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Bike is softail `87, carb is CV40, 48/175. I did the following:
ˇ cleaned the carb, changed carb seals (repair kit),
ˇ changed intake manifold seals (to heads and to carb),
ˇ installed new ignition Dyna S, with mechanical advance unit (because I will install a kickstarter soon),
ˇ new plugs Champion (see picture)
Engine starts right away, runs very well, pulls hard and steady when accelerating.
But, one issue: during constant cruising, at about 50 mph I get a misfire/backfire, I hear it into the exhausts and seems like it pulling the bike back..
This misfire/backfire, is happening very seldom, only one time in about 5 miles of riding, and is only one misfire/backfire, not more.
See the plugs after 40 miles of riding, yesterday.
That would be lean using the Donkey **** our State calls Gasoline!
something for thought; Coughing like out Carb, is usually Carburetion...or intake related, while, Backfires are almost always the Exhaust side of things.
I have the free flowing AC and exhaust like your set up. Based on the wideband monitor: a 45 low and 185 main work well on my set up.
I think your rich on the low end and lean towards the upper end. Double check for exhaust leaks, especially at the crossover pipe if using stock head pipe. The crossover has a small sealing ring and backing ring that can come loose letting air into the exhaust.
My rear plug usually looks a little darker than the front just like yours does.
sounds to me like you are running a rich pilot jet and a fairly lean main jet. You might be finding that at that speed your carb is transitioning from rich to lean and causing a cough / backfire.
As has been mentioned by others, I would definitley bring that 48 pilot down to a 45 and bump that main up to a 185 and you will probably have a smoother transition of power through the rev range.
In manual, I see a quite big difference in the size of the jets, speaking for the same EVO engine..
CV carb was introduce in '90, I think, my engine is from '87 and carb is from '92.
If I recall, the earlier Evos had a different cam to the later emissions compliant "N" grind. The N grind sucked and the carbs ran smaller jets to keep the bike as lean as possible to keep EPA happy. If you have the earlier cam in that motor and are running that combo of jets id not be surprised that you have a lean cough / misfire in the rev range.
If I recall, the earlier Evos had a different cam to the later emissions compliant "N" grind. The N grind sucked and the carbs ran smaller jets to keep the bike as lean as possible to keep EPA happy. If you have the earlier cam in that motor and are running that combo of jets id not be surprised that you have a lean cough / misfire in the rev range.
Aha, so it's even more complicated ...
Also, the carb was changed in '90 or '91, from Butterfly to CV. Maybe this can, also, influence the jet sizes..
Aha, so it's even more complicated ...
Also, the carb was changed in '90 or '91, from Butterfly to CV. Maybe this can, also, influence the jet sizes..
None of my CV's run same jetting as the old Ka-sneeze...and the "N" Cam...does Suck Pond Water...while the "L" is basically the Andrews EV-23.
But, Most Carburetor Problems are actually something else!! We should start with..."is it a Cough, or a Backfire out exhaust"????? Maybe a simple Misfire???
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misfire/backfire
