UKC

One for you bike mechanics out there.....

I'm having an intermittent problem with my drive system...….if I stop pedalling and coast a few yards, when I start pedalling again, the pedals and gears spin freely and don't turn the back wheel. If I then stop for a moment it will be ok again.

Also the bike doesn't like to back pedal at all. These problems seem to happen in very cold conditions and when I bring it inside, seems to be working fine.

Any ideas what the issue may be?

Sounds like your freewheel is knackered.

Sticky pawls. 

New free hub most likely. 

Sounds like sticky pawls in the freehub.  If you have a mechanical mind, and depending on the make of the hub, it's normally quite easy to remove it and inspect. 

If it's not been serviced for a while, the grease in the hub can get much and viscous (especially in the cold) and simply cleaning and relubing could well solve it, however if this has been going on a while, you may find the freehub body is worn and needs replacing

https://www.youtube.com/watch?v=IDwH0QOnn_Y#action=share

That makes sense. The bike is only 6 months old and the problem only occurs in very cold weather......

I am not mechanically minded unfortunately - how would I go about accessing these parts?

Just take it your local bike shop. It's a quick and cheap fix

Six months old? Any chance it's still under a warranty? Most shops offer it as part of the deal as once things start to bed in they need small adjustments. (Though I would say sticky pawls is a bit more than a bedding in problem). 

See the video linked above. It varies by make, but he goes through a few different methods

What bike is it? Is it a halfords special or something a bit more specialist?

If it's only six months old do you a)ride through a lot of mud and sand? b) jet wash the bike?

Sometimes the grease they use is too thick: a thin grease like wet lube is good for freehubs and sticky pawls. However, at 6 months old, you should take it back to the place you bought it and ask 

Sometimes water gets in and freezes in the cold then it is OK when yu get it back inside. Cleanout and re-greasing would be all that was needed in that case.

Yes, thick grease can easily be too much for the springs. A thin oil or wet bike lube is just the thing. Would second Rach's suggestion of letting the shop sort it out. 

thanks for all replies and advice. Since I don't have the tools, skill or inclination to start dismantling my bike, I'm gonna assume that its a cold weather issue. Tonight my bike is indoors, not out in the garage where the current temperature is around 35 below. If the problem has resolved in the morning I will know.

It's not sticky grease, it's WATER inside the freehub. It tends to freeze and stop the pawls moving in very cold weather. 

If it's a sealed freehub, as in Shimano, try dribbling a light oil like 3 in 1 into it. If it's a serviceable freehub as in Mavic, look on YouTube for dismantling instructions and give it a service. 

When you do remove the cassette from the freehub you'll be shocked at the mess of rust between the splines.

-35 would do it.  Oil rather than grease would seem to be prudent at those temperatures, but I'm not sure sure how good the seals would be.  Best speak to a local bike shop who may have wise advice or tell you that Zwift is the only sane answer

chain whip, cassette socket and 10mm allen key, half an hour, front room. Shimano freehubs ain’t worth the bother fixing, just swap it for a new one.

Get it done lad

Voila - night indoors and the bike runs perfectly in the cold. My wife ain't gonna like it. Whats new?!

You mean to tell me your bike doesn't live in the spare bedroom?  You ought to be reported for abuse.