Variable Chain Tension

[onesea]

Ok Honda CBR 125 cc bike chain tension changing as back wheel turns…
Why?
Chain. relatively new, and new chain did not resolve,

Front sprocket? looks ok not visibly of center,

Back sprocket off center? Cush drives?

Being a young riders I have suspicion that it has been ridden with back axle loose than it should be… Following early chain tensioning.

 

Anyone got a clue?
 

[Mickly]

A bent gearbox final drive shaft?

[iangaryprice]

How much does the tension vary? They are never perfect.

Find the tightest spot then set the chain tension.

Ridea few miles then check again.

If it is still bad you will need to check the run out of the sprockets.

To check the runout, fix something near th esprocket you yuo have a gap of about 0.5-1mm. Then slowly rotate the sprocket and watch the gap. Repeat for the other sprocket. This will tell you if the sprockets are runong true.

If they are not running true check the shafts in a similar manner, you may need to remove th esprockets to do this.

If sprockets a and shafts are OK, then your cahin is at fault.

 

[onesea]

58 minutes ago, Mickly said:

A bent gearbox final drive shaft?

That’s was the answer I had been thinking but didn’t want to hear

 

[fastbob]

2 hours ago, onesea said:

That’s was the answer I had been thinking but didn’t want to hear

 

Nah , you always get a tight spot , or a loose spot depending on how you look at it , on small bikes . How is the output shaft going to be bent ? It spins round so it's not being pulled in any particular direction . Just buy a higher spec chain . 

[onesea]

Got to look at this today.. On to paddock stand, chain going from tight to slack.

Marked cogs, turned not convinced about repeatability.  Front cover of no detectable movement.

 

Back wheel off...

I could get screwdriver in gap on oneside of wheel but on the otherside, I was struggling to fit it in I gave it bit of a wiggle...

 

A chunk fell out like it was made of cheese.

The mark made in the grease was on the tight spot.  So it sort of makes sense.
 

Second hand sprocket carrier ordered, if it resolves issue we will fit new chain and sprockets.  

 

It's it that easy to knock a sprocket of center?

 

 

[Mississippi Bullfrog]

By "screwdriver" you mean "paint stirrer."

[billy sugger]

That's a multi tool. Lever, chisel, paint stirrer, tin opener and scriber

[Fish]

I'm guessing that cleaning isn't a regular thing

[onesea]

37 minutes ago, Fish said:

I'm guessing that cleaning isn't a regular thing

He’s 17 and has me as an example, he really doesn’t stand much chance

He also rides it daily in wind & rain even Eunice didn’t stop him
 

His maintenance and repairs are  improving as that’s about the only thing that stops him riding.  First time he’s been to me with a problem in months which is massive improvement from weeks…

[onesea]

So rear sprocket carrier replaced and an improvement maybe...  It's kind of subjective but it's still not right.

 

Could this be a miss match of chain and sprockets and replacements might resolve?

You can see the cleaned link that highlights the right spot.

 

 

 

 

 

 

 

Sorry to disappoint the followers of my red handled multi-tool it makes a brief appearance but does not have an active part during filming. 

[billy sugger]

Vids showing as private so unable to view

[onesea]

29 minutes ago, billy sugger said:

Vids showing as private so unable to view

Think I fixed it…

[Stu]

I think its the chain! 

 

A good way to check is to measure a set amount of links about 15 would do 

 

Measure 15 links in different locations and see if you get the same measurement 

[Bender]

Some of those links don't move and sit properly on the sprocket, looks like chain to me too. 

[onesea]

19 hours ago, Stu said:

I think its the chain! 

 

A good way to check is to measure a set amount of links about 15 would do 

 

Measure 15 links in different locations and see if you get the same measurement 

You should know I am not that technical I just ordered new chain and sprockets.

[onesea]

On 25/09/2022 at 15:51, onesea said:

You should know I am not that technical I just ordered new chain and sprockets.

Well it seems to work new chain and sprockets installed and he’s ridden off into the sunset well grey clouds and rain….