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Just doing some big end bearing clearance checks on my 74 T120V crank, before putting it all together and have had a bit of a surprise!
The crank is still on standard journal size and measures closer to the upper limit than to the lower limit, so all well and good and has since been tuftrided and dynamically balanced. I bought some new std size bearing shells fitted them to a pair of new Thunder Engineering con rods. Having measured and set the micrometer to the journal diameter, I then zeroed my 0.0001" bore gauge to check the bearing clearance after having torqued the bearing cap.
[Linked Image]
The big end bearing clearance from the workshop manual is supposed to be between 0.0005"/0.0020" and the new shells are reading 0.0022", so just out of top limit.
I thought I'd try the old shells as this engine had always had good oil pressure and to my amazement the clearance was 0.0005" bang on bottom limit as you can see below.
[Linked Image]
It goes against my better judgement but it looks like I'm going to have to build this engine using the old shell bearings and not the new ones!
I'd be interested in any thoughts on this as it goes against what is supposed to be good practice.
Cheers, John

Last edited by John Harvey; 10/12/21 1:46 pm.

1971 BSA B25T (built as replica of proposed 1972 B25T)
1971 BSA B50 Project
1972 BSA A65L
1974 Triumph T120V
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John, I have a friend who races with Thunder Engineering rods. They are very nice quality. He told me that he has to touch the big end with a connecting rod mandrel on his Sunnen as they are made .001" small. I don't know if that is true with yours but the dimension that all the bearings are made for is 1.7700". It would be worth checking your rods. Generally rod bearing clearance should be .001" for every inch of journal. On a Triumph 650 that would be .0015"-ish. If the clearance is more that would work but in those cases I prefer to run heavier oil in those cases (40w or 50w monograde).

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The new Hepolite shell bearings seem to be undersized on BSA'a and Norton's and if using them you get the crank journal ground to the bearing not the factory sizes.


So whose shells are they ?

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I've since assembled the rods and found that with the old shells fitted they felt too tight, I could turn them easily enough but they wouldn't fall under their own weight, I tried the new shells and as expected not tight at all. I then checked the fitted clearance with some Plastigauge and I'm getting just under 0.002" Which I can live with more than it being anywhere on the tight side. I'm fitting a Morgo plunger pump so I'd rather have a bit more flow than the pressure relief valve going off at low revs, if that makes sense?
Picture below shows tighter rod supporting its own weight!
[Linked Image]

Dandruff; The quality of these rods looks to be superb and I'm a lot happier using these than the originals as it will be used as intended smile

Kommando; The shell bearings were sold as a higher quality than usual set that are made in the USA, they came from SRM.

Last edited by John Harvey; 10/12/21 5:43 pm.

1971 BSA B25T (built as replica of proposed 1972 B25T)
1971 BSA B50 Project
1972 BSA A65L
1974 Triumph T120V
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Made by Clevite then who do make good bearings, they will be trimetallic with a lead indium overlay plating for good antisieze properties.

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Hi John, I’ve been through the rod bearing measuring a few times recently.

I’ve been using plastigauge for over 50 years now. It is the real deal. However it must be fresh stick or results are skewed. Fresh means the string is soft & pliable, bending into tight curve without fracturing. The journal & insert must be free of oil & rod held steady while measuring. I’m sure you are aware of this, but many are not.

I don’t feel the fall test of the rod is a valid test, depending on the assembly lube. For instance “Bearing Guard” lube Franz & Grubb supplies with bearings is very sticky. Ready good good though. But it will feel tight compared to 40w break in oil. I just did that test on my rods a few weeks ago.

Moving to clearance 2 cranks that measured basically zero wear. Checked original rod clearance with plastigauge at .0016. Oil pressure hot idle was good.

On assembly used standard size Hepolite inserts both cranks. Plastigauge showed more clearance. .0018-.0019”. In real life this lowered oil pressure at idle by 3-5# hot. By hot I mean after 50 miles on 80f day. 50 miles on 105f day down full 5#. Same oil pump & idle rpm. So clearance matters. 100f+ is common all summer here. Using Mobil1 Vtwin 20-50 oil after break in. The larger clearance was disappointing.

On my bike I got Clevite 77 inserts as a hope for less clearance. Plastigauge old & new shows old .00155. Clevite. .0016”. So closer to original Triumph Vandervil. I was pleased to find that.

I’ll know more after break in & Vtwin oil installed.

Regarding oil pumps I did some study on them. Firstly the Morgo is by far the highest quality pump & driving block sold today. Price is not out of line. The volume is larger than say the ‘69 & early due to the slightly larger piston diameter. Just a few days back I installed the new Morgo in my ‘73 Tiger.

However…. The ‘73 version (I think introduced in 1970??) Has 2 oval ports on the intake (upper) holes. The bottom edge of these ports are higher & flat. This allows full fill of bore & at the same time sooner cut off…. The results is a huge increase in volume even over the lager Morgo pistons.

Both versions of Triumuph pumps round & oval port are reproduced. LF Harris sells oval port. Problem is…. With all repro pumps is quality control of relationship of mounting holes to ports which greatly effects volume, as well as overall quality of ball valve seating & materials. So a real crap shoot as to how the example sent to you will work long term.

Morgo has good quality control. Even so the pump must be flushed & bench tested. Mine passed perfectly!

The 4 valve pump is same pump as 2 valve in volume. Don’t think that’s going to increase idle oil pressure.

