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Best B25 Con Rod bearing #578096
12/26/14 6:56 am
12/26/14 6:56 am
Joined: Sep 2014
Posts: 537
Michigan, USA
J
Jeff K. Offline OP
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Jeff K.  Offline OP
BritBike Forum member
J

Joined: Sep 2014
Posts: 537
Michigan, USA
What brand, year, part number etc is the best for the Con Rod shell bearing in the B25? I have heard that the Triumph T100 are the same.
Jeff

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Re: Best B25 Con Rod bearing [Re: Jeff K.] #578121
12/26/14 10:39 am
12/26/14 10:39 am
Joined: Mar 2005
Posts: 10,251
Boston, Massachusetts
J
John Healy Offline
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John Healy  Offline
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J

Joined: Mar 2005
Posts: 10,251
Boston, Massachusetts
Yes, the 500 twin rod shells are a good option, as are the rods.

For years while 500 rods had seemed to have dried up 250 rods languished on dealer's shelves. A 500 rod was often held for ransom, if you could find one, all the while you could find 250 rods going for a song. We often used late 250 rods for our 500 racer.

I might add to the question about the oil hole weakening the 250 rod. We routinely ran the 500 to 9,000, and on occasions it would see 10,000 rpm.

Last edited by John Healy; 12/26/14 6:47 pm. Reason: strength of rod

Re: Best B25 Con Rod bearing [Re: John Healy] #578140
12/26/14 1:16 pm
12/26/14 1:16 pm
Joined: Sep 2014
Posts: 537
Michigan, USA
J
Jeff K. Offline OP
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Jeff K.  Offline OP
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J

Joined: Sep 2014
Posts: 537
Michigan, USA
Hello john
Excellent timing. I just posted on the B50.org about what brand bearings were the best to use and kommando wrote back the "The T100 bearings currently available are Glacier Al/Sn and are the best available. They must have a capital G in a square stamped on the back to be genuine."
And when I asked who was selling them he responded "They were ordered by Velocette who still exist as a parts distributor in the UK, John Healy should know who stocks them as he buys from Velocette."
Any suppliers in the USA or Canada selling these.
Jeff

Re: Best B25 Con Rod bearing [Re: Jeff K.] #578142
12/26/14 1:27 pm
12/26/14 1:27 pm
Joined: Jun 2002
Posts: 937
Jaffrey, NH, USA
Peter Quick Offline

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John,

I know the late T100 con rods are basically the same as the late B25 con rods (part # 70-9911) save for the oil hole for the upper shell. Some folks have told me that they can be used in place of the B25 con rod and that the oil hole doesn't matter. Is this the case? If that is the case then should it also be OK to run the T100 shell bearings without drilling a hole in them for the oil hole in the B25 rods? Looks like the oil hole would be used to spray oil out of the rod onto the cylinder. Is this necessary as none of the other singles seem to require this spray?

I have a new T100 rod without the hole and am wondering if I can just use it or if I should modify by drilling an oil hole?

I read that the B25 oil hole is a possible avenue of weakness, perhaps under high stress super high rev racing conditions, but otherwise?

So current manufacture T100 shell bearings are made of the "right stuff" compared to what was used originally?

Inquiring minds need to know.

Peter



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Re: Best B25 Con Rod bearing [Re: Jeff K.] #578147
12/26/14 2:33 pm
12/26/14 2:33 pm
Joined: Dec 2004
Posts: 9,660
Scotland
kommando Offline
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kommando  Offline
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Joined: Dec 2004
Posts: 9,660
Scotland
Advice I posted in 2009, I would not be drilling oil holes in an alloy con-rod but improving top end oiling by diverting the oil that drains from the top end after it oils the cam into the Crankcases not directly into the sump. I would also put 2 slots in the upper sides of the rod big end to direct oil that comes out of the rod bearings upwards, the con-rod is a lot wider than the bearings so these slots will not decrease the bearing area and polished slots will not be stress risers with smooth chamfered corners.

Quote
The Triumph 500 rods followed the same upgrade path as the B25 rod so the last 500 twin rod is the same strength as the last B25 rod. The exception to this is a rod without the oil hole is stronger as this a a crack propagation point. If you put the best rod in there are still areas that need looking at to keep the oil pressure up. In no particular order and not a full list.

Fit AlSn big end bearings (last batch made by Glacier Vandervell for Velocette for 500 Twins are this type, if you want to retain the oil hole in the rod and use it the top shell will need drilling), all the B25 bearings I have seen are Whitemetal which cannot handle 8K rpm.

Rebuild the crank and seal the sludge plug and any bolts with access to an oil way as they can leak oil pressure

Upgrade to cast iron oil pump

Go to later timing side inner cover with new seals and the oil way O ring and use the extra oil plug to test pressure, for the seal use a good quality seal brand such as Pioneer

Fit new spring and bearing to the pressure release, use loctite to seal thread

Use a good quality oil

Last edited by kommando; 12/26/14 2:46 pm.
Re: Best B25 Con Rod bearing [Re: Jeff K.] #578152
12/26/14 3:23 pm
12/26/14 3:23 pm
Joined: Jun 2002
Posts: 937
Jaffrey, NH, USA
Peter Quick Offline

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Kommando,

So a T100 rod with no oil hole could stand a slots in the center of both sides of the top of the big end eye. With a B25 rod with the oil hole perhaps just a slot on the side without the oil hole?

