Ongoing saga of gerrys a10 (compression)

[Gerry]

OK Guys, Took the plug caps off and wired the lead ends direct to the plugs....seemed to improve the idle but that could be wishful thinking. Checked the slip ring of the mag and absolutely clean and bright brass strip. So off came the tank.....again... and removed the rocker inspection covers and checked the tappet clearance WHATTHA!!!!! I set these with a lot of care and patience and now the right hand inlet is 0.024" should be 0.010" the exhaust is 0.020" should be 0.013" the left hand side all over the place as well....what happened here? So bugger it, took rockerbox off removed the pushrods (straight as), removed the head and placed my palm over the right hand barrel and using my other hand cranked the engine. Couldn't push the kick start too far as the suction on my hand was too much. Did the same on the left hand barrel and could turn the crank over even though there was suction on my palm it was not as much as on the right cyl'. Took the barrel off (difficult) and checked the rings and all seems good. Good clean bore in the barrels, no scoring, no visible problems with the pistons and rings are free and shiny. Looks like I shall be investing in another set of new rings and the alloy head with single carb' manifold bolted on.  Looks like a quick hone to give me the cross hatch pattern to bed in new rings. Would all these problems give me the results I have been getting? Cheers. Geriatric.

[bsa-bill]

Couldn't push the kick start too far as the suction on my hand was too much. Did the same on the left hand barrel and could turn the crank over even though there was suction on my palm it was not as much as on the right cyl'. Took the barrel off (difficult) and checked the rings and all seems good.

HI Gerry
No offence mate but in the absence of a compression tester your not going to get to a reliable result from side to side using your palm over the top of the barrel, also if it sucks your hand down the barrel I'm not sure you've a problem there, head back on and thumb over the plug hole might be better.

The brass segment on the maggie slip ring being smooth will stay cleaner I think than the Bakelite bit which is a bit rougher and black so best way is to have a piece of spirit (or petrol if you must) soaked cloth on a lollipop stick or similar pushed onto the slipring and turn it over, not forgetting petrol and high voltage spark together - not good and painful.

Tappet clearance altering, were the locknuts still tight? if so then this needs look at before you proceed, should be adjusted with engine cold, adjust left hand inlet when right hand inlet is fully down and vise versa same for exhaust. (you probably already know this, just covering bases)

[Gerry]

Hi Bill, Thanks mate but I did a test with a compression tester when I first had the weak combustion on the left hand side and both came out reasonably the same!
I have large plates of meat for hands and I can cover the bore and seal it well enough to feel the difference in compression, as I said earlier the right side vacuum was so good I couldn't turn the engine over using my other hand on the kick start but the left side was noticeably weaker and allowed me to push the kick start down with less trouble and no leakage between my hand and the cylinder. All the tappet lock nuts were still tight so I just don't understand where the excessive clearance came from and being on all four tappets means something has settled or I'm bloody losing it!!! (Which wouldn't surprise me) Yeah I will do the slip ring clean once I have got the barrel back on so I can turn it over. Cheers and thanks again. Gerry

[Triton Thrasher]

I'd have set the clearances and tried the bike out.

[chaterlea25]

Gerry
see  my reply on your other thread

John

[wilko]

Just give up.

[Gerry]

Hi John, Now that's another worry, the camshaft and followers! I did check both before assembly and they appeared ok. How thick is the case hardening? I gather it wouldn't be more than 2 or 3 thou' I doubt they would have been nitrided which would give a deeper hardened face. If that is worn through then I have a total strip down....again. There's a lesson here folks, NEVER TAKE THE EASY AND CHEAP WAY IT CAN BE DEARER IN THE LONG RUN. How many of us have "been there, done that" I did check both the followers and cam shaft before assembly and they all looked ok and the same lift on both inlets and both exhausts but who's to say they weren't already worn through the casing. Anyone know the sizes and lift? Yet the combustion on the near side had improved over the original start up. I wouldn't have thought that would happen with worn cams.  As for the pump, I don't get more than a teaspoon of oil in the sump when its been standing for a while. Timing side bush is new and the crank ground. Oh well here we go again...
Hi Wilko, mate I have given that much thought but am not the type unfortunately. When I was 17 I had a 350cc Manx Norton which didn't leak oil all over my legs from the open rockers like it was supposed to. Had low oil pressure which was not caused by the pump and burned out two exhaust cams. Sold it at 23 to buy my wife an engagement ring!!! Never found out what the low oil pressure was caused by and it still has me wondering today, 53 years later...
Cheers. Gerry

[RichardL]

I think if the cam or followers were worn down by 10 or 15 thou they would look obviously worn and misshapen. Take a good look at the gasket for any leakage paths. Take a flashlight and examine the inner valve springs. Pour mineral spirits in the inlet and exhaust paths to see if the valves leak. Before you disassembled, did you swap the plug leads and pickups?

