guzziriders.org - moto guzzi forum Homepage
Forum Home Forum Home > Social section > The Bar.
  New Posts New Posts RSS Feed - Piston Woes
  FAQ FAQ  Forum Search   Events   Register Register  Login Login

Piston Woes

 Post Reply Post Reply Page  12>
Author
Message
Dave P. View Drop Down
Senior Member
Senior Member


Joined: 12 Jan 2015
Location: Northants
Status: Offline
Points: 2567
Post Options Post Options   Thanks (0) Thanks(0)   Quote Dave P. Quote  Post ReplyReply Direct Link To This Post Topic: Piston Woes
    Posted: 01 Dec 2018 at 19:20
I'm looking for opinions on what may have caused the damage to this piston. It's not from a Guzzi but from a Royal Enfield Bullet. I hope that's OK




What the picture doesn't show is that most of the circlip is still there but deeply recessed so far into the groove that the gudgeon pin can pass through it. The damage above and below the pin hole is a bit strange and is showing a similar trend on the other side of the piston where the circlip is still located as it should be.





Edited by Dave P. - 01 Dec 2018 at 19:31
TO LIVE OUTSIDE THE LAW YOU MUST BE HONEST.

1971 V7 Special. 1972 850GT.
1970 T120 Bonnie. 2009 500 Bullet.
Back to Top
jpc View Drop Down
Senior Member
Senior Member


Joined: 06 Oct 2016
Location: Belgium
Status: Offline
Points: 453
Post Options Post Options   Thanks (0) Thanks(0)   Quote jpc Quote  Post ReplyReply Direct Link To This Post Posted: 01 Dec 2018 at 20:26
Just guessing, but the healthier of the two circlips is positioned at 9 o'clock, which is not very good because inertia forces tend to force the ends out of the groove at TDC and BDC. The effect is even more pronounced with the heavier, curly ends of course. Better to have the ends at 12 or 6 o'clock.
Looks like the other clip jumped out, did the pin score the cylinder wall ?
Back to Top
Dave P. View Drop Down
Senior Member
Senior Member


Joined: 12 Jan 2015
Location: Northants
Status: Offline
Points: 2567
Post Options Post Options   Thanks (0) Thanks(0)   Quote Dave P. Quote  Post ReplyReply Direct Link To This Post Posted: 02 Dec 2018 at 09:56
Most of the clip is still in the groove, but so deeply recessed in the groove that the gudgeon pin can pass through it. The bore is deeply scored and is probably scrap. There were no nasty noises our outward clues as to what had happened. I removed the head to fix an oil weep from the pushrod tunnels, nothing more. The rest was a nasty shock. Big end and small end are showing no signs of wear,I can only assume that the "ears" of the clip broke off thus causing the damage. Any other thoughts are most welcome.
TO LIVE OUTSIDE THE LAW YOU MUST BE HONEST.

1971 V7 Special. 1972 850GT.
1970 T120 Bonnie. 2009 500 Bullet.
Back to Top
iansoady View Drop Down
Senior Member
Senior Member
Avatar

Joined: 23 Jul 2017
Location: Birmingham
Status: Offline
Points: 930
Post Options Post Options   Thanks (0) Thanks(0)   Quote iansoady Quote  Post ReplyReply Direct Link To This Post Posted: 02 Dec 2018 at 10:22
That second picture looks like a manufacturing fault in the piston to me - as if the metal surrounding the gudgeon pin hole and forming the outer side of the circlip recess has just flaked off. Or even it might have come from the factory like that.....

I can't see any way there'd be enough end force on the gudgeon pin to break a chunk like that off.

Bad news is of course all the bits will be in the crankcase so it looks like a full engine strip.
Ian
1982 V50
1952 Norton ES2
Back to Top
Jerry atric View Drop Down
Senior Member
Senior Member
Avatar

Joined: 24 Nov 2014
Location: Wiltshire
Status: Offline
Points: 2095
Post Options Post Options   Thanks (0) Thanks(0)   Quote Jerry atric Quote  Post ReplyReply Direct Link To This Post Posted: 02 Dec 2018 at 12:29
I must say, my first thought was poor quality item fitted but didn't want to sound too cynical. Don't know what the quality control at Enfield is like.
Back to Top
Dave P. View Drop Down
Senior Member
Senior Member


Joined: 12 Jan 2015
Location: Northants
Status: Offline
Points: 2567
Post Options Post Options   Thanks (0) Thanks(0)   Quote Dave P. Quote  Post ReplyReply Direct Link To This Post Posted: 02 Dec 2018 at 16:54
Originally posted by Jerry atric Jerry atric wrote:

I must say, my first thought was poor quality item fitted but didn't want to sound too cynical. Don't know what the quality control at Enfield is like.


