. It's almost certainly NOT going to bind up and turn into a fixed gear when you're coasting down a hill, if that's what you're wondering. The resistance of the dirt that's clogging the freewheel is not nearly enough to push your feet around in circles :) I imagine you don't even notice it when riding the bike. v The worst one I have ever seen was on a 12-speed as well, and it felt like the freewheel was totally locked up, but when I tried riding it I could just barely feel the resistance.

But it's a good idea to clean it out anyway, it'll keep your bike happy!