Convert ATF pump coupler worn, now what?

[Antietam Classic Cycle]

Can a new coupler be machined by someone with   tool and dye  knowledge and the proper equipment?  I hate the thought of our beloved Converts being "dead in the water"  because of a failed couple that is NLA.
Rick.

I'm sure it can. I posted this response in brider's wanted ad: "I've sent a message to a machinist friend to see if he could reproduce the coupler with the deep socket, broached to the correct size, and heat treated properly. I'll let you know when I hear back from him."

Edit: Heard back from him just now. I'll be sending more detailed photos and dimensions to him this evening. For this to be economical, a small batch would need to be made.

[Antietam Classic Cycle]

i think the pump is called a tyycoid gear pump

https://pumpschool.com/principles/gerotor.php

[bigbikerrick]

Hey Charlie, Thats great! Maybe if a group of us Convert owners get together on this we can get a batch made up, at a reasonable price. I sure would be interested.  I am pretty sure I  will have a convert in my garage, as long as I am riding. It has pretty much become my "go to" bike for everyday use.
Rick.

[bigbikerrick]

https://pumpschool.com/principles/gerotor.php

Good information RE; gerotor pumps. Simple and appropriate for the application. I guess Luigi, did it right.....except for this one little pump drive bit,that needs improving. 

[Antietam Classic Cycle]

Here's the pertinent page from Guzziology:





For anyone interested, here's some photos of the coupler, complete pump and a crude drawing with dimensions. Sent all of these to the machinist.

[brider]

Thanks for posting the Guzziology page & pump web link, both great info. I read Dave's analyses years ago but forgot the part about the heat-treated couplers being oversized.....which is a great segue into my next observation: My coupler was INSANELY tight to the pump bore, almost had to resort to vice-grips to be able to turn it and pull it out at the same time; also pitted and slightly scored:





I can't imagine why the fit is so tight, and wonder about the pitting, also. I would have expected the fit to be similar to that of a wrist-pin in a con rod. If anyone can recall how their pumps felt on the bench, or have a pump handy to check the fit, that would be a good check to see if mine is truly too tight.

A custom-machined coupler would be great, but one with improvements would be the only thing to make it attractive enough to justify a small run. Like deeper engagement? Or a larger 1/4" std hex size to reduce the loading at the hex tips?

I discussed a larger hex with Rodekyl previously, but it was in the context of a larger hex also EDM'd into the cam shaft, so that a straight 1/4" shaft could be used. But failures at the cam-end are never mentioned, so maybe a custom shaft ground to 6 mm at the cam end and 1/4" at the pump end might work, and an existing coupler could be modified rather than machining a custom coupler.

So I'm still looking for a replacement coupler, and also looking around for an EDM resource to look at modifying my existing coupler, but the pits, scoring, and tight fit are still an un-resolved problem.

[Antietam Classic Cycle]

Thanks for posting the Guzziology page & pump web link, both great info. I read Dave's analyses years ago but forgot the part about the heat-treated couplers being oversized.....which is a great segue into my next observation: My coupler was INSANELY tight to the pump bore, almost had to resort to vice-grips to be able to turn it and pull it out at the same time; also pitted and slightly scored:





I can't imagine why the fit is so tight, and wonder about the pitting, also. I would have expected the fit to be similar to that of a wrist-pin in a con rod. If anyone can recall how their pumps felt on the bench, or have a pump handy to check the fit, that would be a good check to see if mine is truly too tight.

A custom-machined coupler would be great, but one with improvements would be the only thing to make it attractive enough to justify a small run. Like deeper engagement? Or a larger 1/4" std hex size to reduce the loading at the hex tips?

I discussed a larger hex with Rodekyl previously, but it was in the context of a larger hex also EDM'd into the cam shaft, so that a straight 1/4" shaft could be used. But failures at the cam-end are never mentioned, so maybe a custom shaft ground to 6 mm at the cam end and 1/4" at the pump end might work, and an existing coupler could be modified rather than machining a custom coupler.

So I'm still looking for a replacement coupler, and also looking around for an EDM resource to look at modifying my existing coupler, but the pits, scoring, and tight fit are still an un-resolved problem.

Edited my post above. The coupler spins freely in the pump body - like you wrote: "wrist pin in a con rod".

I feel 11 mm is plenty of engagement, and if the socket was the correct size (not oversized) and the part properly heat treated, then 6 mm would be fine.

[bigbikerrick]

It will be very interesting to see what the machinist comes up with.  Thanks for everything you do for the Guzzi community, Charlie!   
Rick.

[guzzisteve]

Here's an idea you don't want to hear. How bout an electric pump. I thought RK had that sorted out for working. He had more room w/trike.

[Antietam Classic Cycle]

Here's an idea you don't want to hear. How bout an electric pump. I thought RK had that sorted out for working. He had more room w/trike.

