Broke crankshaft ear

[Kt06siggm1]

Opened the right side case to tighten the crankshaft nut for the woodruff key and when I went to put the case back on, didn't realize the slots had to line up for the oil pump. Felt like a real bonehead but I have heard George from uptite say that they aren't necessary. But, I am still nervous and am looking for a local to weld it. Anybody else run into this issue and what was your fix?

 

[Theo]

I'm glad you've opened this thread: talking thorougly about this in the other one would have been off-topic and I think it deserves its own thread.

The same thing happened to me some years ago.
I removed the cover because my Woodruff key was broken and I found out that one of the two tabs was broken and stuck behind the oil seal:





Then I remembered the noise I had heard the previous time I reinstalled the RH crankcase cover. I had thought it was just the cover getting into place; apparently, it was not!
So, I got the crankshaft out of the engine, got it welded and reinstalled it (I disassembled and reassembled the top end and a mechanic did the bottom end).
Here is the result:




A company here in Italy which deals with things like balancing crankshafts etc. welded and machined it with a lathe (and probably deburred it with a file). The last time I checked, it was still there.

When I went to the dealer and bought some parts for reassembly, they told me that they had done something like that to one of their customers WITHOUT removing the crankshaft from the bike and that that bike had been working fine for years afterwards. Of course you can't process it with a lathe and, as they told me, it could be necessary to replace the oil seal of the crankshaft becuse it may be damaged by the heat.

Personally, where I work (we make certain industrial mechanisms) I've seen miscellaneous parts laser welded by a certain supplier of ours, even hardened parts to which hardened metal had been added via laser! and I remember that only once we had to rework a diameter close to the welded zone because the heat had warped it by some hundredths of millimmeter. It's more expensive than electrode welding but its heat only affects a limited zone. I don't know whether it's feasible on a crankshaft installed in a motorcycle. Mine was probably welded with an electrode.

I don't think it will be hard for you to find someone able to weld it, but IMO you have to take care of these facts:
•There is a hole between the two tabs, probably for lubrication; in my crankshaft, the weld covered it only a little: make sure that it isn't clogged by the weld.
•The clearences have to be restored: you can't just use a crooked tab. The zone of the crankshaft with the two tabs was probably a cylindrical zone in which they machined a slot. Before the tab was broken, it would have been easy to measure the diameter; now you should either find a way to do that or hope that someone with a pristine crankshaft tells you the measure (it would be helpful for me, too, because mine works and looks fine but I don't know how straight it is). I am pretty sure that, with some trigonometry, you can deduce the measurement; I'll work on that, too and let you know. Edit: found it out; let me just draw a schematic.

 

[Theo]

•The clearences have to be restored: you can't just use a crooked tab. The zone of the crankshaft with the two tabs was probably a cylindrical zone in which they machined a slot. Before the tab was broken, it would have been easy to measure the diameter; now you should either find a way to do that or hope that someone with a pristine crankshaft tells you the measure (it would be helpful for me, too, because mine works and looks fine but I don't know how straight it is). I am pretty sure that, with some trigonometry, you can deduce the measurement; I'll work on that, too and let you know. Edit: found it out; let me just draw a schematic.

Here are the schematics:

In order to know the final dimensions of the welded parts, you'd like to measure the diameter and the width of the slot, indicated in red:


But you can't because one of the tabs is missing. So, here's a formula to get the diameter with what you can measure:

The reason for which BC=Ø•sinα is that BC is a chord and there is a apecific theorem about it whose name I haven't found in English.
I've worked in quality inspection and I can say that trigonometry works in these situations. I'm just a little worried about the fillets on the A and C edges because the may not let you measure AC properly, but they shouldn't be that big in your unwelded and unremachined crankshaft.

 

[Kt06siggm1]

I appreciate the help

 

[Theo]

You're welcome.
Keep us posted!

 

[Spice Weasel]

Put it back together the way it is, it seems the only way some people have found out that one of the tabs has been broken is when theyve taken the cover off, so it stands to reason that it works fine with one tab.

 

[Theo]

Well, I must apologize because I should have also talked about my experience when I ran the bike with one tab only. Now I don't remember how many miles I put on it with only one tab, but I did, at first, put it back together the way it was, because I din't feel like having the cases splitted.
I would not be surprised to read a post of someone saying that in 50k miles with a tab only the motorcycle had no problem.
I personally didn't feel safe like that, for me it was something like replacing the oil every 6k miles or cheking the valves clearances every 10k miles: maybe the bike will still work fine, but you raise the possibility of a failure.

