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Discussion Starter #1
Hi All, Not wanting to hijack TR25 thread.

I wonder the differences in motor durability between plain bearing(bushing) rod Cub, roller bearing rod Cub, TR25 which has rod cap similar to twins.

With the years of experience & improved parts has that changed anything?? Sometimes just fun to kick this stuff around.
Don
 

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I have read the roller rod was more reliable when the bike was used hard. I also was told the bikes were primarily used by novice riders who jumped on and roared away at full throttle. Fragile engine reputations have some truth .....
 

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Hi Don,
I had the BSA version, the 71 B25T, I still have a 58 tiger cub.

These are hard to compare as the TR25/B25 was tuned to death and the Tiger cub fairly mildly tuned.

The TR25’s woes were mainly brought about by BSA, but they can be improved by some modifications/maintenance.

The big end bearings were not up to the power produced, BSA fitted whitemetal bearings that were far too soft. The ‘fix’ was to fit Vandevell VP2 (Copper/lead/indium) bearings.
If you could not get these then Glacier (aluminium/tin) bearings. Triumph 500 bearings are the same size, but with no oil squirt hole in the shell.

The oil pump was a pot metal rubbish affair. Later engines got a cast iron pump.
SRM make a quality replacement, just make sure you are sitting down when you see the price (still cheaper than a rod through the crankcases)

Pressure relief valve was a ball bearing + spring on earlier engines-you can get a conversion to piston type.

barrel lift plates were pretty common, to tame some of the compression ratio.

Oil filter in the return line, if it does not have one standard, especially after fitting harder big end bearings.

change oil very often-

clean out the sludge trap.

regards
Peg.
 

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Hi Peg,


Is "standard" the Tecalemit one I've read about?

Regards,
Hi Stuart,
I don’t know about the make, it is a separate filter with a little paper element in the oil return line. It was bolted to the rear engine mounting plates on the oil in frame models.

The later oil in frame model had the oil filler behind the steering head, this meant you could walk properly again, as you no longer smashed your leg on the oil tank filler cap every time you tried to start it.?

Regards
Peg.
 

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Hi Stuart,
I don’t know about the make, it is a separate filter with a little paper element in the oil return line. It was bolted to the rear engine mounting plates on the oil in frame models.

The later oil in frame model had the oil filler behind the steering head, this meant you could walk properly again, as you no longer smashed your leg on the oil tank filler cap every time you tried to start it.?

Regards
Peg.
I did a bit of digging around, it looks like the filter unit was made by British filters Ltd of Plymouth.
In this case it might shave been a Tecalemit owned company, as Tecalemit production facilities were at Plymouth and were massive in their heyday.
 

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Hi Peg, Dave,

Thanks. I had a look 'round too and it looks a neat little unit (there's a good image on Triumph T25 - 1971 - Restored Classic Motorcycles at Bikes Restored - but it won't link here :(). One wonders firstly why Triumph didn't fit it to the 1970's twins and secondly, given the now long-term popularity of aftermarket full-flow filter kits on our old heaps and the element's still available, why one of the Britbike bits makers isn't reproducing it? :unsure:

Mind, talking of fitting it to the twins, stuff on the '74 T100D ('disc-brake Daytona') sometimes refers to an oil filter, I'll see if a part number's mentioned and if its the same as the T25's or B25's ...

Regards,
 

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Hi Stuart,
This is the one I remember; I agree it is neat. As you already said, If BSA/Triumph could fit them on the entry level learner bikes and dirt bikes, why not on the larger more premium machines, it does not make sense.

I managed to save the image from the link, and then reposted as a photo.

721205
 
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