It's been done of course. I saw an an Eldovert built by Dale Petersen at the WNY Rally years ago that had a Holley electric fuel pump as the atf pump. When I was planning to build one myself, I bought a pump used to circulate transmission or differential fluid through a cooler on a race car. I don't recall right now what Rodekyll was using.

With a coupler machined to the correct dimensions and heat treated properly, the problem would cease to exist, in my opinion.

[guzzisteve]

That would be the fix. If you could machine & press fit that one piece would be nice.

[brider]

With a coupler machined to the correct dimensions and heat treated properly, the problem would cease to exist, in my opinion.

Aaaaaaand, a coupler-to-housing interface with no play but no excessive drag, either. I like the idea of a larger (1/4") shaft, but that drives a custom shaft. I'd be confident with a 6 mm heat-treated coupler that ran smooooth in it's housing.

[fotoguzzi]

Back when I built the EVert both Rodekyll and I had the cams from the 1100cc engine EDM’d and it worked a charm! I remember we sent the cams to someplace in Florida who did the EDM work, it was pretty inexpensive too. I don’t remember the name of the place tho. I can look but. Doubt I’ll fine it.. that was 16 years ago.

One thing I have wondered about, did the design team make the hex part the weak link on purpose so the other components would not get abused? Would you rather replace the hex drive or the whole pump?

 My Evert foreground and RK’s Pink and Purple JackalVert (ridden from Alaska) at the 2007 National rally, AKA the flood rally at Money Creek Mn.

[bigbikerrick]

I doubt that the design team made that coupler a sacrificial part, on purpose,I think it just turned out that way. The pump, being fed a constant supply of clean oil, should last a long time, I would think. Now that I think back to when I took my pump apart to replace the seal,and O ring, it was very hard to turn, so much so, that I took it all apart again, to see if I had assembled something wrong.  When the cover , or retainer was tightened down, it was hard to turn. I attributed it to the new seal, and re assembled everything, but now I wonder about that leading to coupler failure.  FWIW, I have logged about 4K miles on the bike since rebuilding the pump.
Rick.

[Antietam Classic Cycle]

Aaaaaaand, a coupler-to-housing interface with no play but no excessive drag, either. I like the idea of a larger (1/4") shaft, but that drives a custom shaft. I'd be confident with a 6 mm heat-treated coupler that ran smooooth in it's housing.

That would be covered under by "correct dimensions".

That would be the fix. If you could machine & press fit that one piece would be nice.

What as one piece - the hex piece and coupler? That's what Dave Richardson did, but I'm not sure it's the best idea as it doesn't allow for any misalignment.

[brider]

Edited my post above. The coupler spins freely in the pump body - like you wrote: "wrist pin in a con rod".

Charlie, I'll ask this out in the open for my and Rick's benefit: When you said "coupler spins freely in the body...", are you saying that is the current condition of your "good" pump that you're keeping, or that's the optimum condition of a pump?

For myself and Rick's bike, I am very concerned about the tight fit, and I won't put mine back together until/unless I achieve a wrist-pin type smooth fit. This is the 3rd or 4th failure on this engine with only 51k miles on it, and I don't think it's more than 10k since I fixed it last. I've never looked this closely at the coupler, I always attributed failures to the shaft (and in one legitimate case, a leaking pump seal), but the visual evidence is clear that the coupler has suffered, whether heat-treated or not, and the tight-fit has to have contributed (remember the score marks). Rick: Knowing you have a tight fit on your rig, I would seriously consider pulling back apart and addressing that condition, lest you suffer my fate somewhere in the future. Your Cal 2 Auto may have had a nice-running pump, and I don't know any other way to rationalize your trouble-free time with it.

Thanks for the continueing info, Charlie.

[guzzisteve]

What as one piece - the hex piece and coupler? That's what Dave Richardson did, but I'm not sure it's the best idea as it doesn't allow for any misalignment.

I meant machine out hex in pump side & press in a hardened one. Most likely not enough room size wise.

[/quote]

[Antietam Classic Cycle]

Charlie, I'll ask this out in the open for my and Rick's benefit: When you said "coupler spins freely in the body...", are you saying that is the current condition of your "good" pump that you're keeping, or that's the optimum condition of a pump?

For myself and Rick's bike, I am very concerned about the tight fit, and I won't put mine back together until/unless I achieve a wrist-pin type smooth fit. This is the 3rd or 4th failure on this engine with only 51k miles on it, and I don't think it's more than 10k since I fixed it last. I've never looked this closely at the coupler, I always attributed failures to the shaft (and in one legitimate case, a leaking pump seal), but the visual evidence is clear that the coupler has suffered, whether heat-treated or not, and the tight-fit has to have contributed (remember the score marks). Rick: Knowing you have a tight fit on your rig, I would seriously consider pulling back apart and addressing that condition, lest you suffer my fate somewhere in the future. Your Cal 2 Auto may have had a nice-running pump, and I don't know any other way to rationalize your trouble-free time with it.

