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sdg pro-mini 107 electrical problem?

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zcookie49

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Discussion starter · #1 ·
I am wrenching on my friends SDG 107 speed mini (old school pitster with 107 head pretty much). His problem is that when the bike gets high up in the RPMs, the power delivery interupts for split seconds at various intervals. Starts to give you the herky-jerky feel under throttle. He had dirty carb problems prior, so i swapped out the carb with another. no fix, which i didnt think, but just trouble shooting. I then swapped ignition cdi boxes, no fix. I have also swapped the spark plug wire and coil and double checked the ground, no fix. I have thought that it may be the ignition coil in the bike, just wanted to check the easier items first.

Any other suggestions as to what it is, or is it the ignition coil? Bike runs strong in low rpms and usually in 1st & 2nd gear getting on it. But 3rd gear mid to top rpms, starts getting interupted.

Thanks.
 
Discussion starter · #4 ·
ROBINSONDB22 said:
sounds like it could be ur main jet
Click to expand...
.

well I had swapped a brand new mikuni carb, same style, that I had as a spare and it did the same thing.

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Yeah, once the bike is warmed up, choke off running. I have let the bike warm up for a few minutes then run it a couple of times. I have replaced an ingnition coil on a bike before but the bike wouldnt start at all. would just continuously kick it . . the bike started today on 1st kick.
 
#5 ·
I had the same problem on the SDG 107 that I had, and it ended up being a bad stator. Pull off your stator cover and if it smells burt, that it is gone. The best replacement is an IRK.
 
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#8 ·
Same stator setup as just about any Honda 50 style motor. If you swap plates, it's a good idea to swap flywheels as well, as sometimes the ignition pickup and trigger bump on the flywheel don't line up if you play mix-n-match.



Bikes with failing exciter coils generally tend to run and only show problems at first when hot and under load, aka 3rd gear pinned. They will progressively get worse and worse, eventually bucking in neutral at idle. Then they stop firing at all. Thats on a slow failure, sometimes they just flat out die with no warning.



Best way to diagnose is to swap stator plates and retest.
 
Discussion starter · #9 ·
Thanks man. The bucking is definately what is going on. I guess I could take my stator off my pitster and try it on his to see if that is the remedy. I appreciate the knowledge. I replaced a stator on a pitster in the past after troubleshooting everything, but the bike wouldnt start at all, so that mustve been an immediate failure. Which, BTW, pitster covered even though out of warranty!!!
 
Discussion starter · #10 ·
Well, I replaced the stator tonite, and same problem occurs. I talked with some others and made sure the ground is secure and also disconnected the kill switch. No luck. I didnt replace the flywheel with the stator.. But I dont know if that matters since it does the same exact thing...

Any help is appreciated. thanks.
 
Discussion starter · #13 ·
I re-examined the wiring on the bike tonite and this is what I discovered. Too late to start the bike up at the house. I will check it tomorrow evening. You really couldn't see it that well, but the underside of the rear ignition key module popped open and it was also filthy. I also sanded down the ground contact as well while at it.
 

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Discussion starter · #15 ·
rode the bike again today, does the same thing, with key ignition off. Could it be something in the fuel delivery? It idles fine, and I have replaced his carb with a brand new pitster carb and same thing happened. Should I drain all the gas out, air blow out the fuel line? just to rule that out if it doesnt work? thanks.
 
Discussion starter · #17 ·
cool. I had previously swapped the spark plug wire and the coil with a spare. I didnt have a spare boot, so I used his. I will try with another boot and see how that goes. I recently sanded down the frame area where the ground meets.

I think I will also check the flywheel magnet.
 
Discussion starter · #18 ·
Today I took the spark plug boot off of my Pitster and exchanged it on his bike. Still same problem. I also took the flywheel off to inspect it as well. While I was in the bike, I exchanged out the new stator (wasnt doing any good) and placed the original back in. The flywheel still has magnatism in it, it will go to the spindle when I hold it up close. I saw a little nipple that lines up with the stator. Look fine to me, there was a lil knick on the corner edge of it, kinda of like a small dent. I reinstalled everything. I took off the gas tank and drained all the old gas out. I took an air line and blew thru the fuel line, couple times, then turned the petcock closed, wouldnt blow, then reopened and blew again, seemed to blow strong with no obstructions. remounted, fired up and rode it. Still same problem with the sporatic lurching/bucking... I never have changed the spark plug , but cant really think that would be the problem.

.

Do you think the flywheel itself should be replaced? I couldnt see anywhere on it where you could make adjustments to it.
 
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