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A bit off topic, I know, but these anecdotes add an interesting dimension to it all!
You would have many, many more I suspect, JH.

Last edited by Triless; 07/21/15 9:52 pm.
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Some times a story reaches more than discussion of the technical details.

The moral of the story, don't drill the hole.

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I had a old Triumph Mechanics tell back in the early 70's, what he thought the problem with these was. He stated that the old design of the 250 was made for use with Non Detergent motor oil, like you run in a lawn mower. With Non-Detergent oil, when the motor is sitting for a while. Like all winter here in Michigan. The crud in the oil falls out of the oil and settles to the bottom of the engine and pretty much stays there. He showed me a old oil tank that he a cut open and the bottom did have a 1/2" of hard crud on the bottom.
He said that the problem is that now some one starts using Detergent oil. Detergent oil he said is made to break up the crud and hold it in suspension so it can be filtered out in the oil filter. Something the old bikes did not have.
His theory was that now you have the detergent oil suspending this crud and it is not getting filtered out. It now starts to wear away at the softest parts first, Alloy main bearings. Now once the bearings wear a bit, you get more clearance and this allows the rod to start hammering. And it just gets worst until something gives. I used to pick up 250 very cheap, Normal for the pre 71's to have a spun main bearing, broken kick starter teeth. And a lot of times 2nd gear or the gears would be missing. I was told that the guys racing the B50 tended to bust up the gearbox during motocross racing(lots of hard shifting without the clutch). And that they were scavenging 250s for parts. I was told that they hardened the gears later for the B50 . I still have more then a dozen of the 250.
Jeff

Last edited by Jeff K.; 07/22/15 10:19 am.
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With all due respect to your friend the 250's in question were wearing out rod bearings, breaking rods, having sleeves come loose in the cylinders, etc long, long before an sludge could settle in the oil tank.

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Hi John. I certainly thought I torqued to 22, but I probably also own the worst torque wrench on this site. I went with the undrilled bushings.

I bought the Triumph CD that includes a rebuild manual for the 250 so I'm trying to "do it by the book" literally.

I knew about the crank design issues but on a budget with no intention to race this thing, I went with the unmodified crank. I squirted oil through the crank end and am way happier with the play.
Then on to the next problem.

I put in new bearings (they came with the basket case- thanks PO)and got the cases together as instructed by the manual, using every ounce of my willpower to do it as directed by the manual and resist the urge to pick up a sledge hammer to encourage the union a little quicker.

I checked it a few times to make sure that the crank turned and everything was cool until the last 1/2 to 1/4 inch.

Now the crank will barely turn. ARRGGHHH!

I guess if everything went "text book" on a build, you wouldn't need a forum like this.

I enjoyed the service stories above. They make ya' feel a little less alone with your frustrations.

Last edited by BruceinT.O.; 07/22/15 1:10 pm.

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What I do is relieve the mainshaft and timing shaft bearing journals so the ball and roller bearings are a tight sliding fit on the journals. The crank can then be pushed into one crankcase half and the other crankcase half pushed over without it all binding. Then when you have it all assembled you can check the endfloat by pushing and pulling on the crank before doing up the nuts on the ends of the shafts. Makes dismantling much easier too.

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Originally Posted by John Healy
With all due respect to your friend the 250's in question were wearing out rod bearings, breaking rods, having sleeves come loose in the cylinders, etc long, long before an sludge could settle in the oil tank.

He was the mechanic(long deceased) at a local Triumph shop. He would have only had experience with the rebadged B25/TR25W and not the earlier BSA's. He and his brother Sam used to race triumphs in the early 50's and they owned and operated Saginaw Cycle (Triumph) for decades until they both passed away.
Jeff

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Yes, Saginaw Sam, I visited his shop, and his brother who did the service, several times over the years. They were very influential in the State Dealer's Association and helped organize a lot of events. This included a lot of ice racing events...

Please read what I said again. I stand by it.

