Author Topic: Bewildered ! Help ! (thick blue smoke)  (Read 3834 times)

Offline Gerry

  • Valued Contributor
  • ****
  • Join Date: Nov 2012
  • Posts: 261
  • Karma: 6
Re: Bewildered ! Help ! (thick blue smoke)
« Reply #30 on: 21.10. 2014 12:19 »
Hi Tomtit, If one of the pushrods was resting on the edge of the rocker cup when replacing the rocker box its also possible that you might have bent a pushrod........happened to me twice. When you kicked it over you would certainly have heard a load "click" as the rod seated itself. Good luck and I hope you fix it in less time than it took me to iron out my problems!! Cheers. Gerry

Offline tomtit

  • Moving Up
  • **
  • Join Date: Mar 2014
  • Posts: 34
  • Karma: 0
Re: Bewildered ! Help ! (thick blue smoke)
« Reply #31 on: 22.10. 2014 06:43 »
Thanks Gerry, I checked the pushrods previously and they were fine, just waiting on the compressor tester hopefully arrives in a day or two and I'll go from there.

Cheers
Tom
1950 A10 Golden Flash.
03 Yamaha V Star 1100.

Australia

Online RichardL

  • Outside Chicago, IL
  • Wise & Enlightened
  • *
  • Join Date: Nov 2007
  • Posts: 4979
  • Karma: 48
Re: Bewildered ! Help ! (thick blue smoke)
« Reply #32 on: 22.10. 2014 07:30 »
Tom's slight slip in referring to a "compressor tester" is a well-deserved typo, obviously brought on by fatigue from having assembled and disassembled his bike multiple times in what seems like the last few days, but it got me thinking. If you did not have a compression tester, but did have a good air compressor, it seems you could run a pretty good compression test by pumping air into the cylinder with a spark-plug bodge while adjusting the pressure shut-off valve on the compressor while observing the results for different settings.  Most garage compressors with tanks will go up to 125 PSI. If the cylinder will hold that, or maybe even less, then you could be pretty sure there is no bent valve or dramatic ring problem. However, now that I'm hallucinating about it, I'm not sure both valves are closed at BDC, where the piston will end up upon pumping in air (and there are probably other problems with this idea that I'm not considering, but it's too late to stop writing). Yes I know I could look it up, but I'm already procrastinating work by typing this.

Richard L.
Plan on signing up for the world-wide 2017 DISTINGUISHED GENTLEMAN'S RIDE on September 30, 2018. Watch website at https://www.gentlemansride.com for details.

Offline terryg

  • Valued Contributor
  • ****
  • Join Date: Nov 2012
  • Posts: 453
  • Karma: 6
    • thecarshipenterprise
Re: Bewildered ! Help ! (thick blue smoke)
« Reply #33 on: 22.10. 2014 08:34 »
Richard, that sounds a lot like a 'leak down test' that you're describing.  Pump up the cylinder, shut off the air feed and watch to see (with a suitable gauge connected) how the pressure falls.  Used a lot on multi-cylinder engines to compare the state of seals between cylinders, I believe.

It occurs to me that with bike engines like ours, where we have ready access to the inlet and outlet ports, a bottle of soapy water could help identify whether leakage was through one of the nominally closed valves or, if they prove good, past the piston rings.

There must be someone out there who is used to doing such tests.
Terry
'57 'SR', '59 SR, '63 RGS

Offline duTch

  • Ricketty Rocketty Golden Flashback
  • Wise & Enlightened
  • *
  • Join Date: Oct 2011
  • Posts: 4540
  • Karma: 41
Re: Bewildered ! Help ! (thick blue smoke)
« Reply #34 on: 22.10. 2014 09:20 »

 I'm sure I remember someone describing in detail how to build a leak-down tester a while back....?? RR or TT come to mind...??
Started building in about 1977/8 a on average '52 A10 -built from bits 'n pieces never resto intended -maybe 'personalised'
Have a '74 850T Moto Guzzi since '92-best thing I ever bought doesn't need a kickstart 'cos it bump starts sooooooooo(mostly) easy
Australia

Offline tomtit

  • Moving Up
  • **
  • Join Date: Mar 2014
  • Posts: 34
  • Karma: 0
Re: Bewildered ! Help ! (thick blue smoke)
« Reply #35 on: 17.11. 2014 07:45 »
My apologies to all and sundry for not getting back sooner but recommenced employment and working 10 to 12 hr days for the first week or two anyway the saga continues.

