BritBike Forum logo
BritBike Sponsor BritBike Sponsor BritBike Sponsor
BritBike Sponsor

BritBike Sponsor

BritBike Sponsor
BritBike Sponsor BritBike Sponsor BritBike Sponsor
  JWood Auction  
Home | Sponsors, Newsletter | Regalia | Calendar | Bike Project | BritBike Museum | Spiders Cartoons, "OLD" BritBike Forum | DVD- Manuals & Parts books | BritBike Stickers & Decals
Upgrade to: Premium Membership | Premium Life Membership | Vendor Membership | Site Sponsor Membership
Photo posting tutorial

Member Spotlight
Matt smith
Matt smith
West Chester, pennsylvania. USA
Posts: 462
Joined: December 2009
Show All Member Profiles 
Shout Box
Search eBay for motorcycle parts in following countries
Australia, Canada, France, Holland, Italy, United Kingdom, USA
Random Gallery photo
Who's Online Now
200 registered members (57nortonmodel77), 1,623 guests, and 583 spiders.
Key: Admin, Global Mod, Mod
Newest Members
revans, Gilly, XTINCT, Bruce Roberts, Brian Ellery
9959 Registered Users
Top Posters(30 Days)
btour 184
koan58 99
Stuart 86
NickL 73
Popular Topics(Views)
439,468 mail-order LSR
Forum Statistics
Forums33
Topics65,296
Posts632,518
Members9,959
Most Online3,995
Feb 13th, 2017
Like BritBike.com on Facebook

Previous Thread
Next Thread
Print Thread
Rate This Thread
#429689 - 04/14/12 10:26 pm 72 TR6 piston clearance-ring end gap?  
Joined: Nov 2005
Posts: 706
Fisherman Offline
BritBike Forum member
Fisherman  Offline
BritBike Forum member

Joined: Nov 2005
Posts: 706
Tennessee
What are the correct clearances for this engine? We are having a fit trying to make this engine live...two new sets of .020 over pistons and rings, both seized. The 1st time the teardown revealed Drive side piston 3 thou larger than the other post mortem. We assumed bad manufacturing tolerance. Now we are assuming heat expansion.

This time it was a mild seizure but still seized. (Cooled and restarted)

Drive side piston skirt showed scuffing on the left/intake side. These are Emgo pistons and rings.

What am I missing?


'Never argue with an idiot, they'll bring you down to their level, and beat you with experience'

'72 TR6
'12 Hinckley Scrambler
'95 FLHTC Road Sofa
Support Your #1 BritBike Forum!
Membership Type! Free
Member
Premium
Member
Premium Life
Member
Vendor
Member
Site
Sponsor
Recognition No Premium Member Premium Life member (5 years) Vendor Member Site Sponsor Membership
Post commercial threads No No No Yes Yes
Custom title No Yes Yes Yes Yes
Upload avatar & photos No Yes Yes Yes Yes
Link avatar & photos Yes Yes Yes Yes Yes
Private Message Storage: 10 100 100 100 100
Length of signatures 255 600 600 600 600
Removes this very advert island between post 1&2 No Yes Yes Yes Yes
Price Free $12.90/year $105.00 No End
$55.00/5 years
$210.00/year
($17.50/month)
Email
Click on button >>
  Premium Member Premium Life member Vendor Member Site Sponsor Membership
#429720 - 04/15/12 12:21 am Re: 72 TR6 piston clearance-ring end gap? [Re: Fisherman]  
Joined: Oct 2003
Posts: 11,110
RF Whatley Online content
BritBike Forum member
RF Whatley  Online Content
BritBike Forum member

Joined: Oct 2003
Posts: 11,110
North Georgia, USA
Originally Posted By: Fisherman
...two new sets of .020 over pistons and rings, both seized. The 1st time the teardown revealed Drive side piston 3 thou larger than the other post mortem. We assumed bad manufacturing tolerance.


Not to be snotty, my friend, but measuring the pistons and matching them to the bores is part of building a top end. Manufacturers ship bad parts all the time. It's up to the mechanic to verify the parts to be installed are correct. So you may want to own up to some of the responsibility for yourself.

The piston clearance is .004" min and the ring end gap is .010" min. These are in every Triumph manual printed, even the really bad ones. Does this mean you're building engines with no workshop manual?

