Author Topic: Rebuilding D25 Dizzy  (Read 706 times)

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Offline Bryan Boyle

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Rebuilding D25 Dizzy
« on: Thursday,April 04, 2024, 08:16:23 AM »
Well...after fiddling around with the Pertronix replacement distributor I had installed back when...decided to go back to what was in the car originally...now, the Lucas distributor (25D, type 41225) had come with the car and run it to 50K some odd miles...so could not be that bad, right?  What was roached were the points, the original coil, dodgy cloth covered wiring inside the dizzy, an old cap and probably the original wires.  Didn't want to futz with it when I picked up the car and started working on her 2 years ago...so just dropped in the replacement.

Well...started having issues with the ignitor II module.  Hard starting, occasional stumbling...so...what to do? 

Went back and pulled the original out of the junkque box...and took it apart.  Removed the points, condenser, old wiring to the external terminal, frazzled o-ring on the mount, and cleaned up the inside of dust, and shot lube onto the advance plate/weights. Didn't want to pull down all the way; there are two tiny e-clips that hold the gear pin in place on the shaft at the bottom; decided to NOT fiddle with that...the gear looked ok (no burnishing of the case hardening, no chips on the teeth), and figured if I have to take it down further, I'll deal with it then.  Shaft had no wiggle, turned smoothly, and the weights moved together when I tweaked them.  So, think it was a good base to start from.

First things first: I like the pertronix ignitor...just don't think the replacement dizzy is made to the same quality (!) as the Lucas OEM part.  Strange to say that, but that's my opinion, regardless of the common opinion of Lucas.  So...put an order together from the usual suspect for a new cap, ignition leads, updated rotor, o-ring, and Pertronix Ignitor I kit.

The retard capsule had been removed at one point, but the mount and fine adjustment thumbwheel was still attached.  Well, to clean it up, removed the remaining base of the capsule and thumbwheel, and sealed the capsule end of the distributor with high-temp epoxy, and, cutting off a bit of the thread at the thumbwheel side, epoxied that back in place (to maintain some semblence of originality...lol)  Besides, it seals off that whole assembly, which was long gone. 

Photo 1: Popped (well, broke) the old o-ring at the base out, and installed the new o-ring.

Photo 2: Test fit the new rotor...snapped right into place. Removed and set aside.  Test fit first, right?

Photo 3: Test fit the magnetic ring from the Pertronix kit onto the shaft.  Clicks down.  You'll see a small pin at the red arrow...there was no hole on the Pertronix base plate that matched that pin, so, dremel to the rescue, removed the magnet ring, and just cut it off and replaced mag ring. 

Photo 4: Assembled the module to the provided base plate, and installed in the distributor.  The instructions say to check the clearance between the rotor and the module with the provided gauge (or a feeler..).  The provided gauge showed it was all mounted at the proper clearance.  (30 thou).  Nice.

Photo 5: I was not totally happy with the fact that the leads from the module sat on the mounting stud for the module.  So, slipped on a piece of heat shrink, shrank it down, and put a spot of rtv on the top of the stud/nut to hold the wire in place.  Overkill?  Maybe.

Photo 6: In order to set the timing properly, you have to know 1) where cylinder 1 TDC is, and 2) where the arm should be.  It's a matter of transferring the center of the #1 contact to the distributor body.  So, I eyeballed with a straightedge across the diagonal contact from what is traditionally the #1 contact through the center pin...and gently notched the cap.  Then I placed the cap in place on the dizzy body, and gently notched the flange on the body.  A little black sharpie mark to mark the body...and it was 'close enough'

How to find #1 TDC?  Jack up one side of the rear of the car at its jacking point, pull all the plugs (to make it a bit easier to turn the lump), put a compression tester in the #1 spark plug hole, tranny in 4th gear, and turn the engine by the road wheel until you see a slight rise in the compression gauge.  You should be able to see the timing mark(s) on the flywheel in the bell housing window.  My own additional check: take the compression tester out, put a dial gauge into the spark plug hole, and gently rock the wheel forward and reverse to get the maximum indication on the dial gauge.  Still, after 50K + miles, top of piston travel is close enough to match the flywheel indication. 

Well...set dizzy rotor to the mark made on the dizzy body for #1 position as derived from the contact in the cap, install in the engine and rotate the body so the leading end of the rotor is aligned with the mark.  Tighten down the body enough so it's in place but you can still move the body, install the cap (with the wires already attached), reinstall the sparkers (after checking the tips and clearances), run the leads (1-3-4-2) to the sparkers, and attach the +/- leads from the module to the coil.  Re-connect the battery.  Moment of truth: the test start.

