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#153136 - 12/08/07 10:00 pm Oil feed/quill...Twins ...Yikes!  
Joined: Apr 2007
Posts: 518
Bigtwin Offline
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Bigtwin  Offline
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Joined: Apr 2007
Posts: 518
Southeast Usa
Greetings!!!
Just got back from an over-aggressive ride on my Mk-I Interceptor. Since it was good and hot & cold weather is supposed to be setting in, I figured it was time to change to winter oil. To my dismay I found bits of cork debris in the oil drain screen! Maybe old bits coming loose, but in a panic I checked the oil quill/crank feed bolt to see if the cork seal was disintegrating... It looks just fine but since it was out I figured I would put in a new one for safety... Trouble is, I am out of extras! Oh, well the bike is back together with the old! Oil now changed & this thing pumps like crazy ( looking at the return ). Ok, I am paranoid, so I now look to Hitchcock's for spares & they list a modified quill/feed bolt with nylon seal in addition to the standard stuff. So, how many of you are running cork seals vs. the modern nylon on one of the twins? One of the Bullet websites talks about the modern ones melting and causing crank failure... Any experience out there? Looks to me like a trip to an old fashioned parts house should result in a neoprene substitute for an improvement over the cork original.

Thanks!!!

Bigtwin

Oh, yes: Anyone have a clue as to what kind of oil pressure the twin cylinder engines really produce?

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#153137 - 12/09/07 1:59 pm Re: Oil feed/quill...Twins ...Yikes!  
Joined: Mar 2007
Posts: 557
rotorwrench Offline
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rotorwrench  Offline
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Joined: Mar 2007
Posts: 557
San Antonio, Texas
I have read a lot of reports about the oil feed modifications over the years. From what I can gather, the nylon bobin was made to adjust for machines that had less than perfect alignment between the crankshaft and the oil feed plug. If the cork one works well many figure its better to keep it unmodified. If it wears out the seal on a little too regular of a basis then the mod is in order. The owners that pushed there machines hard usually modified them.

The nylon seal has to be used with a modified feed plug and has to be spaced correctly by use of different thickness washers where the fiber washer goes between the plug and the timing cover. If the fit is too tight the bobin will melt. If the fit is too loose there will be a loss of oil pressure.

As for the difference between cork and neoprene I don't know what to tell you there. I know the cork is probably a little more stable a material when soaked in hot oil than the rubber seal is. Neoprene will swell slightly in a hot oil environment where cork won't. Neoprene will also get harder with age and become less efficient at sealing. I know Royal Enfield used both over the years.

I don't know what the average oil pressure is in the old twins. If I had to guess I would say around 35 or 40 psi max when hot due to the type of pump and the leak down rate around the oil feed plug. The little pistons only have so much displacement and the faster they run the more oil they pump. There is a regulator ball and spring but I think it is for the top end lubrication and is suposed to be set at 60 psi. The returm pump is normally larger than the pressure pump so as not to flood the engine with too much oil.

Kerby

#153138 - 12/09/07 7:03 pm Re: Oil feed/quill...Twins ...Yikes!  
Joined: Sep 2007
Posts: 1,071
gREgg-K Offline
BritBike Forum member
gREgg-K  Offline

BritBike Forum member

Joined: Sep 2007
Posts: 1,071
Ottawa, Canada
The original feed plug seal in the twins was a neoprene cylinder.

The only engines I've seen with a cork seal are the singles, and once in a pinch I used a beveled neoprene tap washer to replace the cork.

The cylindrical neoprene seal fits over a barb on the feed quill, and it might prove tricky to install a cork seal without cracking it.

I've used the nylon bobbin feed plug with good success. One of my pet peeves has been a silly rumor started some years ago that the bobbin seal was developed to compensate for crank flex ... and to that all I can say is that if you believe the Enfield twin crank can flex ... then there is absolutely no hope for the cranks found Norton, Triumph, or BSA twins! (Actually, it is well-known that Norton cranks do flex due to the rather long span between the bearings)

If your original seal or quill shows no sign of side wear due to misalignment, you have no real reason to switch.

.. gREgg


Spyder Integrated Technologies
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#153139 - 12/10/07 6:45 pm Re: Oil feed/quill...Twins ...Yikes!  
Joined: Mar 2007
Posts: 557
rotorwrench Offline
BritBike Forum member
rotorwrench  Offline
BritBike Forum member

Joined: Mar 2007
Posts: 557
San Antonio, Texas
I've got an old case that the crank flexed in and it needs rewelded. I'm sure that would be the most likely result of any flex. Royal Enfield did have problems with some of their machining however. Ol George Helm laughed when I asked him about the new cast as a pair steel sleeved aluminum cylinders that Hitchcock makes. He said that the bores in the crankcase aren't always true enough to fit something like that in there. I've also heard stories about some of the old machinists that worked for the Redditch plant royally screwing up some engines but old Major Smith didn't have the heart to fire them since they had been with RE since the early years and were part of the "Family".

