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I'm trying to remember if the little window in the timing side case half actually aligns with the sludge trap? If so, I'd quick pull the timing cover and see if it's been removed since it's birth. If it has, I'd ASSUME it happened when they went to .060 on the top end.

As a forum moderator, I CANNOT advise you to leave the bottom end alone, @Yazwaz , however if all else visible from outside (after removing all the covers) indicates newer, high quality overhaul parts, you could at least consider it. In the end, it's down to your decision as far as money, time, abilities, etc.
I totally agree ! You can spend 200 or 2000.
My question is why did you take it apart?
 

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And who cares who made the con rods? Trace them back to triumph . Trace back the head . Trace back the crank , the cases , the tranny . The front end ! I mean you bought a triumph but you don’t trust triumph parts?
lol. GP is right. If you aren’t building a street racer , why waste good parts?
 

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Hi, We never want to jump to conclusions. Examine the parts, then decide. The fit of wrist pins, the visual appearance of inserts. Clearance of inserts using plastigauge. The visual appearance of big end of rod, inserts removed. Overall apperance of rod & straightness. I used ground rod through small ends before tear down. It should slide freely through both rod small ends at same time. If in doubt throw it out.

But if good & you just ride bike not using the very high rpm like 6500-7000 you should be fine with old rods.

I’ve personally installed Harris 650 rods. Covered 10k miles so far.

Onviously budget is a factor.

Thing is the motor ridden with these rods. I’ve personally looked at swap meets for good rods. Maybes 70 pairs supposedly matched sets. Every single last set was junk!! Obvious flaws that made them prone to fracture. Overheated small ends common. Blackened alloy (not just oil stained), with pocking rough surface. Many had deep dings on shaft, Damage to sides of big end. T140 doesn’t use small end bushing. Loose bushing on 650 is the warning sign of soon to fracture. Never use oversized bushing. Very risky. The lack of known good used rods forced purchase of new Harris. The Thunder rods were financially out of reach. The weight matched Harris date worth the extra cost. Not matched can be 5+g different. That’s even hard for balance shop to correct.

After you get rods out you’ll have a direction to go.

Scuffing on recent overhaul is most often dirty assembly or too small ring end gap. Dry assembly can cause scuffing. Wet assembly using break in oil is safer bet.
Don
 

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I have unsurpassed levels of mechanical inexperience, so can't authoritively comment on the conrod conversation. I will say my '73 Triumph has a newish crankcase. A broken conrod seems a good contender for that.

But, the conversation goes beyond caution, I'd say. If someone finds joy in old Triumph engines, has pride in their work, I can see why a well engineered and lovely finished element improves that engine beyond just having that element added. I admitted it to Mick a few days ago--my electrical crimps are satisfactory, if ugly, and although I don't see them when on the saddle, I would slightly more enjoy a ride if they were in fact beautifully done like his. Same with a conrod. I might never see it after fitting, but I'd forever know. I accept that's not a very mechanical perspective.

God is in the details
Ludwig Mies van der Rohe (1886-1969)
 

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Common sense, common to ALL classic bikes. The shop manual can be found and downloaded free.
A good manual, with illustrations, is the best way to tackle ANY mechanical job. Seeing what it SHOULD look like and the instructions can prevent many minor mistakes that can be turned into a big mistake.

Ahem, many of us that start projects get things taken apart and then forget how we disassembled then so we forget how to put it back together.

Taking photos of each step of disassembly helps when putting it back together.
 

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Don’t think the frame had been blasted. It looked pretty original, I have repainted it now but used a wire wheel to strip the paint as I didn’t want to blast it for obvious reasons. I’m going to fit an external cartridge filter. I’ll have a look at the oil pump but may stump up for a new one as it looks like the original so presume it will be worn. Don’t know what’s gone on with the pistons but doesn’t really matter as it’s going to get new ones and barrels.
Good idea on replacing the pistons and jugs. To me, they looked badly scored. Those scoring marks are just little channels for oil to escape, burning oil, loss of power, and buildup of carbon that will harden and further score the piston, rings, and cylinders.
 

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I went back and looked, it's been 27 Triumph big twin overhauls involved in refurbs, restorations, scratch builds and custom builds.

In all of those, I the only core parts I ever replaced were two sets of cases (I bought both bikes with horribly blown engines), ONE crank (ruined journals that were already undersize), and 3 cylinders (too bad to overbore).

I've replaced the odd transmission gear or two, due to chipping/brinneling, and of course rebuilt almost every one of those heads, but unless an old Triumph has been seriously abused and/or not maintained, they're pretty tough beasts.
 

