Jump to content

Clutching At Straws :-(


wallo
 Share

Recommended Posts

So, still got the metal on metal noise after the bike has run for around 10 minutes.

I sat looking at the engine tonight waiting for a eureka moment and maybe I had one.

Have a look at the picture, could it be that as the oil heats up it just flows downhill to the inlet rocker and doesn't bother to flow uphill to the exhaust rocker?

The oil starvation from the exhaust rocker then creates the noise.

Link to comment
Share on other sites

 

 

looks like the pipe is flattened (starving oil supply) at the bend where it enters the banjo connector stopping the flow Both my BSA B31 and two AJS's the rocker feed starts below the barrel base on the same system (oil return side) as your engine so uphill should not be a problem

  • Like 1
Link to comment
Share on other sites

 

Its longer than I care to remember since I worked on this type of engine but in general the separate flow to each rocker should have a restriction in it so it can't take all the oil coming up the single feed. This forces equal amounts of oil to both rockers (or camshafts) irrespective of oil viscosity or gravity.

I know of some car engines where people have failed to replace these restrictors resulting in oil starvation to parts of the valvetrain. Perhaps something similar is your bikes problem

Link to comment
Share on other sites

 

Not sure what your engine is, but the British singles and twins I owned had pressure fed rocker assemblies, using one feed pipe teed off to feed both rocker shafts (looked like that in your pic). Start it up and loosen one banjo nut, oil should come out, tighten it up and repeat on the other. If good. Look elswhere, eg loose tappet, broken valve spring, snapped rocker shaft, missing or broken rocker shaft sidethrust springs/shims.

Link to comment
Share on other sites

 

That's a C15 head. I can't see any kinking or flattening of the pipes and I can't imagine the oil not being able to flow up that little rise if it's just managed to get all the way from the bottom of the engine. Have you got a copy of Rupert Ratio? Might give you some ideas. If not then try asking on b50.org forum, some very knowledgable BSA unit single chaps there.

Link to comment
Share on other sites

 

Hi,

The old external rocker oil feeds were often 'awkward' until you got it just right. First off I wonder about the access to the inlet feed - the banjo is obviously not central on the rocker shaft - could the feed holes be not aligned. Try sirdabalot's suggestion of loosening each banjo feed slightly to ascertain whether you have oil to that area and at what sort of pressure? It could even be the oil pump not quite up to scratch and I know just how easily these little oil pipe plumbing bits and bobs can get swarf and other blockage problems that were often easier to solve by starting again with a fresh bit of pipe and making a new bit of plumbing - but being meticulous with the cleaning - we always used to try the first dry test by blowing through the new pipework whilst blocking the banjo's between the thumb and forefinger of each hand, and releasing each separately and testing the 'path' to each one was clear.........

Cheers,

Deryk

Link to comment
Share on other sites

 
 
 

Thanks for the posts. So the latest status is:

Oil pipe feed is working fine I was straightened the pipe and checked that oil is still flowing when the noise starts. I have checked the clearence between the stator and the pick ups which if fine.

I have noticed though that when the noise starts I start to see air bubbles in the return pipe, any thoughts?

Link to comment
Share on other sites

 

The return side of the oil pump is bigger than the feed side so it will draw air once the crankcase is flowing properly My cub and BSA do this as they both have clear plastic oil pipes If not the oil is not being supplied to the engine or it is filling up It take a minute or two for the air to appear as the oil will drain to the bottom while the engine was stopped

Link to comment
Share on other sites

 

So, I think I know the issue now after a chat waiting at sections yesterday. The general consensus was that the liner was moving when hot so when i got home I fired her up and kept the barrel cool with compressed air.

She ran for 30 mins, with no noise. Turned off the air and the noise started after about another 10 mins of running. Putting the air back on the barrel stopped the noise :-)

So just need to figure out how to stop the liner moving now.

Link to comment
Share on other sites

 

Good to see you out on a decent bike yesterday Ken,give yer 30 quid for it when you get fed up with it !

My advice is to take the barrel and piston to South Cerney Engineering and take their advice.Whoever bored the barrel to take the liner didnt get the correct amount of interference.I dont think I'd want to trust Loctite or similar to hold it,plus it wouldnt be good for heat transfer.An oversize OD liner fitted correctly is the best way forward I think,with the bonus that the heat transfer would be much better.

Link to comment
Share on other sites

 

Cheers Jon, I've arranged to go there early doors tomorrow. The Matchless is riding like a dream, the shorter wheelbase has made a massive difference just need to get the turning circle sorted (new yokes need the tank pushed back a little).

See you at the Bath Classic on Sunday :-)

Link to comment
Share on other sites

 
  • 2 weeks later...
 

Join the conversation

You can post now and register later. If you have an account, sign in now to post with your account.

Guest
Reply to this topic...

×   Pasted as rich text.   Paste as plain text instead

  Only 75 emoji are allowed.

×   Your link has been automatically embedded.   Display as a link instead

×   Your previous content has been restored.   Clear editor

×   You cannot paste images directly. Upload or insert images from URL.

Loading...
 Share

×
  • Create New...