Convert ATF pump coupler worn, now what?

[bigbikerrick]

Didnt only the 1975 or very early converts have that flat drive?  The Hex  drive piece, I believe was Guzzis new and improved version.  I would not think the flat drive piece would be less failure prone.
Rick.

[Antietam Classic Cycle]

Mine was built in mid '75 so is fairly early, "normal" hex-piece driven pump. I don't think any Convert had the flat drive from the factory.

[bigbikerrick]

Mine was built in mid '75 so is fairly early, "normal" hex-piece driven pump. I don't think any Convert had the flat drive from the factory.

I was  wrongly under the impression that the pumps with the circlip, and round pump retainer( early version) had the "flat drive", and the ones with the triangular retainer ( later version) have the hex piece. In looking at Briders photo, I can see the circlip version actually has a hex drive coupler. I guess thats just the "shallow" one.
thanks
Rick.

[MattP]

Here is the simplest fix . You want to have made  a replacement pump drive pin hardend ground polished burnt hex concentric.  Ok deside deep spline ect my thinking is that the last desinge thefactory came up with would be the one. Now iwould go with the clearance of the cam match that. Now the only part needing replacement would be the hex shaft.put it back together ride it,it should go twice as far as last. How ever i would take a look at it at a bout 70% of how far it went before. To avoid sitting on side af road.   That part is about as simple as could be. I would advise 20 or so the cost is in thr set up draw up prints and fax to some tool shops with photos ect now you have parts to offset your cost for others

[Danpw]

??? 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?

The tang on the end shown engages with a slot in the end of the camshaft. The end you can not see has the normal hole for the pin that drives the pump lobes.

This bike is in Australia but got here via America,  Holland and England so not sure of original manufacturer  date, but it is early 1976 from what I can tell.

[bigbikerrick]

The tang on the end shown engages with a slot in the end of the camshaft. The end you can not see has the normal hole for the pin that drives the pump lobes.

This bike is in Australia but got here via America,  Holland and England so not sure of original manufacturer  date, but it is early 1976 from what I can tell.

Thats interesting. Your version does not use a hex shaft at all. It uses a flat slotted interface at the cam, and the pin that drives the pump, at the other end
Rick

[brider]

A member here offered up a front cover with a coupler that looks very un-worn and spins freely in it's pump, so I'm going to go with his OEM cover/pump and try to size a custom shaft to take up any excess slack. I think I have a source to hardness-test both my worn coupler and his to establish baselines. For a test run, I also found a correct-size wooden dowel and used 180 then 220-grit paper and some WD-40 and hand-sanded the bore of my pump housing (which was binding so badly I could hardly turn it by hand) and voila! I got my pitted, scored coupler to turn in it like it should, nice and smooth.

So my plan of attack is to utilize a correct-hardness coupler with a good hex, dress the bore it rides in as necessary to get a smooth, minimal-drag fit, and have a shaft ground to minimize slop. Most of the risk minimized with minimal cost.

[Antietam Classic Cycle]

So my plan of attack is to utilize a correct-hardness coupler with a good hex, dress the bore it rides in as necessary to get a smooth, minimal-drag fit, and have a shaft ground to minimize slop. Most of the risk minimized with minimal cost.

That's what I did 30k miles ago, so far so good. 

[barnardini]

On the attached pictures a view of the modified camshaft and coupler as build in in my 1975 Convert and California 1100i Convert
The slotted end in the camshaft is 4,5 mm wide and 12 mm deep

[bigbikerrick]

No hex in your case. Just the flat drive. How does that work out? Did you make it deeper?
Rick

[brider]

On the attached pictures a view of the modified camshaft and coupler as build in in my 1975 Convert and California 1100i Convert
The slotted end in the camshaft is 4,5 mm wide and 12 mm deep

??? Your center photo is the same one DanPW posted for his '76 'vert. Are you and he the same guy? Is this from the same bike? Did this idea exist on the '76 and you reproduced it on the 1100i?

Guess it doesn't matter, really, except to ask if this is a production configuration from '75-'76, or did you or someone else do this mod? Looks like a FAR smarter solution to provide reliable torque to the pump AND allow for mis-alignment. Some might say there's only (2) points of contact between the cam & drive "tang" as opposed to (6) for the more common hex, but I can't see your configuration stripping no way no how.

[barnardini]

There is no hex coupler to drive the pump just the flat. It works out very well. I did over 100k miles with this bike, no problems.
The slotted end in the camshaft was made with a grinding machine. I did not make the hex bore deeper, no need for that modification.

I am not the same guy as DanPW and it is not from the same bike. This modification was made i the mid 70ties by a Dutch Guzzi dealer
to prevend future problems with worn hex drives. There are a few bikes with this modification in the area where I live.
I reproduced this on my 1100i and is functioning now for 17k miles

[brider]

This modification was made i the mid 70ties by a Dutch Guzzi dealer
to prevend future problems with worn hex drives. There are a few bikes with this modification in the area where I live.

Wow. Kind of surprising (and a shame) that this fix did not become a widespread "known" fix....or maybe it did?.....and we spend so much time focusing on the hex coupler. Would require a good machinist and pulling the cam, but do it once and DONE.

[Danpw]

The modified drive does look the same as mine.

My bike was in the Nederlands from November 1998 to December 2007, so I expect the modification was done there. If you have access to a lathe and a mill it would be an easy modification.

Mine has held up well with no signs of wear or damage to the seals.

Could the work have been carried out by TLM?

[bigbikerrick]

Its too bad that this fix requires cam removal. It looks like a good way to put an  end  to this problem.  Hopefully Charlies machinist will come up with a different fix that works.
Rick.

