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Post by bdaughdrill » Sat Feb 22, 2020 6:30 pm

Donor bike for the Wee Green Beast was a 1999 MG Bassa (California Special). It appears (and have limited knowledge on the guts of the actual engine) that the charging system is failing (probably should subject it to a 44 hour run across country) The shop manual shows an alternator but my "searches" keep returning "stators" and I am ignorant enough to visually recognize the difference but not recognize whether the "alternator" is a complete assembly with the "stator" being the outer ring. In any case, struggling to find a replacement part (according to Harper Moto Guzzi, the part number is (#37712405) and their image matches the entire assembly (waiting to hear back from them on whether it is available). The shop that services for me suggests the part is no longer available. So.....
1) Is there an alternative source, I've looked at Harper and at MG Cycles,
2) if the part is genuinely not available, it can't be that I have to find a new engine with one that is working...there has to be a work around.
3) Guidance from some who understands the greasy bits better would be FABULOUS.


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Re: Alternator/Stator

Post by Crozier3 » Sun Feb 23, 2020 10:19 am

My knowledge is also limited but there are three parts that make up the alternator system
1, the rotor that is attached to the crankshaft, this rotates at engine speed.
2, the stator which is attached to the crankcase, it is static and produces alternating current, we want dc current.
3, the rectifier / regulator that is attached to the vehicle in an appropriate location. This unit is a piece of electronics that creates dc voltage from the alternating current from the stator, this runs at 14.4 volts when everything is healthy.

You don't say what the problem is but all parts are available for the Cali engine, and from different manufacturers, and sources in the UK and Europe.
Your mechanic needs to check each item individually, then decide on the best route forward.

Another route would be to abandon the bike alternator and piggy back a car alternator onto the engine casing and rewire the set-up.
Hope this helps Bill

Richard and Pat
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Re: Alternator/Stator

Post by Richard and Pat » Sun Feb 23, 2020 12:38 pm

Have you tried Gutsibits Brian, I'm sure they will export. ... rch=SEARCH

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Re: Alternator/Stator

Post by Spaniard » Sun Feb 23, 2020 3:21 pm


Take a look at this website. They sell an upgraded charging system for Guzzi.

Guzzi electronics are strange. When I built my Triking I noticed that the wiring diagram I found for the model and year of my bike didn't match the actual wiring harness. They changed from model to model and year to year even if the engines were virtually the same. I installed a aftermarket reg/rec on my Triking because I thought the original one off the bike was bad. The volt meter was bouncing up and down after about 10 minutes of driving. I thought the reg / rec was getting hot and and then giving me problems. I later realized that it was the actual volt meter that was losing the damping oil in the gage from the engine vibration and after a while of being off it would settle back to its proper place. After giving the gage a little bit of padding around the dash problem disappeared.

If you find you have a problem with the reg / rec try a Ricks MotorSports Electrics reg rec. You will have to find out if you have a field excited charging system or a permanent magnet charging system. I believe Guzzi used both systems depending on model and year but I may be wrong. Im not an expert on this.

I purchased a Mosfet reg / rec as they don't heat up and should be more reliable. They are made for 3 phase systems but can be used for single phase systems as well by just dropping a leg. They are optimized for Lithium Iron Phosphate batteries but can also be used for lead acid batteries. The only downside is the charging voltage is slightly lower but I haven't had an issue.

I would love to install a small automotive style alternator at some point but can't seem to find the time. This would give me plenty of power for heated jackets for early spring and late fall rides.

This is the unit I purchased. You can also purchase directly from Ricks. ... rectifier/

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Re: Alternator/Stator

Post by bdaughdrill » Sun Feb 23, 2020 7:04 pm

Thanks for the inputs, I'll look into each. Yes mechanic is looking at the entire assembly. I spoke with another company and was told that the stator is, if not the regulator, all that needs replacing and that they carry and that it is the same as is used in some Ducatis. I'll check the volt meter first, because that's the obvious suspect

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