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Aluminum rods are funny stuff , some never break and some will break at moderate rpm's , you never know. A friend who tours on a Commando had a rod break at 4000 rpm... When I rebuilt T140 I reused the existing rods.. The speedo was in op showing 14000 miles,the pistons were 20 over, the seller said he had the valves done...they all say that, lol... so maybe it had 20,000 miles..The rods looked ok, the big ends measured less than .0005 out of round...It's John Healey who says rods out of round more than .001 should not be used if the bike will be ridden like a Triumph...
A set of Thunder Rods for my A10 were just about $400 shipped to me in the USA. I went with USA made $450 R&R because they are only 5 grams heavier than the stock BSA rods...
I just sold the T140D so I will never know if it blows up...
 

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Discussion Starter · #71 ·
Got the clutch puller today. So carried on splitting the cases. I’ve got the clutch side off but can’t get the crank out of the timing side. I haven’t removed the pinion gear could this be the problem.
 

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Got the clutch puller today. So carried on splitting the cases. I’ve got the clutch side off but can’t get the crank out of the timing side. I haven’t removed the pinion gear could this be the problem.
Did this last week on mine. The pinion wheel will pass through with the crank. You probably need to put some heat on the crank case so that the main bearing drops out of its housing. Don’t go over 150 degrees with the heat.
 

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Discussion Starter · #73 ·
I was pondering heat. Ill give it a waft with the map gas tomorrow I had a quick wiggle of the conrods and there seems quite a lot of movement side to side which didn’t look good.

Purple Gas Bicycle part Bag Sewing
 

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Hi Yaswaz
The sideways clearance of the rods is important to allow the big end oil to escape.
also VERY important is the 7’64" radius of the corners as the big end transitions to the web, this is there to reduce stress concentration in the corner, failure to maintain it greatly increases your chances of crankshaft failure.
modern crankshafts tend not to have the radius, so modern crankshaft grinding companies do not always appreciate it’s importance. They have to dress a set of grinding wheels specially with this radius, so ruining them for modern crankshaft work. If you have to have a regrind make sure the regrind company has a special set of grind wheels set up for British bike crankshafts or are prepared to modify a new grindstone.
If the crankshaft was ground on a previous rebuild, (check for oversizes shell bearing) then check that the radius has been maintaine.
When you come to remove the sludge trap plug, there are a couple of things to be careful of:
1) The adjacent flywheel bolt needs to be removed to free the locking device in the trap, these are very high tensile and so are brittle, they can break if shocked. I resist the temptation to use an impact gun on these.
2) If possible avoid drilling into the crankshaft to release the plug locking dot punch mark, try to remove this in the plug only, marks here on the crank web create stress concentration as the crankshaft flexes, crankshafts have been known to crack because of this.
3) If you replace the plug, be ware there are two widths available the correct on is important, there is an oil feed passage near the plug, this must not be blocked off.

good luck
Peg
PS: It looks suspiciously like the gearbox mainshaft seal has been leaking.
 

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Discussion Starter · #76 ·
Had a time getting the crank out but heating it up did the trick. Unfortunately my puller is too big to get the bearing and pinion off so I’ll have to order a smaller one. The sludge trap doesn’t look like it’s ever been touched. The sludge trap plug isn’t left hand thread is it.
 

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Had a time getting the crank out but heating it up did the trick. Unfortunately my puller is too big to get the bearing and pinion off so I’ll have to order a smaller one. The sludge trap doesn’t look like it’s ever been touched. The sludge trap plug isn’t left hand thread is it.
RH thread. You'll probably need an impact screwdriver to undo it. I've heard that sometimes they are thread locked in. So heat it up beyond 100 deg before trying to remove it, otherwise you might muller the screw head. This should melt any glue.
 

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Discussion Starter · #79 ·
I’ve managed to move the sludge nut with the impact diver I haven’t drilled the punch out as it seems quite away from the threads. Just took conrods off and big ends look ok to me. Measured with vernier @1.6235 as best I can. No scoring etc.
Light Purple Rectangle Violet Material property

Fluid Purple Cylinder Gas Tin
 

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I had a quick wiggle of the conrods and there seems quite a lot of movement side to side which didn’t look good.
You can measure the end float clearance with feeler gauges. There is a spec for this in the workshop manual. You will feel some wobble if you do as you said.
You can measure the crank pin diameter with 1-2" micrometer (not Vernier calipers), and if to spec use Plastigage to measure the bearing shell to crank pin clearance (spec also in workshop manual). Do the latter even if your fitting new bearing shells.
 
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