One for the Electrical Gurus

Anything related to Lambrettas... ask tech questions, post helpful info, or just read and learn.
GeorgeS
registered user
Posts: 254
Joined: Fri Feb 27, 2015 1:58 pm
Main scooter: 1961 Series II Granturismo 240
Contact:

Here's two SIL stators, both wired for DC.
Image

The one on the top is borrowed & works fine, the one on the bottom is mine & is not right in some way. With mine I feel down on power, the engine won't rev out and I don't get steady timing.

I'd love to know what the problem is, can anyone give me advice as to what I can test, measure etc to compare the two to find where the fault my lie?

Thanks,
George.
Last edited by GeorgeS on Wed Jul 19, 2017 6:30 pm, edited 1 time in total.
User avatar
coaster
registered user
Posts: 3125
Joined: Wed Jan 07, 2009 12:35 pm
Location: London and Norfolk
Contact:

Have you checked the readings on the LT coil and pickup? The other more likely issue could be the hight of the pick up relative to the trigger point on the flywheel magnets. Sometimes a laminate has to removed or added to get it lined up correctly. I don't know how you measure them though.
Knowledge
Dealer
Posts: 957
Joined: Sun Jan 11, 2009 12:49 am
Main scooter: GP
Location: Ipswich
Contact:

Hi,

I am viewing your photo, and the two stators are side-by-side, not top-and-bottom.

The stator with the smiley face looks to have been sourced from Anthony Tambs, so I would expect that to behave itself. Is this the one that is not so good on your machine? If so, try measuring the relative height of the pick-up between the two stators. The height might need adjusting as suggested by Coaster.
Martin
GeorgeS
registered user
Posts: 254
Joined: Fri Feb 27, 2015 1:58 pm
Main scooter: 1961 Series II Granturismo 240
Contact:

Viewing on a web browser you get left/right, on tapatalk up/down! The one with the smiley face is indeed from Anthony Tambs but is the one with the problem.

When I first started looking at this issue I thought it was a height issue and managed to bend down the laminates to reduce the height which I thought had cured the problem, but it's not so. I'll get nasty and cut it back & try again.
User avatar
Monty
registered user
Posts: 472
Joined: Wed Jan 07, 2009 7:21 pm
Main scooter: Series 1 Muggy, Imola Special
Location: STOCKPORT
Contact:

Guys
Not sure that I understand this correctly but it's not normally a height problem with the LT coil and the laminates it's more physically getting the bobbin to fit over the laminate stack. Remove just enough plates to get it on a bend the last one up to hold it on. The pickup height can be measured from a fixed point like the backing plate up to the 2 metal strips, set into the face of the pickup. they should fall either side of the magnate overlap on the flywheel. I had to lift my BGM one 2mm they now add a spacer to the kit I understand. If I have the wrong end of the stick please ignore
User avatar
Toddy
registered user
Posts: 5979
Joined: Sun Mar 08, 2009 12:01 am
Main scooter: Lambretta Series 1
Location: East Yorkshire
Contact:

GeorgeS wrote:Viewing on a web browser you get left/right, on tapatalk up/down! The one with the smiley face is indeed from Anthony Tambs but is the one with the problem.

When I first started looking at this issue I thought it was a height issue and managed to bend down the laminates to reduce the height which I thought had cured the problem, but it's not so. I'll get nasty and cut it back & try again.
Why not Ask Ant to check it for you ?
As my Dad used to say "Each to their own lad"
GeorgeS
registered user
Posts: 254
Joined: Fri Feb 27, 2015 1:58 pm
Main scooter: 1961 Series II Granturismo 240
Contact:

Fair question, Toddy. I've had a few conversations with Anthony and that might be the route to go. Here's a few extra points as to why I haven't sent it back so far...

As I mentioned above, I thought I'd got it sorted by reducing the pickup height as the borrowed stator pickup was 2mm lower than mine (measured when fitted to mag housing). I couldn't quite lower by 2mm, but got very close. This seemed to solve my 6k rpm rev limit issue, but on the next test ride things didn't go so well & the problem returned but with a much harsher stutter on the 6k rpm limit.

Around this time Anthony started selling his external pickups so I thought I'd go for one of those to solve the issue, but I'm finding this isn't working well at all with my Kheper CDI, I just can't get steady timing at anything below 3.5k rpm. Stick a £15 scootopia CDI on there & it's solid as a rock from tickover upwards.

So my present point is to borrow again the stator that seemed to work ok with my kheper to confirm the Kheper is not at fault (so far seems fine with the timing gun, but not yet ridden), and then take some measurements to compare the two.

I wondering if I should just go for the cheap Scootopia CDI & static 19 degree timing at least while I get the first few 100 miles on this new motor before I start introducing more complexity with variable timing.
User avatar
coaster
registered user
Posts: 3125
Joined: Wed Jan 07, 2009 12:35 pm
Location: London and Norfolk
Contact:

GeorgeS wrote:..........................I wondering if I should just go for the cheap Scootopia CDI & static 19 degree timing at least while I get the first few 100 miles on this new motor before I start introducing more complexity with variable timing.
Good idea, I have fitted one of Ants external pickups to my ne GT240 motor timed at 23 degrees but I haven't connected it yet. The BGM stator is set to 16 degrees and I'll get some miles on it before I start with variable ignition....still need to decide which one yet :?

On the subject of the external pickup, I was fiddling with the tickover prior to strobeing and a piece of wire got caught in the flywheel fins (no cowl fitted) and ripped the pickup coil off, now awaiting a replacement from Ant :oops:
Leo
registered user
Posts: 58
Joined: Sat Apr 25, 2015 1:34 pm
Main scooter: Lambretta
Contact:

I tried to be clever and adjust my timing on the external pick up with the motor running and nearly lost a finger!

My external Adv/Rtd pick up works well, had to richen the jetting on the pilot and the needle which is what I thought I would have to do. Might have to richer on the main as well but not got that far yet with testing. With the strobe you can see the timing moving from around 23 at 2000 rpm fast tick over to full gas where it moves to around 17.

I initially had issues with a mis fire but it was because the gap between the trigger and pick up were to wide. I've set it to .5mm now and all seems fine.

Mines a plain old blue Ducati CDI.
Post Reply Previous topicNext topic
  • Information
  • Who is online

    Users browsing this forum: Ahrefs [Bot] and 21 guests