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
bones_bir
bones_bir
Central TX
Posts: 37
Joined: March 2007
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
212 registered members (68 royalstar tony), 1,756 guests, and 514 spiders.
Key: Admin, Global Mod, Mod
Newest Members
johnguppy, michael morgan, Xavier, J. Grant, Jerry
9952 Registered Users
Top Posters(30 Days)
btour 179
koan58 94
Stuart 83
Popular Topics(Views)
434,796 mail-order LSR
Forum Statistics
Forums33
Topics65,245
Posts631,743
Members9,952
Most Online3,995
Feb 13th, 2017
Like BritBike.com on Facebook

Previous Thread
Next Thread
Print Thread
Rate This Thread
#63564 - 08/06/05 1:00 pm Commando 750 Piston Ring Question  
Joined: Aug 2001
Posts: 676
John Bakker Online content
BritBike Forum member
John Bakker  Online Content
BritBike Forum member

Joined: Aug 2001
Posts: 676
Midland, Ontario, Canada
I just finished doing a top end rebuild on my 1970 Commando 750 with new guides, valve springs and valve job, as well as installing new rings and having the cylinders professionally honed. Problem is I'm experiencing excessive oil consumption. I've done lots of top end rebuilds over the years and have never experienced this much oil burning.
I did install the rings properly with top marks up and staggered the gaps, did everything by the book.
I have read about the slotted pistons requiring different rings than regular replacement Commando pistons. The pistons I have are AE and are what I would call the second generation of slot pistons, in that they have 2 slots on the skirt front and rear but no cut connecting them through the oil ring groove (in other words they are not the flip-top ones). I assumed that these pistons would take the regular replacement rings and not the slot ones.
The rings I received fit the pistons perfectly and end gap was checked before installation. One difference though was that my originals were the 3 piece oil control ring whereas the replacements are a 1 piece ring with a corrugated type of spring that I assumed fitted under the oil ring (which indeed it did). I have not seen this type of device before on an oil ring.
I would appreciate checking for me to see if indeed I did install the correct rings for my pistons, to ease my mind. I did see a note concerning the slot type pistons having a shallower oil ring groove than the later rings. I assumed that this reference was to the infamous "flip top" slotted pistons of early Commandos.
Was I wrong and should I have asked for different rings? Still trying to solve this puzzle and chalking another one up to experience.
In the meantime, I'm riding the bike and trying to break these rings in (yesterday put 150 miles on it). Hopefully the problem will solve itself, but I am concerned.

Thanks again for your time and would appreciate hearing from anyone who can shed some light on the situation. LIVE AND LEARN! smile

Best regards,

John

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
#63565 - 08/06/05 2:51 pm Re: Commando 750 Piston Ring Question  
Joined: May 2004
Posts: 557
jangg Offline
BritBike Forum member
jangg  Offline
BritBike Forum member

Joined: May 2004
Posts: 557
Norway, just south of Oslo
John.
I've just experienced the same problem (run for 8-9000km). Extensive oil consumption - approx one (1) litre per thousand km burnt away. Experts mean 2-3 dl should be more likely.

SO I went to a real expert and he meant that the Commandos are prone to honing granularity. It's a theme that the ("original") piston rings could be too soft and therefore not brake in sufficiently. The oil film then preventing the rings from braking through the honed surface...

Result: No signs of smoke actually, just burning oil through the (microscopic) small remains of the honed surface.

As I just melted down my right conrod big end bearing I've parked the bike and the problem, but I maybe was tricked by the excessive oilburning myself forgetting a refill and bang, Game Over eek

regards
jangg


'73 Commando Basket - new aluminium cyl
'93 Ducati 900 SS

"Better lit a light than cursing the darkness"
(Confucius)
#63566 - 08/06/05 8:35 pm Re: Commando 750 Piston Ring Question  
Joined: Oct 2004
Posts: 307
debby Offline
BritBike Forum member
debby  Offline
BritBike Forum member

Joined: Oct 2004
Posts: 307
Boulder, CO
Mine's a lot worse than that. After today's 2 hr ride in the canyons I had to add a pint of oil. That's maybe 4 dl in 120 km or so eek

The right cyl smokes fairly heavily on acceleration but the bike runs well and has good compression. DPO said it's smoked ever since the rebuild he did some years ago.

