# Bike (motorcycle) Chains???? **URL:** \ **Category:** Factual Questions\ **Created:** [May 12, 2016, 9:36pm UTC](https://boards.straightdope.com/t/bike-motorcycle-chains/754637 "2016-05-12T21:36:12Z")\ **Posts on this page:** 8\ **Page:** 1
**Author:** ![IBuildEm](https://avatars.discourse-cdn.com/v4/letter/i/f475e1/32.png) [@IBuildEm](https://boards.straightdope.com/u/IBuildEm)\ **Post date:** [May 12, 2016, 9:36pm UTC](https://boards.straightdope.com/t/bike-motorcycle-chains/754637/1 "2016-05-12T21:36:12Z")
I’ve been trying to understand different bike chain sizes. I see stuff that is 25H, 420, 410, 425, and on. I know it has to do with the space between the rollers and the width. I am trying to find the right chain for my chinese bike engine kit I put on a beach cruiser. I ordered a 25H chain, it was smaller than the chain on the pedal sprocket. I am trying to find one to fit the engine side and rear wheel sprockets. I had an ATV chain on it before, it was old and rusty and had snapped at the master link. Do any of you mechanics or bike people know how to guesstimate this? Maybe a 420 chain? I am not sure. I have been ordering chains off of ebay hoping they will fit. 25H was WAY too small. Thanks ---
**Author:** ![IBuildEm](https://avatars.discourse-cdn.com/v4/letter/i/f475e1/32.png) [@IBuildEm](https://boards.straightdope.com/u/IBuildEm)\ **Post date:** [May 12, 2016, 9:41pm UTC](https://boards.straightdope.com/t/bike-motorcycle-chains/754637/2 "2016-05-12T21:41:42Z")
I am about to order a #41 roller chain ---
**Author:** ![somepumpkin](https://avatars.discourse-cdn.com/v4/letter/s/7feea3/32.png) [@somepumpkin](https://boards.straightdope.com/u/somepumpkin)\ **Post date:** [May 12, 2016, 9:49pm UTC](https://boards.straightdope.com/t/bike-motorcycle-chains/754637/3 "2016-05-12T21:49:43Z")
I have a few different bikes. Some have had conversions and some are stock. When I need a chain, I take its measurements and then consult a chart. You can Google image search for “roller chain sizes” to find a chart. Many of those charts even show you where to measure. ---
**Author:** ![IBuildEm](https://avatars.discourse-cdn.com/v4/letter/i/f475e1/32.png) [@IBuildEm](https://boards.straightdope.com/u/IBuildEm)\ **Post date:** [May 12, 2016, 10:05pm UTC](https://boards.straightdope.com/t/bike-motorcycle-chains/754637/4 "2016-05-12T22:05:09Z")
> [@somepumpkin](#): > > I have a few different bikes. Some have had conversions and some are stock. When I need a chain, I take its measurements and then consult a chart. > > You can Google image search for “roller chain sizes” to find a chart. > > Many of those charts even show you where to measure. Thank you ---
**Author:** ![John\_Mace](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/john_mace/32/185_2.png) [@John\_Mace](https://boards.straightdope.com/u/John_Mace)\ **Post date:** [May 12, 2016, 11:23pm UTC](https://boards.straightdope.com/t/bike-motorcycle-chains/754637/5 "2016-05-12T23:23:43Z")
The 420 chains are definitely for mountain bikers. 😉 ---
**Author:** ![Kevbo](https://avatars.discourse-cdn.com/v4/letter/k/e47774/32.png) [@Kevbo](https://boards.straightdope.com/u/Kevbo)\ **Post date:** [May 13, 2016, 3:19pm UTC](https://boards.straightdope.com/t/bike-motorcycle-chains/754637/6 "2016-05-13T15:19:24Z")
Not what you asked, but [motoredbikes.com](http://motoredbikes.com) is a place that will be able to answer any and all questions. The motor kit you have is known as a “Happy Time” engine, or HT for short. ---
**Author:** ![Nefario](https://avatars.discourse-cdn.com/v4/letter/n/59ef9b/32.png) [@Nefario](https://boards.straightdope.com/u/Nefario)\ **Post date:** [May 14, 2016, 12:33am UTC](https://boards.straightdope.com/t/bike-motorcycle-chains/754637/7 "2016-05-14T00:33:35Z")
[This reference mentions using a #41 chain.](http://www.mcarterbrown.com/forums/mcb-reviews/91217-50cc-happy-time-motor-kit-bikeberry-com-review-info.html) I assume you have a complete kit with engine sprocket AND the correct rear wheel engine drive sprocket. Read the installation suggestions :eek: toward the bottom of the page. ---
**Author:** ![AskNott](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/asknott/32/5790_2.png) [@AskNott](https://boards.straightdope.com/u/AskNott)\ **Post date:** [May 14, 2016, 10:07pm UTC](https://boards.straightdope.com/t/bike-motorcycle-chains/754637/8 "2016-05-14T22:07:26Z")
When you get a new chain, always check the sprockets. If the teeth are “hooked,” you’ll need to get new sprockets, too. Otherwise, the old sprockets will harm the new chain.