 

[EricV]

Yeah I’ve gotta agree- it’s not at all worth the risk and worry. I think running on one tab has gotta be a time limited option, towards the end of it no longer working which of course means the oil pump ceases and we all know how that turns out. Just not worth it.

 

[Kt06siggm1]

I'm having a competent buddy weld the tab back on since it was a clean break and I have the piece that sheared off. I figure with both sides it would put less strain on the pump and the shaft. However, am I to be concerned that it will throw off the crank balance?

 

[MATPOC]

I agree with "fix it" crowd, single tab will put too much side-load on the pump, maybe wear it out prematurely.
don't think you need to worry about balancing it, too close to the center to cause any problems

 

[Theo]

I agree about the fact that the mass of the missing tab/supplementary weld is too little and close to the rotation axis to affect the balance.

My opinion about the situation has evolved a bit when I started thinking about this statement:

single tab will put too much side-load on the pump, maybe wear it out prematurely.

, which has been written elsewhere, too by other people about the same problem.

I haven't measured neither the slot between the two tabs, nor the width of the tab of the oil pump shaft which meshes with them, but there must be some clearance between them, otherwise they would need a perfect centering of everything (crankcase cover, oil pump in the cover, etc.) to mesh properly and I doubt that such tolerances would be achievable.
A little drawing can explain faster and better what I think about the way they work together and what can happen if they are not centerd; in black the tabs of the crankshaft and in red the one of the oil pump shaft:

I actually have a hunch that even in an undamaged crankshaft the situation is a little like the one in the bottom of the picture and that one of the tabs is just supposed to never touch the pump shaft!.
I'd really like to see the result of some engineer's blue applied to the mating surfaces of an undamaged bike (apply blue - install cover - spin crankshaft by turning the rear wheel with 6th gear engaged - check the contact area).
My ultimate theory so far is that maybe the tolerances are tight and so contact of both the surfaces like in the top of the picture will be achieved when the tabs wear a little, or maybe it's achieved by the fact that the conact points/lines actually become surfaces with just elastic deformation (read page 2 here: «In reality, a small contact area is being created through elastic deformation, thereby limiting the stresses considerably»).

So the bottom line is that if you weld the tab too close to the other one, they won't let the pump shaft slide between them and if you weld them too far apart, the one welded will never touch the shaft anyway. An idea could be to weld it a little too close and adjust it with a file until it meshes, if the steel of the crankshaft is not too hard; if it is, a little rotary tool should work. But maybe some clearance is needed... I'm not so sure about what should be done anymore.

And here is another solution, a compromise:
consider that, in our engine:
•the crankshaft is soaked in oil
•the timing chain delivers oil to the head
so, probably, if that oil pump fails, the engine won't seize in a second.
You could even not weld it, reinstall everything and use the bike. Once in a while, you turn on the engine and loosen a little the banjo bolt over the oil pump, the one which brings oil to the head, and make sure that it leaks some drops of oil: in that case, the pump is probaly working. If it doesn't leak oil, you turn the enine off immediately and check it.

 

[Spice Weasel]

http://advrider.com/index.php?threads/sheared-crank-oil-pump-te610.255593/#post-5316839

 

[Kt06siggm1]

Seems the consensus is that it will be fine with one tab but I'd still like to get it welded for peace of mind

 

[MATPOC]

I'm sure your education level far exceeds mine, but I do have much hands on experience with all things motorized so I will do my best to explain things as I see them and I'm certain that loss of oil pressure in the motor such as 610/630 will cause catastrophic failure probably within minutes if it happens while under load.

I agree IF there is splashing going on much like lawn tractor it can operate for a while with low engine load (idle) however those tractors are designed and engineered to use splash method (also have low power=low stress) they have made provisions to take advantage of crank rotation to throw oil where needed (I can elaborate but I feel it's off topic) meanwhile this motor was designed to rely on forced lubrication to crank bearings and top end also to make most power (more stress) It does have ball/roller bearings everywhere so it can last longer without oil pressure than more common flat bearing type motor but also it's a dry sump, no oil under the crank, crank sealed on both ends and whatever collects under it gets pushed out on the downstroke through the reed in to the flywheel cavity, which is also "dry", it gets scavenged to prevent friction losses so nothing gets pulled up to the head with chain drive. Of course there is some oil that gets in there through forced lubrication but it is instantly scavenged out by the oil pump so if pump fails no new oil gets in, it stays trapped in the transmission (simple proof: there is only minimal amount oil that comes out from the front drain plug) There are 2 oil screens because there are 2 oil pumps, 2 separate oil systems, one feeds the motor, other scavenges oil from the front part.

