Derbi Motoplat ignition timing

So I have this Derbi. I got it last fall, and I had been waiting to for parts to get it running. The bikes in great condition, but it doesn't run. I thought it was poor compression, as that is what the previous owner thought its problem was. So I install new rings, and its the same as before. The old rings looked fine, so compression is good. I now think its the timing. The points open 8mm before TDC, which a bit more than the 1.8mm Derbi recommends. Heres my problem. The ignition is Motoplat, a system akin to CEV. I can't get at the screws that hold the stator in place, because the flywheel covers them. Does any one know what pullers will work on Motoplat? Will CEV match? Has any ever pulled a Motoplat Flywheel off before? I've heard there is some crossover between Bosch and Motoplat, and some sachs have motoplat magnetos. Any Ideas?

Re: Derbi Motoplat ignition timing

the only motoplat I've messed with is on a sachs 504 It uses the small bosch puller.

I remember reading in a moped repair book that bosch,

CEV and motoplat can be interchanged. I imagine it would depend on the size and set up.

You can't get to the strator plate screws thru the windows in the flywheel?

You could also adjust the timing the old way- bending the points.

Re: Derbi Motoplat ignition timing

You can see the screws, but I can't get a big enough screwdriver onto them. They're a little stripped already.

Re: Derbi Motoplat ignition timing

I got a puller and advanced the timing. I then got it to start on ether, and even to pull me down the driveway. I think if i upjet the new 15mm dellorto it should work well. i may try the old 12mm to see if it likes that.

Re: Derbi Motoplat ignition timing

I like to swap out the screws with allen head- that way it's at least harder to strip.

Don't forget the threadlock.

It freaked me out when one of the strator screws worked it's way out and jammed the flywheel. Thought for sure the engine was seized.

Re: Derbi Motoplat ignition timing

Yeah I want to do that once its running. I upjetted the 15 Dellorto to a 57 but it won't start still. My spark is a little whiteish. I can't figure out why this thing doesn't go. I haven't really had time to fiddle with it further. Maybe the spark is too retarded and cool to start the gas/air mix. There is one thing i am worried about. On Derbis, should the piston be arrow to exhaust like everybody else, or is it switched? When I got, a lot of things were backwards and upside downIn the cylinder, and i reversed the piston. Could that be it?

Re: Derbi Motoplat ignition timing

I'd try running an additional ground, directly from the magneto to the frame- just for getting it running.

as for the piston, if you are going to take it off anyway, check with the ports on the side- they should line up, unless they are exactly in the center.

I haven't seen any standardization in piston orentation- the arrow either points to the exhaust or the intake, but no telling between brands.

« Go to Topics — end of thread

Want to post in this forum? We'd love to have you join the discussion, but first:

Login or Create Account