I tested both cylinders with the compression tester and got a reading of 125 PSI in both cylinders and checked about three times and got the same reading each time, that was kicking it over about ten times with throttle open and cold.
Pulled off the head and the right side had plenty of oil in cylinder but not as much on the left, looks like it was the head gasket after all as there was oil all over and under the gasket.
Cleaned the pistons and cylinders with petrol and kicked her over to check the rings and there is very slight oil getting through on both cylinders. I removed the barrels to check the rings, all the rings on both pistons feel like new there is a sharp feel to them all the way around also the pistons look in as new condition.

I removed the rings off the LH piston and inserted each one into the cylinder, there should be a 0.011Thou gap according to the Haines manual but there is no gap whatsoever that I can see, you wouldn't get a fly's pubic hair in the gap.
I tried a 0.0015 Thou feeler gauge but no joy, the bores are really smooth but no scoring as far as I can see so I'm guessing the pistons and rings were fitted but no rebore or honing of the cylinders also no damage to pistons from the valves.
The pistons are +.030 and look to be HC pistons, as I recall the Flash I had back in the day had concave pistons.

Tom

Attaching some photos for your perusal.





1950 A10 Golden Flash.
03 Yamaha V Star 1100.

Australia

Online muskrat

  • Global Moderator
  • Wise & Enlightened
  • **
  • Join Date: Jul 2009
  • Posts: 8101
  • Karma: 106
  • Lake Conjola NSW Oz
    • Shoalhaven Classic Motorcycle Club Inc
Re: Bewildered ! Help ! (thick blue smoke)
« Reply #36 on: 17.11. 2014 12:04 »
G'day Tom. A hone of the bores, gap the rings, check the head & barrel faces for flatness (deck if needed) and a new annealed head gasket she'll be brand new.
Lucky the rings weren't broken from fitting with no gap.
Cheers
'51 A7 plunger, '57 A7SS now A10CR,  '83 CB1100F, .
Australia
Muskys Plunger A7

Online chaterlea25

  • Wise & Enlightened
  • *
  • Join Date: Jun 2009
  • Posts: 3144
  • Karma: 45
Re: Bewildered ! Help ! (thick blue smoke)
« Reply #37 on: 17.11. 2014 12:11 »
HI Tom,
Yup !!! thrown together by either an inexperienced  or uncaring person   *sad2* *sad2* *sad2*
Ok so what to do???
First have a look at the pistons to see if theres  makers name or part number on the underside
If not then the pistons are more than likely of far eastern origin, none the worse for that, but the rings fitted to them are crap!!!
Hone the bores and check piston to bore clearance, if this is ok  buy a new ring set, (proper ones)
and gap the rings as per manual
I would also remove the valves and check the guides etc out
Check head and cylinder faces for flatness

HTH
John
1961 Super Rocket
1963 RGS (ongoing)

Offline terryg

  • Valued Contributor
  • ****
  • Join Date: Nov 2012
  • Posts: 453
  • Karma: 6
    • thecarshipenterprise
Re: Bewildered ! Help ! (thick blue smoke)
« Reply #38 on: 17.11. 2014 12:32 »
Top of cylinder liner not flush with head mating surface in the left bore? Is that an issue?  Has it moved? Others will have seen something like it before, no doubt.
Terry
'57 'SR', '59 SR, '63 RGS

Online RichardL

  • Outside Chicago, IL
  • Wise & Enlightened
  • *
  • Join Date: Nov 2007
  • Posts: 4979
  • Karma: 48
Re: Bewildered ! Help ! (thick blue smoke)
« Reply #39 on: 17.11. 2014 17:12 »
Terry,

Thought the same thing, at first, but that's the ring sitting in the bore.

