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reverb Offline OP
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Hello;
I have 2 sets of T140E used rods; a set of new Harris (these are the replacement the shops sell; the rods have the same number) a set of new ARP bolts.
Two crankshafts are STD, the broken one is at 0.10.. Two bores STD, the other at 0.40
I do not have here the jewelry scale so I used a kitchen scale that is +/- one gram so not accurate but for now worked as a reference.
I inspected the used rods with a magnifying glass and did not perceived filing

The rods that were with the broken crank both weight (with this scale) 245 grams each one, of course. All the other parts weight the same; so complete (without the shells) are in 430 grams each one. Seems paired...very possible that with a precise scale would be differences but not so much I guess.

However, the other stock rods weight 233 one and 230/231 the other! Seems a lot of difference with 245.
The total weight is 423/424 grams in one and 420 grams in the other

If PO matched the set, did it without let any trace.

Besides the matching thingy, seems that many problem with vibration could be caused due to these differences between sets of rods; pistons.
Do not know who fabricated the original rods. One rod cap has a "V" inside a rhombus besides a number.

-The Harris rods weight complete 434 grams one and 431 the other; alone, one is 242 and the other 245.

The ARP bolts weight 21 grams each and the nuts a bit more than 3 grams each.
The original bolts and Harris´s weight 24/25 grams. Both together weight 49 with this scale.

So, originals;
-430
-424/420
Harris (at least this set. I have other installed few years ago but do not remember)
-434/431

The pistons that were with the matched pair, are 0.40 and modified all around the edge to have kind of a squish band and to sort out the bathtub chambers so I think weighted a bit less. I need to check that. They are JCC, 8.6:1

The point is that with all this combo the engine did not vibrated too much. Of course all these bikes vibrates but we can call it normal vibration.
A combo that is not the same that out of the factory for a 79. That put me in a guessing situation, to what exactly to do regarding weight and possible vibration etc.

I had the 430 weight + the modified 0.40 pistons that with all the filing weight less and crankshaft at 0.10
then I have the Harris rods + STD pistons (JCC too) that would weight more + ARP bolts and nuts that weight less and STD crank

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Hi Reverb, My '73 Tiger had a difference of 4g on the big end as the caps were totally different looking & shape. I weight matched the rods by grinding steel off cap & getting heaver nuts for one side, lighter for the other.

On the road made a huge difference. Just today I was on highway 70-72 mph. Big difference. In you position with out an accurate scale to .1g, so a tenth of a gram you're kind of guessing. Usually the pistons are pretty close. Within .2g.

If possible, I'd put rings on pistons. Shells in rods, bolts in rods, nuts on loose. Set pins & clips inside pistons. Weigh all the parts & swap rods/pistons left to right to get close as you can.

Did you get weight matched Harris rods? Or 2 separate? I've personally weighed 2 sets of Harris weight matched rods. They were withing .1g.

Here's what Triumph did. Measured bores. Had a box of 3 diameters of pistons. Pulled the piston diameter needed for bores from box. They grabbed the top 2 rods from a big box. The crank came off a big rack. Put the first crank that fell to hand in jig. Installed the first 2 rods from box. Put the closest piston to hands on first rod, then the other. They had no thought of balance at all. After spending several hours weighing genuine Triumph pistons, rods, I was shocked. No wonder some motors are smoother by far. Others vibrate horribly. Some motors were off by 1g, many off by 4 g. some of by 6-7g +.

Cranks.... Look at the differences in the forging & how much they took off pork chop when grinding off flash from forge. Some are 1/8-1/4" different. That is huge. The '69 bonnie shaker, they ground off a good 1/8" of top of one pork chop. I'd guess 8-10g+. After the bike is very smooth to ride.

Point is you just don't know. You're pretty much luck of the draw. What if pork chop is heavy & you put light rod on that side? You get smoother. You put heavy rod on that side you get rougher. So you're basically guessing. Still you wouldn't be worse than Triumph if your only 2g off.
Don


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This backs up my theory that some Triumph engines were closer to a "blueprinted engine" than were others.

My cousin Mike had an exceptionally smooth, fast '67 Bonneville right out of the crate.
My '67 was decent, but couldn't catch HIS.