Took me a couple tries to get it dialed in.  Had to bump the dizzy in a couple directions a little bit, but it finally fired off and continued to run.  A spritz of ether helps...lol. 

After settling the idle down (it's been cold here the last couple days, so had to manually goose the carbs to keep it running until it was OK off the starter mechanism of the Strombergs), set the timing when the engine idled smoothly.  (I have a video, but even 5 seconds is too big to upload...)

Figured while I was there (famous last words?), loosened up the inter-carb linkage, resync'd the carbs to be close (within a half of that red pill on the unisyn device...close enough...no stumbling on acceleration, etc.) and tightened up the linkage. 

Went back and tightened down the dizzy clamp.  But then, it was 8 PM, so time to shut her down for the night.  Will revisit this afternoon and clean up the wiring, reinstall the airbox, etc.

Hope this hasn't been too long a treatise...but wanted to get it out there for the corporate memory.

Oh, yeah, she fired right off this morning after cold soaking all night.  So, that's a plus.  Now, when the rain stops...will take her out for a test run.

Cheers!



« Last Edit: Thursday,April 04, 2024, 12:39:59 PM by Bryan Boyle »
Bryan Boyle
Morrisville PA
Commercial Pilot/CFII/FAA Safety Team
Amateur Extra Class Operator & FCC Volunteer Examiner
Currently working on 3291R, ex 444R, 693R, 65/2163, 004R, 65/2678
http://www.lotuseuropa.us for mirror of lotus-europa.com manual site.

Offline BDA

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Re: Rebuilding D25 Dizzy
« Reply #1 on: Thursday,April 04, 2024, 11:43:45 AM »
Great writeup Bryan! I would note that I've heard bad things about the Pertronix dizzy from another source I have great trust in so that is two strikes against their dizzies (I love their Ignitors though!). So I'm happy just to use my Ignitor I in the 23D I have.

On the subject of Pertronix Ignitors, the Ignitor I can be statically timed but can get fried if you leave the ignition on too long. The Ignitor II cannot be statically timed (according to the tech guy I talked to at Pertronix) but it is protected from getting fried if you leave the ignition on too long. However the guy I mentioned above swears he was able to statically time his TC with the Pertronix dizzy with Ignitor II guts in it! Anyway, I switched back to the I for static timing.

Offline Bryan Boyle

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  • 1974 Europa JPS #142 3291R
    • Lotus Europa Collection
Re: Rebuilding D25 Dizzy
« Reply #2 on: Thursday,April 04, 2024, 12:34:37 PM »
Great writeup Bryan! I would note that I've heard bad things about the Pertronix dizzy from another source I have great trust in so that is two strikes against their dizzies (I love their Ignitors though!). So I'm happy just to use my Ignitor I in the 23D I have.

On the subject of Pertronix Ignitors, the Ignitor I can be statically timed but can get fried if you leave the ignition on too long. The Ignitor II cannot be statically timed (according to the tech guy I talked to at Pertronix) but it is protected from getting fried if you leave the ignition on too long. However the guy I mentioned above swears he was able to statically time his TC with the Pertronix dizzy with Ignitor II guts in it! Anyway, I switched back to the I for static timing.

I've heard about frying the I with the ign on too long, but have never run into it personally on any of the I's I've installed (well, they were in the Ducellier units for the 821...but that's another story).  You'd think they'd put the warning in the instruction sheet if it was the case, but didn't see any blackbox warning.  Good to keep in mind though. 

Took the buggy out in the rain here in Fall River (we got the storm you all had a couple days ago), and it ran fine (I timed it to 10 degrees BTDC; seemed  that is where it wanted to run the best, could always dial in a couple more, but)...smooth acceleration, idling steady at 1K once the engine warmed up and I got off the starter mechanism on the strombergs.  Good temps, oil pressure around 40...happy camper so far. 

As above, also resync'd the carbies...so, that may have something to do with it.  The carbs will need to be looked at, when I did a quick refresh a couple years ago, could not figure out how to remove the o-ring in the air valve...or put in the shaft seals.  I've since been educated...had a machinist friend build the tool for the shaft seal install from the diagram in the service manual, and watched a couple vids on refreshing the o-rings on the needle adjustment.  I have some joe curto rebuild kits and new floats...so...will try my hand (again) at these infernal devices...lol. 
« Last Edit: Thursday,April 04, 2024, 12:40:53 PM by Bryan Boyle »
Bryan Boyle
Morrisville PA
Commercial Pilot/CFII/FAA Safety Team
Amateur Extra Class Operator & FCC Volunteer Examiner
Currently working on 3291R, ex 444R, 693R, 65/2163, 004R, 65/2678
http://www.lotuseuropa.us for mirror of lotus-europa.com manual site.