Yes, the same thought had occurred to me, but this is a 2008 Bullet with a " European made" piston. Mind you, in its self that offers no guarantees.
TO LIVE OUTSIDE THE LAW YOU MUST BE HONEST.

1971 V7 Special. 1972 850GT.
1970 T120 Bonnie. 2009 500 Bullet.
Back to Top
Glawster View Drop Down
Senior Member
Senior Member


Joined: 14 Sep 2015
Location: Cheltenham
Status: Offline
Points: 429
Post Options Post Options   Thanks (0) Thanks(0)   Quote Glawster Quote  Post ReplyReply Direct Link To This Post Posted: 02 Dec 2018 at 17:41
Bad luck Dave.  Clearly I have no idea how it was caused but just wanted to make sympathetic noises.

1979 Guzzi T3 California
1973 Guzzi V7 Sport
1955 Guzzi Falcone Sport
2015 Triumph Tiger 800
Back to Top
nab301 View Drop Down
Senior Member
Senior Member
Avatar

Joined: 29 Oct 2017
Location: Dublin Ireland
Status: Offline
Points: 212
Post Options Post Options   Thanks (0) Thanks(0)   Quote nab301 Quote  Post ReplyReply Direct Link To This Post Posted: 02 Dec 2018 at 20:31
The joys of Enfield ownership ... I was leaving a machine shop earlier this year with a rebored  Enfield barrel when the new piston fell out ( the untaped) bottom of its box Cry.
I have an old Ae Autoparts  piston component fault diagnosis  chart  which may help answer your question although it won't ease the pain.
Online version



Nigel
Keep smiling , it makes people wonder what you've been up to!
'04 Breva 750, '99 Bmw R1100S, '06 Triumph Bonneville '05 CBF 250, '03Bullet 65 500, '93 MZ301 Saxon fun
Back to Top
Jerry atric View Drop Down
Senior Member
Senior Member
Avatar

Joined: 24 Nov 2014
Location: Wiltshire
Status: Offline
Points: 2095
Post Options Post Options   Thanks (0) Thanks(0)   Quote Jerry atric Quote  Post ReplyReply Direct Link To This Post Posted: 02 Dec 2018 at 20:42
Originally posted by Dave P. Dave P. wrote:

Originally posted by Jerry atric Jerry atric wrote:

I must say, my first thought was poor quality item fitted but didn't want to sound too cynical. Don't know what the quality control at Enfield is like.


Yes, the same thought had occurred to me, but this is a 2008 Bullet with a " European made" piston. Mind you, in its self that offers no guarantees.


That could mean made just about anywhere, 'Europe' is a big place these days... Obviously it will be a bit smaller in March, May-be.
Back to Top
Mike H View Drop Down
Senior Member
Senior Member
Avatar

Joined: 21 May 2014
Location: East Anglia
Status: Offline
Points: 5998
Post Options Post Options   Thanks (0) Thanks(0)   Quote Mike H Quote  Post ReplyReply Direct Link To This Post Posted: 03 Dec 2018 at 01:01
Originally posted by nab301 nab301 wrote:

The joys of Enfield ownership ... I was leaving a machine shop earlier this year with a rebored  Enfield barrel when the new piston fell out ( the untaped) bottom of its box Cry


I remember you saying that. Ouch


"Chicken nuggets don't dance on a Tuesday."
Back to Top
iansoady View Drop Down
Senior Member
Senior Member
Avatar

Joined: 23 Jul 2017
Location: Birmingham
Status: Offline
Points: 930
Post Options Post Options   Thanks (0) Thanks(0)   Quote iansoady Quote  Post ReplyReply Direct Link To This Post Posted: 03 Dec 2018 at 11:14
Handy little reference that. And the piston in the pic does look vaguely similar to yours.
Ian
1982 V50
1952 Norton ES2
Back to Top
Dave P. View Drop Down
Senior Member
Senior Member


Joined: 12 Jan 2015
Location: Northants
Status: Offline
Points: 2567
Post Options Post Options   Thanks (0) Thanks(0)   Quote Dave P. Quote  Post ReplyReply Direct Link To This Post Posted: 03 Dec 2018 at 12:40
Thanks nab301. That illustration looks just like my piston. As I've had the bike from new I can only assume that the fault originated in the factory. Bad show!!!

The scoring of the bore is bad and the only remedy may be to bore out to 535 cc and fit the appropriate piston. Higher C/R additional capacity,what about the additional stress on the bottom end?
TO LIVE OUTSIDE THE LAW YOU MUST BE HONEST.

