Pops and sputters before warm up.

[Stickysteve44]

So I went to work earlier in the day. Bike ran fine. When I was leaving work, it started to pop and sputter until it fully warmed up.

When I left for work it was 95 and sunny. Leaving work, it had been raining and was down to 77 degrees. Maybe the low pressure system coming through had something to do with it? It's a mostly stock 1982 Heritage Special. Only difference is the K&N filters. One up on the pilots, and mains. Oil (10w-50) was lowish but still between the two lines. Just went through the basic maintenance arround 150 miles ago or so ago. Adjusted cam chain, valves, mixture, synced carbs, drive chain, and changed oil. Carb boots seem pretty decent. So I don't think it's a vacuum leak, but I'll check.

What y'all think I should look at?

 

[Stickysteve44]

Bike is new to me. Had it for around three months. Two of which I spent trying to get the title transferred due to covid and dmv shutdowns. Hence, only having put about 150 miles on it. I went through the charging system as well when I first got it. Got a rewound rotor from Jim (Thanks again, Jim!). And checked everything else out. So that's been working quite well.

 

[Stickysteve44]

Also, I reckon I should mention that it wasnt sitting in the rain while I was at work. It was under a covered garage.

 

[Bushyeyed1]

Are the pops coming from the carbs or the exhaust? One or both? Pops are usually a lean condition. Also is it only at idle or when do you get the pops?

 

[Stickysteve44]

Seemed like the carbs. They were small pops not exhaust pops. Kinda crackly. From right under me. It was when I gave it a bit of throttle. And like I said, I've been riding the bike with no troubles until now.

 

[5twins]

It's possible some dirt or gunk has made it's way into the carbs and plugged or partially plugged something, most likely the pilot jet(s) or idle circuit. Unfortunately, this seems pretty common after putting an old bike that has sat some time back in service, even after cleaning the carbs. Regular running seems to break loose any remnants of gunk in the carbs you may have missed during your cleaning, and stuff can plug back up. It's happened a couple of times to me already on my '83.

 

[Stickysteve44]

Well if that's the case it seems to have worked itself out mostly. I road arround the neighborhood without a helmet just now. Pops at low rpms in second gear but not first. I guess that's still probably the pilots doing?

 

[5twins]

Yes probably. Although the pilot jets have their biggest effect and influence on idle, they never stop flowing. They're adding their small part to the overall mix through the entire RPM range right up to red line. Granted, you don't notice their contribution much in the higher RPMs, but it's there. Most of the fuel for the higher RPMs comes through the mains.

As I mentioned, I had the right pilot jet partially re-plug up on my '83. It happened twice. Luckily, both times I was able to clean it without removing the carb set. I just dropped the float bowl, removed the pilot jet, and blew it clear. Although not totally plugged, I could see some black junk in there partially obstructing the hole through the jet. It really effected the idle and made it run badly, practically killing that cylinder at low RPMs.

 

[Stickysteve44]

I figured I could just drop them without removing the carbs. Didn't get a chance to do anything with it today. But I rode around and its acting like it was before. Just happened the one time. I'm off tomorrow so I'll go through everything. Thanks y'all!

 

[15cherries]

my 79 special was doing the same after I rebuilt the carbs once in a while until I installed inline fuel filters and it has settled down now, mine seems to like hugs and pet the tank, lol! ride it and enjoy it, some times it spits and sputters a little but it will always get you home.

 

[Stickysteve44]

my 79 special was doing the same after I rebuilt the carbs once in a while until I installed inline fuel filters and it has settled down now, mine seems to like hugs and pet the tank, lol! ride it and enjoy it, some times it spits and sputters a little but it will always get you home.

I know it's a good precaution. The only reason I didn't add an inline filter was because of how nice my tank looks inside.

 

[5twins]

I've never used them and feel they're more trouble than they're worth on this bike anyway. It's too cramped under the tank to easily fit them in. My buddy has been wrestling with them on his 650 for several years. He has the aftermarket big tank from MikesXS along with two manual petcocks and he's trying to fit it to an '80 with BS34 carbs. It's a nightmare and his fuel lines are constantly kinking and cutting off fuel flow, lol. He's about to redo them for the 3rd or 4th time but I'm not sure he'll succeed. He kinda lacks common sense when it comes to mechanical things, lol. Cable routing confuses the fuck out of him too, lol. Or at least it used to until I showed him what needed to be done for lower bars.