175TS with 125S engine project

[George]

Thanks for reply Max. Searching the forum yesterday I found a wiring diagram in the Italian manual that was more clear than my copy and what I thought were smudges on rectifier terminals were markings and agreed with your answer, centre green wire +ve, earth to frame -ve, other two terminals AC one brown one yellow. Did the three checks with multimeter all readings are showing approx 175 and with black and red leads reversed 1850. Rectifier knackered.

With regards to alternator wire colours. Original wires were crumbling and it is possible that one of the wires was a discoloured white and not yellow as I thought. I replaced with new cable 2 yellow and 1 red. Reading through manual again generator wires disconnected and bike running shorting between yellow and white produces 6.5Amp, yellow to red produces 2Amp. I do not have AC facility on my multimeter and have no way of testing.
It is a possibility that I have got the 2 yellows (should be 1 yellow 1 white) the wrong way round and this maybe destroyed rectifier. I am inclined to reverse the two yellow wires when I fit new rectifier and do voltage tests across battery with bike running at fast tickover and at high revs.

Thanks again for your help and have a good Christmas break

[veloduke]

I believe selenium diodes have more forward voltage drop than silicon diodes, hence the lower efficiency.

I would be a little surprised if George's selenium rectifier is still OK. My selenium rectifier was kaput when I got the bike. I hid my replacement silicon rectifier in the toolbox, but left the selenium rectifier on show.

Merry Christmas

[George]

Actually, just checking, are you sure you have two yellows (and red) from the alternator, and not one yellow and one white (and red)?
That would make a difference according to the electrical diagram of the alternator for the 125. Of course, someone may have changed it at some point.
I'll have to check mine to be sure. Two yellows and a red come out of other alternators that I have (not 125).

The three connections that you can see are for +ve output and AC, I think AC will be the outside two. The one in the middle will be the +ve output. The -ve output is the mounting stud. The relplacement rectifier on ebay has four terminals.
I'll try to get some pics together, but it's Christmas so I'll be busy for a bit.

I will say that your original rectifier is made from Selenium rather than Silicon, and is a bit less efficient. The original may be broken anyway (mine was), but we can establish that with the meter.

It sounds to me that your wiring is correct aside from checking the alternator wire colours.

Searched through my box of parts removed during restoration ( I never throw anything away from restoration for at least a year) Found the old three wire cable stripped outer and yes one cable is a dirty discoloured white. Appling sods law I am going to assume that I fitted what should be the white wire to the rectifier +ve and the yellow to the white number 4 terminal, through to 'A' connector in headlight and finishing at main light switch.

When new rectifier arrives will wire in and reverse the two yellow stator wires then check charging voltage across battery with bike running, lights on and lights off. hopefully worse can happen I will destroy new rectifier.
I charged up battery three days ago and it is still showing 6.3 volts, perhaps battery is OK

When I was an apprentice 100s of years ago ONC Mechanical course introduced electrical subject into third year. Not surprising I failed electrics for two consecutive years and never did get my ONC Mechanical diploma
Time to forget motorcycle electrics and treat myself to a few glasses of whisky.
Merry Christmas

[tweaky beast]

Hi. I am interested what camshaft you have fitted to your bike. I have a 160 motor in a special frame which has a STD cam in it. I have seen a " hot" cam in a ex Mick Walker. I was told that 160's came with 2 types. Have you got a 'end' view picture. I want to send mine to Mr Joy's but want to find a correct profile. Regards Andy

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[George]

Hi. I am interested what camshaft you have fitted to your bike. I have a 160 motor in a special frame which has a STD cam in it. I have seen a " hot" cam in a ex Mick Walker. I was told that 160's came with 2 types. Have you got a 'end' view picture. I want to send mine to Mr Joy's but want to find a correct profile. Regards Andy

Hi my engine is a Mototrans 125 from early 1960s. Jon Pegler tells me that I have a 125 sport cam. See post viewtopic.php?f=3&t=2963&start=20
I do not have image of end view of cam. best image i have is attached. I believe Mr Joy is familiar with Ducati cams and perhaps you should give him a call after the Christmas break.

[tweaky beast]

I spoke to Phil yesterday, he has no info on the 125 cams. I've seen 2 different cam profile's for the 125/160. One hot and one STD. The STD one looks like a peardrop whereas the hot one is more angular.

[George]

Try asking Jon Pegler or Nigel Lacey, both experts.

[tweaky beast]

If anyone has a 125ts cam for sale let me know please

[tweaky beast]

Where can I find Jon Pegler. Nigel doesn't know I'm afraid. If it was bigger he does

[George]

You could post question to Jon on this forum or send him a private message, don't expect any answer this side of christmas