While I whole heartily agree that putting high detergent oil in a motor that only ever saw non-detergent years before is problematic, but many of these engines failed before the first oil change. Remember, not only where the rod bearings failing, the sleeves were turning in the alloy casting. This made an interesting problem as the rod would not clear the turned sleeve.

Not to mention the kick starter and transmission kerfuffles. An awful lot of them hardly made it through one season unless ridden VERY sensibly.

As they left the factory these bikes were perfect for trips too, and around town. But people were buying them trying to commute on the Interstate at 60 plus (something you could do routinely on a Japanese 250). Now, and in the day, guys like Ed at E&V Engineering, sort this engine out and make it a pretty nice bike capable of being raced or ridden on the Interstate. There are happy 250 owners out there!!!

For example: Edsel, riding his 250 around the campus, relayed to Lindsay Brooke author Triumph in America etc) that he was left with very positive memories buzzing around the back lanes. He might have gotten it up to 40-45 on Route 135 in the 35 mph zone between Babson and Wellesley colleges, but I doubt if the bike ever saw the Interstate.

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Sam and Donny. I miss both of them, A true mom and pop operation. I think you nailed it. I knew of a couple of BSA Starfire owners that drove moderately in town with a occasional run at 55 mph. They never had a bit of problems. Then you look at the bulk of the 250's up here. People bought them and their buddys all had Suzuki X6's, 350 Yamaha's, 350/450 Honda's etc. And they flogged them to death trying run with them. And then add to that that in the 60's many of these bikes were stripped down and a huge rear sprocket was added so they could run off road and compete with all the two strokes. I still come across a lot of them. I just purchased another complete 71 frame and the seller had at least one more.
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Hello!
I think it's good to use this topic for my question.

Was I luck to find a cheap TR25W...?

THe reason why it was so cheap was
[Linked Image]

OK, now fitting a new rod... I can get a NOS 71-3667 rod. Still in original Triumph package with Triumph Parts sticker and the securing tabs..

But I read about the risk of splitting the rod because of the oilway drilling. I also have a late T100 Daytona rod. Would it be a better idea to use this? Or is it enough to fit an oil-filter after replacing the rod with the 71-3667 and cleaning the sludge tube?
Then I would have still a set of new rods for my 500s and not one more replacement rod for a 250..

Thank you and bet regards, Martin

Last edited by Lincoln Green; 10/08/15 8:27 am.
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The late T100 rod will be the the same as the B25 rod but without the hole and the T100 rod would be my preference, just be aware the thickness changed and increased so your crank may need relieving to get the correct clearance. You can then fit Al/Sn T100 bearings with no holes, also look at removing the sludge trap completely, fit an oil filter and use a good modern detergent oil.

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Thank you for the quick reply!
OK. Because of my B40, I have the Rupert Ratio Book still in the workshop. There he give a measurment for machining the flywheel. I willdo itlike that!
Thank you.

But what is the oil bleed hole good for?
On one late 500 Unit (TR5T) I found a rod with oilway but on no other 500 (I have 6 of them).
One guy told me it should cool the cylinder bore. But does it work really?

Thank you, Martin

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If you want the oil to cool the piston then read this thread from the top, I made the second one down from the top and it shows how to have the oil but without the hole so keeping the con rod strength. What I do is block the direct route for the oil that drains down from the top end going straight to the sump on the timing side and instead get it to drain through the crankcase wall where it can hit the flywheel and be distributed inside.

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I don't know if I want this. But I know that I don't want a broken rod... ;-)

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Well leave the con-rod, look inside the timing crankcase where the oil pump sits, below this there is a cast floor with 2 holes, the oil that runs from the head and past the camshaft drains through these 2 holes directly into the sump via these 2 holes marked D, that oil does not get a chance to go near the piston.

Holes to block
[Linked Image]

So you block these 2 holes off and drill a horizontal hole just above the floor directly into the crank chamber, so now the oil drains into the crank chamber and gets flung around including up to the piston, this is plus all the oil coming out of the big end.