Thanks for the continueing info, Charlie.

Both - current condition of my spare pump and the optimum condition. That's probably why I only have one with the deep socket coupler - I've replaced at least two tight ones with better/free turning ones. If I can't turn it easily with a 6 mm T-handle allen wrench, then it goes into the bin and I find better one.

[bigbikerrick]

I plan to open up the front cover again this winter, to check the pump for tightness, to see if things have loosened up, or it remains tight to spin. I should to replace the cam chain tensioner anyway, and it will be a good time to address the hex drive issue. I think I will wait a while, to see what Charlies machinist comes up with.  It would be awesome to replace the couple with something better.  As far as the tightness, is there a chance the fit between the two parts can be sanded , or polished to make it spin with less resistance?  I am pretty confident this tightness is at least partially responsible for failures.
Rick

[Bulldog9]

Keeping my eye on this thread. I've had my Convert going on 4 years now.

Because everything works and works well
(Good oil temps, clean fluid, no slipping, leaks or
Issues) I've left it alone, but I'm sure it will need
Something eventually.

Granted I've only put less than 1000 miles this last
year due to my travel schedule, but retirement is
coming and I plan to put more miles on the magic
Carpet

[Antietam Classic Cycle]

I plan to open up the front cover again this winter, to check the pump for tightness, to see if things have loosened up, or it remains tight to spin. I should to replace the cam chain tensioner anyway, and it will be a good time to address the hex drive issue. I think I will wait a while, to see what Charlies machinist comes up with.  It would be awesome to replace the couple with something better.  As far as the tightness, is there a chance the fit between the two parts can be sanded , or polished to make it spin with less resistance?  I am pretty confident this tightness is at least partially responsible for failures.
Rick

Definitely. I've chucked the coupler up in the lathe and polished the o.d. with fine emory cloth until the fit was more to my liking.

Brider: Did you get my message with links to timing covers and pumps?

[bigbikerrick]

I should have done what you did, Charlie, with the emery cloth, on the pump coupler to get it to turn easier, while I was in there to reseal the pump. Live and learn!

Message with links to timing covers and pumps?  was that for me, or for Brider?

Thank you
Rick

[Antietam Classic Cycle]

I should have done what you did, Charlie, with the emery cloth, on the pump coupler to get it to turn easier, while I was in there to reseal the pump. Live and learn!

Message with links to timing covers and pumps?  was that for me, or for Brider?

Thank you
Rick

Oops, sorry, links were for brider.

[brider]

Definitely. I've chucked the coupler up in the lathe and polished the o.d. with fine emory cloth until the fit was more to my liking.

Brider: Did you get my message with links to timing covers and pumps?

Yes I got the links, thanks. Another member replied to my Swap ad and has a pump with a coupler that looks great, exchanging data with him now. If I go that route, I think dressing the coupler surface for a smooth fit and having a hex shaft surface-ground to a better fit would be my least-invasive and most cost-effective fix.

[bigbikerrick]

Hey, Brider, Im happy you found a coupler that will get you back on the road. Please keep us posted in how you polish it up, for smoothness,and how the reassembly goes when you get it. I am also keeping my fingers crossed, that Charlie's Machinist friend can come up with some improved solution for us.  I will wait to hear from Charlie, before tearing mine down for inspection, etc.  The next couple of winter months lend themselves to these types of projects, even in Arizona!
Rick.

[Danpw]

Just to open up some more options, this is the pump shaft from my 1976 Convert.




noble emojis


As you can see it has a tang rather than a hex drive, the end of the camshaft has a corresponding slot.

[Alfetta]

haven't been in my '76 yet...   but i hope it has the tang drive !

[Antietam Classic Cycle]

Just to open up some more options, this is the pump shaft from my 1976 Convert.





As you can see it has a tang rather than a hex drive, the end of the camshaft has a corresponding slot.

I've seen that modification before, always wondered how well it would work (durability).

[brider]

Just to open up some more options, this is the pump shaft from my 1976 Convert.




noble emojis


As you can see it has a tang rather than a hex drive, the end of the camshaft has a corresponding slot.

??? Camshaft has a slot? Hard to see from the photo, is the other end a hex? Looks too short, and the shoulder limits engagement. The shaft needs SOME axial clearance, so both ends of that shaft are limited by the cylindrical shoulder and engagement is going to be either net or less than the length of the drive feature (tang or hex).

Do you think that was a factory setup? Is yours a very early Convert?

[fotoguzzi]

?

 Is yours a very early Convert?

my thought too. I’ve seen one like that on a part out bike.