Author Topic: Sticky Crank  (Read 1614 times)

Online RichardL

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Sticky Crank
« on: 25.03. 2014 04:28 »
Gents,

I'm distressed. The issue of "Sticky Rod" was solved to my great satisfaction and now appears ridiculously minor. Now that the engine is tight together and mounted in the frame (without top end), I have found that it rotates smoothly in the top half of the stroke and tightens up a lot in the bottom half, but can still be forced around. The rods are still free at the bottom. No bolts are installed in the front three chain-case holes. Have I made the end float too tight? A horrible thought, considering it would mean another near total tear down.

Any uplifting ideas?

Richard L.
Plan on signing up for the world-wide 2017 DISTINGUISHED GENTLEMAN'S RIDE on September 30, 2018. Watch website at https://www.gentlemansride.com for details.

Online RichardL

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Re: Sticky Crank
« Reply #1 on: 25.03. 2014 04:40 »
Another thought: I might have been too heavy-handed when tightening up the crankcase studs. Is it possible I've compressed the crankcase casting 0.0005-0.001" My recollection is that the crank turned free when the case was assembled while fitting the shims.

Richard L.
Plan on signing up for the world-wide 2017 DISTINGUISHED GENTLEMAN'S RIDE on September 30, 2018. Watch website at https://www.gentlemansride.com for details.

Online KiwiGF

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Re: Sticky Crank
« Reply #2 on: 25.03. 2014 06:28 »
is the primary on? i ask as the front 3 bolts and 2 inner bolts if too long can contact the crank, usually of course it would stop it turning altogether tho  *eek*
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1956 A10 Golden Flash EA7-168x, CA10 913x, left BSA together for Liverpool, 5th Dec 1955.

1949 B31 rigid “400cc hot rod” (favourite bike)

1949 C11 rigid, but why!!! (cos it was cheap)

1937 B21, missing parts so mission impossible?

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Online orabanda

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Re: Sticky Crank
« Reply #3 on: 25.03. 2014 07:00 »
Richard,
Could be a mis-alignment issue between the main bearings.

What was your set-up procedure for line boring the timing bush?

The Other Dick

Offline duTch

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Re: Sticky Crank
« Reply #4 on: 25.03. 2014 08:32 »

 Well you do say the front three case screws are not in, but the bottom one of the two rear ones could cause grief As Kiwi says (if in the same place as plunger ones, I think the top one clears all?), I had a similar issue long time ago caused by that.
 Over-tightening maybe- if there was a gasket in there, which I think isn't normal...?
Started building in about 1977/8 a on average '52 A10 -built from bits 'n pieces never resto intended -maybe 'personalised'
Have a '74 850T Moto Guzzi since '92-best thing I ever bought doesn't need a kickstart 'cos it bump starts sooooooooo(mostly) easy
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Online bsa-bill

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Re: Sticky Crank
« Reply #5 on: 25.03. 2014 10:40 »
Had exactly the same problem with my last rebuild, The primary front bolts were catching but imagine my thoughts when I cured that to find it still stuck when put together.
The other Dick is correct (in my case anyway) I took it back to the shop, showed the problem to the desk guy, they did it again (with another new bush) and it was fine.
I've had a bit off stuff done at that (local) shop, all good apart from the last two ( crank and rebore) shame but I think the old guy's eyes are not what they were, however they put everything right at no extra cost (apart from the extra bush).

PS I'd check alignment before be tempted to take any action re shimming other than checking it, you could and up costing yourself time and money DAMHIK
All the best - Bill
1961 Flash - stock, reliable, steady, fantastic for shopping
1959 Rocket Gold Flash - blinged and tarted up  would have seizure if taken to  Tesco

Online RichardL

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Re: Sticky Crank
« Reply #6 on: 25.03. 2014 11:18 »
Richard, Bill and all,

Well, the alignment procedure for the timing side bush was left to the machinist. I think he described a conical alignment center that set in the main outer race. I should have asked to see it because it's already feeling like an issue while I sit here typing. On the other hand, this shop is doing all types of very serious engine machine work (albeit, not BSA, specifically) so it's just hard to imagine that he did not understand the gravity of proper alignment. I suppose I should ask him if he did the work himself. I'm wondering, if it is alignment, why would it not be tight all around?

I notice no one is suggesting running-in as a solution. Also, no bites on the case-too-tight possibility. I guess I'll be torquing the studs to a lower value to see if it helps (oh, I hope it helps). I tightened by feel originally, but think I'll need to use a torque-wrench to get them evenly looser.

Thanks gents.

Rrichard L.
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Online Seabee

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Re: Sticky Crank
« Reply #7 on: 25.03. 2014 11:55 »
Richard, you might try adding your front three bolts and torquing them first.  It could be a slight case misalignment (skew) from not being torqued evenly all around.  I know it's a stretch, but easy enough to eliminate that as a cause.

