Suzuki 125 kicking my ass | GTAMotorcycle.com

Suzuki 125 kicking my ass

Mad Mike

Mad Mike

Well-known member
I just put a cyl and piston into a 84 SP 125 and can’t get the bugger to fire. I’ve rebuilt a lot of motors, this little biitch is killing me! Got compression, got fuel, got spark. I’m thinking a flaky cdi but not sure. It gives a sputter then farts back. Timing and valves are triple checked... I’m licking my leg off trying to get this pig running.

any tips for a Suzy 125 4 stroke?
 
Mad Mike said:
I just put a cyl and piston into a 84 SP 125 and can’t get the bugger to fire. I’ve rebuilt a lot of motors, this little biitch is killing me! Got compression, got fuel, got spark. I’m thinking a flaky cdi but not sure. It gives a sputter then farts back. Timing and valves are triple checked... I’m licking my leg off trying to get this pig running.

any tips for a Suzy 125 4 stroke?
Click to expand...
I like to fire engines on propane. Put an unlit torch on full in the airbox and start kicking. They normally start easily on propane and don't mind switching over to gasoline after they have a few seconds of heat and vibration.
 
GreyGhost said:
I like to fire engines on propane. Put an unlit torch on full in the airbox and start kicking. They normally start easily on propane and don't mind switching over to gasoline after they have a few seconds of heat and vibration.
Click to expand...
Tried that. Start fluid, gas in spray bottle... I’ve never had a motor stump me like this one.

got spark, got compression, got fuel. gonna deep dive into igniter and cdi this week.
 
Mad Mike said:
Tried that. Start fluid, gas in spray bottle... I’ve never had a motor stump me like this one.

got spark, got compression, got fuel. gonna deep dive into igniter and cdi this week.
Click to expand...
I'm assuming it sparks every revolution? If not, it there a chance it is sparking on the wrong cycle?
 
How do you know you have compression? Just because you feel wind coming out of the hole with your finger, doesn't mean you do. Ask @Brian P .
 
Given that this is evidently a fresh rebuild with a new cylinder and piston, I doubt if it will be the same issue that I had (which turned out to be a cracked piston). But still ... a compression and leakdown test will be instructive. Mine had "finger over the spark plug hole" compression as well, but it had 60% leakdown through the crankcase.
 
Wingboy said:
How do you know you have compression? Just because you feel wind coming out of the hole with your finger, doesn't mean you do. Ask @Brian P .
Click to expand...
I stick my tongue in the spark plug hole. I can hold back 110lbs.
 
I work on vintage but small displacement two-stroke marine racing engines and your symptoms are only too familiar. If it was a two-stroke, I would have questioned the induction issues and condition of the crank seals, etc. Hope you found the cause of the non-start so you can update us.
 
  • Sad
Reactions: TK4
Mad Mike said:
Tried that. Start fluid, gas in spray bottle... I’ve never had a motor stump me like this one.

got spark, got compression, got fuel. gonna deep dive into igniter and cdi this week.
Click to expand...
Alright, this is going to sound dumb... but, have you tried replacing the ignition cables and cleaning out the carbs 100%?
Spark may be intermittent if the cables are bad - as I'm sure you well know.
Just a thought, considering the rest sounds like you've done it properly.
 
is it a strong blue spark every time? is if so why question the igniter/cdi?

"sputters and farts back" sounds like timing which you triple checked. Have you double checked the specs with another source? We've all found typos in the manual before.

past that I got nothing
 
timtune said:
is it a strong blue spark every time? is if so why question the igniter/cdi?

"sputters and farts back" sounds like timing which you triple checked. Have you double checked the specs with another source? We've all found typos in the manual before.

past that I got nothing
Click to expand...
OP, any luck with a resolution?
This is an intriguing problem!
 
You must log in or register to reply here.

Back
Top Bottom