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1930 Big 4 'Normal' engine sounds????

Submitted by david_lawson on Wed, 24/03/2021
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So, I've finally got my 1930 Big 4 on the road.  I've taken it for a couple of shakedown rides in my local area.  Really enjoyed myself.  First ride I broke down 3 times and identified a petrol starvation issue.  I'd replaced the cork seals in the petrol tap and a little fragment of cork had lodged itself in the hole in one of the cork washers partially restricting flow.  Pain in the behind but easily rectified.  Just got back from my second ride...faultless!  I need to learn some techniques for better riding.  One that I read about was adjusting (retarding) the ignition slightly to slow the idle speed when in slow moving traffic.  This worked a treat.  As soon as I got moving I fully advanced the ignition.  First question is, is this the right thing to do or should I adjust the carb to a slower idle?  The idle speed seems great when I first set off, it was only when the engine got properly warmed up that it seemed a bit racey on closed throttle.  Any other tips, tricks or advice regarding the ignition postion during riding would be greatly appreciated.

Question number 2.  Everything about the bike seemd fine, gear change, clutch operation, a little blue haze from the exhaust.  The only thing I did notice was a noise from the upper engine.  It occurs when in gear and moving along when the throttle is close to or properly closed....so really when I was coasting to slow down a little.  The closest thing I could describe would be the type of sound a kick starter makes that has not returned when the engine fires up.  So a kind of 'rachetty' sound.  Let me stress, it wasn't as 'metalic' as a kick strater...it wasn't alarming and it didn't sound as if anything was grinding as such, but it's a sound I've not heard before, this being the first bike I've owned from this era.  I'm guessing it might be the valves or push rods or the like???  The sound didn't happen when stationary or when accelerating.  Does anyone have any views on this matter? 

Submitted by robert_tuck on Wed, 24/03/2021

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Primary chain a little slack ?,  Carb slide a little slack?  Mag chain a little---------.Dynamo brushes chattering ?. , can't think of anything else.

Submitted by richard_payne on Wed, 24/03/2021

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Odd sort of noises on the overrun would make me think of chains first too...maybe even final drive. Is it the same in every gear ? Does it change with the clutch in ?

Is the bike fitted with a speedo and if so, what sort of drive ? dry or worn speedo drives can make some odd noises.

Submitted by david_cooper on Wed, 24/03/2021

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What is primary chain tension like?  Admittedly the easy mistake to make with it is to leave the final adjustment the wrong way round so the backlash gets pulled out by the rear chain and you end up with a tight primary chain - which will cause a different set of problems.

Being side valve, you don't have all the clatter from overhead valves - but are your valve clearances correct?  Hopefully it isn't the little end...

Submitted by don_anson on Thu, 25/03/2021

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I had an M20 BSA that made a quiet rattley noise that I could only hear when idling. 

It turned out to be the valve lifter taking up the valve clearance. 

I trap for the unwary with side valve singles.

Don Anson

Melbourne. 

Submitted by david_lawson on Thu, 25/03/2021

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As part of going through the bike when taking ownership I checked the final drive and primary chain tensions.  They were more or less OK but I had to take a bit of slack out of the final drive.  I will check if the noise happens when the clutch is in.  When riding, the sound seemed to come from the right side of the engine (so the opposite side to the primary and drive chains).  Perhaps it might be the magneto chain?  I've not been into the mag chaincase yet and so I've looked in my books and it says the mag chain should not be too tight and to avoid a 'bending moment' on the armature spindle and that it should be 'perceptibly slack' in all positions.  All might become apparent when I take the cover off and have a looksie, but the manual seems a bit vague to a novice like me, especially when the manual gives clear measurements for the slack on the two other chains.  Can anyone offer any advice on how I tell if the slack on the chain is correct?

...can be a little difficult to gauge but the key is that it remains a minimum of a "little"slack in all positions.  This mean it may be a bit more slack at  various points as you rotate.  Check  the  boss  that accepts the cover screw for  abrasion...

Submitted by richard_payne on Thu, 25/03/2021

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Is it fitted with a Magdyno ? Could it be damage to the dynamo drive gear that rides over the tooth form on the over run ? Otherwise it probably means looking inside the timing chest.

 



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