Advice needed - engine tightening up - help - tips

[trevinoz]

Nigel, I feel that if there was anything wrong with your oiling system, you would be replacing big end bearings and grinding your crank.
As I said before, your case is typical of a too close piston/cylinder clearance.
The cam followers are worn and most likely were not serviced on the last tear down. Hopefully the sludge trap was cleaned.
Originally the Flash would have had split skirt pistons which run at closer clearance and should make the engine run quieter.
Solid skirt pistons are OK as long as you have the correct clearance, which you didn't on one side.
If you are worried about your oil pump, strip it and have a good look at it. Strip the relief valve and ensure the ball and seat are in good condition and replace the spring if you are concerned about it.
Oil is probably leaking past the check valve behind the oil pump. It is a major job to access it.
Trev.

[RichardL]

Not that I expect the decision to be made on my opinion, alone, but I don't see the immutable necessity of replacing the pistons. Maybe I'm too cheap, or, maybe pistons are just getting too hard to get.

If it were I, I would emory the scuffed piston until the high spots were worked down, measuring as I go to be sure the diameter and ovality stay within spec. If there is a lathe available, wrapping the emory around a wide flat file and moving about evenly(and gently)should avoid ruining the profile. From what I am seeing, there is at least as much unscuffed surface as scuffed. Then, I would hone the cylinder myself with a common cylinder hone until the fit of the scuffed piston was correct.

If you do happen to go the new pistons and professional shop route, get the pistons and new rings first, so both can go with the barrels to the shop. I say this because of your statement "I will get the bores sorted out and pop in a set of new pistons."

As we say around here, just my 2p worth.

Richard L.

[nigeldtr]

Well, I have manged to clean up the piston in the lathe and to be honest it looked far worse that it actually is, there are a few scores but his tends to happen in time anyway. I tend to agree about the pump, I had an oil pipe blockage on a B40 and at first I heard it start to rattle then in locked up. Result was shot main bearing, big end and piston. As the big end on the LHS is good (where the seized piston was), I suspect the piston  is getting enough oil. The piston looked like it hard 3 - 4 pinch spots which would to me indcate it is just too tight.

I will buy a hone, get some new rings and do a bit of fitting. I can give it out to be done but heck I may as well have a go seems I probably can't make a worse job. will drop some more pictures on later.

Just had another look at the oil pump. The body does not seem to be porous but there is a slight leak aroud the joint where the drive extension is. Will strip and give it some TLC!


Thanks 

Nigel

[BSA_54A10]

I've often wondered, how come the dynamo chain area is stuffed full of grease, but there is never any on the chain? 

This is because the wrong grade of grease is in there.
It should be a low melt grease so that under operating temperatures it melts and lubricates the chain.
IF high melt grease is used the chain picks it up and throws it to the extreamities of the enclosure and eventually runs dry.

[nigeldtr]

Trevor,

Seems logical, at bit like the tea lights, liquid when hot a hard when cool. Do you know if there is any particular make or grading for this?

[BSA_54A10]

Well because I am an Aussie and we got a lot of sheep down here I use Lanotec which is a lanolin based grease.
I also use it liberally on electrical contacts as that was its original use so it is oft called "contacts grease"
Bought a big tub of it years ago and will probably never buy another as I have switched to "liquid Electrical tape" to water proof all of the places where the Lucas smoke gets out.

[nigeldtr]

Hello All,

Well, finally got some time and bits are now starting to arrive so on with sorting the A10 out!! I bought myself a hone and old MZ bike cylinder to practice on and then gave the A10 clyinder the works this evening. After a couple of hours of measuring cleaning honing etc etc finally got both cylinders almost exactly the same size! In the end I used a 4 thou brass strip to check that both pistons moved with the same effort in the bores. To double check, I popped the same top ring into the bores to check the gap. One bore has a gap of 15 thou the other 12 so one side is probably 1 thou bigger. As the gap is recommended between 10 and 15 thou, I will leave things as they are, measuring plus or minus 1 thou is a bit beyond me and my fingers :-)

Next tricky job is to drill through the crankcase into the bottom end of oil pressure release valve housing so that I can fit an external pressure gauge - I want to see what is going on in there!

Regards

Nigel

[nigeldtr]

All,
Just wanted to say thanks for all the helpful advices and tips finally got the engine fired up tonight and running nice and sweet. With all the discussion about oil pressure, I decided to drill trough the crankcase and pick up the oil pressure before the release valve, I have now fitted a pressure gauge near the top york and can see it from the riding position. Already been useful as it took ages for the return to pick up the oil and the engine almost filled with oil before it started to return to the tank (had to drain the sump as it started to come out the breather). I was not too worried as I had a good 20 to 30 PSi on the gauge with no oil returning! At tick over it shows 10 psi and when the revs are lifted goes up to about 30 psi - nice and reassuring.