[ridingron]

If I were doing this repair, I don't think I would want the trouble and expense of pulling and modifying a cam. Should things go astray either in making the slot or afterwards, you've probably lost that cam. I would go with a square drive. Creating a square hole in the standard type coupler would be easier than a hex. The coupling connection to the cam hasn't been mentioned as a problem, has it? Creating a "fitting" square drive would also be easier than a hex.

[bigbikerrick]

Hey, Thats thinking outside the box.....Or would that be considered "inside the box", since its a square !   
Rick

[John A]

I would get a sporting cam , have it modified and install it at my leisure.

[brider]

If I were doing this repair, I don't think I would want the trouble and expense of pulling and modifying a cam.

This is my current mindset. But finding a hotter cam and modifying in my (non-existent) leisure time sounds like a great idea.

So, a drive piece with a square coupler end.....square on one end and hex on the other? Would that have to be a machined part (and heat-treated?), or could a stock hex (1/4") be surface-ground?

[bigbikerrick]

                                                                                                                         



                                                                                                                                           

[brider]

UPDATE: I received the replacement cover with "good" pump (good hex shape, spins freely & smoothly) from a member here. Couple of questions though:

In the photo, you can see I pulled the pump housing out of the front case and separated the coupler from the housing and re-inserted it into the pump-well and star-shaped thingy that rotates in there. The empty pump housing is sitting to the right in the photo.

In the bottom/center is my old, worn coupler turned upside-down with the female hex pointing down for reference.

Q: I didn't pay attention to its position when I pulled it out, so what do those punch marks on the larger star-shaped thingy and the one pinned to the coupler shaft have to do with anything? Are they used for some kind of alignment?
 
Q: On my worn coupler, the punch mark is on the side opposite from the shaft as opposed to the coupler on the replacement. Which configuration is the proper placement?

Note the flattened surface on the larger sealing o-ring. This seal contributed to a slipping condition on one of my TC-slipping bouts. Replaced the o-ring and the slipping went away. Fresh o-ring & seal will go in with the new pump.

[Shiny Hat]

The shaft is offset in the housing. Align the dots with the threaded hole between the cast oil tubes.
This will allow the housing to slide on. The other inner rotor was upside down. Is that a picture of the new pump?

That O ring is normal for a used one. It sits flat against the housing but the case side is coned so it set in that shape.

[brider]

Align the dots with the threaded hole between the cast oil tubes.
This will allow the housing to slide on. e.

Huh? The "female" star-thingy with the punch mark is 5-point, but the "male" star-thingy with the punch mark is 4-point, and there is no physical way to align the punches in any orientation that I can see.  So what are they for again? I might want to look at the factory manual before I comment further.

Putting the pump together and back in the front cover is no problem, as the coupler can be turned with a 6mm hex wrench as you're inserting the pump. Clocking the coupler with the hex shaft inserted as you mount to the engine is a different challenge, but not rocket science.

[Shiny Hat]

Huh? The "female" star-thingy with the punch mark is 5-point, but the "male" star-thingy with the punch mark is 4-point, and there is no physical way to align the punches in any orientation that I can see.  So what are they for again? I might want to look at the factory manual before I comment further.

Putting the pump together and back in the front cover is no problem, as the coupler can be turned with a 6mm hex wrench as you're inserting the pump. Clocking the coupler with the hex shaft inserted as you mount to the engine is a different challenge, but not rocket science.

When aligned the peak of the 4 point inner rotor, opposite the punch mark, will drop into the valley of the outer rotor. This will allow the inner rotor peak with dot to align with the dot on the peak on the outer rotor. It will cause drive shaft. to be offset and allow the housing to drop on.
The dots are just for alignment, once the pump rotates it doesn’t matter where they are.

If you can get the housing on and the pump assembled by fiddling with the shaft you are done. The marks are just to aid in assembly, no more no less.

[brider]

When aligned the peak of the 4 point inner rotor, opposite the punch mark, will drop into the valley of the outer rotor. This will allow the inner rotor peak with dot to align with the dot on the peak on the outer rotor. It will cause drive shaft. to be offset and allow the housing to drop on.

Used your technical engineering drawing and re-fit the coupler and sure enough, I see the concept now. Thanks for clarifying it.

[Dieself]

I'm a new member. I recently purchased a 1977 convert. If Charlies machinist comes up with a fix for purchase I would be interested in being in on it.
Dan

[bigbikerrick]

I'm a new member. I recently purchased a 1977 convert. If Charlies machinist comes up with a fix for purchase I would be interested in being in on it.
Dan

Excellent, Dan. I sure would be for sure, and I am sure that a few other "Convert Perverts" would be interested!    We will have to wait and see, if he is able to do it.
Rick D.

[Antietam Classic Cycle]

Excellent, Dan. I sure would be for sure, and I am sure that a few other "Convert Perverts" would be interested!    We will have to wait and see, if he is able to do it.
Rick D.

I've contacted two machinists so far, waiting to hear back from both.

[bigbikerrick]

I've contacted two machinists so far, waiting to hear back from both.

Thank you very much for that , Charlie. Much appreciated.
Rick D.

[brider]

Re: Surface grinding

I'm ready to have a 1/4" std hex tool (measures ~6.223 mm) ground down to the 6.15 mm dimension I need (measured the replacement female coupler I got my hands on), but I'm wondering what instructions to give the shop; grind equal on all 6 sides, or grind 3 adjacent sides to achieve the desired 6.15 mm across the flats? Theoretically it seems that just grinding 3 flats gets to where I need, but is there a concern about heat-treat depth being ground away on only 3 sides?

The amount to be ground off turns out to be ~.003", so to grind all (6) sides means .0015" off each side, seems too small to control.

I plan on giving the shop a 3" section of tool, then I'll cut it to length myself.

Am I over-thinking this?