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On checking you chain clearance...do you press down lightly on the lower run of the chain...so the top run pulls taught....then take your measurement...

And again push the chain up tiill the top run goes taught...Wonder how much pressure you apply to the chain...never seen that mentioned.


Recently bought my 1st ever motorcycle...a humble 1969 BSA Bantam B175...I am enjoying using my Bantam so much...does all I need.
My car that I use daily is an old series Landrover that I bought new 40 years ago and has just become tax free.
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Not sure about Bantams but usually the way to adjust the rear chain is to place the bike on the centre stand so the rear wheel is raised. Then check for free play on the lower run by pushing lightly upwards and then downwards, note the difference and adjust accordingly. You dont need to worry about tension on the upper run.

Last edited by gunner; 10/12/20 7:06 am.

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I'm with gunner on this. Just tug the chain up and down at the center of the run; total movement should be 1 to 1-1/2 inches. You may ask, how hard do you tug? That's hard to answer; I'd have to say, not too hard. You develop a feel for it after a while.

Adjustment should be done after lubrication, and check the tension at various points. Set your adjustment at the tightest point.


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If the chain on a Bantam is lighter than that on an A65, the designated free play may be less than the 1 to 1-1/2 inches I quoted.


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I always check this while sitting on the bike off the stand. Reach down and check in the middle of the chain run, 3/4".


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Sorry guy its prob me not explaining myself....its the amount of pressure to put on the chain with your fingers I am trying to get my head around.

Is it lift/push down on the chain with the lightest finger pressure...or till say the top run and lower run are taught.

Its easy to put more finger pressure on the chain and end up with a tight chain.

The bike I am at present working on is not a Bantam...but the same question no matter what bike I would be working on would be the same.

I can get the req figs from the manual.


Recently bought my 1st ever motorcycle...a humble 1969 BSA Bantam B175...I am enjoying using my Bantam so much...does all I need.
My car that I use daily is an old series Landrover that I bought new 40 years ago and has just become tax free.
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Its not a precise check for the chain. And as the chain wears check for play at the tight spot. The key here is, not to have it too tight.


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I agree with DavidP. Sit on the bike and check drive chain free-play with your weight on the bike, or have someone of your approximate weight sit on the bike while you check it from the side,

(this applies to swing-arm frame bikes, rigid frames don't have this problem.)

Here is why you do it this way:

The swing arm travels through an arc as it is doing it's job.
The gearbox sprocket is located forward of the swing arm's pivot point, the rear wheel sprocket is located at the rear end of the swing arm.
Because of the distance between the gearbox sprocket's center and the center of the swing arm's pivot axle, the distance between the
center of the gearbox sprocket and the wheel sprocket will not be consistent as the swing arm moves up and down.

If there was a sprocket on a jack-shaft running through the center of the swing arm's pivot point, and TWO chains were used, one connecting the gearbox
sprocket to the one on the jack-shaft, and a SECOND sprocket on the jack-shaft connected the rear chain to the rear wheel's sprocket, the rear chain
would always operate at a consistent length between those two points, and except for normal wear, chain slack would not be a problem.

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Put an egg in your palm, press on the chain with the egg, if the egg breaks you are pressing too hard.


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a raw egg or a hard-boiled egg?

soft-boiled perhaps?

details are important, gavin


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If you want a tighter chain, a guinea fowl egg has a very thick shell.


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A free range brown egg from a Red Rocket ( use leghorns for lesser marques) , one day old, held lengthwise. not cooked.


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Sounds like the bottom line is, "no harder than you want YOUR chain pulled".


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One thing's for sure, if you downshift and you hear some clattering under you the chain is too loose and slapping your chain guard.


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Make sure the engine is stopped and wheel not turning else you might end up with scrambled egg.


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Just move the chain up and down with light hand pressure.

In the manual for a 650 Triumph it says: The correct chain slack is 3/4" with the bike on its wheels and the chain at its tightest point or 1 3/4" with the bike on the centre stand and the chain at its slackest point. The bit about tightest and slackest points has always confused me.

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Thankyou Dave...thats interesting them giving on stand and on wheels...my bike calls for it only to be done on its wheels...supported by other means than the side stand.

Guys its just the amount of presure I want to know....A lot say press the lower of chain down till you see the upper run start to lift....note position....then lift the lower chain till you see the upper run start to lift...note postion....difference in those 2 is the free play.

I am going with that.

Thankyou everybody.


Recently bought my 1st ever motorcycle...a humble 1969 BSA Bantam B175...I am enjoying using my Bantam so much...does all I need.
My car that I use daily is an old series Landrover that I bought new 40 years ago and has just become tax free.
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I just lift the chain up till it won’t lift any note without effort (finger pressure if you will) Turn the back wheel and check it at several points (start near the split link so you know where your at) Some points will be tighter than others, keep going until you’ve gone all the way around. Adjust it according to its tightest point.

A lot of this is based on suspension and rider weight, if you have stiff suspension and a light rider the swing arm isn’t going to move much, if you weight as much as the bike or carry a pillion and have suspension like a pogo stick then the swing arm will move a lot more and the chain run will require more slack.

As noted earlier, the tightest point on the chain is when the wheel spindle, swing arm spindle and gearbox sprocket are all in alignment. So the more compressed the suspension the tighter it gets.


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Thanks for clearing the tightest point bit up.

I infer from that that he slackest point on the stand means the swinging arm is hanging on the shocks so the chain is as slack as it can be.

I always thought that it meant to revolve the rear wheel until the tightest point is found and to adjust at this point (the difference being due to uneven wear).

Last edited by dave jones; 10/14/20 5:26 pm.
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Originally Posted by dave jones
I always thought that it meant to revolve the rear wheel until the tightest point is found and to adjust at this point (the difference being due to uneven wear).


I’m sure that’s what I wrote?

If you still take your bike to an MOT station and the tester does more than shoot the breeze with you whilst having a woodbine, then checking the chain tension is one of the things that is (or should be) checked on the MOT. The above method I gave is what we were shown how to check on the DVSA training I had.


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Originally Posted by dave jones
Thanks for clearing the tightest point bit up.

I infer from that that he slackest point on the stand means the swinging arm is hanging on the shocks so the chain is as slack as it can be.

I always thought that it meant to revolve the rear wheel until the tightest point is found and to adjust at this point (the difference being due to uneven wear).

You're right Dave, the "tightest point" thing is to allow for wear. That is, chains tend to wear unevenly, more in one spot than another. A brand new chain should feel the same all the way around. (If your chain varies wildly from one spot to another though, it's time to replace it.)


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When sitting on the bike: for pressure, thumb down and one finger up. If you dislocate your thumb when pushing down then that's too much pressure. Then use the petrol that leaks from the carb during tickling to clean the grease from your digits.

The true enthusiast will remove the rear dampers and check chain tension through the full range of swinging arm movement.

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"The true enthusiast will remove the rear dampers and check chain tension through the full range of swinging arm movement."

I think you spelled idiot incorrectly, you have it as enthusiast........................

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Sorry, Allan. I did repeat what you said. I completely missed your post as I was concentrating on the one above.

Dave

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Once again, something so simple made so complicated.


Bill
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