Back to inserts. As we know new inserts are not round. They are sprung into place, with final sizing shape after tightened rod bolts/nuts to crush them to fit the individual rod. They can be removed & refitted carefully to same rod. However moving a crushed insert to different rod is risky as the bore of rods vary leading to less than perfect fit. Will bearing spin later? Probably not. But it’s not a best practice. As we know the rod bore & back of inserts are wiped free of oil as even a thin oil film compromises crush & fit.

John exactly what was brand of your new inserts that felt loose?

The clearance is such the oil provides a hydraulic wedge so not metal to metal contact. This wedge creates heat & a little friction. The oil passing out the clearance allows cooler incoming oil to cool journal. Too much clearance oil leaks out too fast compromising hydraulic wedge. When I worked at the speed shop each motor brand liked it’s own clearance. High rpm most but not all wanted a little larger clearance. But not. We had the luxury of several oversized pump volumes to increase volume, thus pressure. Triumph we don’t.

Amazing how the simple becomes complicated on these bikes. Mostly due to reproduction parts that are not the same as originals. Worst part 98% of NOS parts on eBay is they are not Triumuph, but Harris or Wassell. But the photo often shows Triumph. Now you have to send them back.
Don


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Hi Don

Looks like we're singing from the same hymn sheet, I've been using Plastigauge for 30 odd years, mainly for shutting out mould tools, it's a useful tool to have to hand.

Having looked at the used shells under magnification I think the tightness is due to tiny particles embedded in the bearing surface at the sides of the bearing, so there's no way I'll be reusing them! I used straight 40 oil on the bearings to check them and that is what I'll be running it in on, I will be changing it to an ester-based synthetic once run in.

Some interesting info on oil pumps, my original oil pump is a Meriden oval port one and was working fine, I bought the Morgo pump at the same time as I bought the big bore kit, all as an upgrade. The big bore kit doesn't use pressure-fed exhaust cam followers so I'll be running with R-type inlet followers all around. Probably be okay with the old pump as it was working well as the crank was in perfect shape, not sure what to do now? Probably fit the new pump as it looks very well made, as you say Morgo quality control seems good, how do you test your pumps?

Reproduction parts can and are a royal pain in the arse sometimes, I bought new pair of Spitfire profile cams, the journal diameters on my old cams are still within the factory 0.0005" tolerance and the new cams are -0.001" below the bottom limit, new parts more worn out than the old original parts!!!. I've ended up making new camshaft bearings to get the tolerances back in spec, something I've done before without problems.

John


1971 BSA B25T (built as replica of proposed 1972 B25T)
1971 BSA B50 Project
1972 BSA A65L
1974 Triumph T120V
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Hi John, What brand bearing inserts are your new ones. I’m tacking this clearance issue.

Test pump like shop manual shows. Fool around with it & you’ll. Soon see how the test works. Basically fill the entire bore with oil from your pumper oil can. Finger over fill port.

Put in piston. Allow oil to exit fill port until goes down a little. Then hold tight & bleed air out discharge port until piston is nearly to bottom of stroke. Then with finger very tight on fill port pull piston outwards to create strong vacuum on check ball. Hold this vacuum for at least 15 seconds. During test hold pump horizontal with light reflecting on oil in discharge port.

Oil must not drop in port. Not even a trace. Any drop is a failure.
A good pump will hold for a long time. Sure eventually air will bleed around piston, but the should seal 100%. My new Morgo held for over 3 minutes. My hand got tired & I quit.

The feed valve seat seems show little wear even after 30-40+k miles. Return (scavenge) seat can take great wear. Gets deeper, rough, out or round. Ball stays pretty round though. I’ve seen this wear on 100% of higher miles pumps now.

I’ve not had good results seating ball with punch. Could you lap it with new new ball & replace ball? Sure, but compared to the width of new seat, it’s too wide. So I replace worn pumps.

Wear in drive block shortens effective stroke, reducing volume.

A worn pump or leaky check ball in pump, will reduce volume. Worn/ leaking enough you have problems. Small leaks you can’t tell until oil light winks at idle or the like or return becomes erratic.
Don


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John, PM me your email & I’ll send video on pump testing. I’m sure you’ll see exactly what to do though.
Don


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Hi Don

It looks like the shells I have are good quality US made Clevite ones.

I'm okay with the measured clearance when assembled using Plastigauge, it was under 0.002" and as I'll be using the Morgo uprated plunger pump, with the bleed to the exhaust cam followers blanked off in the cases, it should be fine.

I will test my new and old pumps to be sure everything's as good as it can be, pm sent.

Cheers, John


1971 BSA B25T (built as replica of proposed 1972 B25T)
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1972 BSA A65L
1974 Triumph T120V
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The overlay plating on the Clevite and the VP trimetallic bearings (VP bought a manufacturing license from Clevite for their VP2 bearings so both are Clevite 77) is microns thick. It's very soft to improve embedibility ie to absorb grit and stop it wearing the journals but once the overlay is full it has the opposite effect as the grit is hard. So fit an oil filter so the oil is clean and the grit build up in the overlay is minimised. Also as the overlay protects the next layer of leaded bronze from the acids in the oil attacking it as soon as any bronze shows from behind the overlay then the bearings need changing.

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I have got a nice purpose made filter assembly ready to go on as well has a magnetic drain plug for the frame sump plate, something the bike was lacking. It's clear to see some debris caught in the shell bearings, although the crank journals are relatively unscathed, guess they did there job!


1971 BSA B25T (built as replica of proposed 1972 B25T)
1971 BSA B50 Project
1972 BSA A65L
1974 Triumph T120V

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