What oil are you using and what break-in procedure are you following? Everything has to be spot-on for one of these engines to hang together.

beerchug


Don't hide 'em, Ride 'em !!

RF Whatley
Cornelia, GA

"Shop Boy" at Rodi British Bikes
#429758 - 04/15/12 2:42 am Re: 72 TR6 piston clearance-ring end gap? [Re: Fisherman]  
Joined: Jan 2006
Posts: 1,835
Mike Baker Online content
BritBike Forum member
Mike Baker  Online Content
BritBike Forum member

Joined: Jan 2006
Posts: 1,835
Asheville, NC
Is it possible that with 1 piston .003" bigger than the other that the holes were bored correctly and you got the pistons switched?
Were clearances confirmed on the second go round?
Timing off on that side?
Intake air leak?

Just fishing........
Mike

#429788 - 04/15/12 10:58 am Re: 72 TR6 piston clearance-ring end gap? [Re: Fisherman]  
Joined: Jun 2010
Posts: 504
MikeinBiddeford Offline
Private sponsor
MikeinBiddeford  Offline
Private sponsor

Joined: Jun 2010
Posts: 504
Maine
I'm no expert. mater of fact I a bit of a hack. I screwed up my first top end build so I paid for and experienced, respected Triumph mechanic to do it the second time. Guessing the right answer is very expensive, so I didn't mind paying for the lesson.
Did you know that after a cylinder has been honed, that it can take on the shape of whiskey barrel? Smaller at the top, wider in the middle and tight at the bottom. I didn't.
Not just anybody can bore and hone these things. He mentioned at least a half a dozen ways my jugs were wrong. I thought he was being a fanatic and was wondering when he was going to mention that I should only torque the engine with the bike pointed north and under a full moon and quench the bolts with stump water and eye of newt.
But I did what he told me to do, to the letter and the pistons ran in in the first ten miles.
These Triumphs are their own beast and the advise that the measurements have to be spot on must be followed.
Or you can always do it a forth time.


Please do not believe anything I write. I am a hack but I like to guess the right answers.
#429800 - 04/15/12 11:58 am Re: 72 TR6 piston clearance-ring end gap? [Re: Fisherman]  
Joined: Nov 2005
Posts: 706
Fisherman Offline
BritBike Forum member
Fisherman  Offline
BritBike Forum member

Joined: Nov 2005
Posts: 706
Tennessee
Yes, the builder IS responsible. I have been working from the ancient Clymer manual I have used for the 27 years I have had the bike. We couldn't get the bore done by the machine shop that I have used for the 66 TR6, 66 A65, 68 T120 (as yet un tested) the two MG engines and the GM 400 small block that I have done in the past 30 years because they have finally gone out of business. Ask me if I miss them...

Thanks for confirming that the bore clearance and ring end gap we have been using are correct.

We shall look elsewhere.

Thanks to all.

Last edited by Fisherman; 04/15/12 12:01 pm.

'Never argue with an idiot, they'll bring you down to their level, and beat you with experience'

'72 TR6
'12 Hinckley Scrambler
'95 FLHTC Road Sofa
#429839 - 04/15/12 4:55 pm Re: 72 TR6 piston clearance-ring end gap? [Re: Fisherman]  
Joined: Jun 2010
Posts: 504
MikeinBiddeford Offline
Private sponsor
MikeinBiddeford  Offline
Private sponsor

Joined: Jun 2010
Posts: 504
Maine
Oil pump is piped backward?


Please do not believe anything I write. I am a hack but I like to guess the right answers.
#429958 - 04/16/12 2:15 am Re: 72 TR6 piston clearance-ring end gap? [Re: MikeinBiddeford]  
Joined: Oct 2003
Posts: 11,110
RF Whatley Online content
BritBike Forum member
RF Whatley  Online Content
BritBike Forum member

Joined: Oct 2003
Posts: 11,110
North Georgia, USA
Originally Posted By: MikeinBiddeford
Did you know that after a cylinder has been honed, that it can take on the shape of whiskey barrel? Smaller at the top, wider in the middle and tight at the bottom.

That would totally depend upon the brand of hone you use, and the honing technique employed.


