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Discussion Starter #1
I thought I installed the oil seal too far towards the inside of the timing cover so tried to push it back out by putting a socket on the inside of the seal and lightly hitting it with a hammer. To my surprise a housing holding the seal popped out of the timing cover. :Eyes

Is this normal? Have you seen anything like this before?:dunno
 

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I never noticed something like that I thought it was one piece. I would just clean the parts and JB weld it back in place It looks like it was glued in place there is no irregular break in the cover and the piece holding the seal looks machined.
Juan
 

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Hi Codeman, Yes, once at swap meet. Looked like cover fractured while driving seal in/out.

I looked at my spare timing cover & cover on my bike. It looks different where seal is. The casting is raised, but the only part machined is the actual bore for seal.

On yours the raised casting part looks machine at outer area around seal. Not seen that before.

Looking a '76, 73, 72 parts book they are all the same part # 70-9249 (E4296). I'll let you go back farther, but the oil pressure switch threads are different on earlier type. I don't know what year they changed.

Make sure the rivets are not broken on the patent plate. Broken ones are very hard to remove. The rivets are tricky to remove. If badly rusted they can fracture before coming out.
Don
 

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Oil pressure switch threads

Hi Don,


oil pressure switch threads are different on earlier type. I don't know what year they changed.
During the '69 model year.

The very first triples, although officially always '69, were built from calendar June 1968 - aiui so every US Triumph and BSA dealer would have at least one triple on their showroom floor on the September 1968 launch date.

Early triples have a pressure switch threaded 1/8"NPT (National Pipe Tapered); their part number was D1943.

Twins weren't fitted with pressure switches 'til the start of the '69 model year (there are several other changes at the same time - tacho. gearbox mounting thread from BSF right-hand to UNF left-hand, several other engine threads from British Standard to Unified, blah).

According to the parts books, all twins were fitted with the first of the two 1/8"NPS (National Pipe Straight) thread switches - part number D2133.

In reality, they weren't - my T100 is from the early '69 batch still numbered in the pre-'69 format (H-prefixed number) and the timing cover thread is 1/8"NPT. There was also a batch of early '69 650's numbered "pre-'69" (DU-prefixed number) but I can't be certain whether their timing covers were Taper- or Straight-thread or a mixture. :(

However, fwiw I am 99% certain all twins built after October 1968 with date-code format numbers had D2133 Straight-thread switches/timing covers originally.

I don't know why some early '69 twins have Taper-thread switches (and timing covers), when the two switches had different part numbers. However, speculating, I wonder if it was a supply problem? All '69 Triumph and BSA models have a hole for an OP switch, but the '69 singles' are filled with a (1/8"NPT) plug; for such an important component in production, they're single-source, from Smiths; triples were changed to a Straight-thread switch during '69; the singles finally got the - Straight-thread - switch from '70.

Aside, it seems the early '69 confusion between twins' parts books and reality, coupled with Meriden's habit of never putting thread details in parts books, is at least one reason why the Taper-thread switch is now supplied under the D2133/60-2133 part number; although, as I say, it was originally a Straight-thread switch. :(

Hth.

Regards,
 

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However, fwiw I am 99% certain all twins built after October 1968 with date-code format numbers had D2133 Straight-thread switches/timing covers originally.
I've always wondered if it's possible to identify the thread type visually, or would one need a micrometer or vernier calipers to tell the difference between NPS and NPT? Or, put another way, just how great is the NPT taper over the length of the thread?
 

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Hi Bruce,

I've always wondered if it's possible to identify the thread type visually, or would one need a micrometer or vernier calipers to tell the difference between NPS and NPT? Or, put another way, just how great is the NPT taper over the length of the thread?
NPT taper is 6% (iirc) and the switch thread is ~3/8" long ...

I need my "close-up" glasses just to read the micrometer or vernier ...

Regards,
 

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Discussion Starter #10 (Edited)
This is a brand new timing cover that was purchased about 4 or 5 years ago from CBS or The Bonneville Shop. Made in England by LF Harris and designed to allow space for the 4 valve oil pump.
I put red Loctite on the mating surface and pressed the part back in where it was. Think it'll be ok. I'll take it for a couple more rides then check it for seepage.
 

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i looked at a spare cover and it looks like no insert piece. Checked to see if there was any steel part and found just alloy.
 

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Hi Codeman, are you saying this is a repro cover? If so I am suspicious it may have been supplied with a fault I posted about concerning repro pre-unit covers. These were found (after lengthy measuring) to be bored off center, and while they would fit on, the seals would be stretched, sufficiently enough to leave a gap in the seal. The only way around this was welding and re boring the seal holes, or in your case (Unit) over boring and using an insert sleeve. I would check this before reuse. Center the cover on the oil feed spigot and intermediate pinion shaft and look to see the crank pinion is exactly in center of PR hole.
 

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This is a brand new timing cover that was purchased about 4 or 5 years ago from CBS or The Bonneville Shop. Made in England by LF Harris and designed to allow space for the 4 valve oil pump.
Perhaps it was manufactured that way? I'm sure Harris wouldn't mind confirming one way or the other.
 

