HELP! Bottom end noise

Information relating to the Matchless G85 500cc Heavyweight, AJS 7R, Matchless G45 and Matchless G50
Matchymarty
Member
Posts: 202
Joined: Sun Oct 25, 2015 8:19 am
Location: AUSTRALIA

HELP! Bottom end noise

Post by Matchymarty »

Hi all, just put a new big end in father in law's '49 350 Compy and on start up, a 'clatter' emmitted rather loudly from somwhere down below. I thought it may have been the timing chain, and re-adjusted it, then the noise went away with engine warmth and oil flow it seemed.

On start up from cold today, the noise re-appeared and now i'm quite concerned. It seems to be coming from either the bottom end, or, cam area. Any ideas? I couldn't be 100% sure, but, I think the noise was louder on the cam side. It seems to disappear with higher revs and also with i assume, oil flow etc as wee test ride did show up the noise.


Hoping it's not the big end?? Arrgh!
SPRIDDLER
Member
Posts: 8542
Joined: Wed Sep 01, 2004 1:00 am
Location: WEST SUSSEX UK

Re: HELP! Bottom end noise

Post by SPRIDDLER »

Crumbs, Marty, that's a difficult one to answer. I'm just passing time waiting for a visitor so can throw in a few thoughts but I think you'll have to use the a listening stick to more precisely locate the noise....Could be many and all sorts of things but if the new (?) big end felt o.k. when you fitted it it will hopefully not be the problem. Did you replace any other major parts: Bearings, flywheel axles, valves, springs, bushes.......?
Fitting a new big end is quite a demanding job; splitting the flywheels, removing the crank pin, refitting and truing/balancing the flywheels..................

Assuming the noise IS coming from the timing side:

1. Is oil returning to the tank? With th'engine ticking over a series of bubbly spurts is all you'll get after th'engine has run for a minute or so, not a continuous flow.
2. Is the oil pump guide screw correctly fitted? e.g. reduced diameter end in the holder.
3. Are the pushrods still in place or has one settled down with a large (20 thou or more?) clearance.
4. Did you establish the correct crankshaft end float?
5. Have you fitted the valve cam and mag drive sprockets in their correct positions? They are not interchangeable, so the mag chain could be clattering against/within its housing even though it is tensioned correctly.
6. Do the cam gears have the correct (i.e. virtually Nil) shaft end float? Too much can cause a fairly loud metallic rattle/clatter. It is mostly noticeable at low revs or when easing th'engine over with the kick-start.
7. An air leak in the oil pump end covers will mean that it will take a while for pressure to build up and oil to circulate every time you start the bike after a rest of a few minutes.

That'll do for now. We won't even think about the primary side just yet.
'There is a tide in the affairs of men
Which taken at the flood............'
Matchymarty
Member
Posts: 202
Joined: Sun Oct 25, 2015 8:19 am
Location: AUSTRALIA

Re: HELP! Bottom end noise

Post by Matchymarty »

Spriddler,

Yes, just put in a new crank pin and big end. Had help from an old fella who's done over 100 of them. I was helping Father in law and other old dude do it, but, didn't get to see them put the crank and fly wheels in the cases. NOT sure if they soaked the big end in oil before putting it in or not, but don't suppose it would have done too much damage if they didn't ... after all, only takes a minute or 2 of 2000rpm to get oil thru.

1. OIl is returning to tank well. as it should.
2. Oil pump screw is correctly fitted. - Old fella with 100 builds experience did that bit too.
3. Father in law rang tonight to tell me he had no compression today when he went to restart. He adjusted Intake pushrod. From that I gather that it was too tight, and held open the valve - ie,. no compression. At time of first start, push rods were well adjusted and turned freely with engine running.
4. Crankshaft end float? Again, I didn't see this part of the build. But I suspect not. The old fellas don't believe in precise tolerances like 'normal' people do.... ie "ooh when we were racing we would have just put new bearings on this crank pin and thrown it back in..." even though the pin was pitted badly and shot to hell - hence I bought a new one for him. :rofl:
5. We checked the mag chain. I suspected the noise was the chain slapping, and well, it wasn't. we still tightened it up a tad though to be correct. Did we put the cam gears in correctly? I think so. THough, I'm beginning to doubt that.
6. Hard to check this one, but we used new gaskets and goo, so should be fine.

I think we need to check the cams. Say for example the cams are in around the wrong way (ie, exhaust in intake postition) how would that cause a clatter noise? The cam follower should just follow it regardless of the profile? or, are the bushes and shafts different sizes?... or... could the gears be clattering together? hmm....
SPRIDDLER
Member
Posts: 8542
Joined: Wed Sep 01, 2004 1:00 am
Location: WEST SUSSEX UK

Re: HELP! Bottom end noise

Post by SPRIDDLER »

Matchymarty wrote:NOT sure if they soaked the big end in oil before putting it in or not, but don't suppose it would have done too much damage if they didn't ... after all, only takes a minute or 2 of 2000rpm to get oil thru.
Not ideal obviously, but agreed in principle. It would be very remiss if it wasn't oiled by 'the old fella who has done over 100 of them'. (However, we're all getting forgetful - just a couple of weeks ago I looked high and low in the shed for a headlamp bulb that I had put on the bench. When I came in to make a brew I found it in the fridge :roll: )
3. Father in law rang tonight to tell me he had no compression today when he went to restart.
Is the decomp assembly, return spring and cable assembled/fitted/adjusted correctly? Maybe slack right off or disconnect or twiddle with the cable or the decomp lever on th'engine during tick-over. It would certainly make a 'clacking' noise if it wasn't fully clear of the zorst rocker arm (ali head) or cam follower (iron head).
Did we put the cam gears in correctly? I think so. THough, I'm beginning to doubt that.
You can't fit the cam gears incorrectly as one has an extended shaft to carry the mag sprocket.

