Hello,

I own a Softail, 1987, pipes with baffles, CV carb (48/175), 1.5 turn mixture screw, and foam air filter.
The bike starts OK, idles OK and is running OK for complete rev range, with one exception => at about 1/5 or 1/4 WOT it backfires a lot, impossible to run. If I open the choke, at that time, it runs OK, no backfires at all. Thinking that pilot jet (48) is too small. I have spare pilot jets 50, 52 & 55 and also main 180.

Could you please share your toughts.




Thank you in advance.
Marcel

 

The low speed jet sounds part clogged pull the bottom bowl in place un screw it and spray and blow it out and see if that does it

if it was running fine and now it just started do it then its dirty if you do not know the bike then maybe a bigger jet

 

I vote 180.

 

Is a new bike for me, don't know how it run before.
The carb is clean, just did it before the ride.
in the 1/4 range of WOT, the "active" jet is the pilot one, not the main jet.

Can I change the pilot jet, w/o taking apart the carb, by just removing the bowl?

 

Make sure the carb is clean first. If still does it, toss a couple washers under the needle..

 

Just do the 180, check float level (tons of YT vids on that), and go easy with the needle. If you screw it in too far it will get damaged.

 

Does the accelerator pump squirt? Last time you had it off did you change the carb/manifold seal? Have you ever had the manofold off?

Stock cam you would be fine with a 45/175. And bolt-in cam you're OK with 45/180 or 185. You can run a 48 but if you "need" a 48, it has an intake leak - period.

 

Thanks for the answers.

• the carb is clean,
• jets no clogged,
• I changed all rubbers into the carb,
• the accelerator pump squirt,
• I did not change the intake manifold seal,
• I did not had the intake manifold off,
• I don't know what cams the bike has.

What I just did : I have changed the 48 pilot jet, with a 52 one and went for a short 20 miles ride. Bike run very well, the backfires almost gone, I only had 4 backfires, all of them when I pulled clutch to change gears. Maybe I need to play a bit with the mixture screw,actualy is at 1.5 turns. Also idle, I think, is quite too low.
But, considering your advices, maybe the 52 pilot jet is only covering the real root cause.

 

The 48 was covering the root cause and with a 52, I'm surprised it ran long enough to get home. If those are the lowest jets you have, I wonder if that is a CV40 or CV42

I need to know - when you removed the carb, does it have a clamp or does it just pull off.

 

Didn't know there was a CV42. Only thought there was a CV40 and CV44..