Gregory Bender

I-Convert ATF pump drive failure: caues and remedies

Moto Guzzi V7 Sport, 750 S, 750 S3, 850 T, 850 T3, 850 T3 California, V1000 I-Convert, V1000 G5, 1000 SP, Le Mans, Le Mans II, Le Mans CX 100, Le Mans 1000, 1000 SP III, 1000 S, California II, California III, California 1100, California Jackal, California EV, California EV Touring, California Aluminium, California Titanium, California Special, California Special Sport, California Stone-Metal, California Stone-Touring, California Classic, California Touring, and California Vintage models

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Thanks to Wayne Guntzel for sending me this information via email. In Wayne's own words:

Guzziology has an excellent section on a common Achilles' Heel of the Convert/Cal II Auto ATF pump, describing bike-disabling failures caused by the stripping out of the male/female parts of the cam-driven ATF pump. I experienced this weakness firsthand when my Cal II Auto lost forward motion. The transmission started slipping about 3 miles from home. I made it back (barely) to the safety of my garage. A quick inspection revealed that the ATF lines were VERY hot: much hotter than normal and the ATF cooler (radiator) was too hot to touch. I concluded that the ATF pump was not circulating the fluid through the ATF radiator, and the hot ATF fluid could no longer do its job of transferring energy in the torque converter.

After reading Richardson's discussion of this problem, I decided to measure the hardness of some ATF pump drive parts using the Rockwell C scale, compare my findings with those of Mr. Richardson, and hopefully remedy the situation by replacing the my originals with harder parts.

I found an industrial steel treating facility about 40 miles away, and (fortunately) met a VERY helpful gentleman who agreed to help me with my project. He would test the Rockwell C on any parts I brought in, and would harden parts using the Carburize Harden & Temper process.

First I put together a collection of male 6 mm hex bits, including OEM guzzi, replacements from Guzzi suppliers, and off-the-shelf bits extracted from 38 drive sockets. The Rockwell C testing results appear below:

BrandRockwell C Hardness
Snapon43
OEM Guzzi45
Harper's50
DeWalt52
Craftsman52
Crescent54
Husky59

As described by Richardson, there was a difference in hardness between Guzzi OEM and aftermarket bits but perhaps not enough difference to put all of the blame for pump failures on the male bits.

We then tested 4 OEM used Guzzi female hex drive sockets (extracted from pumps purchased on eBay).

OEM Drive SampleRockwell C Hardness
119
225
325
439

Clearly these results are consistent with Richardson's findings as reported in Guzziology ; all four hex drive sockets were much softer than the Guzzi intended specs of Rockwell C 58.

AFTER heat treating the above 4 oem drives, all 4 tested out to Rockwell C 58

When putting things back together, I selected the DeWalt hex bit for the male part of the pump drive because with a hardness of 52, I figured it would most likely fail before the much harder-to-find female drive (with its new hardness of 58).

Most of the store-bought hex bits I removed from their sockets were VERY slightly larger than 6 mm on the portion which inserted into the socket. I used this to advantage by very carefully dressing this larger part of the bit with a file until it fit tightly into the female drive part (the OEM bits were just a bit too sloppy for my liking).

Hopefully my efforts and findings resulted in a more reliable ATF pump for these amazing bikes!!