Kerby

#153140 - 12/13/07 2:08 am Re: Oil feed/quill...Twins ...Yikes!  
Joined: Sep 2007
Posts: 1,071
gREgg-K Offline
BritBike Forum member
gREgg-K  Offline

BritBike Forum member

Joined: Sep 2007
Posts: 1,071
Ottawa, Canada
Quote:
Originally posted by gREgg-K:
Quote:
Originally posted by rotorwrench:
I've got an old case that the crank flexed in and it needs rewelded. I'm sure that would be the most likely result of any flex. <<SNIP>>
Kerby
Kerby,

Are you sure the damage you saw wasn't due to something loose inside the case, or perhaps that it happened when a rod started to let go?

Those marks can also result when you use the later style connecting rod in an early case.

Without even considering the one-piece construction and material, have a look at how robustly the crank is made: the rod journal diameters actually overlap the mainshaft diameters. I question how the Enfield twin crank could possibly flex enough for it to contact the cases and damage them enough to need welding, and yet not break itself. I doubt the crank could withstand that degree of plastic deformation without permanent damage.

.... gREgg


Spyder Integrated Technologies
Lucas, BTH, & Miller Magneto & Dynamo Restoration
SMITHS Chronometric Restoration
magneto@spyder-it.com
#153141 - 12/13/07 2:10 am Re: Oil feed/quill...Twins ...Yikes!  
Joined: Sep 2007
Posts: 1,071
gREgg-K Offline
BritBike Forum member
gREgg-K  Offline

BritBike Forum member

Joined: Sep 2007
Posts: 1,071
Ottawa, Canada
Quote:
Originally posted by gREgg-K:
[QUOTE]Originally posted by gREgg-K:
[qb] [QUOTE]Originally posted by rotorwrench:
[qb] I've got an old case that the crank flexed in and it needs rewelded. I'm sure that would be the most likely result of any flex. <<SNIP>>
Kerby
Kerby,

Are you sure the damage you saw wasn't due to something loose inside the case, or perhaps that it happened when a rod started to let go?

Those marks can also result when you use the later style connecting rod in an early case.

Without even considering the one-piece construction and material, have a look at how robustly the crank is made: the rod journal diameters actually overlap the mainshaft diameters. I question how the Enfield twin crank could possibly flex enough for it to contact the cases and damage them enough to need welding, and yet not break itself. I doubt the crank could withstand that degree of plastic deformation without permanent damage.

.... gREgg


Spyder Integrated Technologies
Lucas, BTH, & Miller Magneto & Dynamo Restoration
SMITHS Chronometric Restoration
magneto@spyder-it.com
#153142 - 12/13/07 2:12 am Re: Oil feed/quill...Twins ...Yikes!  
Joined: Sep 2007
Posts: 1,071
gREgg-K Offline
BritBike Forum member
gREgg-K  Offline

BritBike Forum member

Joined: Sep 2007
Posts: 1,071
Ottawa, Canada
Quote:
Originally posted by gREgg-K:
[QUOTE]Originally posted by gREgg-K:
[qb] [QUOTE]Originally posted by gREgg-K:
[qb] [QUOTE]Originally posted by rotorwrench:
[qb] I've got an old case that the crank flexed in and it needs rewelded. I'm sure that would be the most likely result of any flex. <<SNIP>>
Kerby
Kerby,

Are you sure the damage you saw wasn't due to something loose inside the case, or perhaps that it happened when a rod started to let go?

Those marks can also result when you use the later style connecting rod in an early case.

Without even considering the one-piece construction and its narrow span, have a look at how robustly the crank is made: the rod journal diameters actually overlap the mainshaft diameters. I question how the Enfield twin crank could possibly flex enough for it to contact the cases and damage them enough to need welding, and yet not break itself. I doubt the crank could withstand that degree of plastic deformation without permanent damage.

.... gREgg


Spyder Integrated Technologies
Lucas, BTH, & Miller Magneto & Dynamo Restoration
SMITHS Chronometric Restoration
magneto@spyder-it.com
#153143 - 12/13/07 6:33 pm Re: Oil feed/quill...Twins ...Yikes!  
Joined: Mar 2007
Posts: 557
rotorwrench Offline
BritBike Forum member
rotorwrench  Offline
BritBike Forum member

Joined: Mar 2007
Posts: 557
San Antonio, Texas
I mentioned that more as a joke. The damaged was caused by high rpm abuse that disintegrated the timing side bearing. The rollers were probably trying to swap ends. The drive side bearing and rod bearings survived but were rough. I figure who ever owned it was trying to set a land speed record or something. Those old cranks are so solid I doubt if they would ever flex more than a thousandth or two in that little motor.

I had George Helm weld and align bore a case that wasn't quite so badly damaged and he says it turns just fine now. I hope I can get it back from him someday and find out for myself. I've got several other good cases but none that were replacement type "numberless" cases like that set was. I can make it a number match bike/engine combination someday. It probably would have been easier to weld up the numers & restamp it but I would always know and the government frowns on that.

Kerby



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