1971 V7 Special. 1972 850GT.
1970 T120 Bonnie. 2009 500 Bullet.
Back to Top
Dave P. View Drop Down
Senior Member
Senior Member


Joined: 12 Jan 2015
Location: Northants
Status: Offline
Points: 2567
Post Options Post Options   Thanks (0) Thanks(0)   Quote Dave P. Quote  Post ReplyReply Direct Link To This Post Posted: 03 Dec 2018 at 13:13






It looks to me like a casting fault in the barrel (I've been advised of this on the RE forum)

A similar indentation exists diametrically opposite where the gudgeon pin has not protruded.As can be seen in the other photo the circlip remains in place. And yet there is similar damage on that side of the piston though not as extensive. Looks like I'll be digging deep in my wallet.Such a shame to disturb the moths.




Edited by Dave P. - 03 Dec 2018 at 13:16
TO LIVE OUTSIDE THE LAW YOU MUST BE HONEST.

1971 V7 Special. 1972 850GT.
1970 T120 Bonnie. 2009 500 Bullet.
Back to Top
nab301 View Drop Down
Senior Member
Senior Member
Avatar

Joined: 29 Oct 2017
Location: Dublin Ireland
Status: Offline
Points: 212
Post Options Post Options   Thanks (0) Thanks(0)   Quote nab301 Quote  Post ReplyReply Direct Link To This Post Posted: 03 Dec 2018 at 21:36
Originally posted by Dave P. Dave P. wrote:


The scoring of the bore is bad and the only remedy may be to bore out to 535 cc and fit the appropriate piston. Higher C/R additional capacity,what about the additional stress on the bottom end?

Personally I'd keep it as near standard as possible...   well, other than the usual intake and exhaust de restrictions based on nothing other than you have basically a 50's motorcycle with a marginal lubrication system .Short of redrilling all the oilways (I think) there is little point in upgrading the pumps etc. 
Spend your money ensuring the valves and seats are good ,and seal properly  and purchase a secondhand barrel  , get it bored properly and all should be good.  Even a standard bike should need the decompressor when kicking over , plenty don't!!  Many acquaintances with standard bikes have had bearing failures  , piston failures etc, and one fitted a high compression piston with a compression plate thinking that would be "bullet  proof " but that piston disintegrated  too ( although he did tow a trailer with that bike.)
My first Enfield was a '98 Indian import  350 bullet purchased as a non runner with low mileage in '01.
I sorted it  and then got bored,  leading  me down the path to eternal "debtnation* (© umg magazine I think..) in trying to create a sleeperLOL
I fitted a "Higher" compression piston and cams  among other things  but at one stage it recorded  6 bhp on the dyno...Embarrassed  I eventually put it back more or less to standard and nearly doubled the output to 12 bhp!  A while later I saw the the cams I'd fitted were now only recommended for the  500 and after eventually selling  that bike with a "never again  "comment   i've ended up more recently with a 500 but so far resisted the urge to fit the cams..  at least the 500 doesn't have a wide ratio 4 speed box.



Edited by nab301 - 03 Dec 2018 at 21:44
Nigel
Keep smiling , it makes people wonder what you've been up to!
'04 Breva 750, '99 Bmw R1100S, '06 Triumph Bonneville '05 CBF 250, '03Bullet 65 500, '93 MZ301 Saxon fun
Back to Top
Dave P. View Drop Down
Senior Member
Senior Member


Joined: 12 Jan 2015
Location: Northants
Status: Offline
Points: 2567
Post Options Post Options   Thanks (0) Thanks(0)   Quote Dave P. Quote  Post ReplyReply Direct Link To This Post Posted: 04 Dec 2018 at 21:09
I've ordered a second-hand barrel and piston from Hitchcocks. They are in good condition, standard bore and standard C/R. I thought about boring the original pot out but I don't know how deep the apparent casting fault reaches. I'm also replacing the rockers and rocker bearing blocks as they are quite badly scored, presumably by debris from the circlips picked up from the sump and pumped up top. My 500 has a wide ratio 4-speed box. OK, no more Royal Enfields,I'll stick to Guzzis' now.
TO LIVE OUTSIDE THE LAW YOU MUST BE HONEST.

1971 V7 Special. 1972 850GT.
1970 T120 Bonnie. 2009 500 Bullet.
Back to Top
 Post Reply Post Reply Page  12>
  Share Topic   

Forum Jump Forum Permissions View Drop Down

Forum Software by Web Wiz Forums® version 12.00
Copyright ©2001-2018 Web Wiz Ltd.

This page was generated in 0.063 seconds.