New hole red dot marks the spot
[Linked Image]


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Thank you. So the trick is to higher the level of oil in the crankcase...? Any suggestion what size the hole should be?
Would you recommend it also on my BSA B40WD?

So it looks like using a Daytona conrod...

Regards, Martin

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No higher level just more being thrown about, the level in the sump stays the same until the engine stops and its appicable to a B40. 3/8 hole or 10mm is fine.

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Thank you for your help. I will go this way.
In the end it should give no problems, even if the theory for cooling piston not work.


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Originally Posted by John Healy
As they left the factory these bikes were perfect for trips too, and around town. But people were buying them trying to commute on the Interstate at 60 plus (something you could do routinely on a Japanese 250). Now, and in the day, guys like Ed at E&V Engineering, sort this engine out and make it a pretty nice bike capable of being raced or ridden on the Interstate. There are happy 250 owners out there!!!



So I'm currently working on a rebuild for my '69 TR25W with Peter Quicks (bsa unit singles) modified crank, '71 external oil filter and new '71 conrod. Once complete, would it be wise to operate it on the Interstate at 60+? Only asking because I've heard other guys advise against this type of use, even with the more robust mods.


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So I thought I would stop in for an update on this. I really haven't had much time to work on the bike lately, but I found some spare time and with the nice weather starting to arrive, the pressure is on to make some progress if I want to have the trophy on the road this summer.

Thanks to Kommando, John and others for the advice thus far. I polished the crankshaft a bit as suggested and now the bearings can be pressed on and removed by hand, with what I think is an adequate amount of resistance. I used some 80 emery cloth and it didn't take that long. An hour as suggested would have been way too long.

I then put my cases in the new oven in the kitchen at 150 c/ 310 F and heated them up. My wife is out for the night and it didn't smell the house up to much. The new bearings dropped right it.

So I cleaned the con rods, crank and my big end shell bearings. I've decided not to upgrade to the T100 connecting rod and delay the upgrades offered by Peter Q, although Peter was incredibly generous with some advice anyway (thanks Peter). It think they are in decent shape.

[Linked Image]

When I went to put the con rod on the crank with the new big end shells, it just doesn't rotate the way one would expect. In fact with the nuts only hand-tight (not yet torqued to 22), the cod rod barely moves on the crank. I can't figure out what I'm doing wrong. Probably something basic but I'm at a loss.

I have a good supply of used and new parts that came with my basketcase and the PO seems to have bought a fair number of parts before abandoning the project. I am starting to wonder if some of the parts are mismatched? I've checked the big end of the con rod and there seems to be adequate clearance from the flywheels.

[Linked Image]

Any ideas folks? Like I said, I just get the feeling that I'm overlooking something really simple.

Last edited by BruceinT.O.; 03/12/16 12:01 am.

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You need to check the shells as properly seated, a spec of dirt or a rusty back on the shell is enough to stop them seating,and check the crank journal for size.

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Also check that the rod and cap are a matched pair, put the cap on with no bearing and see if the inside edges align perfectly. When parts aren't bored as a pair you'll feel a little lip inside the hole at mating surfaces. Parts could have been mismatched along the way. Happened to me once.

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Thank you both. I cleaned them well,wiped everything down and used some fresh drops of oil pre assembly. I also dry fit everything together and from the naked eye and touch everything seems a go. I just had another look to confirm. Without the shell bearings in place the joints seem smooth. It wasn't hard to get the right pair as most of the Pistons and rods in the crate were toast.

Last edited by BruceinT.O.; 03/12/16 12:05 pm.

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I will measure the journal again.


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Maybe assemble and move it a little (as long as it's not too tight) and look for rub marks. Also, if you have a decent set of used shells maybe try them. They shouldn't be tight, provided they're the proper undersize for the crank, of course. No burrs on the crank journal?

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