BannedCR500Riders.com

: bling : and how the hell is everyone? Ok, so you may know I sold my Dual Sport 500AF to a great guy here on the island (durkn..you still around?) and now I'm vintage racing several bikes including a 1980 CR125R Elsinore. I have a motor problem I'm hopin you genius' Hoon's can help me with.
The 1980 Cr125 was the last year of air cooled/twin shocked CR125's. It has a CDI ignition and it feels like the plug isn't firing consistantly at high revs. Sometimes it'll rip like nobody's business...other times it's 4-stroking (almost like a rev limiter is cutting in).
I'm 99% sure it's NOT a carb issue (so it probably is) because there is no consistancy to the RPM the problem occurs at. The bike is an old 125 so it's pinned and screaming most of the time and it's crapping out at the higher rpm's. I've fiddled with jetting with absolutely no changes in performance at all...none...
The plug looks too clean (read SPOTLESS..yes, I know that's bad) but she smokes like a canary in a coal mine at 40:1. I might have a crank seal leak, but that's not confirmed as of yet.
What pops into your minds on this one??
Mahalo,
Skiddy"

Looks like I need to update my signature....

close the plug gap to .015 and see if the brealup goes away.

if it does than you have a weak spark and you need to find bad connections or replace parts

i'd run the plug gap at .025
take the sill switch off

try what rsss396 said too

http://alp-sys.com/vintagedbforums/
Post your problem here and in particular look out for a guy called Dr. Robert Hawes who specializes in C125R Elsinores.

IMHO, I would want to be sure the crank seals and main bearings are good and then I'd rebuild the carb (needle jet, needle, pilot and main) so you've got a good baseline. From my experience the ignition systems on these bikes are very reliable.

Kill switch eh??...sounds viable...it's original.
Carb is rebuilt and stunning..if I say so myself.

Spark gap...will do.

My theory wraps around the coil not getting a proper feild charge at high rpm... spark gap may help. Good one.

I'll look for Dr. Elsinore thanks rocket.

Keep the ideas coming my way.

Skiddy

Have a look at the flywheel and see if its tight on its hub. We had an 82? cr80 that had loose flywheel rivets and was doing exactly what you are describing, run great then wouldnt rev out or come on the pipe and smoke like a train. We played with chasing wires and new plugs for a while before I finally pulled the cover and discovered the rattley flywheel. Its worth a look, id never even heard of this happenning until i saw this bike.

Excellent idea! Thank you!

Skiddy

Jetting not making any impact and smoking badly all points at tranny oil getting into the cranckase to me.

Crankseal and collar
Center case gasket leak
Crack somewhere

In my completely unproffessional opinion

Anything smoking related, Chris is the expert.

Boy that looks like the native "weeds" we have growing around here!

Skiddy

AlisoBob wrote:Anything smoking related, Chris is the expert.

Mmmmmm......Sativa

Skidmark wrote:: bling : and how the hell is everyone? Ok, so you may know I sold my Dual Sport 500AF to a great guy here on the island (durkn..you still around?) and now I'm vintage racing several bikes including a 1980 CR125R Elsinore. I have a motor problem I'm hopin you genius' Hoon's can help me with.
The 1980 Cr125 was the last year of air cooled/twin shocked CR125's. It has a CDI ignition and it feels like the plug isn't firing consistantly at high revs. Sometimes it'll rip like nobody's business...other times it's 4-stroking (almost like a rev limiter is cutting in).
I'm 99% sure it's NOT a carb issue (so it probably is) because there is no consistancy to the RPM the problem occurs at. The bike is an old 125 so it's pinned and screaming most of the time and it's crapping out at the higher rpm's. I've fiddled with jetting with absolutely no changes in performance at all...none...
The plug looks too clean (read SPOTLESS..yes, I know that's bad) but she smokes like a canary in a coal mine at 40:1. I might have a crank seal leak, but that's not confirmed as of yet.
What pops into your minds on this one??
Mahalo,
Skiddy"

Looks like I need to update my signature....

Yep, I'm still around.
Rode Mana again today, in the rain.
Nice ride - bit it going pretty fast.
Couldn't see in the rain.