Joe
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Online muskrat

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Re: Sticky Crank
« Reply #8 on: 25.03. 2014 12:28 »
G'day Richard.
When you measured for end float did you use bolts in the holes that are used as engine mounts as well as the studs. When you've mounted it in the frame these bolts may have closed it up a tad. I'm with you in thinking misalignment of the mains would cause stiffness all the way round.
Cheers
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Online RichardL

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Re: Sticky Crank
« Reply #9 on: 25.03. 2014 14:32 »
Musky,

In my final measurements I used more than just the four dead-ended studs, but can't recall which hole or how many. I'keeping fingers crossed for getting some relief by loosening-up on all studs and hoping there has been no plastic deformation.

Richard L.
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Online bsa-bill

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Re: Sticky Crank
« Reply #10 on: 25.03. 2014 14:48 »
Quote
hoping there has been no plastic deformation.

I stand to be corrected but think you'd strip threads before you deformed the crankcase, it is after all two bell shaped casting (extremely strong shape) clamped around the circumference of a mid join.
thoughts - was the timing side bush seated firmly square against the case before it was line bored, surely it was and have you tried it with the cushdrive fitted
All the best - Bill
1961 Flash - stock, reliable, steady, fantastic for shopping
1959 Rocket Gold Flash - blinged and tarted up  would have seizure if taken to  Tesco

Online orabanda

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Re: Sticky Crank
« Reply #11 on: 26.03. 2014 01:57 »
Richard,
I wouldn’t attempt "running in". It is likely that the machine set-up wasn’t quite accurate enough.

You are aiming for 0.0015" clearance on the crank journal. If the set-up is say only 0.002" out between the machined housing for the drive bush and the timing bush centre, then the crank will be tight like you describe (if it turns!).

The most accurate methodology is to set up off the main bearing bore (in the LH case) so that radially and axially there is zero concentricity (no run-out).
Then bolt the RH case to it (undersized bush installed), and machine to 0.0015". The bore of the timing bush is then perfectly concentric with the bore for the drive side bearing.

This job is commonly done in a horizontal borer (or mill), but mine are done in a lathe.
I made a jig out of an old aluminium bellhousing (used to mount a hydraulic pump onto an electric motor; it didn’t cost me anything).
The forum won't let me paste the pics; sorry!

Richard

Online RichardL

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Re: Sticky Crank
« Reply #12 on: 26.03. 2014 02:47 »
The forum won't let me paste the pics; sorry!

Richard, and all,

Huh, can't post pictures? I seem to recall seeing your setup in a previous (years ago) post. I appreciate the effort spent in explaining the right process, but maybe, just maybe, things are going to be OK for me and my engine (if this was a Vincent, I would have so enjoyed saying "me and my shadow").

When I got home today I intended to start loosening things up until the stickiness went away, starting with the new dynamo pulley. Lo and behold, when I put the socket to the idler nut the crank seemed to turn over more freely. Not exactly sure why, though, last night I had poured a quart-and-a-half of oil into the crank case to be sure everything was well and fully lubricated (even though I had used assembly lube). After turning the engine over many times via the idler nut, I'm beginning to think I might be OK, and what was seeming excessive tightness had loosened up. I have posted a video on YouTube to show this and, hopefully, you and the gathering hoard will confirm my pending happiness.

 https://www.youtube.com/watch?v=ufQyjM_EpPQ&feature=youtu.be

(by the way, the white crap on the floor is the oil absorbent that I through down after forgetting that oil would come out the chain-case front three holes.)

Looking forward to all comments. Don't worry if they are negative, I'm well past the jumping off my workbench phase.

Richard L.[/size]
Plan on signing up for the world-wide 2017 DISTINGUISHED GENTLEMAN'S RIDE on September 30, 2018. Watch website at https://www.gentlemansride.com for details.

Online KiwiGF

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Re: Sticky Crank
« Reply #13 on: 26.03. 2014 05:49 »
hi maanosound, I thought you had just the crank spinning in the cases, but youve got the barrel on and timing on as well, could the stickiness be caused by something other than the crank eg an oval mag gear, or dynamo belt?
New Zealand

1956 A10 Golden Flash EA7-168x, CA10 913x, left BSA together for Liverpool, 5th Dec 1955.

1949 B31 rigid “400cc hot rod” (favourite bike)

1949 C11 rigid, but why!!! (cos it was cheap)

1937 B21, missing parts so mission impossible?

1952 Armstrong Siddeley Whitley for rainy days (with wife).

GL1800 Goldwing not sure why, maybe cos it always starts

Online muskrat

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Re: Sticky Crank
« Reply #14 on: 26.03. 2014 06:18 »
Umm, your turning the crank backwards  *ex*.
Yes a bit hard to track a sticky with all the ancillaries bolted on.
Cheers
'51 A7 plunger, '57 A7SS now A10CR,  '83 CB1100F, .
Australia
Muskys Plunger A7