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Messages - m in sc

#1
pretty sure I found the culprit.  weirdly it didn't smoke more on the rh side but I think it was just  enough to foul the plug.  as said, the airgap was large, adjusting it down helped, but probably juat by giving a better signal to fire thr plug better to help prolong the fouling.

the wear it's bad enough to feel the curve of the grooves.  its wild.  I rebuilt this motor a year ago. weirdly don't remember this being that bad. luckily I had a spare. so, not the ignition,  not the carb. I think this might be the downside of running synthetic  trans oil. can't really tell when the seal is seeing on the plug.
#2
Turning Wrenches / Re: Are 155 mains enough?
May 04, 2026, 08:25:58 PM
if the lid is on the airbox thats pretty close on the main. def drop the needles one clip and see how it is.
#3
the airgap def helped. however the issue came back, but nowhere near as aggressively.  but still there, killed a rh plug at lunch today for no obvious reason. I can't find a def smoking gun, but im goung to check the rh crank seal. even though its only a year old, and everything else has been exhaustively checked. the plug didn't look overly oily but maybe juat enough to kill it
#4
lots of sleds run similar,  and are ok, and I have ridden a reverse cyl banshee powered ninja w one that was pretty fast. but, still, for a street bike id stick w individual pipes. some of the gt750 guys love them,  but..  depends what you're after. on an rd though? no. id bet they would work well on a radjoot low torque motor though
#6
id be more inclined to get the spitfire ones out of indonesia than these. 2-into-1 2 stroke pipes kill all topend on a street bike. I have ridden a triple, and a twin w them. def not great most of the time. my 0.02
#7
Turning Wrenches / Re: 1974 RD250 - Coil Issue?
May 03, 2026, 07:15:15 PM
yeah go up to like 190s and work diwn
#8
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.
#9
Turning Wrenches / Re: Look at this swinging arm
May 02, 2026, 07:57:43 PM
zero difference. it pinching in when you tighten the swingarm isn't a bad thing at all.  :twocents:  also, that arm is made for a 350. the wider adjuster slot is on the LH side . 400s have that on the rh side.
#10
Turning Wrenches / Re: Look at this swinging arm
May 02, 2026, 04:33:47 PM
thats not a stock rd swingarm, it's from another bike
#11
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.
#12
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.
#13
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










#14
its the same file I had, just tested w the blue.
#15
you can email them and ask,benji knows what unit works for the rd, I think its a 210