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Smooth is all relative with big bore 360 twins at higher rpm…Some are just not as obnoxious..
Running hard on backroads with my modified T140D at 4000-6000 it was entertainment…the engine would run up to 7000 without feeling like it was going to explode..Cruising at 4500 made my butt itchy and squirm around, 15 minutes was enough of that …This was after rebuilding the engine, I weighed the rods and pistons , all was close, good enough…It was smooth before the rebuild ,just slower…


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"The Rise and Fall of the British Motorcycle Industry" describes why British motorcycle manufacturing was of "variable" quality. One example being when the Triumph factory in Coventry was bombed by the Germans in 1940

">
.... a twin-spindle boring machine that had been split in two by the bombing was quickly welded back into shape and was still in use by the company 30 years later a testament to the ingenuity of the British but also a clear indication why no British motorcycle company could possibly keep up with Japan s leading-edge technology in the 1960s.
<"

I wouldn't be surprised if the Meriden Coop was using pre-WW2 machine tools in the early 1980s.

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Hi TR7RVMan;
I cannot change the nuts due to are ARP; I do not see how can remove from the rod itself without hurting the rod; yes, I can remove material from the cap; but very little; I do not compensate with that; may be debilitate too much too?
With the pistons would be easy to remove some from the inside or may be widen the pockets for the valves (that in my opinion are too small)
I do not see how I can remove material from the pins.
-Regarding the accurate jewelry scales; cannot weight all the stuff together because overpass the limit; so in that case I need to use a kitchen scale (+/-1 error) but I can weight the rod; then the piston; then the other things in the accurate scale then check in the other.

Hi Hillbilly; did you sent the crank to dynamic balancing after the changes?

Hi Dibnah; however; new bikes that are fabricated with robots and new machinery HAVE errors in the parts. Almost all the smaller cc bikes have errors in weight of parts and details on the cases.
Even big bikes have problems. Last year I went to the Ducati importer and in the wshop they had 2 engines apart; an 848 and other; they were removing material from the rods to match the pair...; engine not well balanced etc


Hi IrishSwede; I think that plenty of the vibration with new bikes are "hidden" to the rider due to the counter balancer; the way they anchorage the motors and couple of other things.

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Hi Reverb, Don’t remove alloy from rod. Remove it from steel cap by widening the “slot” on steel cap. 2g is about all you can remove.

Did you buy weight matched rods?
Don


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TR7RVMan; as mentioned; is plenty of difference in weights to compensate with only 2 grams or less that I can remove.
As you see with the other comment, is that the weight is different so evident is not a pair; also only have 1 punch mark in each; would have 2 in one of them.

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Hi Reverb. Both weight matched sets I got came in one box. The had a sticker stating weight. The sticker & my scale agreed.

My scale has full set of calibration weights. It is very accurate. To less than .05g. Uncanny accurate.

I know the cost of weight matched Harris rods is way higher, but it's worth it in the long run.

In real life I don't know you'd be able to feel the 2g much if at all. It depends on how well your crank was in dynamic balance after it came from the forge.

Regarding the balance factor 2g is nothing. When you get into the 20-30g range it starts effecting factor. I would weight pistons, rings, wrist pins. Put heaviest on lightest rod & ride it.
Don


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Originally Posted by TR7RVMan
Regarding the balance factor 2g is nothing. When you get into the 20-30g range it starts effecting factor. I would weight pistons, rings, wrist pins. Put heaviest on lightest rod & ride it.
Don
My first Bonnie (my 2nd Triumph) was a 71 with a blown engine. I got a set of cases and a rod from somewhere, and put it together with a Morgo 736 kit. It became a fast and quite smooth engine that was a match for anything around here in the late 70s. I didn't really know what I was doing so it was purely by chance. Later, when an overhaul was needed, I dicovered that my two connecting rods where very different, one being skinnier. I can't recall the difference in weight, but it was quite substantial. I matched the weights either end as best I could and got them very close. Here's the thing; I had expected to feel a big difference in engine vibrations, but couldn't really detect any. I never understood that.

