Stalls and bogs down when Hot

[rmclaughlin]

79 Special, Hugh's PMA and PAMCO, Rec/Reg, mechanical advance, pods, cut exhaust, EMGO mini mufflers, new wiring, fuse panel. Running 10amp blade fuses. Up 2 on the main jets, 1 on the pilot jets, #2 on the needle. Carb is super clean and totally rebuilt. Cam is adjusted and valves are as well. Litterally everything on the bike is new except the engine.

Hey all. So ive seen a few posts from guys having the exact same issue but every bike is different.

Bike will start and idle perfectly and run super strong for 15 or 20 minutes. Then she starts to feel like she is going to stall and does. Like she is gasping for air or fuel. This happened on the freeway at 70 mph or so when I was testing her. Scared the crap out of me. It will also happen at a stop light also and she will just die. Then starts right back up and will go for a bit then just shut off completely.

All opinions welcome.

Thanks boys!

 

[Brassneck]

My initial thought is fuel flow...perhaps venting/air lock...but that seems less common on these bikes.

So then I think perhpas it's a charging issue. My first XS use to run great, and then bog/die at random times...and after a little while, I'd be able to kick it over and on my way for a bit...then it would do the same. Turned out to be a charging issue. I was running the stock charging system though...and it sounds like you've changed that up. Check your voltage/battery? Maybe your regulator overheating?

Those are just initial thoughts.

 

[CDNTX650]

Ride with the tank cap cracked open and see what it does.

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[rmclaughlin]

Eureka! The gas cap vent was clogged. Runs perfect now!

 

[Brassneck]

Eureka! The gas cap vent was clogged. Runs perfect now!

ha, well that was easy!

 

[rmclaughlin]

Yea right. After pulling the carbs numerous times assuming it had to be them, but in actuality it was something so simple and yet it never occurred to me. The Devil is in the smallest of details.

 

[builder]

what did your plugs look like are they black or normal , i have the same problem but my plugs are black and am using the pamco pma kit as well

 

[Brian902]

Quick test for fuel tank venting issues.

Fill tank with gas (close gas cap as you would normally do), remove one of the fuel lines from either side and hook up a short clear run of gas line into a gas can. Open fuel cock to the on/reserve or prime position to get fuel flowing and see it it runs for at least 5 minutes.

None vented tanks will stop the flow of fuel or at least slow it to a trickle.

If you were smart and used a clean fuel container, reuse the fuel after fixing the vent.

Done.

 

[builder]

did that , and had the carbs apart now 3 times plugs still black thinking of looking at the ignition system now, pamco might not be set up properly could be the plugs are not giving off enough of a hot spark for proper combustion, do have all the pamco recommended parts, coils, plug caps plug,s and fuse, has a bit of a stumble when you roll on the throttle.

 

[retiredgentleman]

did that , and had the carbs apart now 3 times plugs still black thinking of looking at the ignition system now, pamco might not be set up properly could be the plugs are not giving off enough of a hot spark for proper combustion, do have all the pamco recommended parts, coils, plug caps plug,s and fuse, has a bit of a stumble when you roll on the throttle.

If you go on a 200 km trip, and when you come back the oil level has dropped a lot on the dip stick? Do you see puffs of black smoke occasionally from the exhaust (have someone follow you in a car or bike). If you wipe the inside of the tail pipe, is it black?

If you see any and especially if you see all of the above, its likely that the head gasket is passing oil from the camchain tunnel.................time for a top-end rebuild.

 

[builder]

If you go on a 200 km trip, and when you come back the oil level has dropped a lot on the dip stick? Do you see puffs of black smoke occasionally from the exhaust (have someone follow you in a car or bike). If you wipe the inside of the tail pipe, is it black?

If you see any and especially if you see all of the above, its likely that the head gasket is passing oil from the camchain tunnel.................time for a top-end rebuild.

yup all of the above , well i have to say with the plethora of xs's I have build this will be my first top end rebuild, it shows imo that these motors are pretty hardy. any idea whats in the list I am going to sat cam chain tensioner and guide, pistons and rings gasket set crush washers maybe rocker bushings. that about right am i missing somthing ?what would it run me ? =(