Idle gear

[Jasonash]

Good evening all I am new to this web site and pretty new to a10s, I have brought another a10 and found it to have a sr bottom end and a7 barrel and head with a short stroke conversion, which I don’t want so putting super rocket top end back on , I removed the inner timing cover today and when it came of the idle gear came of but the cam or crank did not move do you think I could just put it back and should be ok ,

Would like your thoughts.
Thanks

[bsa-bill]

No, use the timing marks, presuming you have the head off
You will want to time it anyway

[Jasonash]

No not took head of yet because I still putting bit together it was running sweet I just wanted to change the inner timing cover, so what you think.

[JulianS]

You must align the timing marks, it is the only way to be safe from damage.

[bsa-bill]

Ok, if you are 100 % sure nothing has moved you can just slide the idle gear back in, the risk is that if anything has moved the valve timing will be out and could result in a bent valve next time it is kicked over.

[Jasonash]

Thanks all will let you no tomorrow.

[duTch]

 If you're 'fairly' sure the gears didn't move- (sometimes the valve-spring pressure pops the cam down a ramp and it moves one way or t' other), the idler can be reinstated as-is, and the crank & Cam marks should align within a couple of crank revolutions (maybe 4 strokes max-2 full cycles? nah I reckon 2 ), at which point the idler gear can be removed and reinstalled on all the correct marks.

 **The crank and cam align every two revs, but the idler only aligns something like every 97 revs (haven't done the mathematical calculation yet)

 Be *very* careful doing it in case anything did move...or you could bend a valve, but should be within safe parameters.

 Before moving anything, and to be a bit more certain you could do a tooth count from alignment- if yea kenows what I mean..

[RichardL]

Jason,

Personally, I would not trust putting back the engine without aligning the timing marks, but I'm chicken. You already have the timing cover off, so if you don't know how to time the engine, this is a good time to learn. Not saying it won't be challenging the first time, but lots of folks here can offer advice on the fine points.

Richard L.

[Greybeard]

Welcome Jason 

[duTch]

 I should point out what is probably obvious to most but not all,  that any potential damage is most likely to be done as the pistons approach TDC/timing marks, which is (should be) fairly easily monitored...

[bsa-bill]

any potential damage is most likely to be done as the pistons approach TDC/timing marks, which is (should be) fairly easily monitored...

Granted - that is in a perfect world populated by young folk with good memories 

[muskrat]

G'day Jason.
You MUST make certain the marks line up correctly. Do NOT assume nothing has moved. Remove the dynamo drive sprocket and remove the idler. Check whether the pistons are on the up or down stroke by turning the crank pinion clockwise just a little (screwdriver down plug hole). If on the up stroke turn it anti-clockwise or if on the down stroke turn clockwise till the pistons are well down the bore. Now turn the cam pinion till the mark is pointing to the center of the idler hole. Now turn the crank till its mark is also pointing to the idler hole. Now insert the idler, both the crank and cam pinions may need a little turning to line it all up.
The reason for moving the pistons down the bore is that if the cam is in a position where a valve is at full lift and you turn the crank it WILL bend a valve.
The down side is after all that the ignition timing might be 180 out (just swap the leads over).
Cheers

[bsa-bill]

Do NOT assume nothing has moved.

That is the pertinent line

[duTch]

 

Granted - that is in a perfect world populated by young folk with good memories 

 Fairly much *note to self*... (me)

 Given that the inner cover was/is already off for my version, El Musko's version is more convincing- I was a bit lazy...

[Jasonash]

Put cover all back on bike started and running ok ,thanks for all reply to this post.