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Classic, Vintage & Veteran For Coventry and Meriden Models. Anything pre-Hinckley goes.

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Old 08-04-2011, 06:18 AM   #1 (permalink)
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Crank end float in late model T100R

Hi,

I just replaced the main bearings in my T100R (71MY). It's the type that doesn't have a seal on the primary side bearing (breathes via primary case).

I'm pretty sure there were no shims anywhere when I took it apart, and I don't recall there being much end float, but on trial assembling the cases I find about 1/16" of end float on the crank.

Anyone know what's the proper way to remove this float (where do shims go etc) and what's the reason (cases are definitely seated together tightly).

Cheers

Stu.
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Old 08-04-2011, 08:16 PM   #2 (permalink)
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The amount of end float in the crank is not important just as long as there is some.Tightening up the timing side crank nut locks the crank to the timing side and any changes with temperature are catered for by the roller on the drive side..If you are using balls bearings on both ends of the crank end float would be more of an issue.
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Old 08-05-2011, 04:17 AM   #3 (permalink)
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Thanks mate,

That's how I thought it may be but didn't want to put it all together with sealant and bearing lock compound only to find I was wrong.

I have a Haynes and Original workshop manual but neither was clear on this.

Stu.
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Old 08-11-2011, 12:55 AM   #4 (permalink)
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You blokes have to be kidding!
Conrods should be central in cylinder bores.Within 0.005" or maybe even 0.008" difference between one side of the small-end and the other to the bore.What's your chances here,1/8" difference and it can change at any time?Primary chain alignment can change by 1/16" and wander around too?
You can put shims between the bearing and the crank shoulder,either side as required.
Anyone who believes a timing-side main can never move in the cases might also believe in Santa Claus.Just clamping the crank to that bearing won't keep it in one place.

The amount of end-float limits how far the rods can move off-centre in the cylinders.
Triumph reckon 0.003"-0.017" end float is OK.Not good at 0.017",but it will run.

I'd have about 0.003" difference on either side of a conrod,relative to the cylinder.
When you've got the timing-side bearing shimmed to that (with the crank pushed toward timing-side),then adjust total end float with shims on the drive side. 0.003" total gives you the least chance of variation;crank rods and timing-side main can't move much when the engine is hot.
There is almost no interference fit holding the timing-side main on a hot engine.If a rod is 0.020" off centre,you've got about 20 ft-lb twisting the rod and piston on a firing stroke (at full throttle).

Last edited by Mr.Pete; 08-11-2011 at 12:57 AM.
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Old 08-12-2011, 04:30 AM   #5 (permalink)
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I take your point Mr Pete, the bearing will be loose if it is cold and the case is hot (that's how I fitted it), In fact the old bearing dropped out at about 150 deg C in the oven (when both were hot).

However the, guy who reconned the cylinder head for me, who has a lot of years experience building Triumph twins, reckons that it is OK and no shims are required.

Anyone else have an opinion on this?
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Old 08-12-2011, 05:13 AM   #6 (permalink)
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How central are your conrods when the crank is pushe toward the timing-side main?
50 degree C temperature rise will loosen the inteference fit of the bearing in the case by more than 0.0015".That leaves about 0.0005" interference,or 0.001" if it's a very tight one.
Put 3000 lb load on a bearing with 0.0005" interference,and you may see daylight between the top of the bearing an the case.Bearings and shafts can walk,even when they are reasonably tight.
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Old 08-12-2011, 09:40 AM   #7 (permalink)
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With a nod to petes concerns checking the rods are central is important,I myself install the ringless pistons and clamp down the barrel before tightening up the cases to ensure proper alignment, then spin the crank watching the pistons to check they are central and any for signs of a cocked bore/s
The timing side bearing in Daytonas seem almost trouble free unlike their driveside partner,mine has shown no signs of movement in 90,000 often hard ridden miles yet the driveside inner and outer show polished surfaces so it has been creeping.I have seen inside a few other end feed T100,s and they both had perfect timing sides and rat**** drive side bearing seating on crank and in housing
The timing side ball bearing must give the end location of the crank otherwise they would have used a roller for it greater load carrying ability ala Nortons and the whole setup being a product of years of successful racing , any faults would have shown up and been addressed before going into production bikes.
As for side thrusts ,as long as the rods are central and the primary sprockets are lined up there are no helical gears to try to push the crank sideways so the crank should stay quite happily where it is .
1/16" end float seems quite a lot but it obviously has survived this long with it and even Stan Shentons book says as long as there is end float all is good
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Old 08-12-2011, 10:34 AM   #8 (permalink)
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The only way to check rod centrality is to bolt the barrel on with no pistons,and measure between each side of the small-end and the bore.This is best done when you're pulling the engine down;it saves time later.
The differential expansion I quoted is correct.The 3000 lb force is conservative.You could double that,if you're heavy on the throttle.
The outer race of the timing side bearing doesn't have to spin in the case to creep and walk.They didn't put shoulders in the case beside the main bearings for nothing.If it's all built to factory spec ,the crank could "only" move 0.017" max.
There are forces pulling on the crank,even if the rods are perfectly centred;but even the rods have side-float and don't stay exactly in one place.
Just my thoughts .
I centre the rods in the bores,within about 0.003" side to side difference.Shenton doesn't even mention the effects of this being wrong.I can't see any problem with then taking end-float to the minimum.I can see other possibilities if it's more than the minimum.
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Old 11-02-2012, 06:03 PM   #9 (permalink)
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I did a search (on Google) and found this thread.
I just checked the end float on my T100R whilst checking the belt drive after the first 200 miles of running and found it to be 0.0315"
I can't really remember if this was checked when the new bearings were installed but it seems really excessive and I think I'd have noticed that much end play.
The bearings were both tight in the crancase and required lots of heat and persistence to remove the originals and the new ones were similarly tight when installed.

So I have two questions for Mr Pete:

1/. Is it possible this has increased in 200 miles? ( I found no alloy in the sump strainer and the oil was crystal clear)

2/. Are the shims you mention Triumph parts (I ony have a parts book for the timing side bush engine) and if so whre can I get the part numbers for various thickness ones?

Thanks in advance.
Davy-J
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Old 11-02-2012, 08:23 PM   #10 (permalink)
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1./ It's not likely to have changed any.0.020" is not uncommon;0.0315" is a little more than usual.Even replacing a timing-side bearing can change it by 0.003" (the inner and outer races are rarely perfectly centred).
2./ I can't find any part number for shims,even though shims were sometimes used under the crank sprocket for sprocket alingment.The same shims would fit between the bearing and crank,with a little attention at the crank corner radius.It always seems to be that most shimming needs to be on the drive side.
Enginering suppliers should have shims in various thickness.

You could try bearing supliers too.
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