The mag and cam sprockets can be swapped but one has a deeper boss than the other and would throw the mag chain out of true if wrongly fitted.
I think we need to check the cams. Say for example the cams are in around the wrong way (ie, exhaust in intake postition) how would that cause a clatter noise?
as comment above: You can't fit the cam gears incorrectly as one has an extended shaft to carry the mag sprocket.
The cam follower should just follow it regardless of the profile? or, are the bushes and shafts different sizes?... or... could the gears be clattering together? hmm....
The cam lobes contact the follower foot off-centre, in theory to reduce/even out wear on the foot as it is intended to turn a bit with each contact of the cam lobe. This off-centre contact creates end thrust on the cam axle.
If the cam axle has excessive end float the axle will oscillate sideways (i.e. 'in' and 'out'), causing a tapping/rattling noise. You can check for this on the mag drive sprocket with th'engine running by removing the mag chain cover and pressing, say the wooden end of a hammer handle, (with great caution), against the nut of the rotating cam sprocket and (if that's the problem) the noise may stop. You can't check the other one as its axle end is concealed behind a blanking disc (looks like a car core plug).
'There is a tide in the affairs of men
Which taken at the flood............'
Matchymarty
Member
Posts: 202
Joined: Sun Oct 25, 2015 8:19 am
Location: AUSTRALIA

Re: HELP! Bottom end noise

Post by Matchymarty »

Thanks for the reply....

Thinking further about #5. Have you fitted the valve cam and mag drive sprockets in their correct positions? They are not interchangeable, so the mag chain could be clattering against/within its housing even though it is tensioned correctly.
I didn't fit these, but I believe they are in the correct position. The one with the deeper offset of the sprocket belongs on the Mag?
Matchymarty
Member
Posts: 202
Joined: Sun Oct 25, 2015 8:19 am
Location: AUSTRALIA

Re: HELP! Bottom end noise

Post by Matchymarty »

Got the Stethescope out. Seemed to be a clatter in the bottom end no doubt. Pulled the chain case and the spacer between crank and primary drive sprocket/shock absorber was not installed. Found it and installed it.

Opened timing side. Cams definitely installed to numbers 2 and 2 on cams. For giggles we installed them 1 & 1 and the cams try to open valves at the same time. So 2 & 2 it is. Noise is not evident with cam cover off, once we put cam cover on, even with no screws, the noise emits. It seems the exhaust cam floats and taps the back of the cam cover? Does this seem right? Is there supposed to be float in it? I understand the timing gear takes up a lot of that slack, but there seems to be some float still with it pushed on by hand.

Should we put a washer between the timing gear and the cam cover to minimise the float?
Or just not worry about the noise..... now that we know what it is.... ???
SPRIDDLER
Member
Posts: 8542
Joined: Wed Sep 01, 2004 1:00 am
Location: WEST SUSSEX UK

Re: HELP! Bottom end noise

Post by SPRIDDLER »

Matchymarty wrote: Should we put a washer between the timing gear and the cam cover to minimise the float?
?
Couldn't get on the site yesterday and short of time now, but.........

Yes, but shims of various thicknesses are available.
You could ignore it but would be annoying and not recommended.

The end float is normally set by moving the cams shafts bushes but you can't do that without splitting the crankcase.
'There is a tide in the affairs of men
Which taken at the flood............'
Matchymarty
Member
Posts: 202
Joined: Sun Oct 25, 2015 8:19 am
Location: AUSTRALIA

Re: HELP! Bottom end noise

Post by Matchymarty »

Thanks heaps... I've just made up a shim to leave a little tolerance.
Cheers for the advice. Fingers crossed :)
Matchymarty
Member
Posts: 202
Joined: Sun Oct 25, 2015 8:19 am
Location: AUSTRALIA

Re: HELP! Bottom end noise

Post by Matchymarty »

Thanks to all who responded.
Well, after shimming and re-starting... noise remained. Quite horrid knocking noise.

I decided to pull the rocker gear off and replace it with a spare cover and gear, which had the original amount of float in the exhaust rocker assembly.
Funny.... That was the only thing we changed, and, on start up, the motor is quiet as a mouse.

So, question is, why, when we put a spacer in between the exhaust rocker spindle, to space it to match that of the intake assembly, did it cause the knock, and, what is the specified float in the exhaust rocker spindle?

Now,.. if only we can get the clutch to work correctly....
SPRIDDLER
Member
Posts: 8542
Joined: Wed Sep 01, 2004 1:00 am
Location: WEST SUSSEX UK

Re: HELP! Bottom end noise

Post by SPRIDDLER »

Matchymarty wrote:the rocker gear .......the exhaust rocker assembly............. the exhaust rocker spindle.......... what is the specified float in the exhaust rocker spindle?
Marty, I'm assuming you're referring to the valve cam gears, shaft, and cover, not the 'rocker' ditto. which is at the top of th'engine.

Without sight of the bits I can only suggest that you compare the substitute gear, it's teeth, cam profile and the cover with the one you removed to see if there is any physical difference.
I'm not sure how you could be precise in shimming the zorst cam by ""putting a spacer in between the exhaust rocker spindle, to space it to match that of the intake assembly"" as the intake gear spindle is not visible when the cover is fitted. Perhaps you over-shimmed the zorst gear creating excessive end float in the (now noisy) intake gear spindle. The spindle end float required is just sufficient to give running clearance as there is no significant heat to cause any expansion.

Personally I'd just throw another shrimp on the barbie, pour a beer and enjoy the silence.
'There is a tide in the affairs of men
Which taken at the flood............'
Locked