So I have to tear it down and try to improve things. I'll probably try to wait until the end of the season though.

Debby
71 750 Roadster

#63567 - 08/09/05 6:23 pm Re: Commando 750 Piston Ring Question  
Joined: May 2004
Posts: 557
jangg Offline
BritBike Forum member
jangg  Offline
BritBike Forum member

Joined: May 2004
Posts: 557
Norway, just south of Oslo
Feel I'm with you gentlemen !

Debby, you know of course the prob sources:
- Valve guide leak
- Oil stop rings of course
- The more exotic "hone granulation & brake in" scenario
- Cyl top gasket - remember to assure sealing from pushrod tunnels-to-front-studs. Very little distance in between can get a frustrating oil leak through the stud nuts...

And what the heck do we do? I soon will have a new conrod - and I am very anxious to get an approx clean machine.

regards
jangg


'73 Commando Basket - new aluminium cyl
'93 Ducati 900 SS

"Better lit a light than cursing the darkness"
(Confucius)
#63568 - 08/13/05 1:31 pm Re: Commando 750 Piston Ring Question  
Joined: Jan 2004
Posts: 1,106
Kommandokenny Offline
BritBike Forum member
Kommandokenny  Offline
BritBike Forum member

Joined: Jan 2004
Posts: 1,106
McKellar,Ontario
John ; You probably know this but just in case .....After doing a ring job the "crust" at the top of the cylinder is cleaned off and until it builds up there again the bike can use a bit of extra oil.kk


If Norton made an airplane,would you fly in it?
#63569 - 08/13/05 2:58 pm Re: Commando 750 Piston Ring Question  
Joined: Mar 2005
Posts: 9,962
John Healy Online content
John Healy  Online Content


Joined: Mar 2005
Posts: 9,962
Boston, Massachusetts
KK posted:
After doing a ring job the "crust" at the top of the cylinder is cleaned off and until it builds up there again the bike can use a bit of extra oil

Hmmmmmm...... Could you explain this one?
john


#63570 - 08/14/05 1:56 am Re: Commando 750 Piston Ring Question  
Joined: Jan 2004
Posts: 1,106
Kommandokenny Offline
BritBike Forum member
Kommandokenny  Offline
BritBike Forum member

Joined: Jan 2004
Posts: 1,106
McKellar,Ontario
The Clymer manual recomends that you dont remove the carbon ridges from around the tops of the cylinders when doing a valve job or decarb. [page 39]
I researched this a little further, and was "told" it would increase oil consumption if you did.
So it would seem that if you did a ring job the ridges would be taken down and the bike might use a little extra oil on break in?
Mine seemed to use extra oil on break in last time I did a ring job, and I attributed it to this.kk


If Norton made an airplane,would you fly in it?
#63571 - 08/15/05 2:55 pm Re: Commando 750 Piston Ring Question  
Joined: Mar 2005
Posts: 9,962
John Healy Online content
John Healy  Online Content


Joined: Mar 2005
Posts: 9,962
Boston, Massachusetts
Checked all of the Clymer manuals ,except for BSA A65 which is out of stock, and could not find this reference.
john


#63572 - 08/16/05 8:02 am Re: Commando 750 Piston Ring Question  
Joined: Jan 2004
Posts: 1,106
Kommandokenny Offline
BritBike Forum member
Kommandokenny  Offline
BritBike Forum member

Joined: Jan 2004
Posts: 1,106
McKellar,Ontario
It's in the Clymer Norton manual page 39.[valve job section]Its in a little footnote format.
The way I see it is, if the rings are not seating very well and some oil is getting by, this ridge or crust would help contain some of the blowby.
Not much you can do about it, as honing will take it off.
The advice is aimed more towards any head work being done and may be a moot scenario when doing a ring job .
I was just throwing it out there as it could be a "factor"in some of your main problem.
It won't be your #1 concern.kk


