so, on the 70 r5 i have recently had the RH cyl hav issue, i figured it was just carb stuff but i went thru everything, and to make along story short, even swapped another r5 carb onto it known good, and still same issues. :rolleyes:
compression is good. 120 each cyl even +/- 4 psi
fire up and idles. rides ok..for about 5 mins then the RH cyl starts failing. misfiring at idle, then just cutting out and eventually not firing.
cools down, fresh plug, fired back up 'resets'
new crank & seals a year ago, no excessive smoking, def doesnt appear to be a crank seal. plug not oil fouled.
changed wires. caps. same thing
swapped wires left to right. SAME THING, stays on RH cyl. this is what i have a hard time understanding.
you can run it hot, (fan in front of motor) with a plug on the head and watch it start to fire intermittently on the rh side.
this bike does NOT have a zeeltronic on it (the 72 does).
ive NEVER seen one of these fail, much less like this.
i have a spare new rotor and pickup, but thats it. It cant be the coil as it doesn't matter if i swap wire sides
anybody ever seen this before on an mzb/vape? unit was installed new in spring 23. its acting just like a cingle coil going out on a stock rd ignition system and dropping one side. its sooo weird
Seems like the rotor may have problems. You have the 2 raised square pieces, on the rotor, 180* apart that trigger the pick-up coil, one for left cylinder, one for right. The right hand one may have a problem, when hot, it's not causing the pick-up coil to send a signal. You could remove the rotor and turn it 180* and reinstall (set up the rotor install using the other cylinder) and see if the problem switches to the left side. :umm:
I know you a talking about vape but my HPI ignition failed on me and I found out the rotor magnet was cracked. This was a no spark condition on both not one side. Could it be spark leakage on the side that is failing? If you start it up in a darkened room can you see the spark arc to ground?
thats a good theory, but to your pount if it loses one, it should lose both. however, 76rd400 made a good point. while its nearly impossible for a trigger to fall off or break, I think it was def something affecting the trigger process at the rh cyl side. took cover off and the trigger to rotor gap was a mile wide. closed it up to .020" and seems to have cured it.
Check the coil resistance after it warms up.
Quote from: RDRoy on May 02, 2026, 12:49:50 PMCheck the coil resistance after it warms up.
Nope, already ruled that out with tests
Quote from: m in sc on May 01, 2026, 10:01:31 PMchanged wires. caps. same thing
swapped wires left to right. SAME THING, stays on RH cyl. this is what i have a hard time understanding.
was for sure pickup air gap.had it out for about 30 miles ran awesome. like said, that was a new one on me. ill def take it out a few more times but ive never had it affect just one side before. im guessing that it was juat on the cusp on the left trigger, but the right one was beyond and when warmed up would miss on that cycle. wild.
Glad you got it sorted.
sounds like some crazy FB group diagnosis come to life... but took it back out, running like a top. go figure totally my own miss.
Air gap ha? You know what's funny? I just had that issue on my damn lawnmower. I had to replace the coil because of this shit. I thought I needed a battery. But, I'm glad the engine didn't start because I woulda had a fire. :dawg:
Anyway, air gap wasn't quite right and the engine was really hard to start.
lol. man.
my post got lost but it turns out it was actually a cran seal leak due to a worn primary gear.
the crank and seal is a year old. primary gear is 57 and has 28k on it.
:bang:
Thats wild. I didn't know that was possible. So this means the gear itself was worn therefore the oil made it's way into the combustion chamber regardless of the condition of the crankseal itself?
yup. the seal was fine, but i replaced it anyway
Oh... haha, well, mine could be that as well. I never replaced it, but I think it looked ok last I had it all apart.
so did mine last year. :boom: