Making sense on ignition, cdi and pv servos

[ifixbikes]

Hi all, hoping someone can help fill in the gaps for me here. I appreciate all and any help.

I’m currently rebuilding a dtr 125 motor, now the bottom end is stamped 4BL But the top end is 3MB (cylinder and head). Iv purchased a new (used) crank marked 3MB as the one I removed had slightly chewed threads stator side, this is where I meet my first issue.

The crank spindle on the stator side of my new crank is about 15mm longer and by tho looks of it the magneto (marked 3NC)once fitted if the tapers actually match might not go inside the casing cover. Can’t see the code on the old crank as yet to remove the bearings so I’ll know that soon.

Can anyone enlighten me as to wether I need a different magneto/stator set up?

2nd issue would be that iv also purchased a pv servo with pulleys and cables but not sure now if this will work with my cdi unit? (Marked 3NC)

Even the stator plate has a different code 3BN..

Some clarification on what will and will it work together would be greatly appreciated or any advice will be well received as I’m not familiar with this particular engine nor do I like electrics.

Regards, Alex.

Can’t seem to upload any pictures either

[Calum]

Website doesnt' support image hosting due to the cost of it. Use Imgur to host images.

I suspect you have gotten a DTRE/TZR RR crank which inverted the magneto and stator plate. And yes the taper will be different.

It should fit however, you will just need the stator/flywheel, pickup and generator cover off the Belgarda or RE. Easier to get ahold of the whole engine and or DTR crank though.

The Stator will put out more power so will probably need the RE rectifier...

[declan]

@Calum I heard the inside of the left case is different for the re/x crank not sure if I believe that though

[ifixbikes]

@Calum Good work! this makes sense as the extra length on the left hand side would accommodate the flywheel/starter ring that goes on the back of said magneto.
Rookie mistake there. It’s not a major issue as I do need a new stator side cover and the wiring on the stator I have has been butchered abit so could replace the lot.

Either that or get a different crank again

Is there a “best” or “better” model of ignition system?

Back to my second point will the cdi unit/ electrics I have support a 5 wire pv servo?
If not again what would I need? 3 wire or different cdi? And would that mean I need a different stator &or magneto?

I really do despise electrics

[SpookDog]

It all depends on what stator you end up going with. The early 3 coil stator needs a 3 wire power valve servo. You’ll also need loom and CDI to match...
I think they changed it in 1999 then again in 2004. Each one will need loom and CDI to match...
I’d just get another crank if I was you. If you convert to e start you’ll need to cut a hole in the case for the starter motor and a pin for the idler gear...

[SpookDog]

Just done a quick search and 3NC is the 1989-99 variant. You’ll need a 3wire servo for it. Your stator should have 3 distinct coils on it that are screwed on...
Also your CDI has an embedded controller for the power valve servo...

[ifixbikes]

@SpookDog thanks for the help much appreciated, I’ll be getting the correct crank just makes sense.
As for the pv, again iv basically got the wrong servo for my engine electrics cause iv brought a 5 wire Could just pin it but that’s no fun.

I will say the engine isn’t actually going in a DT so I won’t need the loom, I have read that I will need to hook up a battery tho if I want to run the servo as they can act erratically without one.

[Nottsbiker]

Depending on how bad the crank threads are you could use a thread restoring file on them which may restore it enough to use.

[ifixbikes]

@Nottsbiker I am going to use it, to be honest it’s not that bad there’s actually a small flat spot on the threads only about 2-3 threads, and it’s not at the end it’s about 15mm in from that so it’s not actually where the nut does up more where the washer goes so I’m happy to run it, I only was going to change it cause I got the 3MB crank cheap.

[Calum]

@declan Probably because the Stator mounts to the case. However since we won't need to mount the stator there, as the flywheel mounts inverted, you might get away with it,

Either way, it's a big faff to do.