Author Topic: Advice needed - engine tightening up - help - tips  (Read 14533 times)

Offline chaterlea25

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Re: Advice needed - engine tightening up - help - tips
« Reply #60 on: 25.06. 2009 22:26 »
Hi again Nigel,
I did not believe that an oil pump could be porus either until I saw it with my own two eyes on a test rig!!
A quick check is to wash off the outside of the pump with some solvent, wait a while, minutes/hours and wipe the pump body with some tissue, you probably wont need to as you will see the oil on the metal
My Super Rocket wet sumped even though the pump had been overhauled and passed fit, because the oil leaked through the pump!!
For your own safety and peace of mind take off the timing cover and at least give the main bush a careful look at
Also remove the pressure relief valve and make sure its clean and operates properly,
IF THIS DOES NOT OPEN THEN NO OIL GETS TO THE CAM!!!! (and you r back to square one)
I know what you are saying about the bores, What make are the pistons?
Piston ring end gaps should be around 12/15 thou, did you have 40 or was it 0.40 mm

With a plain bush type crank engine it is possible to momentarily start the engine with the timing cover off to see whats going on regarding the pump and main bush

Regards
John O R

1961 Super Rocket
1963 RGS (ongoing)

Offline nigeldtr

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Re: Advice needed - engine tightening up - help - tips
« Reply #61 on: 26.06. 2009 06:14 »
Hello John,

Thanks for the coments and tips. Once I have the top back on, I will take off the timing cover and have a look and fire her up to see wha is happening. How can I check the pressure release valve?

RE the rings, the gaps I mentioned are in thou.

Nigel
1951 Golden Flash (engine now rebuilt) 1953 M21 a pain to start and 1961 GF that is turning into a black hole!

Offline chaterlea25

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Re: Advice needed - engine tightening up - help - tips
« Reply #62 on: 26.06. 2009 13:40 »
Hi Nigel,
Do you know anyone who works in industrial instrumentation, pressure testing services, or anyone who works in  instrument calibration services
It can be tested on a dead weight tester or on a safety valve test setup,
The BSA relief valves use a ball bearing and spring , Triumph type ones have a piston, which can get stuck when shrapnel gets between piston and bore
You can mail pump and relief valve to SRM for testing if you like, testing is free if you have to buy a new pump (I think)
Regards
John O R
1961 Super Rocket
1963 RGS (ongoing)

Offline nigeldtr

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Re: Advice needed - engine tightening up - help - tips
« Reply #63 on: 26.06. 2009 13:53 »
Hi John,

I have a hydraulic tester here and can probably set something up to check it out I don't know at what pressure it should open and close at though - any ideas - perhaps I will give SRM a ring

Nigel
1951 Golden Flash (engine now rebuilt) 1953 M21 a pain to start and 1961 GF that is turning into a black hole!

Offline nigeldtr

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Re: Advice needed - engine tightening up - help - tips
« Reply #64 on: 27.06. 2009 16:02 »
Just for informtaiton, I spoke ot one of the guys at SRM and they said that the the pressure relif valve should lift off at 60 lbs and close between 30-40 lbs.

Regards

Nigel
1951 Golden Flash (engine now rebuilt) 1953 M21 a pain to start and 1961 GF that is turning into a black hole!

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Re: Advice needed - engine tightening up - help - tips
« Reply #65 on: 27.06. 2009 19:24 »
I'd test a relief valve by fitting a temporary oil pressure gauge to the bike.

Offline trevinoz

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Re: Advice needed - engine tightening up - help - tips
« Reply #66 on: 28.06. 2009 07:57 »
Nigel, get that scored piston measured, you will be lucky if it hasn't collapsed by the look of the grab marks.
For Richard and others who are interested in the performance of the reground cam followers, I have had no issues with them, everything seems to be normal. The ones I and a couple of mates had ground were worn but the grinding didn't take an excessive amount of metal. There are quite a few engines running with these followers and all seem OK.
Trev.

Offline nigeldtr

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Re: Advice needed - engine tightening up - help - tips
« Reply #67 on: 28.06. 2009 13:03 »
Hi Trev,

Appreciate the comments. I have spun the piston up in the lathe and cleaned it up a bit. Some of the alloy had "dragged" and formed little hi-sptos which I have also taken off. As I have probably a 4 thou undersize bore, I can probably take a bit more off the piston and do some "fitting".  I am not too happy about this as there may be hair line cracks etc etc, so I am considering buying new pistons and starting again. However, what concerns me a little more is, I heard that certain "new" pistons are prone to smoking and or seizing as the skirts are not turned with a fine taper (4 thou smaller under the rings than at the base of the skirt) to allow for the extra heat expansion at the top of piston. Whether this is only necessay with solid pistons or also applies to split skirt types, I don't know?

I have measured my "good" piston and taking the diameter above the gudgeon pin holes as zero reference, I found that the base of the piston, below the pins, to be approx +.005 bigger - OK holds to theory. However, do the same but at 90 degress,  under the rings (below the "split") +.009 wider and at the base of the piston also +.009 wider, so would appear not to taper here!

So to sumarize:

Above Gudgeon pin "zero"  same height turned through 90 dgress 9 thou wider
Base of skirt below pin + 5 thou, same height turned through 90 degress +9 thou wider

It would appear to my simple mind that they have turned the OD and then milled the split which means the stressed material "springs"  I wonder if this- is common?

This really begs the question do I pay 150 pounds for a pair of pistons of questionable engineering quality or do I just do the fitting on the ones I have? If someone out there has perhaps a hepolite they can compare this would be great.

