KX85 Ignition on A Minarelli V1

I really want to get away from points and want a CDI with a true advance curve. I dug up a complete KX85 Ignition system and decided it can be made to fit my V1 engine. I decided the KX ignition could be adapted for various reasons including:

The height of the stator is very close between the two ignitions.

The KX flywheel is smaller and with the ignition trigger coil outside, extra room helps.

The KX stator is easy to add a 40 watt 12 volt coil to.

The KX flywheel has a riveted hub that can be replaced.

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Re: KX85 Ignition on A Minarelli V1

mini magneto hpi v1!

Re: KX85 Ignition on A Minarelli V1

The complete KX85 ignition can be purchased for about 60 bux and parts are everywhere. I like to use what I have and make it work, the budget is limited.

First I cut the rivets and most of the KX hub away.

Next I made a hub by cutting an old CEV flywheel.

Here are the results so far.

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Re: KX85 Ignition on A Minarelli V1

Here is the hub just set in place on the KX flywheel. I will be getting back to it when I know where it needs to be riveted based on the location of the trigger coil.

I could not grasp the KX stator plate in the jaws of the chuck because of the odd shape so I mounted a plate to the coil mounting locations to make a fixture to hold it by.

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Re: KX85 Ignition on A Minarelli V1

I counter sunk the heads of the screws holding the fixture plate so I could turn it round and face it. This will allow it to be held quite true in the lathe so a recess can be cut in the back.

Here you can see I have the plate held by the fixture and a recess the same diameter as the old CEV plate is cut in to it about 3mm deep. I am starting to cut the OD here.

To adapt the KX plate to the engine case I cut a ring CEV diameter, 80mm and thick enough to hold screws. It is marked for drilling and threading.

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Re: KX85 Ignition on A Minarelli V1

The OD of the KX stator is trimmed a little in the lathe but the mount for the trigger coil is in the way. The rest is easily cut with a hacksaw and file. The mounting holes for the adapter plate are counterbored so the heads of the screws are below flush.

Here I have cut slots for adjustment and am milling flats for the screws.

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Re: KX85 Ignition on A Minarelli V1

As you can see the case and inner fan housing must be cut to allow the trigger coil to stick through. Everything fits together so far. I have to put a crank in the case and mount the flywheel to check the height of the stator in relation to the flywheel. I may have to fly cut the stator mounts for more clearance.

TBC

Re: KX85 Ignition on A Minarelli V1

>>>taykoff [s2m] /

Way to work with what you've got, and it appears that you have the skills to pay the bills...Great work!

Looking forward to hearing more about this...

Re: KX85 Ignition on A Minarelli V1

🇮🇹💦 Of the Loin /

looks awesome, and clearly youve got some machining skills

but 60 bux + time and effort engineering this thing is probably way more than getting an hpi.....

Re: KX85 Ignition on A Minarelli V1

Love it!

Re: KX85 Ignition on A Minarelli V1

You might notice this engine case has cracks around the chain area and a hole through in the flywheel cavity. It is a good experimental part, and still good enough to run.

In this pic I have the adapter plate with the KX stator plate on it. This is the back showing the cutout I made for the wires.

I glued the CEV hub to the KX flywheel and installed it on a crank inserted in the case to check the depth. The Minarelli crank threaded end is almost flush with the outside of the flywheel when installed. There was no clearance so I put the case on the mill and cut the stator plate mount areas down to close to the height of the outer edge of the seal hole. The hub of the flywheel will have to be on the inside to get the clearance I want, but this is no problem. The tops of the stator mount posts must be cut down to allow for clearance also.

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Re: KX85 Ignition on A Minarelli V1

I cut the edge off the adapter plate and the stator plate in the sprocket area for clearance. The post for the stator plate on the sprocket area is not used but it is no problem because the rest of the posts still hold the adapter plate captive. The adapter plate is somewhat thick and stiffness will be no problem.

This is what the complete mount is going to be like, just gotta clamp the wires.

A view showing the pickup sticking out of the top of the flywheel cavity.

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Re: KX85 Ignition on A Minarelli V1

Next I have to true up the CEV flywheel hub and rivet it to the flywheel in the correct spot. The CEV hub has a point cam that makes impossible to chuck it in a lathe so I am going to take an old crankshaft and cut the flywheel shaft off the cheek, and mount the hub on it so it can be turned true. This should be the most accurate way to get the flywheel true to the crankshaft and make it suitable for high RPM.

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Re: KX85 Ignition on A Minarelli V1

I have to check but I think the KX engine turns counterclockwise and the CEV is clockwise. This is very important when figuring the position of the flywheel trigger block in relation to top dead center. I usually look at pictures in a manual so I have to keep in mind the flywheel trigger block approaches the trigger coil from the other side.

I don't think many of you are old enough to remember Allen Dumont, but I like the way he thought. He started his company, building TVs, by buying the cheapest parts from the other manufacturers and assembling a set that was cheaper than theirs. There are enough parts out there to build just about anything you want, you just gotta figure out what fits.

Re: KX85 Ignition on A Minarelli V1

Too late to turn back now. The crankshaft has had an amputation.

Here I am turning the hub section from the CEV flywheel with it mounted on the crank stub. I faced the top and left a small shoulder to center it on the KX flywheel. I cut the point cam off and lightly trued the other side for balance.

The hub is ready to rivet to the flywheel.

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Re: KX85 Ignition on A Minarelli V1

I love my HPI, but this is awesome. Keep it up! Very interested to see the timing curve.

Re: KX85 Ignition on A Minarelli V1

couldn't you have just pressed the crank apart instead of cutting it?

Re: KX85 Ignition on A Minarelli V1

if only I had your shop/tools then I would do this too! great work

Re: KX85 Ignition on A Minarelli V1

Derek,

One reason I selected the KX85 parts is because I can use a few different CDI boxes, including the KX100 parts to try different ignition curves. I have not found information on the actual curves in any manuals so I will experiment and see what the timing light says.

Arnie,

The stub I cut off is part of the cheek of the crank, only the rod pin can be pressed out. We rebuild all 2 stroke crankshafts at our shop so I will press the pin out, so I can use it and the bearing to rebuild a bad crank. Not a total loss.

The cheek of the cut crankshaft makes a good small anvil on the work bench.

Re: KX85 Ignition on A Minarelli V1

Will this be the heaviest flywheel in moped history?

I bet you idle real smooth....

Re: KX85 Ignition on A Minarelli V1

Weight as actually only one of the things to consider, look at how much smaller it is in diameter. It will be much easier for the engine to turn.

If you can't find information on the curves though, are you sure it HAS one? I haven't looked but my gut would say no.

Re: KX85 Ignition on A Minarelli V1

Shit, it is way smaller!

Re: KX85 Ignition on A Minarelli V1

so is a hpi!

naz, did a ktm igniton i think .. for pug. i remeber seeing .. static i think.

Re: KX85 Ignition on A Minarelli V1

The flywheel is smaller and lighter, I have not checked the weight yet to know how much. Even if it were the same weight, with the smaller diameter will rev quicker. I will measure the diameter and weight. I think it is static timing.

Re: KX85 Ignition on A Minarelli V1

briny briny /

You gonna fire that thing up or not?

Re: KX85 Ignition on A Minarelli V1

Sorry, I only get a couple hours a week to work on it.

The CEV flywheel is about 23 ounces and the KX is around 18 ounces.

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