Later still, my last season with it, I stuck in a 67 crank and flywheel, using another set of old matched rods, and vibration over 110 kph/70 mph became an issue. I've built many engines over the years, matching pistons and rods with the crank statically balanced, but they're all different on the road. I suppose dynamic balancing is the way to go, but as I can't have it done locally, costs becomes too high.
A Norton 650SS I rebuilt had a dynamically balanced crank assembly (by a well known outfit in the UK) but it vibrated as bad as anything, which put me off a bit to be honest. Others seems to have good results though.

Triumph rods and bolts have never failed me and as long as they're straight and round, I re-use them. I do polish rods and bolts as a matter of course. As long as you stick with a 7000 rpm redline they'll last for as long as you need. Racing is a different story, not to be told by me.

My ramblings probably aren't useful to anyone, but I guess my point would be that they're all different and that dynamic balancing may possibly reduce vibrations to a tolerable level. And that Triumph rods are plenty strong enough for road use.

SR

Last edited by Stein Roger; 04/16/22 9:08 am.
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Was the 'well known outfit in the UK' Basset Down by any chance? They seem to have been good quite a long time ago but changed ownership at least once since then. I've seen quite a few of their balanced cranks and they all look like Swiss cheese, an unbelievable number of large diameter holes in the flywheels. Many people say the vibration levels were worse rather than better.


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Reverb, I did not balance the engine, the replacement pistons were only 6 grams heavier.
Far as I know Ducati and Moto Guzzi do not use balance shafts or rubber mounts..Vibration is managed by proper engine and frame design..
High performance auto engines are often balanced with 2 grams…Many néw auto engines are within 5 grams right from the manufacturer..


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Originally Posted by Tigernuts
Was the 'well known outfit in the UK' Basset Down by any chance? They seem to have been good quite a long time ago but changed ownership at least once since then. I've seen quite a few of their balanced cranks and they all look like Swiss cheese, an unbelievable number of large diameter holes in the flywheels. Many people say the vibration levels were worse rather than better.


I’ve had 2 cranks done by them and both have been fairly smooth. But it’s not just the crank balance that determines that, that’s an A65 with oversize pistons and new rods but a similar weight to factory ones.

The other motor is an A65 again, but A10 crank and B44 pistons. So far so good with that one too.

I asked for the 650 A65 to be balanced to be nice at 4500rpm. I said 3500-4000 for the 823 motor.

Yes they do look a bit Swiss cheese like but they they function nice enough.


Now let’s all have a beer beerchug

68’ A65 Lightning “clubman”
71’ A65 823 Thunderbolt (now rebuilt)
67’ D10 sportsman (undergoing restoration)
68’ D14 trials (undergoing transformation)

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...time ago I decided to not do the dynamic balancing. I do not trust in most shops anymore and the situation with this purchased crankshaft was a pain with the customs...I doubt that I could do that again if all goes wrong with the balancer. Besides the money; of course. I spent 1100Dollars on that used crankshaft
from UK to my house and that is a lot of money here (by the way; I am not a collector etc I am a working man so all these things represent months of hard earning money)
Ok;

Hi TR7RVMan; but I have more than those 2 grams; I referred that you say that I can remove max 2 grams and I said that 2g is not so much regarding all what I need to remove actually.

Hi Stein Rogers; I decided to buy new connecting rods due to I do not feel comfortable with the set that I removed from the broken crank. The previous owners really put stress on all the parts so I do not know if these ones are good to go or will break in no time.
In my opinion if the rods are Aluminum in a total rebuild, should be new; of course that if you ride at 60 80 km/h as a Sunday bike, that do not represent a problem mostly.

Hi Hillbilly; yes; but how do you feel vibration in a new car? I do not feel anything. Yes; in an old VW bug you can feel it at speed but.

-For now I still think that the choice is to check all the older stuff to weight to compare the difference with the new parts.
One thing is the overall difference and other is the difference between cylinders...

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“Hi Hillbilly; yes; but how do you feel vibration in a new car? I do not feel anything. Yes; in an old VW bug you can feel it at speed”
Auto engines have specialized motor mounts and many have balance shafts to deal with occupant comfort. the precise engine balancing is for better efficiency and longer engine life…A 360 degree twin could be balanced for what’s best for the engine, but then then it would shake the rider badly..