If Norton made an airplane,would you fly in it?
#63573 - 08/19/05 10:08 pm Re: Commando 750 Piston Ring Question  
Joined: Aug 2001
Posts: 676
John Bakker Online content
BritBike Forum member
John Bakker  Online Content
BritBike Forum member

Joined: Aug 2001
Posts: 676
Midland, Ontario, Canada
Just wanted everyone to know that after about 450 miles of break-in, there is no visible smoking any longer, much to my relief, so be patient if experiencing oil burning after new ring installation. I have also just changed the oil and filter and went from 20W50 to straight 50 to further assist in keeping the oil where it belongs.
Thanks for all your input everyone!
John

#63574 - 08/20/05 12:40 am Re: Commando 750 Piston Ring Question  
Joined: Jan 2004
Posts: 1,106
Kommandokenny Offline
BritBike Forum member
Kommandokenny  Offline
BritBike Forum member

Joined: Jan 2004
Posts: 1,106
McKellar,Ontario
I know the other John probably wont be able to find it but the Clymer manual also recomends a monograde for break in then if you like switch to a multi grade after break in.[Ionce spent an hour putting a tire on backwards] I doubt it was the reason for smokin on break in, but you never know?
Its good to know things worked out for you!kk


If Norton made an airplane,would you fly in it?
#63575 - 08/20/05 3:50 am Re: Commando 750 Piston Ring Question  
Joined: Aug 2001
Posts: 1,850
dave - NV Online content
BritBike Forum member
dave - NV  Online Content
BritBike Forum member

Joined: Aug 2001
Posts: 1,850
Elko, Nevada USA
**IF** you Oil the Rings on engine assembly, oil Will be Trapped between the rings as it has no where to go. This oil will burn up and turn to a carbon coating both on the face of the rings and on the cylinder walls, preventing the rings from seating.
I know, I know, everyone wants to "lube everything", to help your engine, but Don't oil the rings on reassembly. Read the instructions supplied with any/all modern rings.

Have you noticed when disasembling an engine that the rings and cylinder walls appear to be near dry? Yup, that's how the engine happily operates if all is well.

The Proper drill:
With a small amount of engine oil on a white cloth, wipe down the cylinder walls. After a bore job and hone, continue wiping until the white rag is dead clean which will indicate all/most of the carburundom particles from the honing stones and metal particles are cleaned off the bore.

Then with a clean/dry cloth wipe the bore as dry as possible. This will leave a slight oil film in the pores and hone marks.

Now with the rings dead dry install the piston. Do Not be tempted to oil the rings! It is advisable to apply a slight bit of oil to the skirt of the piston below the bottom oil ring.

Start the engine, but Do Not allow it to idle in the shop for any length of time thinking you are being kind to it, or think you will be seating the rings this way.
Warm it up as quickly as possible and go for a ride on the open road.

Now .. Make the engine "pull", in a high gear at 3-4k revs, say 50 - 60 mph with our BI. This will generate enough but still modest pressure Behind the rings, with the engine only making 8-10 hp, pushing the rings against the cylinder wall and clearing the surfaces of any excess oil and "fitting', the ring face to the cylinder.
In mere minutes or 5-10 miles max you have seated your rings with No None Nadda problem. And with never a bit of smoke out the exhaust.

This business I hear of riding a bike several hundred miles to "seat rings", indicates something is/was done wrong somewhere. And the talk of using low grade "break in oil", umm seems strange to me. 'Whatever' on the oil used ...
But All of the ring manufactures do caution against using the "modern synthetic oil", during engine break in due to possible ring seating issues.