At this point, before you reassemble, I suggest you use some of that energy to learn how to post photos, and then post a bunch so that those of us who are guessing, and trying to help, can see what you are seeing.

Don't give up. Take a rest, or take some time away from it. These are really simple machines and when the problems are revealed they are usually head slappers. I myself have done so so many times i have a permanent hand impression in my forehead.

Richard L.

[bsa-bill]

cam or followers were worn down by 10 or 15 thou

even stranger to think this would happen over such a short period, I imagine the crankcase when the engines running to be a turbulent place with oily mist charging about such that the small end gets enough of it to survive so the camshaft should get a similar lube at least to prevent rapid wear.
Something has moved Gerry or the original tappet setting was not quite right, as has been suggested reset the tappets and try the bike out again.

head slappers - Richard - first time I set the tappets as a young innocent I set them all at once at the same engine position  , such forgiving things these BSAs it still ran - in a fashion

[Gerry]

Hi Richard & Bill, Yes one of the followers is really badly worn. I believe they were already down below the hardened surface when I fitted them. although it didn't show and perhaps thats why the excessive wear. I have a friend who overhauls BSA's and they turn out like brand new bikes, how he does it I have no idea cos' I get chips and scratches...probably due to the number of times I have had the thing apart and back together!! I will take some pics' of the followers which I am going to exchange for a set of re profiled and hardened ones from him for $150AU not bad considering how hard they are to find, even in secondhand condition. The head I have re ground the valves in and poured petrol (gas) into the ports and all was good, no leaks after 5 minutes or so. As stated before I had the head faced and the barrel also. 0.007" off the barrel and 0.011" off the head. Also annealed the solid copper head gasket. Now I am going to take a closer look at the camshaft and maybe replace it with either an SRM or get a good secondhand one off the same mate with the followers. I'm hoping this will also get rid of the low compression on the near side cyl'. with a hone and another set of new rings although the present rings look quite good so don't understand why the low compression on that side as bore looks good also, no step and smooth polished finish where the rings travel. Cheers and thanks fellas. Gerry

[chaterlea25]

Hi Gerry,
Usually the wear on cam and followers is accompanied by scoring, usually theres a ridge at one side of the cam or followers where they have not been rubbing
Case hardening would be probably 40thou thick (1mm)
As the cylinder has been skimmed make sure the pistons do not hit the head gasket

Inspite or despite of all this I'm still puzzled why it was not running evenly ???? unless the inlet cam was completely worn away
Cam dimensions depend on which cam is fitted
Cam wear will occur rapidly as there are two hard surfaces involved
small end bushes and so on have a soft bronze bush and a hard pin, they will survive on remarkedly little lube
The cam trough is filled by oil when the prv opens usually when cold at start up , as the engine is runniing oil is thrown from the crank to add to the supply
Did you recon the oil pump? and have the prv checked??

HTH
John

[Gerry]

Hi John, Yes on one follower there is a ridge where the cam didn't touch, a narrow area on one side. I have yet to do a check on the actual cam shaft and am hoping it will be ok. From what I can remember from my old work days case hardening (gas carburising using cyanide) gave a thickness of only about 0.010" if my memory serves me correctly (what memory!!) Later on nitriding was a preffered method due to a deeper hardened surface and less distortion of the item. I am absolutely sure that one follower is stuffed and maybe beyond redemption. When I reassembled the engine after the head and barrel skim I left the plugs out and turned the engine over on the crank to make sure nothing was touching and my current disassembly shows no sign of contact between piston and head or gasket thank goodness. No I didn't recon' the oil pump I just turned it to make sure nothing was stuck or binding and on assembly of the engine no wet sumping, so clearances in the pump are good plus the oil return is healthy also. I distrubed the oil feed line to the rockers on an earlier occasion and got plenty of oil all down one side of the engine so the return is excellent. Cheers. Gerry

[chaterlea25]

Hi Gerry,
Hopefully your oil pump is ok, not wet sumping is down to the ball and spring in the crankcase
more so than the pump
As you have had the crank main sorted it "should" be ok now
I would check the PRV and make sure its working and lifting at the correct pressure (cant remember??what)
For the system to work the PRV has to open and supply the cam trough

John

[Gerry]

Hi Guys, Firstly let me wish you all a very happy and prosperous New Year. Secondly I am still getting a problem with not firing constantly on the left hand cylinder. Took the left hand plug cap off the lead and held the lead close to the left hand plug when running on the right side and got a very weak spark, so swapped the plugs left to right and tried again and got a much better spark at the plug and it ran better on both cylinders so went and purchased a pair of new plugs and fitted them. Still the same result, missing intermitently on the left side. Gets better when warm so am taking it out for a run to see what transpires. Wish me luck. Cheers. Gerry.

[muskrat]

Still sounds like induction bias to me. Running weak/lean on the left if it improves a bit when hot. Pull the plugs after your run put them side by side and take a photo. Post the photo here.
Cheers