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home grown alternator conversion

6046 Views 8 Replies 7 Participants Last post by  nsjoe
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Just like to say thanks to all those that have posted about Poorboy alternator conversions over the years.

My Stator failed, second time in 9 years, this time it's only kicking outb 25v ac on all three phases.

So took the plunge, after studying the various links and photo's posted by others, thought I'd have a go at fitting an external alternator myself.

It took one weekend to do, total cost was around £45. I used a Mitsubishi 45amp micro alternator which is smaller unit than seen in the links, two v drive pulley's I already had in my spares box,both about 3" dia. a piece of steel 1"angle for the bottom mount and a 1" flat bar for the top support, I made the adjusting slot from a scrap piece of metal and welded it to the top support.

The new crank shaftbolt (75mm long) with a spacer of about an inch was used to bolt the driven pully to the crankshaft through the freshly cut hole in the timiing belt covers (cutting the hole is the hardest part, it's nearly impossible to get it concentric)

The fairing support was cut and ground away and the top mounting bracket fitted.

The bottom bracket was cut and drilled to fit the engine mount bolt and two alternator split spacers used to align the alternator pulley with the crank pulley. The belt (Halfords 735) was fitted and the bottom mount and adjusting bolt tightened.

The radiator lower mounting studs were ground off and holes drilled and tapped to take longer 8mm studs which were then welded in place.A nut then penny washer placed on the studs used to allow the position of the radiator to be adjusted after fitting.

The radiator fan mount had to be trimmed along with the air guide for clearance and to allow the removal/fitting of new belts without having to remove the radiator.

I got away with using the original bottom hose, but it will need replacing with a slightly longer one in the future.

The lower left side fairing had to be heated and bent around the alternator and the inner had to be cut to give clearance for the alternator.

the wiring was simply large to bat pos, one small to ign pos and one small wire to a light and then to an ign pos

I've left the small air dam off as it dosn't seem to be held by the fairing sides now, maybe some fixing brackets will help or I might just leave it off.

first test of 80 miles showed no problems then another 100 miles and today with an led monitor connected across the battery, 500 miles with lights and spotlights, alternator showed 14.5v and no battery drain.:)(although the voltmeter fitted to the bike only showed 11v :?)

So thanks again to all those that have posted and tried differant types of alternators, I'm glad I have finally taken the plunge, it's well worth a weekends work.
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Good to see there is another "rigger" out there. Good job.
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Did you get any pics by any chance? I don't have a 1200, (have a friend that never heard of the conversion) but seen a few go real cheap due to the stator problem. I stayed away from the 1200 myself because I was told the engine had to be pulled.

THen I seen the poorboy conversion,now if one pops up and I got the $$$$, I may grab one. JR
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I will take some pictures and post them on this thread, i didn't take any during the fit just in case it all went horribly wrong :shock:

As I needed the bike for my 500 mile commute I just knuckled down to get the job done ;)
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Your voltmeter showing 11V probably a faulty gauge although they can show less unless connected directly to the battery but in that case the drop would only be in the .02v range
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Your guage is still looking at the output of the stator. You will have to rewire it to look at the voltage from the new alt. It will require a gander at the wiring diagram.
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As Promised, some pictures. Sorry about the quality!

In riding trim

The bulged lower fairing to accomodate the alternator

The bulged out air vent to accomodate the pulley and belt

Lower fairing removed

showing the engine mount bolt used to bolt the angle iron and bottom alternator mount to

Dosn't seem like a lot of clearance, it's about a fingers width, the engine guard mountwill be thinned down at the next oppertunity

just see the engine drive pully, the bubble on the timing belt covers was ground down to get the pully closer in

Alternator top mount and wiring and also shows the inner fairing trimmed down.

next two are of the longer lower radiator mounting studs, no spacers used just a washer and nut to allow radiator position to be adjusted.

Lower alternator mount, angle iron and split pipe for aligning the pulleys

in positon

Ive now disconnected the voltmeter and will look for a better place to wire it in, thanks for the pointers.:)
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thats what i call out of thin air fix great job good time must have realy stayed on it with out any road blocks
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nicely done.
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