Now just need to run her in!!

PS I found a company that supplies a liquid grease!! ideal for the dynamo chain drive, is like a jelly when cold and becomes liquid when warm.

Regards

Nigel

[RichardL]

Nigel,

Congratulations on getting her back together and running again. There is a certain reward in riding the bike one has fixed oneself.

One thing, I don't think you ever told us what you did about the followers. I assume, replaced.

Richard L.

[alanp]

I don't want to hi-jack this important thread but I just noticed back in June by Trevinoz it was posted that there is a check valve behind the oil pump which can be the cause of wet sumping but is hard to access. I heard someone locally say once that with an SRM conversion (pump?) access to it is easier. Can someone clarify this hidden check valve situation for me please? The reason I ask is that I have recently bought an A10 which had a holed piston before I bought it and the owner may well have not thoroughly cleaned the debris out of the engine (as well as a subsequent seizure!, which is why I read this thread) which actually now severely wet sumps. I intend to strip the engine right down so any advice on this check valve would be appreciated. Thanks.

[nigeldtr]

Hello Richard,

I decided to change the followers and leave the cam alone. I could not find any convincing reason reason for replacing it. While I had everything stripped, I serviced the mag and the dynamo. The nervi bit was honing out the undersize bore which I did until both pistons moved freely as described earlier. The pistons where cleaned up in the lathe with some fine wet and dry and new rings fitted (the old/new rings were way undersize with too big a gap!). One lesson I have learnt is never take it for granted that a cylinder has been bored correctly (check it) and secondly, that pistons and rings can simply be taken out of the box, popped in and forgotten. It is time well invested to ensure that all the tolerances are correct and that everything fits and moves freely.

The oil pressure gauge is nice to have and when first started, the pressure shoots up to around 40/50 psi and then drops back to about 30 when warm. I am now seriously thinking about putting an oil filter in the return line as there is plenty of room behind the gearbox. It was a joy to fire her up and the sound is what dreams are made of.

Alan,
Concerning the wet sumping, my A10 was slowly draining down the oil tank all by itself while in the workshop.  In normal daily or weekly operation, I can't see this ever being a big problem, just fire her up once a week. Alternatively, drain the oil out and top up with new - one way to keep the oil fresh. How much oil is actually flowing back into the sump ? how fast?

Do you know why it had a holed Piston ? was it mechanical failure (valve problems) or did the crown melt?

Nigel

[chaterlea25]

Hi Nigel,
30psi is not enough to operate the pressure relief valve, this is Very Necessary to keep oil to the camshaft and followers, going back through the replys you got from your initial problems there are figures for the valve!
When you started the engine, the sump should not have filled with oil!
The scavenge (return) side of the pump has a greater capacity than the pressure side, and it will in normal conditions will clear the sump faster than it can fill!
As I have said to you in previous replys I feel very strongly that there is a serious problem with your lubrication system????????

Alanp,
After an engine holes a piston the debris gets absolutely everywhere!!! (and amazingly quickly)
You will have to completely strip the engine also the oil pump,
clean out the crank sludge trap, oil pipes and tank as well!
I have used aerosol brake and clutch cleaner with a long nozzle to clean out the oilway to the cam gallery
You can remove the plug for the valve from inside the crank case,
Its up to you if you replace it in the same way or modify to the SRM (A65) type setup where the ball sits against the back of the pump
Regards
John O R

[nigeldtr]

John,

I can't remember but is the camshaft only fed when the pressure release valve opens? The engine does not wet sump any more, it took while for the scavange to pick up and now it returns fine. Have you or anyone else fitted a pressure gauge as it would be good to know what others have found. I can change out the pump, I think Draganfly do a reconditioned unti for about 100 pounds.

Thanks

Nigel

[a10 gf]

is the camshaft only fed when the pressure release valve opens

opposite, valve redirects whatever is left after crank gets it's oil dose.

Nice pressure gauge mod, just some quick thoughts, you are reading the pressure after feeding the crank and may get a quite low reading, still everything will be ok (or plain bearing is very worn and leaking direct to crankcase, if you get a very high reading I'd think maybe the big ends\plain bearing are not fed properly!) Corrections welcome.

[nigeldtr]

John,

I did a little digging and just found the attached showing as you say the oil feed to the camshaft. I am going to take out the pressure release valve again and check the operating pressure. If the pump is not opening it then I will replace the pump.

Thanks for the tip - reminder!

Nigel