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Discussion Starter #15
Hi Codeman, are you saying this is a repro cover? If so I am suspicious it may have been supplied with a fault I posted about concerning repro pre-unit covers. These were found (after lengthy measuring) to be bored off center, and while they would fit on, the seals would be stretched, sufficiently enough to leave a gap in the seal. The only way around this was welding and re boring the seal holes, or in your case (Unit) over boring and using an insert sleeve. I would check this before reuse. Center the cover on the oil feed spigot and intermediate pinion shaft and look to see the crank pinion is exactly in center of PR hole.
I've got 4000 miles on this new cover and it has never leaked. I'm thinking that the cover was originally made with an insert that had the hole bored just slightly off center just so they could position the insert where ever necessary to center the seal directly over the camshaft's end. If that's the case, (since it popped out), the insert would have to go back in exactly the same previous location. I'm pretty sure I didn't put the insert back exactly where it was. After a couple more rides I'll pull electronic ignition plate off to see if any oil is pooling behind it.
 

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Hi Bruce,
NPT taper is 6% (iirc) and the switch thread is ~3/8" long ...
I need my "close-up" glasses just to read the micrometer or vernier ...
Regards,
Thanks for that StuartMac. First time I can pull myself away from drawing firewood (3 cords down, 12 to go) I'm going to pull the switch out of my ('69) Bonnie and inspect it. I purchased a blanking plug (NPS) years ago and never put it in for fear of splitting the case after someone told me the original would be tapered. I suspect it's straight.
 

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I've got 4000 miles on this new cover and it has never leaked. I'm thinking that the cover was originally made with an insert that had the hole bored just slightly off center just so they could position the insert where ever necessary to center the seal directly over the camshaft's end. If that's the case, (since it popped out), the insert would have to go back in exactly the same previous location. I'm pretty sure I didn't put the insert back exactly where it was. After a couple more rides I'll pull electronic ignition plate off to see if any oil is pooling behind it.
I don`t think you will have any problems the part you glued back in place was turned in a lathe so it won`t have the center hole offset.
Juan
 

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Hi Bruce,

going to pull the switch out of my ('69) Bonnie and inspect it. I purchased a blanking plug (NPS) years ago and never put it in for fear of splitting the case after someone told me the original would be tapered. I suspect it's straight.
Depending how the plug's supposed to be fitted - hex., slotted or cross-head - turning the hex. or driver just with thumb 'n' forefinger shouldn't split a NPT thread with a NPS plug? Anytime I've encountered the NPS/NPT problem (e.g. fitting the expected NPS switch into my T100's timing cover), the switch stopped turning with much of the thread still exposed. Ime, what splits a case is people then using additional force trying to continue to tighten a NPS thread. :Not again

Alternatively, aiui the '69 Triumph/BSA 250 singles were fitted with a 1/8"NPT plug in the putative OP switch hole in the crankcase. Despite much staring at parts book pictures, I haven't been able to identify it and its number; :( Peter Quick at BSA Unit Singles might be able to help and supply? With a NPT plug, it shouldn't matter if your Bonnie's timing cover is NPT or NPS?

Hth.

Regards,
 

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I don`t think you will have any problems the part you glued back in place was turned in a lathe so it won`t have the center hole offset.
Juan
That's absolutely correct. But if it has been sleeved, the only reason is, it was not centered in the first place. The inner sleeve's hole may be correct and centered in relation to it's outer circumference, but the 'new' hole it sits in may not be.

I have found that if one hole is wrong, the others may/will be as well. I went to a great deal of trouble re-centering these covers using the (all important) crank spigot PR seal hole as the datum in order to re-aline the oil feed spigot hole, only to find the rev-counter drive pinion was then mis-aligned. The amounts are minute, but the discrepancy is amplified by the square of the distance the holes are spaced. This means for a 0.005" misalignment on one hole, upto 0.015" can exist on another.

This is why I suggested they are checked. It's OK making good on the points seal hole, but if this is as a result of off center boring you must question the accuracy of all the holes. In my case, running the machine with an off set PR seal would have wrecked the engine. So I will be interested to see if this problem extends to Unit as well as Pre-Unit repro covers.
 

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That's absolutely correct. But if it has been sleeved, the only reason is, it was not centered in the first place. The inner sleeve's hole may be correct and centered in relation to it's outer circumference, but the 'new' hole it sits in may not be.

I have found that if one hole is wrong, the others may/will be as well. I went to a great deal of trouble re-centering these covers using the (all important) crank spigot PR seal hole as the datum in order to re-aline the oil feed spigot hole, only to find the rev-counter drive pinion was then mis-aligned. The amounts are minute, but the discrepancy is amplified by the square of the distance the holes are spaced. This means for a 0.005" misalignment on one hole, upto 0.015" can exist on another.

This is why I suggested they are checked. It's OK making good on the points seal hole, but if this is as a result of off center boring you must question the accuracy of all the holes. In my case, running the machine with an off set PR seal would have wrecked the engine. So I will be interested to see if this problem extends to Unit as well as Pre-Unit repro covers.
You are correct. I`m also weary of brand new Primary covers I bought one a few years back for my 1969 and I`m not to happy with the quality.
Juan
 
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