OP
@xantufrog avatar
UTC

Moderibbit
1980 P200E - "Old Rusty", 1976 ET3 Primavera
Joined: UTC
Posts: 8892
Location: Atlanta, GA
 
Moderibbit
@xantufrog avatar
1980 P200E - "Old Rusty", 1976 ET3 Primavera
Joined: UTC
Posts: 8892
Location: Atlanta, GA
UTC quote
I'm assuming this is a mixture problem, because I've only noticed it since moving to GA and only when it's hot/humid as hell out, but... Something about that seems too easy.

The bike: 76 ET3 with 135 kit but otherwise stock

The symptoms: seems to be ok at speed, and *usually* idles fine. But in low throttle ranges (takeoff or gradual decel) it will suddenly and severely splutter, sputter, and occasionally vocally misfire (not a "bang" but a big "puff").

Since it doesn't do this at all Fall/Winter/Spring I'm inclined to say something is off with my mixture at the low throttle range with regard to hot dense air. However, what's fishy is 1) it only does this maybe 1/3 of the time (e.g. takeoffs), and cranking the throttle certainly helps but it isn't a magic bullet - sometimes it just keeps it alive while spluttering at higher RPMs for a bit (10s?) before it ACTUALLY clears up.

These caveats have me worried it could be some weird electrical gremlin (CDI going out, etc)

Any thoughts?
@poidog avatar
UTC

Drama Free
79p200e 66smallstate 85pk50xl 84p125ets 63GL
Joined: UTC
Posts: 369
Location: Flatness, TX
 
Drama Free
@poidog avatar
79p200e 66smallstate 85pk50xl 84p125ets 63GL
Joined: UTC
Posts: 369
Location: Flatness, TX
UTC quote
I've had something similar happen to me twice and both times, it was simpler than I originally thought the problem was.

First time turned out to be a plug that just started to foul up. Very simillar symptoms to yours and a new plug solved it.

Second time was water in the fuel. Modern gas with ethanol is hydrophilic and will pull the moisture out of the air and into your tank, especially in a humid area like Atlanta. The moisture eventually collected in the bottom and made it to the carb which then needed to be burned out through the engine before the engine would run normal again. I drained the tank and put in fresh gas, and problem solved.

Hope your issue is this simple, and hope this helps.
OP
@xantufrog avatar
UTC

Moderibbit
1980 P200E - "Old Rusty", 1976 ET3 Primavera
Joined: UTC
Posts: 8892
Location: Atlanta, GA
 
Moderibbit
@xantufrog avatar
1980 P200E - "Old Rusty", 1976 ET3 Primavera
Joined: UTC
Posts: 8892
Location: Atlanta, GA
UTC quote
Thanks for the reply! I'll give that a try before tearing my hair out
UTC

Hooked
Stella
Joined: UTC
Posts: 106
Location: USA
 
Hooked
Stella
Joined: UTC
Posts: 106
Location: USA
UTC quote
I bet it is ignition.
@poidog avatar
UTC

Drama Free
79p200e 66smallstate 85pk50xl 84p125ets 63GL
Joined: UTC
Posts: 369
Location: Flatness, TX
 
Drama Free
@poidog avatar
79p200e 66smallstate 85pk50xl 84p125ets 63GL
Joined: UTC
Posts: 369
Location: Flatness, TX
UTC quote
If it is ignition related, the green kill wire is the easiest to isolate and diagnose.

Hope this helps.
⬆️    About 2 months elapsed    ⬇️
OP
@xantufrog avatar
UTC

Moderibbit
1980 P200E - "Old Rusty", 1976 ET3 Primavera
Joined: UTC
Posts: 8892
Location: Atlanta, GA
 
Moderibbit
@xantufrog avatar
1980 P200E - "Old Rusty", 1976 ET3 Primavera
Joined: UTC
Posts: 8892
Location: Atlanta, GA
UTC quote
realized I never followed up on this - although my conclusion is only more valid with more time/testing:

big thanks to poidog on the gas separation idea, because it turns out that flushing the gas and starting afresh completely turned things around. Not a sputter since...

Really quite striking. On a related note I took a gander in my jerry can around the same time I did the tank flush, and a half gallon of spare gas I had in there from about a month prior was a mess! A white powder had separated out of it and lined the surfaces of the canister the gas had been in contact with.
@v_oodoo avatar
UTC

Style Maven
'74 50s x3 '78 P200 E '84 Cosa '91 PK50XL2 - & - '58 AllState '68 Sprint '66(?) Super125 and '72 DanMotor Super150
Joined: UTC
Posts: 9512
Location: seattle/athens
 
Style Maven
@v_oodoo avatar
'74 50s x3 '78 P200 E '84 Cosa '91 PK50XL2 - & - '58 AllState '68 Sprint '66(?) Super125 and '72 DanMotor Super150
Joined: UTC
Posts: 9512
Location: seattle/athens
UTC quote
Thanks for the follow up. Have you tried ethanol free gas?

After your post I feel better about driving 5 miles with my 2 five gallon cans to get ethanol free premium. Even premixed I've had it sit in bikes for a year through summer and winter but then it fires up & runs fine.
OP
@xantufrog avatar
UTC

Moderibbit
1980 P200E - "Old Rusty", 1976 ET3 Primavera
Joined: UTC
Posts: 8892
Location: Atlanta, GA
 
Moderibbit
@xantufrog avatar
1980 P200E - "Old Rusty", 1976 ET3 Primavera
Joined: UTC
Posts: 8892
Location: Atlanta, GA
UTC quote
Voodoo yes it was disgusting. I can remember as a kid in the country we'd have jerry cans sitting around for long periods without that nasty powdery separation forming (although im sure it was still not ideal to do). Not sure where to find ethanol free gas near me, but I'm very tempted to look now...
UTC

Addicted
1974 Rally 200, 1974 Rally 200 with sidecar, Vespacross bike
Joined: UTC
Posts: 605
Location: Atlanta
 
Addicted
1974 Rally 200, 1974 Rally 200 with sidecar, Vespacross bike
Joined: UTC
Posts: 605
Location: Atlanta
UTC quote
Non-ethanol isn't always needed but be careful where you get gas in Atlanta because some of these low end stores fudge there inspections and have had water in tanks for years before it gets so bad it takes out a car's engine but water will affect our motors way sooner.
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