1971 XLCH "Coughs"

[kizzletruck]

Hey everyone..

Just thought I would give an update on the '71 XLCH I picked up a short while ago. The bike seems to be running pretty dang good. I think I have the starting procedure down pretty good. (Enrichener on, 3 squirts with the accelerator pump, 3 kicks off, turn on ignition, and it usually fires on the first and starts on the second kick.)

I have not checked the timing with a timing light, but then again I don't have the 100+ bucks to buy one. So here is my question:

While riding, seemingly at a low RPM (putting around town in 4th at maybe 45-50 MPH) I will occasionally get a 'cough' or 'puff' back through the carb. Would this be due to a timing issue, or would it be related to too low of RPM while in 4th gear (meaning I should keep it in 3rd until after 50 MPH).... ?? I am just a little confused as I have never had to deal with this. It does not sound like a backfire, but maybe this is it. I will be riding it quite a bit today since it is supposed to be 75 and sunny here in MN! I will let you know what I come up with. (I also will be replacing the plugs today - as I am still running the plugs from the previous owner - maybe this will cure it).

Thanks again for all the help - Got the 18" 1 1/4" Dia. apes in as well. Should look good on the bike! :banana

[IronMick]

It does depend on the gearing and sprockets. Assuming normal 51T rear and 21T front sprockets, 4th gear is not correct for putting around town - go down to 3rd. In 4th it would be lugging.

45 to 55 would be the bottom for using 4th gear. Like on the hiway, going downhill with the wind at your back.

[ryder rick]

Or intake leaks?

[RambleRider]

Usually a cough through the carb is a lean fuel issue. A backfire (actually, technically. an afterburn) through the exhaust would most likely be a timing issue. rider rick may be right with the intake seals or your slow/pilot/idle jet may be too lean. If you've recently messed with or replaced the carb i would look at the jets closely.

[lucky23]

My '72 use to do the same thing, even after switching out a few different intermediate jets. My bike seemed to lack a little midrange power, but I recently replaced it with a Mikuni VM38 and the problem disappeared. Plus, the bike starts a lot easier. Not saying the S&S is a crappy carb, I personally have had better luck with the Mikuni. S&Ss are sure pretty, though.

[tracbike]

Ramble rider is right just the carb but a weather change could have cause effect. Timing issues would be more related to hard start or knocking when you lug the motor.

I think your right there. That cough would be intermediate jet. (s&s)

[kizzletruck]

The only thing I did to the carb (S&S Super E) is pull it apart and soak it, and then reassembled it and adjusted it to the S&S website presets - and fine tuned it from there. Seems to run great except for the cough. I can't remember exactly what jets are in it (should have written it down) but I want to say the intermediate is a 26 and the main is a 68. Either that or it is 28 and 66. I will have to pull the bowl off again to make sure.

Now, I replaced the plugs (Champion CH8) and the Napa by me only had some Autolite 216's... Put the new ones in (gapped to .025) and noticed it starts harder. Jumped on it to see how it rides, got about a mile down the highway, and the bike nearly cut out on me... Back fired and popped a couple times then took off and kept going. Figured maybe low gas, but was not the case. I am thinking I will put the champions back in it to see what happens there.

Let me know what you guys think now... Lol. Change one thing and something else goes funky.

[Moon Wolf]

All of my S&S carbs (3) have the same cough. You can tune it mostly out, but I've never been able to eliminate it completely.