Motorcycle gearbox - Examine the output shaft splines

How to check the gearbox output shaft splines - the more they are worn the worse it will be for the gearbox and chain and jerky riding.

[@Daschickenify]

I just found out my virago 250 has this problem, it got pretty bad before i finally discovered what it was. The part of the shaft that the sprocket rides on is probably 20% gone. Rather than put it back together and sell it on to the next sucker, im going to replace it! Be a good previous owner!

[@EngineTuning]

Good move! Keep the receipts, and raise the value of the bike ;)

[@robinhood8119]

Interesting ,thank you,i hope you will make more videos about am6 engine.

[@johnnyt7965]

If you are replacing the output shaft, it looks like it's a total rebuild of the engine. I don't see any way of keeping the drive sprocket from wearing down the shaft again. Is this correct?

[@EngineTuning]

Yes it's a rebuild job. RE the longevity... Fundamentally, the change from no drive to drive, must force the shaft splines against the sprocket splines. Any gap, or play, between the splines exasperates the problem. The splines momentarily accelerate in free space, before slamming into the sprocket. Therefore, once play is present, the splines degrade at an accelerating rate. From this, we can see that we need the tightest fit possible. This neatly explains the term 'blueprinting an engine'. Manufacturing produces a small to large shaft - within tolerance. Similarly - a small to large sprocket ID. Bad luck will get you the smallest shaft OD, and the largest sprocket ID. You actually need the largest shaft OD, and the smallest sprocket ID. Race engineers scour the parts bins to find those perfect matching components. ---- You can ameliorate the problem by having the output shaft peened. This will increase hardness and carry more lubricant. You could also buy the bits from a retailer in person. This would increase the cost, but you could then find the shaft with the largest OD, and simply try their stock of sprockets on the shaft, to find the tightest fit. :)

[@Snurre86]

What happens if you just run it with that slack?

[@EngineTuning]

It just gets worse... for everything. Every time you throttle down, and then throttle up. the shaft slams into the pinion. The pinion jerks, and stresses the chain... and that stress is transmitted back through the gearbox.

[@simonrice3036]

I have been told the am6 engine needs building with the engine in gear is this correct?

[@EngineTuning]

This statement makes no sense. Take your time. Be careful. 😎

[@simonrice3036]

@@EngineTuning iv build engines plenty of times but it's my first time on an am6 engine was told if I select neutral before assembling the rest of the engine once complete it won't select gears completely if at all. I'm guessing this is not the case

[@EngineTuning]

@@simonrice3036 Correct!

[@porcgardenEducational]

Cheers bro u have the same as me I have concluded my problem cheers very much help

[@EngineTuning]

That's great porc garden. The shaft circlips are a pain to remove and fit, but it is an unavoidable task.

[@drewtaylor6623]

I've noticed on my Honda cbr 650f when I changed the sprockets mine has about a hair line movement rotational movement . Is that something to worry about? It also had alllot of surface rust stain . so I tried clean it up the best I could with a cloth and I refitted the sprocket with some Cooper greece. My bike is a year old with 10k on the clock I do ride it kinda hard sometimes as it's restrcted .It has just under a year left on warrenty so I thought I would check again in 4 months time to see iff it's gone worse . Do u think I'm worrying to much ?

[@EngineTuning]

You must judge the play, though from your description, it doesn't sound bad. In principal, the more mileage ridden the more that the play between the pinion and shaft splines will increase. However, careful riding, and a correctly tensioned chain, will reduce this wear to an insignificant amount. It is the hammer effect that does the most damage. Hard acceleration from rest causes the splines to go from zero compression to high compression. My old Royal Enfield Crusader had a rubber buffer in the rear sprocket. This was a great design, as the rubber took the impact, protecting the chain, pinion, and shaft splines :)

[@drewtaylor6623]

thanks allot for the reply ! do you think the movement, I'm talking about could litterly ,just be the tolerance it needs just so you can accturaly attach the sprocket? as the movement is small. I could even send you a video of it on a email iff you could please kindly see for yourself ? I know moveing parts on anything only go worse after time but I just don't half find it bugging at the back of my mind. knowing my luck it would go bad as soon as my warrenty ends. It's just a worry for me incase it is just going to go worse it's very petty how I'm worrying about this on a year old bike I just want be able use it without thinking I may need rebuild the whole engine in anouther 20k :(.... also I believe the hammer effect is when you just snap the throttle back in a quick motion from low revs without the smooth motion??. But my guess any sort of riding other than sensible isn't going do it no good. Is there any chance that the movement I can see will just stay how it is ? How common is this problem? Sorry for all the questions I appreciate the help thanks allot Drew !

[@EngineTuning]

Honestly, I don't think that you need worry. You could buy a new pinion and the play could be worse, the same, or tighter. Note the mileage, and check it every 1000, to see if it is degrading.

[@drewtaylor6623]

Ok yes thanks allot . I am just being picky to be honest as it's not even 1mm of movement. Its just made me worry seeing the surface rust and the fact splines have been known to go bad sometimes like on this video.. But my movement must be the tolerance so u can accturaly get a sprocket on and off. I understand that fast starts such as pinning the throttle back from zero without being smooth can be bad . What i would like to know is iff it's also bad, iff your in let's say 4th gear at around half throttle, then you just bring the throttle back to zero without slowly bringing it down is that action also bad for this ? Or is it just when you get on the throttle to snappy to accelerate that it can cause the damage?

[@drewtaylor6623]

In shorter words is it when you just throttle up hard it causes the compression to be high? Or does it also cause high compression when you throttle down fast ?

[@sanjibsonowal4558]

good one........ im going to change mine 2

[@EngineTuning]

Nice move ;) When there is a lot of play, the impact will affect the life of the gears, pinion, chain, and rear sprocket.

[@moforockband]

Suzuki ones are notorious for wear. Just fitted a new one and even after greasing, new sprockets etc etc there is play on it after 1000 miles! You have to use common sense. What can slow down the process is using the rubber damped front sprocket.