This sounds like one would then be liberated from having to look for B25 shell bearings with the oil hole or drilling a T100 shell bearing to get an oil hole to line up with the oil passage on a B25 rod. Am I on the right track?

I'm rebuilding a B25 motor and plan on doing the modification suggested by Ed V about plugging the crank to force better oil flow to the shell bearings. I have a new T100 rod like the 71 B25 rod. The motor is a 1968 so I am using a 68 crank and will swap out the flywheels with 71 crank flywheels so the internal rod clearance is correct with the stouter rod. I have a pile of B25 cranks and it is amazing / sad how trashed most of them are. Most of the timing side ends have been hammered and mushroomed. Also on the primary side the splines seem to be really prone to distortion. Very soft items. So I have lots of flywheels and not lots of good cranks.

Peter


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Re: Best B25 Con Rod bearing [Re: Jeff K.] #578153
12/26/14 3:32 pm
12/26/14 3:32 pm
Joined: Dec 2004
Posts: 9,660
Scotland
kommando Offline
BritBike Forum member
kommando  Offline
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Joined: Dec 2004
Posts: 9,660
Scotland
Quote
This sounds like one would then be liberated from having to look for B25 shell bearings with the oil hole or drilling a T100 shell bearing to get an oil hole to line up with the oil passage on a B25 rod. Am I on the right track?


Yep, put a shell bearing in the rod and look to see how much the con-rod is wider than the shell, and remember the chamfer on the sides of the shells are not acting as a bearing either, the slot can be very shallow say 1 to 2mm but could be 10mm wide and will just direct the oil coming out of the bearing upwards. Using the oil after it has been used to create pressure rather than releasing pressure from a marginal bearing is preferable.

Take a fully assembled crank and using an oil can apply oil under pressure and then look where it escapes, sludge plug, flywheel bolts and crank to flywheel joint are all fair game.

Re: Best B25 Con Rod bearing [Re: Peter Quick] #578155
12/26/14 3:36 pm
12/26/14 3:36 pm
Joined: Sep 2014
Posts: 537
Michigan, USA
J
Jeff K. Offline OP
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Jeff K.  Offline OP
BritBike Forum member
J

Joined: Sep 2014
Posts: 537
Michigan, USA
Peter
Same here, it seems like the "standard" method of separating the case halves is to grab a big hammer and pound it out. If you order a die to clean up the threaded end for the Rotor nut. Be careful it is a BSC and not a UNEF, same thread count, but cut different.
Jeff

Re: Best B25 Con Rod bearing [Re: Jeff K.] #578156
12/26/14 3:40 pm
12/26/14 3:40 pm
Joined: Sep 2014
Posts: 537
Michigan, USA
J
Jeff K. Offline OP
BritBike Forum member
Jeff K.  Offline OP
BritBike Forum member
J

Joined: Sep 2014
Posts: 537
Michigan, USA
I just pulled the box with the shell bearings in it and it is a mixed bag, about 1/2 Glacier and 1/2 Vandervill. It looks like back then that they were two different companies. And the stamp on the back of the Vandervill bearings is a V inside a circle with what looks like another small circle going around the V. I am guessing that these being old NOS are not the ones that you would recommend. These are mostly T100 sets.
Jeff

Re: Best B25 Con Rod bearing [Re: Jeff K.] #578157
12/26/14 3:42 pm
12/26/14 3:42 pm
Joined: Jun 2002
Posts: 937
Jaffrey, NH, USA
Peter Quick Offline

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Doing the modification suggested by Ed V will eliminate all the pressure leaking points around the joint between the crank and bolt on flywheels you mentioned. The entire flow will go to the big end. One just has to check to make sure the pressed in plug does not leak.

Peter


check out: www.bsaunitsingles.com
2500 BSA part numbers with inventory in stock just for the unit singles!
Re: Best B25 Con Rod bearing [Re: Jeff K.] #578158
12/26/14 3:46 pm
12/26/14 3:46 pm
Joined: Dec 2004
Posts: 9,660
Scotland
kommando Offline
BritBike Forum member
kommando  Offline
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Joined: Dec 2004
Posts: 9,660
Scotland
Loctite 515 works there, that's what I used the first time I did the test and saw the bubbles of air coming out before the crank filled with oil.

Re: Best B25 Con Rod bearing [Re: kommando] #578181
12/26/14 8:01 pm
12/26/14 8:01 pm
Joined: Sep 2014
Posts: 537
Michigan, USA
J
Jeff K. Offline OP
BritBike Forum member
Jeff K.  Offline OP
BritBike Forum member
J

Joined: Sep 2014
Posts: 537
Michigan, USA
I grabbed a few rods off the shelves. From the left:
1. Early T100 with small end bush, Narrow H beam same width full length
2. Late T100 No small end bush H beam tapers to top
3. Later B25 No top bush
4. 1971 B25, thicker
5. Late 750/850 Norton, note that it also has a hole drilled in it in the same spot as the B25 and I am not aware of Norton having a problem here.
Interesting, both of the Triumphs, the 71 B25 and Norton all show some degree of polishing. The late model B25 appears to have a matte finish almost like it was shot peen at the factory and then machined.
Jeff
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