Hi, Ive just fixed a really annoying issue with my st1100 - so thought i would post the results.
When I bought the bike second hand 2 years ago the owner had just spent more than ?600 on replacing the alternator.
A few months into ownership I had battery charging issues, and 1 new battery later and some debug discovered that the alternator was faulty. When I removed it turned out the rotor coils were open-circuit. After researching the options from ?650 for a new alt, too the bandit fix, to refurb, I noticed on this forum that someone had noticed that yam denso alts are superficially similar.
I bought one and the extruded lip is the right diameter, and the rotor shaft has the required 18T spline fitting.
The honda has its lugs (when viewed from the rear with the alt removed) at roughly 10 , 12 and 5 o'clock.
The standard denso alt is part number 101211-1570.
The yamaha denso part is 100211-4930.
I bought the 100211 part from a re-seller/breaker for just ?30 - they're a lot more plentiful and much cheaper than the st1100 part.
Minor lug hole filing is required but its now fitted and running and charging fine.
The 100211 part needs all 3 lugs filed to widen the 8mm hole to make a 8mm slot/oval.
Only 2-3 mm filing is required - for 2 if the lugs.
The 10 and 12 oclock lugs fit with a 2.5mm washer to compensate for the 100211 part having a slightly deeper lip.
The 100211 part then has a lug at about 7 o'clock - a long way from the engine case hole however it can be used using a 2/3mm steel strap suitably shaped, but I didn't because there is an unused 8mm taped lug on the engine casing in exactly the right place.
This unused lug will be dirty so I ran a 8mm tap through it before using it to hold a bolt (or set-screw in my case), to secure the last alt lug.
The unused lug is not in the same plane as the machined holes in the engine case - so a 7-7.5mm spacer is required.
I'll post up some pictures, and more info as I continue testing it.
I needed 3 M8 set screws cut to length (20mm thread goes into the engine case holes), a couple of nuts and washers (2.5mm).
Seems to be running without any issues and producing a good charging voltage.
regards,
Alastair
When I bought the bike second hand 2 years ago the owner had just spent more than ?600 on replacing the alternator.
A few months into ownership I had battery charging issues, and 1 new battery later and some debug discovered that the alternator was faulty. When I removed it turned out the rotor coils were open-circuit. After researching the options from ?650 for a new alt, too the bandit fix, to refurb, I noticed on this forum that someone had noticed that yam denso alts are superficially similar.
I bought one and the extruded lip is the right diameter, and the rotor shaft has the required 18T spline fitting.
The honda has its lugs (when viewed from the rear with the alt removed) at roughly 10 , 12 and 5 o'clock.
The standard denso alt is part number 101211-1570.
The yamaha denso part is 100211-4930.
I bought the 100211 part from a re-seller/breaker for just ?30 - they're a lot more plentiful and much cheaper than the st1100 part.
Minor lug hole filing is required but its now fitted and running and charging fine.
The 100211 part needs all 3 lugs filed to widen the 8mm hole to make a 8mm slot/oval.
Only 2-3 mm filing is required - for 2 if the lugs.
The 10 and 12 oclock lugs fit with a 2.5mm washer to compensate for the 100211 part having a slightly deeper lip.
The 100211 part then has a lug at about 7 o'clock - a long way from the engine case hole however it can be used using a 2/3mm steel strap suitably shaped, but I didn't because there is an unused 8mm taped lug on the engine casing in exactly the right place.
This unused lug will be dirty so I ran a 8mm tap through it before using it to hold a bolt (or set-screw in my case), to secure the last alt lug.
The unused lug is not in the same plane as the machined holes in the engine case - so a 7-7.5mm spacer is required.
I'll post up some pictures, and more info as I continue testing it.
I needed 3 M8 set screws cut to length (20mm thread goes into the engine case holes), a couple of nuts and washers (2.5mm).
Seems to be running without any issues and producing a good charging voltage.
regards,
Alastair
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