Rich exhaust smell, low power

[1983lux]

Hi all,

I’ve got a 1975 gl1000. Carbs rebuilt with a Randall kit about 6 years ago by me, took my time and followed Instructions carefully. Recoated fuel tank by radiator shop. Plugs fairly new. Static Ignition timing done recently, was a little off. Electric fuel pump conversion with pump that does about 2-4 psi. Valve lash done about a month ago. I have sportster mufflers on it.

Ever since putting on a new big plexifairing, I notice how bad my bike smells like rich, Rae fuel while cruising. Gets strong under hard acceleration. Doesn’t smell bad when idling at a stop. People behind me notice the bike smells bad too, like an old muscle car, very rich.

I’m wondering, maybe something in the carbs is plugged up causing too rich a mixture? All my intake runners feel warm after a run, same temp. Is my fuel pump putting out too much pressure?

[1983lux]

To elaborate n the low power, the bike moves along fine, but the acceleration is just not as snappy as I’d expect. I feel like it was quicker in the past. When I roll on the throttle, it feels like it makes more noise but gains speed pretty gradually, definitely doesn’t pull me back in the seat at all. My 83 gr650 is much snappier.

I’ve wondered if the clutch might be part of the issue? It has a brand new cable and was adjusted according to the manual. Didn’t look at clutch plates or springs though. It doesn’t feel like it slips at lower speeds, not sure how else to test that.

[Fred Camper]

How do the plugs look after a longer run. That can let you know if one or all are rich or lean.

[1983lux]

Here's some pics of the plugs (arranged how they'd be installed on the bike looking down from driver's position).

Seems like the 1&3 plugs (right side) are much blacker than the 2&4 plugs (left side)

plugs1.PNG (613.73 KiB) Viewed 217 times

plugs2.PNG (1016.06 KiB) Viewed 217 times

[Fred Camper]

Carb sync is the first connection I would try.

[gltriker]

Hello! Yes, the frontal area has been significantly increased and now the engine has to work harder to plow through the additional wind resistance. Greater throttle plates opening consumes more fuel.
Other than my feedback on the new big plexifairing turning your personal space behind it into a carbon monoxide chamber,
Yes, those spark plugs portend a lot of historically recognized and addressable with focused time and money to be invested issues are present.

My experience with a handlebar mounted Plexifairing on a 1980 CB900 Custom I had triked 20plus years ago, and the triked 1975 GL1000 I presently own with a full Pacifico Shadow fairing and tall windshield can be useful.
The add on wind buffer may be creating a vortex that actually draws exhaust gases back into your personal space. Headaches will present.
How did I discover the phenomenon? Wrap a long scarf around your neck and allow the loose ends to fall onto your chest.
When you are driving along at highway speeds you may suddenly see the loose ends of the scarf drawn away from your chest and dancing back and forth behind the windshield. Then the probable cause of totally unexpected headaches has been discovered.

[1983lux]

Did a carb sync recently, but found it was really touchy and hard to get right! Maybe worth trying it again.

Yes, as GLtriker says, the big plexifairing creates a lot of backdraft! Mounting it up high so that there's a hole above the gauges under the windsheld seemed to help a lot. I guess the good side of it is I was able to realize how rich my exhaust was smelling, where only people behind me would notice it before.

I'll have to look harder into what can cause rich running on just one side if a resync doesn't help. I suppose 6-7 years since carbs were rebuilt is enough time that something might've failed or gotten plugged up.

[robin1731]

How many miles are on those plugs? What kind of gas are you using? Is the b0ttom of the plenum dry or wet?

[1983lux]

Hi Robin,

The plugs are not new, about 4000-5000km on them. However, I did remove them about a month ago and hit them with a wire brush before re-installing, so the black gunk on the right side is what has collected on them in the last month.

I used to run supreme gas, but now run regular last few months after reading there's no need for supreme online. Probably contains 10% ethanol. I figured with the Randakk kit the ethanol is alright?

Bottom of plenum was pretty dry after sitting at night, but could see a touch of wetness in the bottom right corner. Ran the bike for 5 minutes while observing the plenum, didn't see any new fuel, stayed pretty dry.

carb1.PNG (801.75 KiB) Viewed 113 times