Thanks

Nigel
1951 Golden Flash (engine now rebuilt) 1953 M21 a pain to start and 1961 GF that is turning into a black hole!

Offline A10Boy

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Re: Advice needed - engine tightening up - help - tips
« Reply #68 on: 28.06. 2009 18:56 »
Wiseco are making what they call "Rocket" pistons and these are / were available in the UK via cake street classics. Not sure about the other lower compression ratios.

Tel Roger Shirman  on 01986 798504

Then of course there is-

J P Pistons Uk
The Glebe Keighley Road, Colne, Lancashire BB8 7HF
p: 01282864739  f: 01282864739
Regards

Andy

1960 A10 - Black Golden Flash
Plus
1974 Kawasaki Z1a
Yam XJR 1300

Offline chaterlea25

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Re: Advice needed - engine tightening up - help - tips
« Reply #69 on: 28.06. 2009 21:43 »
Hi Nigel,
The measurements you have taken on the good piston seem OK,
Pistons generally are tapered, but they are oval as well, then they are stepped down in diamater between the rings nearing the crown.
In general terms the only relavent measurement that needs to be taken is at 90 degrees to the pin at the Bottom of the skirt,
This measurement should be the nominal bore size less the piston clearance, ie, 71mm minus 0.1mm(0.004in) for example
Stick the piston in the bore in the running orientation and an accurate measurement can be done with a feeler gauge.
With split skirt pistons the clearance is normally smaller than solid skirt, that said my Ariel 500 single 81.8mm bore has a split skirt piston and runs on 0.001-0.003in. clearance
My Super Rocket with solid skirt pistons is running fine with 0.003in (GPM pistons)
If you buy new pistons, the bore size will be marked on the box, not the piston size if you follow me, so have your engine shop finish the bore to that size.

Nigel You will have to believe Me and start looking at the oiling system in your bike ( I know the bore sizes appear or are different)
But the fact that the cam followers wore so badly and then its the left hand piston that siezed makes me very sure thats there is an underlying lubrication problem.

Triton Thrasher, its not an easy thing to attach an oil pressure gauge to an A7/10 engine, neccitating drilling into the crankcase to the oilway inside the pressure relief valve, its a bit easier on SRM type end fed conversion engines, by drilling in to access the end of the pressed in oil pipe, or into the outer cover

Regards
John O R

1961 Super Rocket
1963 RGS (ongoing)

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Re: Advice needed - engine tightening up - help - tips
« Reply #70 on: 29.06. 2009 08:10 »
Triton Thrasher, its not an easy thing to attach an oil pressure gauge to an A7/10 engine, neccitating drilling into the crankcase to the oilway inside the pressure relief valve, its a bit easier on SRM type end fed conversion engines, by drilling in to access the end of the pressed in oil pipe, or into the outer cover

Interesting, thanks.  Can one drill and tap into the dome of the relief valve, for a gauge takeoff?  Not that I'm that keen on oil gauges, but the guy wanted a test for the operation of the valve.

Edit- that's silly isn't it! You'd only be measuring pressure in bypassed oil.

Offline MikeN

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Re: Advice needed - engine tightening up - help - tips
« Reply #71 on: 29.06. 2009 12:30 »



This really begs the question do I pay 150 pounds for a pair of pistons of questionable engineering quality or do I just do the fitting on the ones I have? If someone out there has perhaps a hepolite they can compare this would be great.

Thanks

Nigel


Nigel.
  If you are going to buy new pistons ,heres my .02p,s worth.
  SRM bored and supplied pistons for my A10 .Unfortunately i dont know the make but they are new pattern parts . They are solid skirt .I have done nearly 7000 miles and my engine goes fine and does not appear appear to  burn any oil.
Mike
 

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Re: Advice needed - engine tightening up - help - tips
« Reply #72 on: 29.06. 2009 14:47 »
Only my opinion, but a new piston of the type you have on the other side, or a pair of new pistons, is a better bet than prettying up and resizing that scored seized mess.

Buy from a seller you trust.  There are good Taiwanese pistons.

Offline nigeldtr

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Re: Advice needed - engine tightening up - help - tips
« Reply #73 on: 29.06. 2009 19:52 »
Guys,

Thanks very much for all the valuable comments. I have popped in the good piston in and in the RH bore roughly 5 thou clearance LH bore approx 3 thou, so is a little tighter. I will get the bores sorted out and pop in a set of new pistons. Are they normally solid skirt for a 1951 GF or does it make no difference?

I have taken the timming cover off and cleaned  the outer of the oil pump, I will take a look in the morning. There is oil building up in the sum so its leaking back somewhere! I have tried to move the crankshaft up and down but there seems to be no play or very little in the main bearing (also tried pulling up and down on the rods but nothing noticable. Is this sufficient to check the main bearings?

Must admit I am seriously tempted to fit a new oil pump and pressure relief valve, will perhaps send the old ones off to SRM to be tested.

PS the dynamo chain area was absolutely stuffed full of grease never seen so much, hardly any room for the chain!

Thanks Nigel

1951 Golden Flash (engine now rebuilt) 1953 M21 a pain to start and 1961 GF that is turning into a black hole!

Offline A10Boy

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Re: Advice needed - engine tightening up - help - tips
« Reply #74 on: 29.06. 2009 21:50 »
I've often wondered, how come the dynamo chain area is stuffed full of grease, but there is never any on the chain?  *conf*
Regards

Andy

1960 A10 - Black Golden Flash
Plus
1974 Kawasaki Z1a
Yam XJR 1300