The BSA A7-A10 Forum

Technical => A7 & A10 Engine => Topic started by: ellis on 21.04. 2016 07:41

Title: A10 Valve clearances
Post by: ellis on 21.04. 2016 07:41
 Could anyone tell me the correct way to adjust the tappet clearances on a Feb 1960 A10 s/a Eng number  DA10.16377 Frame number GA7.5279 as Haynes Manual seems to contradict itself. i.e. Engine position-valve position and the sequence to adjust the valve gaps and clearance settings properly.  *help*
Title: Re: A10 Valve clearances
Post by: kiwipom on 21.04. 2016 08:15
hi, guys/Ellis, when the piston is at T.D.C. on the firing stroke the valves should be fully closed that is the time to adjust tappets on that side only, turn engine to the same position on the other side and do the same on that side,  that's how I would do it,  cheers
Title: Re: A10 Valve clearances
Post by: Klaus on 21.04. 2016 08:41
hi, guys/Ellis, when the piston is at T.D.C. on the firing stroke the valves should be fully closed that is the time to adjust tappets on that side only, turn engine to the same position on the other side and do the same on that side,  that's how I would do it,  cheers

Oh that's new for me *conf2*
I thougt the BSA cams has a special loop profile with a little ramp, so I adjust the the valve clearence when the oposite side is fully opened. Allways the inlet or the exhaust oposite.

cheers Klaus
Title: Re: A10 Valve clearances
Post by: cyclobutch on 21.04. 2016 08:51
Err - I just stick something down the plug 'ole and turn the motor gently whilst watching the valves ... until the piston is coming up with both closed. When the stick stops moving it's time to set the clearances. I use a stick with something on the back such that if I were to slip it wouldn't fall all the way in (fave is a T bar screw driver). I do that for all my bikes.
Title: Re: A10 Valve clearances
Post by: Greybeard on 21.04. 2016 09:15
My method: when tappets are rocking, (one closing then other opening) when a piston is at TDC. Adjust the other side. Getting the engine to the correct positions is easy if the machine is on the centre stand and you put the bike in fourth gear and turn the back wheel.
Title: Re: A10 Valve clearances
Post by: duTch on 21.04. 2016 09:29


 I don't concern myself with TDC, but do what I think I interpret as what Klaus does; left ex/in.full open, adjust right side.
 Right ex/in.full open, adjust left side.

 Think a full crank Rev per adjustment. Think laterally.

 GB rounded me up, much the same
Title: Re: A10 Valve clearances
Post by: Greybeard on 21.04. 2016 10:35
OK, so I may have it wrong; the following text is copied from the BSA workshop manual.

The cams are of special design. Because of this it is essential that when checking or adjusting the clearance of any valve it should be closed, with its tappet on the base circle, or neutral portion of the cam. To obtain this position for the drive-side inlet valve turn the engine until the gear-side inlet valve is fully open. Similarly, to set the gear-side inlet valve in the correct position, turn the engine until the drive-side inlet valve is fully open. Follow the same procedure exactly for the two exhaust valves.
Title: Re: A10 Valve clearances
Post by: muskrat on 21.04. 2016 14:12
Yep L inlet fully open adjust R inlet and so forth.
Cheers
Title: Re: A10 Valve clearances
Post by: RichardL on 21.04. 2016 15:38
Hmm. I just adjusted my valves by my typical method (TDC-based) and my bike  seems to be running great. I don't think I'm prepared to pull the valve covers right now in seach of whatever improvement might emerge from the adjust-opposite-of-open method. Does anyone think a lowly hobbyist (as opposed to racer) such as myself would detect the performance difference, if any.

Another side of this is that confirming fully open is a bit trickier than the stick-in-a-hole method (to which we are anthropologically inclined) to find TDC. Is everyone who is using the adjust-opposite-of-open method just eyeballing the movement of the rocker or is anyone using a dial indicator?

Richard L.
Title: Re: A10 Valve clearances
Post by: ellis on 21.04. 2016 21:02
Thanks for all your replies, I think I will go for the one down set the other which seems the most popular setup.  *thanks*
Title: Re: A10 Valve clearances
Post by: muskrat on 21.04. 2016 21:09
G'day Richard.
The TDC method is OK. There is a slight chance the followers are just starting on the quieting ramp and this will give you a slightly larger gap (only a thou or two).
Cheers
Title: Re: A10 Valve clearances
Post by: KiwiGF on 21.04. 2016 21:53
I just turn the engine over and watch a valve open then close and then turn the crank a little more to ensure the follower is on the base circle part of the cam, and then adjust the clearance of that valve. No messing about finding tdc.

The base circle makes up the majority of the cams profile and it should not be hard to ensure the follower is on the base circle as opposed to the lifting part of the cam.

works for me anyway..... *smile*
Title: Re: A10 Valve clearances
Post by: duTch on 21.04. 2016 21:57
 Richard, in addition to what Musky said, I do the one open adjust the other partly because I'm lazy and want the quickest way, and it seems most logical as that's the way the cams are (valve is closed longer than it's open), and I figure it can't go wrong *beer*

 Having said that, I still always lose track of which one I'm up to aand usually do them a couple of times *eek*

 Kiwi rounded me up there, and said much as I did (except the lazy and last bit *smile*)
Title: Re: A10 Valve clearances
Post by: cyclobutch on 22.04. 2016 11:24
I'm gonna stick to my stick. I've yet to burn out or clout valves with my method.