errr...... best to measure it before changing it!
Here's something I posted years ago:-
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Discovering the cause of chain tension problems
You can easily check all the rotating items on the 'driven side' as follows:-
1) Remove engine-side wheel
2) Remove chain
3) Get a wire coat hanger, straighten it, clamp ONE end of it (with mole grips) to a SOLID part of the kart and bend the 'loose' end round to act as a 'pointer'
4) Bend the pointer so that it points EXACTLY at the SIDE of the TIPS of the sprocket teeth
5) Spin the axle
If the distance/position of the sprocket changes by more that 0.5mm in relationship to the pointer..... you have a problem.
6) Point the pointer at the BOTTOM of the Teeth (i.e., the bottom of 'valley' between each pair of teeth.
7) Spin the axle and see how the relationship changes.
8) Now bend the pointer to point at the TOP of the sprocket.
9) Spin the axle and see if the sprocket is bent, side-to-side
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* Nota Bene!!! *
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If you have ANY 'excess movement' in ANY of the above tests, it may NOT be the SPROCKET that is at fault, so, if you DO note a problem, CONTINUE with the 'testing' until you DON'T find a 'problem'
10) REMOVE the sprocket
11) Bend the pointer to point at the side (and then the TOP) of the sprocket carrier
12) Spin the axle and note the relationships. Because the sprocket carrier is smaller than the sprocket, it only needs a MUCH smaller 'error' to produce BIG faults at the 'chain', so, you now need to be sure that and 'movement' is LESS than (say) 0.2mm.
13) If the 'sprocket' showed a 'wobble' but the carrier does NOT, then the problem WAS the sprocket! If it DOES still show a wobble, it COULD be the carrier or it COULD be the axle so you MUST do the next test to eliminate THAT possibility
14) Remove the sprocket carrier
15) Bend the pointer to point ACCURATELY at the axle.
16) Spin the axle.
17) The axle is VERY much smaller and thus if you find ANY discernible 'wobble' in the axle, then that is enough to cause the problem!
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Doing that lot has tested and eliminated each stage and tested each component. However, if the FIRST three tests show no 'run-out', then the axle/carrier/sprocket are NOT the problems!
18) It COULD be the DRIVE sprocket or the crank shaft or the bearings. You can (again) use your 'pointer by pointing it at the teeth, valleys and crankshaft tip and rotating the engine. This will show if you have a problem at THAT end!
19) Check your AXLE BEARINGS to make sure THEY are not loose or worn! Do this by JERKING the axle up-and-down and then side-to-side to see if there is excessive movement.
19) Finally, the chain. If you STILL have problems, refit the chain, mark the DRIVE AND DRIVEN sprockets (with marker pen or tape) and mark the Chain (marker pen or tape) and rotate the axle a LARGE number of times 'feeling' for the 'tight spot'. Note the position of the sprockets and chain at EACH tight spot. If it coincides with the rotation of the DRIVEN sprocket.... it's the DRIVEN sprocket of axle or carrier. If it coincides with the rotation of the engine, it’s the Crank or DRIVE sprocket or engine bearings, if it coincides with rotation of the CHAIN..... then it DEFINITELY is the CHAIN!
That should have eliminated 95% of the possible problems and whatever remains is PROBABLY the problem!
Ian
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axle by 'SGracing' (26 Apr 2015 @ 19:47)