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But a V8 engine is a good start for me
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Hello; just weighted the Harris new connecting rods again, on a jewelry scale.

The rods have 1 punch on the sides and one should have 2 punch marks hence a pair...

-One rod weight 241.8 grams
and the cap: 131.7
Rod complete + bolts + nuts = 429.6 (7) no shell bearings

-The other weight 244.7 (8)
and the cap: 126.7
Rod complete + bolts + nuts = 427.5 (6) no shell bearings

ARP bolts: 24.1 each
Nuts: 3.8 each

The originals weight the same the rods alone; and with the caps...

If I remove material what about that mass turning at 4500 6000RPMs? I mean; is only important the overall paired weight? because I think a lighter rod in one cylinder is actually lighter...besides that is attached by 2 bolts with the bottom cap...but may be that is not the way to reasoning. this.

The point that is very frustrating to buy a new set but actually is not a set...letting me with a problem that do not let me start with the rebuilding.

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Are these going back on a known crank that you have used with known old con rods?
If so, were you happy with the vibration characteristics of that engine?
If so, again, you should be attempting to emulate the (im)balance of the original rods/pistons.

If you simply balance the ends of the rods, and the pistons, without dynamically balancing the crank itself, you have a 50% chance of improving the situation, and a 50% chance of making it worse.

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Hi Koan; in the first comment are the details.

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Hi Reverb. I've been involved personally with 2 pairs of Harris weight matched rods. They came in a box as matched set marked such. The rods had weight stickers on them. My scale which is spot on showed both sets were within .1g. I'll call that as good as any balance shop would do.

It is extremely bad when shop says a pair or set & in fact they are not actually a weight matched set. I know the weight matched sets when we purchased them were about half again more costly. So way more costly. I felt it was worth it.

Your overall is difference is 2.1g. That's getting pretty far off. My balance guy says anything over a gram can be felt.

The way I read it you have a heavy assembly on one side 429.6 A heavy cap, but light rod.
You have a light assembly on the other side 427.5 A light cap but heavier rod.

That puts you in a bad spot if you can't weigh each end of rod.

Your rods alone has a difference of 2.9g. 2.9g of aluminum is a large mass of metal. Can you see larger areas on the heavy rod, like it's fatter than the other one.

My feeling is rotating weight is more critical than reciprocating. Meaning the big end is spinning in a circle, the shaft & small end are mostly going up/down.

My hunch is the extra metal is around the big end of rod & where shaft is coming out of big end section. Look & see. If that's the case I'd take about 2g off the steel of the cap. But.... if the small end is fatter by a visible amount that looks like a lot, I'd leave it.

You could also put hardened washers under rod nuts on the light side.

When your rods don't match it puts you in a bad position.

Look at the rods side by side very carefully & see what you can see for differences.

Weighing original Triumph rods from same motor so the rods motor came with from factory, they were often 2-3g different overall. Mine was 4g! Making the rods match on my bike made a world of difference. Prior at 6000 it felt like motor was going to blow up. Entire bike especially the handle bars felt like they were going to vibrate off. Hard to keep your hands on them. Now 6000 is not bad at all.
The pistons were all over the place also as well as dynamic of crank. I personally would try to weight match your rods if possible.
Don


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Hi TR7RVMan; I measured the big ends with a caliper but is not possible to be precise however, the differences are not seeing by eye.
Possible one of the shafts is thicker in that middle curved part.
I do not see a safety way to remove material from the rod; even I do not see how I can remove 2 grams from the cap without letting it too thin.
Also; the rods still would be wrong; even the caps would be wrong removing 2 grams. Yes; the overall weight would be near but I still think that the differences of 3 grams in the rods could be not so good at 4000-6000RPM no matter if the overall weight is similar.
I think the pistons is the less important factor; PO modified a lot the pistons; then when I changed pistons etc; I put the same brand and modified its similar to what PO did but I think that I did not weighted the pistons nor matched and the vibration vibes were the same.but these other connecting rods are weight matched and that seems to be the ticket.


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