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Discussion Starter · #1 ·
I've got a '77 Shovelhead, 74 CI, stock carb. Once it's warmed up, it randomly pops through the carb. It only pops once, then idles fine again. Sometimes it'll pop every 15 seconds, sometimes I can sit through a whole stoplight with nothing. It's more annoying than anything. Any suggestions? Thanks.
 

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It's running lean. I'd first check for an intake leak. 77's had the rubber bands right? Either way, I'd replace your intake seals first before you do anything else. At the very least get a screwdriver and tighten them up. HD's of that era were also known to be jetted lean out of the factory too.
 

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Bugman said:
I've got a '77 Shovelhead, 74 CI, stock carb. Once it's warmed up, it randomly pops through the carb. It only pops once, then idles fine again. Sometimes it'll pop every 15 seconds, sometimes I can sit through a whole stoplight with nothing. It's more annoying than anything. Any suggestions? Thanks.
intermediate jet...sounds like you need to go up in size...adjust top mixture screw believe it or not the weather changes all the time that is all it takes...adjust accordingly to weather changes...also push the timing just a touch ahead should take care of that...had 3 Shovels in the shop this year and each of them done that...that is the areas I worked to get rid of it...
 

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I worked in the dealerships back them and it was a common complaint. HD was trieing to meet EPA emision specs and leaned the engines out added a retarded timing cam and low compression pistons. The engines were never happy. At the dealer level there wasn't a lot we could do except to tell the coustomer that it was Normal!! Such was the 70's... Raise the compression, up grade the cam, richen up the carb, add a good exhaust system, and play with the timing and not only will the Hick-Up go away the engine will wake up and be happy and quit running Crappy..
 

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Ah yes, the "de-tuned" engines...
I'd check the intake seals, then points, then go up a few sizes on the intermediate jet (which may already have been done). Those Keihin carbs of that era were damn good carbs (when tuned correctly) until they wore out. Which also may be the case here. the aluminum carb body with the little hole for the slow speed circuit may be worn. I nursed my 1983 shovel's keihin for over 100,000 miles before I tossed it. But I should have tossed it about 10 years before I did.
 

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Discussion Starter · #9 ·
Thanks for the info. I'll give the things you suggested a try and let you know how things turn out.
 

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One other thing that it could be is loose busings in the advance weights making the timing bounce all around. Of course that's assuming you've done everything else.
 
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