Make sense? I hope so.


dave - NV
#63576 - 10/10/05 3:37 pm Re: Commando 750 Piston Ring Question  
Joined: Oct 2005
Posts: 4
Dre Offline
BritBike Forum
Dre  Offline
BritBike Forum

Joined: Oct 2005
Posts: 4
Montreal, Canada
I have recently bought my older brother's bike. It's a 1972 750 Norton Commando. It has been kept in a barn for the past 18 yrs so you can just imagine how dirty she was when I picked her up. I took her apart to make sure that nothing was seized and to change all the seals. Im now at the engine and changing the piston rings but I was told by my local supplier that there are different types of piston rings for this model. Any suggestions or confirmations as to wich ones are the right ones.

thanks

Dre

#63577 - 10/10/05 11:56 pm Re: Commando 750 Piston Ring Question  
Joined: Jan 2004
Posts: 1,106
Kommandokenny Offline
BritBike Forum member
Kommandokenny  Offline
BritBike Forum member

Joined: Jan 2004
Posts: 1,106
McKellar,Ontario
Before 1972 the piston oil ring "groove" was a little bit shallower than the piston oil ring groove for the 1972 piston. "[sheeww"]If your motor is above ser# 147259 and your oil ring or groove width is .182"you can use062461[SE].If your oil ring groove is .130 you can use oil ring 061180[apex]. If you have the older piston's it might be worth upgrading to some new pistons?
As far as two different ring sets for the 72 Commando I believe there are two different pistons [combat and standard] but it looks like the rings are suitable for either.
Do you have a combat?kk


If Norton made an airplane,would you fly in it?
#63578 - 10/11/05 12:06 am Re: Commando 750 Piston Ring Question  
Joined: Jan 2004
Posts: 1,106
Kommandokenny Offline
BritBike Forum member
Kommandokenny  Offline
BritBike Forum member

Joined: Jan 2004
Posts: 1,106
McKellar,Ontario
from Daves thread above **IF** you Oil the Rings on engine assembly, oil Will be Trapped between the rings as it has no where to go. This oil will burn up and turn to a carbon coating both on the face of the rings and on the cylinder walls, preventing the rings from seating.
I know, I know, everyone wants to "lube everything", to help your engine, but Don't oil the rings on reassembly. Read the instructions supplied with any/all modern rings

This sure makes a lot of sense ,but after reading the piston manufacturer's installations instructions I'm not so sure.
They recomend lubeing up the bore and just about everything else [except rings],but if its oil on the bore it's gonna end up on the rings?
Because I am putting the pistons in now and not riding the bike for a few months I;m inclined to lube eveything up to ward off corrosion over the winter.
Any input on my potential plan is welcome kk


If Norton made an airplane,would you fly in it?
#63579 - 10/11/05 7:56 pm Re: Commando 750 Piston Ring Question  
Joined: Oct 2005
Posts: 4
Dre Offline
BritBike Forum
Dre  Offline
BritBike Forum

Joined: Oct 2005
Posts: 4
Montreal, Canada
thanks for the quick reply...how can I see if I own a combat??

#63580 - 10/11/05 8:27 pm Re: Commando 750 Piston Ring Question  
Joined: Jan 2004
Posts: 1,106
Kommandokenny Offline
BritBike Forum member
Kommandokenny  Offline
BritBike Forum member

Joined: Jan 2004
Posts: 1,106
McKellar,Ontario
The head will be stamped RH3 .Factory black on barrells.Serial # 200976 -to 204166 [and she'll be a pigmy wh#r% to kick over]kk


If Norton made an airplane,would you fly in it?
#63581 - 10/11/05 9:40 pm Re: Commando 750 Piston Ring Question  
Joined: Oct 2005
Posts: 164
78AMIgrad Offline
BritBike Forum member
78AMIgrad  Offline
BritBike Forum member

Joined: Oct 2005
Posts: 164
Juneau, AK
I beleive RH6 is the Combat designation.