Anyway, that's my 2¢, if you want to have a failsafe, install an oil pressure switch instead of the banjo bolt and wire a simple idiot light... or fancy pressure gauge, but that is more complicated and you have to keep checking it, I think light is more user-friendly

And here is another solution, a compromise:
consider that, in our engine:
•the crankshaft is soaked in oil
•the timing chain delivers oil to the head
so, probably, if that oil pump fails, the engine won't seize in a second.
You could even not weld it, reinstall everything and use the bike. Once in a while, you turn on the engine and loosen a little the banjo bolt over the oil pump, the one which brings oil to the head, and make sure that it leaks some drops of oil: in that case, the pump is probaly working. If it doesn't leak oil, you turn the enine off immediately and check it.

 

[MATPOC]

as for oil pump drive, i'm sure they have tolerance down to a thou'... both, oil pump and crank are machined quite precisely (otherwise they would fail) and outer case cover sits on 2 dowels so it's located pretty accurately in relation to the main engine case

 

[Theo]

I have been alaways taking for granted that the space under the crankshaft was filled with oil and that it was like a reservoir from which only a fraction of oil was sent to other parts of the engine. Apparently, I was wrong, so my aformentioned compromise is not a solution.

Especially if you think that the tolerances are quite good, don't you think that a non precise weld would be useless? If one welds the broken tab half a millimeter too far, or not square or somehow out of position by a little bit, it would probably never touch the oil pump shaft, or it could not let it mesh.
I still point out that the dealer years ago told me that they welded one missing tab without removing the crankshaft from the bike, but now that I have thought a little more about it, that baffles me.

 

[MATPOC]

seems many performance oriented thumpers run dry sump under the crank and they try to run lower air pressure on 610 (and few others) using reed valve, I assume to decrease friction and pumping loss, I have not been inside my KTM but assume it's similar since it also has 2 oil pumps, but also carried part of the oil in the frame as well as in the transmission . Not having oil under crank means you can position crank lower in the motor, which lowers center of gravity, probably other reasons too, but those are the ones I could think off on my own.
AFAIK no car or modern bike motor has oil level high enough that crank would splash it around, there are 2 reasons, one would be friction loss, another is that oil would get aerated and bubbles would enter the oil system making it less efficient, non-issue for ball bearing crank, big issue for flat bearings also hydraulic valve lifters (I worked on cars mostly)

As for crooked weld, you are probably right, if its not precise it will not be touching both sides, so pretty useless... I can see someone with skills being able to tack on a piece with TIG in precisely right spot, was told once that a skilled professional can weld a chewing gum foil wrapper, seems quite impossible to me... some people have amazing hands on-skills, jewelers, surgeons... so who knows...

I have been alaways taking for granted that the space under the crankshaft was filled with oil and that it was like a reservoir from which only a fraction of oil was sent to other parts of the engine. Apparently, I was wrong, so my aformentioned compromise is not a solution.

Especially if you think that the tolerances are quite good, don't you think that a non precise weld would be useless? If one welds the broken tab half a millimeter too far, or not square or somehow out of position by a little bit, it would probably never touch the oil pump shaft, or it could not let it mesh.
I still point out that the dealer years ago told me that they welded one missing tab without removing the crankshaft from the bike, but now that I have thought a little more about it, that baffles me.

 

[Baroquenride]

OP, I'm baroquenride on ADV and if you have any questions about my fix feel free to ask. It's holding up very well btw and I've got over 15,000 miles on my bike now. Somewhere I wrote that I believe the original owner had broken it and I had bought it at about 4,000 miles. I think I fixed it at about 12,000 IIRC.

 

[Kt06siggm1]

OP, I'm baroquenride on ADV and if you have any questions about my fix feel free to ask. It's holding up very well btw and I've got over 15,000 miles on my bike now. Somewhere I wrote that I believe the original owner had broken it and I had bought it at about 4,000 miles. I think I fixed it at about 12,000 IIRC.

I appreciate it. I am having it welded whenever my buddy can get some free time. (Hopefully this weekend, been itching to ride)