Cafe Racer Forum banner

1 - 8 of 8 Posts

·
Registered
Joined
·
239 Posts
Discussion Starter #1
How tight (or Loose) should my chain be? I threw it the other day at around 70mpg. It went to the inside but looked like it could have caused a problem if it went to the outside.

How tight should it be? Any play and all?

thanks.
 

·
Registered
Joined
·
23,303 Posts
what bike?

if it is a cb750 I would check to make sure you didn't window the back of the case block.

On a cb750 I usually shoot for 1/2" of movement if I press down on the chain halfway between the sprockets. If I pull the chain from the back of the rear srpocket it should expose 1/2 of the surface face of the teeth.

If you tossed a chain check to make sure you don't have a chipped or bent sprocket tooth.
 

·
Registered
Joined
·
2,135 Posts
quote:Originally posted by mut

How tight (or Loose) should my chain be? I threw it the other day at around 70mpg. It went to the inside but looked like it could have caused a problem if it went to the outside.

How tight should it be? Any play and all?

thanks.
betch you shit yourself too!!! deflection gauges are pretty cheap. the spec's in the manual. i know if i dropped a chain, that'd be my immediate next purchase.
 

·
Registered
Joined
·
4,508 Posts
Have you checked the alignment of your rear wheel? I run a lot more than 1/2 inch and have never had a problem with a chain jumping off. You were just riding down the road at 70mph and the chain jumped off? I'd think something else is causing it. Chain worn out? Sprockets worn out?

Craig
 

·
Registered
Joined
·
239 Posts
Discussion Starter #5
It is a cb750.

I have no idea what "window the back of the case block" means.

I looked over the engine and did not see anything unusual.

The Sprocket is worn down some. Sprocket size is my next post. I would like to maximize the pickup. I doubt I'll ever take this on the interstate. The bike is a fun commuter and mountain riding machine.

When the chain flew, I was moving down the road and a cop came around the corner toward me. I pulled the clutch to downshift and slow down ( I was 35mph over the limit and the bike did not have a seat, tailight, tags, or registration. Oh, and I don't have a license. But that has all chanegd and now it is legal. Before I get blasted, I did have full riding gear on.). When i let go of the clutch, I didn't slow down. I had just been acceperating and thought that accelerating then pulling in the clutch was the cause.

It was not scary at all, It was a non event. I thought something else happened and I was pissed becasue I thought something broke.

Mut
 

·
Registered
Joined
·
23,303 Posts
when cb750s chuck a chain the chain hits the back of the engine block and makes a hole. Check behind your motor sprocket cover and make sure you didn't breach the cases.
 

·
Registered
Joined
·
585 Posts
WOW! I once had an identical, ideal chain throw. It was on a mid- 80's Yamaha SR250, just like THIS ONE except mine was ugly and had a big milk crate strapped down to a handy luggage rack. Anyway, when I found the chain I didn't find the master link. I was a bike mechanic at the time, so only a 1/2 stupid kid. Either the master failed (it was an older chain with a "clip-style" master), or I failed to get it clipped correctly. It is possible to get that master mostly clipped so that at a glance it looks clipped, but not actually get the clip locked into place. Very dangerous.

I was going down the interstate at the bike's top speed of about 69-71mph, surrounded by 18-wheelers, when the engine suddenly revved up and I suddenly began an "unpremeditated deceleration." LOL! I did not have any damage to the bike, so apparently the chain magically flung off the back of the rear sprocket. I did look back fast enough a the right moment to see the chain fly through the air, hitting the ground right in front of an 18-wheeler that was suddenly dramatically bearing down on me....

I still thank God that nothing locked up when my chain was thrown. I am confident that I would not be here today to tell you about it.

The humble chain is a very serious thing.

What an adventure!

Mut, I am glad you and your bike both seem to be OK.

As a side note, I later sold this same SR250 to a dear friend to be his first bike. Soon after buying the bike he was driving down the interstate at about 55mph near his house and had a couch fall out of the back a pickup right in front of him. It all happened instantly, and the couch hit the ground immediately in front of my friend. The bike stopped, but he didn't. He was flung over the bars and tumbled to a stop, banged and bruised, but mostly OK. Traffic eventually slowed down, and my friend pushed the bike to the side of the road, and I think he even drove it home (even the the forks were somewhat pretzeled). It was a hit and run situation, but there were no medical bills involved, just total loss of the little bike.

Peace and grease,
-steve
 
1 - 8 of 8 Posts
Top