Originally Posted By: MikeinBiddeford
I thought he was being a fanatic and was wondering when he was going to mention that I should only torque the engine with the bike pointed north and under a full moon and quench the bolts with stump water and eye of newt.

Now that is total BS!

Everyone knows that before torquing, the front wheel must point toward Coventry, and the mechanic must first say a prayer at their personal Edward Turner shrine. laughing


Don't hide 'em, Ride 'em !!

RF Whatley
Cornelia, GA

"Shop Boy" at Rodi British Bikes
#429960 - 04/16/12 2:17 am Re: 72 TR6 piston clearance-ring end gap? [Re: Fisherman]  
Joined: Oct 2003
Posts: 11,110
RF Whatley Online content
BritBike Forum member
RF Whatley  Online Content
BritBike Forum member

Joined: Oct 2003
Posts: 11,110
North Georgia, USA
Originally Posted By: Fisherman

We shall look elsewhere.



Ignition timing.

bigt


Don't hide 'em, Ride 'em !!

RF Whatley
Cornelia, GA

"Shop Boy" at Rodi British Bikes
#430042 - 04/16/12 2:24 pm Re: 72 TR6 piston clearance-ring end gap? [Re: RF Whatley]  
Joined: Nov 2005
Posts: 706
Fisherman Offline
BritBike Forum member
Fisherman  Offline
BritBike Forum member

Joined: Nov 2005
Posts: 706
Tennessee
Originally Posted By: RF Whatley
Originally Posted By: Fisherman

We shall look elsewhere.



Ignition timing.

bigt


Yes....(sigh)...static timed only, not strobed....

I BET IT WILL THE NEXT TIME!!!!!

Thanks Professor.

Last edited by Fisherman; 04/16/12 2:28 pm.

'Never argue with an idiot, they'll bring you down to their level, and beat you with experience'

'72 TR6
'12 Hinckley Scrambler
'95 FLHTC Road Sofa
#430077 - 04/16/12 5:39 pm Re: 72 TR6 piston clearance-ring end gap? [Re: Fisherman]  
Joined: Oct 2003
Posts: 3,524
dave jones Offline
BritBike Forum member
dave jones  Offline
BritBike Forum member

Joined: Oct 2003
Posts: 3,524
Emsworth, sunny south of Engla...
To be pedantic, static timing actually means setting the timing to the idle setting. Did you do this? It is best to set the timing to the fully advanced figure with the aau locked against the springs as this is where the engine requires accuracy. This should be ok if carefully done on each cylinder. I set the engine to 36 degrees rather than 38 to cope with any bad fuel and do strobe it but the timing would have to be a long way out to damage the engine. Mine will run ok after the battery and bulb technique (or ammeter flicking to zero with ignition on).

You can't set a Boyer without strobing as it could be miles out

#430083 - 04/16/12 6:30 pm Re: 72 TR6 piston clearance-ring end gap? [Re: Fisherman]  
Joined: Nov 2005
Posts: 706
Fisherman Offline
BritBike Forum member
Fisherman  Offline
BritBike Forum member

Joined: Nov 2005
Posts: 706
Tennessee
Yes, set with no centrifugal advance, idle setting. It is the original points/condenser ignition. I agree, it seems as if I would have noticed pinging (pinking I think you gents call it) from an engine so far out of time to cause it to heat seize, but I'm grasping at straws here.


'Never argue with an idiot, they'll bring you down to their level, and beat you with experience'

'72 TR6
'12 Hinckley Scrambler
'95 FLHTC Road Sofa
#430087 - 04/16/12 6:42 pm Re: 72 TR6 piston clearance-ring end gap? [Re: Fisherman]  
Joined: Mar 2005
Posts: 9,970
John Healy Offline
John Healy  Offline



Joined: Mar 2005
Posts: 9,970
Boston, Massachusetts
The face of the rings, color of the wrist pin, condition and color of the underside of the piston, condition of the carbon on the top of the piston, and the actual type and location of the seizure will tell you a lot.


