Installing treats cdi on derbi pics

I found no pics on treats link from cuperteens about putting an e50 cdi onto a derbi piston port or pyramid reed.

This is how I did it, no grinding cases or anything except a lil lengthening on all 3 screw slots.

It works good. Had to flip the high voltage coil over, then time it with no reference point. Wires route out easily.

Found that flywheel woodruff key slot needed to be rotated counter clockwise around from the matching crank key slot by about 140deg. That's for a retarding cdi I'm using. Also had to lap the crank to flywheel taper with coarse grinding compound to make sure it sticks tight.

Thinking of cutting a slot in the crank to accept the new position for the flywheel, cuz then I can set it more precisely and easily with a known position. I think some good masking and a few dremel cutting discs should make it easy af.

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Re: Installing treats cdi on derbi pics

yeah one of my many gripes about the treats CDI's is that the machining or the metal used for the hub doesn't stay put very well. Even after lapping the snot out of it, the thing still wanted to spin- didn't help that it would backfire and have other problems when coils and CDI boxes would burn out in testing.

a key would help... maybe practice on a junk crank?

Re: Installing treats cdi on derbi pics

This one seems to stick pretty well after lapping. I use coarse so it really grabs with just a lil tension.

I'm not worried about practicing, I'll just mark it well then nibble away. Then I'll lengthen the 3 slots to get some more motion. I hate timing without a key, takes forever to find the perfect spot.

Re: Installing treats cdi on derbi pics

that is a good point about coarse compound, i always use fine and polish the living snot out of them... maybe thats my problem.

Re: Installing treats cdi on derbi pics

Polish? Really? Why?

Every taper I've ever lapped with coarse gets so stuck even with a slight push. My moby has never slipped after doing this.

I just dull both sides. Doesn't need much.

Re: Installing treats cdi on derbi pics

I had trouble with one slipping. I use a little red locktite on the crank. Waited for it to dry, then never had a slipping issue after that. It was not hard to remove either. I just made sure to clean the taper up with carb cleaner, before I did it again.

Re: Installing treats cdi on derbi pics

i dunno i get that lapping compound in one hand and i guess i assumed it would stick best if it was ground like a valve seat?

kinda the way morse tapers are always ground nice and smooth on machine tools.

Re: Installing treats cdi on derbi pics

Yes to coarse paste. I'm pretty sure I invented the process. Just check my sweet sweet Wiki page.

Re: Installing treats cdi on derbi pics

Well looky here.

Electrical issue I think.

Runs for about a minute under load, then it backfires and dies.

Roll to a stop

Restarts immediately.

Then dies again under load.

Fuel flow looks great.

Will swap out the trigger and see if that the issue. Stator smells a lil electrical burnt-ish

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