The BSA A7-A10 Forum

Technical => A7 & A10 Engine => Topic started by: Zander on 12.06. 2017 07:08

Title: Timing Gears
Post by: Zander on 12.06. 2017 07:08
After assembling con rods and crankcase assembly, I turned my attention to the timing gears.  First off, getting the cam shaft gear on wasn't the easiest job I've come across - it was piggin tight and difficult to hold away from the bushes during assembly. Once on, having fitted the idler gear  I checked that the two gears meshed and ran smoothly.  They don't, and no amount of inspection and careful dressing with a diamond needle file sorted it.  I spent a lot of time on this, and for the first time with this engine, was more than a little jarred off!  Having said that, I could have caused the problem myself when I put the cam gear on, despite the fact that I was very careful.  I'm aware that the idler is supported by the timing side case, but it's a good fit in the bush so for test purposes it should run ok just being located in that.  Aside from the meshing problem both gears show signs of age and according to the Draganfly site, they have them in stock, but don't have the crankshaft, one, so as mine looks ok, I'll have to make do with what I've got and buy just the two.
Re the cam shaft, I'm surprised it has such a lot of end clearance.  Am I correct in assuming it finds it's own position once running and under the load from the valve springs? 
Title: Re: Timing Gears
Post by: duTch on 12.06. 2017 07:32

 There is a very recent thread on this very issue; if you do a quick search should find it
Title: Re: Timing Gears
Post by: duTch on 12.06. 2017 07:35

 Try here :-
 https://www.a7a10.net/forum/index.php?topic=11791.0  (https://www.a7a10.net/forum/index.php?topic=11791.0)
Title: Re: Timing Gears
Post by: Zander on 12.06. 2017 08:13
Doh! What a pillock  *bash* I'd forgotten about the cork!! Problem solved.  *thanks*
Title: Re: Timing Gears
Post by: muskrat on 12.06. 2017 08:38
G'day Zander. The key coming adrift on assembly could have damaged the bush. Even without the inner cover on the gears should mesh.
 The cork doesn't rectify the problem. Due to ware of the thrust face of the bush or incorrect bush's fitted, camshaft endfloat is excessive. On extreme cases I have seen the followers try to pick up on the adjacent cam lobes. These motors had in excess of 1.5mm endfloat. You should be safe at 0.5mm but it needs addressing at next strip down.
Cheers
Title: Re: Timing Gears
Post by: Zander on 12.06. 2017 12:46
Thanks, muskrat.  I obviously failed to think it through, yesterday - I was sidetracked by working on my '72 Guzzi 500 as well, but no excuses, I should have  concentrated properly. Fortunately, I gave myself a break until I was in a better frame of mind cos I think my problems may have in part, been self inflicted.  I've ordered replacement gears and will take it from there. Going for a ride tonight, and again all day tomorrow so will come back to it refreshed and raring to go, complete with thinking cap! *wink2*
Title: Re: Timing Gears
Post by: coater87 on 12.06. 2017 15:16
 Hi Zander,

 I had trial fitted the bottom end together just to get an idea of what might cause me trouble. The camshaft timing gear was really the only nasty looking job .

 So besides the oil pressure release ball, the camshaft was the first thing I installed. It went pretty easy at that point of the rebuild.

 It added a little difficulty later when when fitting the case halves, but much less than trying to fit the cam gear with the cases assembled.

 Lee
Title: Re: Timing Gears
Post by: Zander on 12.06. 2017 15:30
NOW he tells me😄 Why didn't I think of that?!!!
Title: Re: Timing Gears
Post by: chaterlea25 on 12.06. 2017 21:46
Hi All,
If the cases are together, and the cylinder is still off, you can place a suitably sized
block of aluminium between the most left hand cam lobe and the crankcase that keeps the cam all the way to the timing side
This will keep the cam key away from the bush while pressing the pinion on the cam
Repeating myself there should be minimal endfloat when the cam gear is on fully,
If theres excess endfloat with the pinion tight then the cam bush(s) need attention

John
Title: Re: Timing Gears
Post by: duTch on 12.06. 2017 22:28

 In Anji's post of a similar issue (as posted above), I started to write " when doing my camshaft pinion (after doing new bushes), I put the barrels on without the lifters/cam-followers, to have a look down the pushrod tunnel to see where the cam sits in relation to the lifter bores, and I was happy to see the cam nice and central with the cam flange hard up on the bush"....but I decided that would be a pointless comment so deleted it.

 Now I think it's still pointless, but worth doing just as a double check...


 
Quote

 Try here :-
https://www.a7a10.net/forum/index.php?topic=11791.0
Title: Re: Timing Gears
Post by: bikerboy on 13.06. 2017 00:54
I have to ask myself why you never fitted the camwheel before you put the cases together?

That way its pretty easy really just a firm tap with a mallet
Title: Re: Timing Gears
Post by: Zander on 13.06. 2017 07:15
I have to ask myself why you never fitted the camwheel before you put the cases together?

Lack of thought is why!  I'd forgotten how tight it was to get off, and I'd even made an extractor to remove it, which makes it worse!  The barrels are still off, so I can take the necessary steps to fit the gear without damaging anything (hopefully)! .  Regarding camshaft end float. all of the cam bush faces and diameters are in good condition so I don't think I have any problems there, but will check end play when the gear is on and take it from there.  all comments and advice gratefully received - thanks to one and all. *wink2*