#430090 - 04/16/12 7:02 pm Re: 72 TR6 piston clearance-ring end gap? [Re: John Healy]  
Joined: Nov 2005
Posts: 706
Fisherman Offline
BritBike Forum member
Fisherman  Offline
BritBike Forum member

Joined: Nov 2005
Posts: 706
Tennessee
Originally Posted By: John Healy
The face of the rings, color of the wrist pin, condition and color of the underside of the piston, condition of the carbon on the top of the piston, and the actual type and location of the seizure will tell you a lot.


It no doubt would tell YOU a lot and I'm willing to learn but as of now it would unfortunately tell me very little.
If pictures would help, I'll get some.


'Never argue with an idiot, they'll bring you down to their level, and beat you with experience'

'72 TR6
'12 Hinckley Scrambler
'95 FLHTC Road Sofa
#430102 - 04/16/12 8:23 pm Re: 72 TR6 piston clearance-ring end gap? [Re: Fisherman]  
Joined: Mar 2005
Posts: 9,970
John Healy Offline
John Healy  Offline



Joined: Mar 2005
Posts: 9,970
Boston, Massachusetts
Aren't we here to learn. I do every day!

I hope we are a little bit farther along than Bob Seger's Night Moves. But as it is we ARE "working on mysteries without any clues". Description of colors, location, etc. would be nice... Pictures would be better.

Close up of the face of the rings (important), piston dome inner and outer, pin to show how much heat it has been exposed to, and the location and type of seizure on the piston.

It might tell us nothing, but then again it might give you some clues as to the reason of the seizure.

The only thing we know at this point is "the piston got bigger than the bore."


#430121 - 04/16/12 9:49 pm Re: 72 TR6 piston clearance-ring end gap? [Re: Fisherman]  
Joined: Jun 2007
Posts: 1,636
DPO Offline
BritBike Forum member
DPO  Offline
BritBike Forum member

Joined: Jun 2007
Posts: 1,636
Douglasville (Atlanta) Georgia
Not really associated with your problem, but this did remind me of an article I have at home concerning piston ring "end gap". I dont normally read such technical articles, but the more I read, the better it got! They took an internal combustion engine, and added new rings at a wide variance of end gap. The first, I think, was just about flush, or close to it, and they ran the engine and took readings and so forth. They again, removed the piston and rings, and using something like .080 gap on the last run, and all along positioning the gaps in line with each other, opposed, and just about any way you can put them, and there was no significant difference in any of the results....I may be wrong on some of these statements (disclaimer), but I'll bring the article with me to the BIBR...(If I remember)....


If you love it, let it go. If it comes back, you've highsided!"

1971 Triumph T120
2005 Triumph "America"
1976 BMW R90/6
#430229 - 04/17/12 3:01 pm Re: 72 TR6 piston clearance-ring end gap? [Re: Fisherman]  
Joined: Mar 2005
Posts: 9,970
John Healy Offline
John Healy  Offline



Joined: Mar 2005
Posts: 9,970
Boston, Massachusetts
DPO: There is ring gap as measured when the rings are new, and there is ring gap after many thousands of miles of use.

When new, rings have a lot of spring pressure they exert to seal the face of the ring against the cylinder wall.

When old and worn the rings have lost most of their tension because of heat and wear and can no longer can seal as they once did. The result is loss in compression and high oil consumption.

When we take the engine apart, what we can see is the rings now have a wide gap and we attribute our problems to that. What we can't see is the face of the ring, and the cylinder bore has worn, and for each .001" of wear the ring gap increases by approx. .003". So it is easy to assume that the gap is the problem, while ring tension is overlooked.

While one would not assemble an engine with an .080" gap, what some would assume to be excessive will have little, if any effect upon performance. But go less than recommended and the ends of the rings can come together and cause all sorts of expensive problems. So in ring gap more isn't bad, while less can be very, very bad.



Moderated by  John Healy 


Home | Sponsors | Newsletter | Regalia | Calendar | Bike Project | BritBike Museum | Spiders Cartoons | "OLD" BritBike Forum | DVD- Manuals & Parts books | BritBike Stickers & Decals
Upgrade to: Premium Membership | Premium Life Membership | Vendor Membership | Site Sponsor Membership
UBB.threads™ PHP Forum Software 7.6.0
Page Time: 0.841s Queries: 16 (0.198s) Memory: 0.9155 MB (Peak: 1.1684 MB) Zlib disabled. Server Time: 2017-11-24 03:46:30 UTC