Richard L.
Plan on signing up for the world-wide 2017 DISTINGUISHED GENTLEMAN'S RIDE on September 30, 2018. Watch website at https://www.gentlemansride.com for details.

Offline morris

  • Wise & Enlightened
  • *
  • Join Date: Aug 2012
  • Posts: 1544
  • Karma: 23
  • Antwerp, Belgium
Re: Bewildered ! Help ! (thick blue smoke)
« Reply #40 on: 17.11. 2014 21:23 »
Hi Tom, did you measure the gap with the ring sitting on top of a piston? If the ring isn't dead square in the bore it can give you a misleading impression. The gap will close up if the ring is skewed in the bore. Also check if the gap's the same up and down the bore.
'58 BSA A 10 SA
'52 BSA A 10 Plunger
'55 MORRIS ISIS
The world looks better from a motorbike
Belgium

Offline terryg

  • Valued Contributor
  • ****
  • Join Date: Nov 2012
  • Posts: 453
  • Karma: 6
    • thecarshipenterprise
Re: Bewildered ! Help ! (thick blue smoke)
« Reply #41 on: 17.11. 2014 22:14 »
Thanks Richard, about time I had new specs!  As I typed that it did seem a bit simplistic.

Also, was wondering about John's condemnation of the rings. What do you see that made you say that, John?

[edit] Just looked again on a bigger screen and I see what Tom means about the small ring gap!
Terry
'57 'SR', '59 SR, '63 RGS

Online chaterlea25

  • Wise & Enlightened
  • *
  • Join Date: Jun 2009
  • Posts: 3144
  • Karma: 45
Re: Bewildered ! Help ! (thick blue smoke)
« Reply #42 on: 17.11. 2014 22:39 »
HI All,
Terry,
The provisio I made before condemming the rings was to check if the pistons are "no name"
I have found that the rings fitted to earlier versions of these are crap,
No way of knowing where those  rings came from ??
Also the bores have glazed so will have the rings,

For the amount of work involved in having to rebuild the top end again if the rings are crap
I would choose to fit a new (known) set

As an aside another issue I have come across where bores have glazed and engines "smoked" after rebuild was tracked down to the oil used !! it seemed to contain a sticky substance that coated the innards preventing the rings bedding in !!

John
1961 Super Rocket
1963 RGS (ongoing)

Online muskrat

  • Global Moderator
  • Wise & Enlightened
  • **
  • Join Date: Jul 2009
  • Posts: 8101
  • Karma: 106
  • Lake Conjola NSW Oz
    • Shoalhaven Classic Motorcycle Club Inc
Re: Bewildered ! Help ! (thick blue smoke)
« Reply #43 on: 18.11. 2014 06:49 »
I agree with John re the oil. I am a life long fan of Nulon additive but never in a motor till it's got at least 1000 miles on it.
Cheers
'51 A7 plunger, '57 A7SS now A10CR,  '83 CB1100F, .
Australia
Muskys Plunger A7

Offline tomtit

  • Moving Up
  • **
  • Join Date: Mar 2014
  • Posts: 34
  • Karma: 0
Re: Bewildered ! Help ! (thick blue smoke)
« Reply #44 on: 18.11. 2014 09:38 »
Thanks for the replies guys, much appreciated. John the ring was square so to speak even all the way around with no gap.

I was intending getting the bores honed and buy new rings as I was a bit suss about the no gap, not very healthy.

In regards to the pistons I will have to wait till the weekend to check for make/manufacturer as I'm pretty knackered by the time I get home from work.

Correct me if I'm wrong but the original pistons for a '51 Flash should be concave, because these are domed I'm assuming the head may not be the original either which leads me to the compression @125PSI would that make it 8.5.1 ratio ?.

Thanks again.

Tom
1950 A10 Golden Flash.
03 Yamaha V Star 1100.

Australia