#63582 - 10/11/05 10:00 pm Re: Commando 750 Piston Ring Question  
Joined: Jan 2004
Posts: 1,106
Kommandokenny Offline
BritBike Forum member
Kommandokenny  Offline
BritBike Forum member

Joined: Jan 2004
Posts: 1,106
McKellar,Ontario
The Combat head is an RH3.
I did however mistakenly tell you it was stamped RH3. It is stamped with a C on top of the head. Or thats what the Tech digest says anyway.
Of course I don't own a combat, but most books I've looked at peg it as an RH3
The RH 6 is a 73 stock 750. kk laugh beerchug
http://atlanticgreen.com/images/cylhead.jpg


If Norton made an airplane,would you fly in it?
#63583 - 10/12/05 12:26 am Re: Commando 750 Piston Ring Question  
Joined: Oct 2005
Posts: 4
Dre Offline
BritBike Forum
Dre  Offline
BritBike Forum

Joined: Oct 2005
Posts: 4
Montreal, Canada
I'm kinda new at this, sorry. I found a MS5 17903, that's about it.

#63584 - 10/12/05 2:24 am Re: Commando 750 Piston Ring Question  
Joined: Jan 2004
Posts: 1,106
Kommandokenny Offline
BritBike Forum member
Kommandokenny  Offline
BritBike Forum member

Joined: Jan 2004
Posts: 1,106
McKellar,Ontario
OK, Than I guess you are the proud owner of a 1971 750.They did not stamp the head with any RH number before 72
Back to the rings, you want to have a good look at the pistons to make sure there ok.
If they are, the only thing you need to do is measure the oil ring groove[.130"/OR/.182" and check the bore size to make sure it is within tolerance and hasn't been bored out.You can order your rings based on that info.KK


If Norton made an airplane,would you fly in it?
#63585 - 10/12/05 6:52 pm Re: Commando 750 Piston Ring Question  
Joined: Oct 2005
Posts: 4
Dre Offline
BritBike Forum
Dre  Offline
BritBike Forum

Joined: Oct 2005
Posts: 4
Montreal, Canada
Great. Thanks alot for the help. She needs alot of work but mostly just a good cleaning. I took everything apart and Im not changing all the seals. Things that look good and dont require new seals I leave along but so far so good. I was also thinking of switching the points over to electric. Any suggestions??

#63586 - 10/12/05 7:04 pm Re: Commando 750 Piston Ring Question  
Joined: Jan 2004
Posts: 1,106
Kommandokenny Offline
BritBike Forum member
Kommandokenny  Offline
BritBike Forum member

Joined: Jan 2004
Posts: 1,106
McKellar,Ontario
Electronic ignition is a great upgrade. I have a Boyer analog system and its works fine.
They have a digital kit now, but I can't help much with which one you want.
They are easy to install and mine is 10 years old and all that happened was a wire broke at the pickup [common problem until you cut the restricting "tie"that cut into the wire].
Anyway, go for it.kk


If Norton made an airplane,would you fly in it?
#63587 - 10/14/05 1:01 am Re: Commando 750 Piston Ring Question  
Joined: Feb 2005
Posts: 564
MarksterTT Offline
BritBike Forum member
MarksterTT  Offline
BritBike Forum member

Joined: Feb 2005
Posts: 564
San Francisco Bay Area
John, perhaps your shop honed your cylinders with a fine hone as used on modern engines. As John Healy and others have said on other posts, the old style iron rings need a 220-240 grit hone to seat those rings and true them to the bore. It takes combustion pressure to force those rings against the cyl. wall thru the film of oil and taking it easy w/out making some manifold press. wont do it. Dave-NV has the right idea. Your engine may break-in fine or may never have the seal it should hence,power & oil control. Be interesting to know what grit stones your shop used. You may know all this but thought I would mention it in case you aren't happy with oil consumption in the future...Mark


Moderated by  Dave Comeau 


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: 0.102s Queries: 14 (0.006s) Memory: 0.9814 MB (Peak: 1.3081 MB) Zlib disabled. Server Time: 2017-11-18 10:23:13 UTC