If you will have any questions, this forum is here only for you at this moment Running should not be problem, maybe alternator will be faulty, but nothing unfixable.. It's nice you want keep it as it is, I know your first plan was to build a dirt track bike.
Alternator was rewound and should be better than new. New rectifier as well. New clutch assembly. The guy who sold it was fixing it up but got really sick and didn´t have energy to continue. I have many receipts of various parts that he bought for this bike.
I have an old Honda mtx 125 maybe I will turn that one into something like a dirt track in the future. A lot of projects and not a lot of time.
Today I had time for my Jawa. My plan was to change to the new ignition plate that came with the bike. Found that something was wrong with breaker axle? (Don´t know the right word for it)
Someone had broken the bolt that holds the rotor thing in place. Managed to drill it out so no worries.
Put the new ignition plate in place but it´s a bitch to set ignition timing. The breaker gap should be 0,3mm right? I can get timing perfect on the right cylinder but there isn´t enough adjustmen left to get it correct on the left cylinder. Wrong plate?
It ran like crap on the left side and blew out my muffler with a beautiful explosion.
Wow... That bearing is weird I think, smaller ring should be more inside engine. But I know only 634 engine. If rubber seal sealing properly, it should be like that. I didn't find any picture on google Gap is 0,3mm on upper position, then you must set piston 3mm back in front of upper position, and set breaker to position, where you can put between interrupter contact cigarette paper with rezistance. But I think you know it. Plate looks right, I googled some pictures and it looks same. I have an idea. If you don't have left space for set left cylinder, maybe camshaft isn't centered. Measure, if one cylinder is exactly in upper position, other cylinder must be in exact lower position. Maybe if you have one cylinder in upper position, other cylinder is only on his way to lower position. Maybe crankshaft is twisted in flywheels... Maybe, if you wanna go to extreme, you can grind holes for adjusting screws little bit. But it don't solve problem, only work around the problem. Aaaaa! I must learn english. Btw. it must be nice explosion, if it twisted that muffler.
Phew the pistons was ok. One in top and one in bottom. Took pictures today of what looks like splines. Maybe just to keep the copper rings from spinning? It´s fun to work on my Jawa, there is alot of stuff I haven´t seen on my other bikes.
Wow I have never seen it before. That copper ring maybe shoud rotate and splines should transfer torque. But It's spanish village for me. :-D where do you think is problem? You wrote you don't have enough space for adjust left cylinder. I don't see anything, I don't know this ignition. I'll try google some photos. Is camshaft properly installed?
It maybe is JAWA original, but I don't know 638 engine. But I google JAWA 638 alternator and it should look like yours.
so I think there's no problem, where is right cylinder, if is set to correct shift? I mean screws on plate, is it on any outer position? Or you can move plate more? If no, fault maybe is in camshaft position. Crankshaft on right side, where is mounted camshaft maybe can be displaced. You can solve this problem by increasing space for adjusting screws by edging.
Well, charging is common problem on JAWA. Do you have any wiring diagram?
Maybe one of the grey wires are alternator excitation and if you will remove it, there will be no current.Also try to measure stator: X-Y 766 µH Y-Z 702 µH X-Z 809 µH (not exactly, but values should be of the same order)
and try to check embers, or carbon, or...? I don't know word for it:
Yeah, VAPE. The best thing you can buy. It's contact less, it's reliable, and it's not expensive. It works like magneto, you don't need battery and and it's bolt on. But I'll recomend to install battery also, it's not good for charger charging to short circuit or to nothing. I have VAPE on my JAWA too and I'm satisfied.