Took the SuperGlide out for a couple-hour shake down cruise last night and after an hour wasn't sure I would make it back home.

Cruising along in 3rd gear at 2500 RPM I cracked the throttle to wide open and was greeted with missing and popping and then the engine cutting out completely as if I'd flipped the key off. Backing off the throttle brought the engine back, but I had to be careful after that to use only light throttle. Anything more and the symptom reoccurred. I couldn't use 4th gear as the load required enough throttle to make the condition return.

I suspect the bike sat for extended periods, maybe I caused some sediment or dirt to be sucked into a venturi when I cracked the throttle, but I really have no idea. It has the Bendix carb, which seems to be a decent unit based on Google searches.

My first impulse is always to replace the offending component with new or tear it completely apart and swap old internals for new. But I thought I'd call on the wisdom of the forum prior to acting, and see if there might be a good sequential set of steps that I should take to diagnose and remedy the problem. For all I know the real problem may be upstream of the carb - bad points for example. Or as simple as a richer mixture setting.

This is my first shovel, so plenty to learn about diagnosis and tuning. Thanks in advance for suggestions on where to start and what to look for.

 

I'd start with fuel delivery and float level......

 

have the carb sonic cleaned and install a new low speed jet and a new acc pump = try again

 

Is it the stock Bendix carb on there?

If the bike sat for an extended period, you may have developed an intake maniforld leak.

If the bike sat for an extended period, I would take the carb apart and get a rebuild kit for it

 

It has the stock Bendix carb. Impressive how simple it is. Took it apart today and it looks brand spanking new. Not a hint of residue or gum anywhere. All the needles look like new with no wear. But - I shot brake cleaner through all the openings including jet orifices and anything else that had a hole in it. Reassembled and set the low speed jet 1.5 turns from from seat per the manual. She fired right up and ran fine. Matter of fact, ran real fine when I slightly cracked the throttle. Apparently it wasn't making good power when I took possession, but I had no point of reference.

Now I have a high speed idle issue, the motor turns a consistent 1200 RPM. When I adjust the throttle stop screw slightly, the idle comes down to 5 or 600 RPM briefly, but then drops down to the point she dies. If I blip the throttle to keep her running the 1200 RPMs come back. There is a minute bit of free play in the throttle cable, so I don't believe a too snug throttle cable is the issue.

I'm guessing that I have an intake leak now? I have the carb and manifold bolts pretty snug, hesitant to crank them any tighter. Maybe the next step is adding a light coat of gasket sealant to the carb/intake manifold gasket?

 

take off the intake and re seal it like pans has said or you will be chasing your tail

 

Adding to what john suggested, get new manifold o-rings. The old ones may look okay, but they do get stiff and hard over time. And you made sure your float level was properly set correct?

 

Thanks for the O ring suggestion, looks like that may be the winner.

Reinstalling the carb with a thin film of gasket sealant on both sides of the manifold gasket and tightening the carb, I noticed that the entire carb/manifold assembly moves up and down about 1/8 inch. Gotta think there is room for some air to sneak by the manifold at the cylinder and lean out the mixture. Looks like new 'O' rings are in order.

And since there is no carb support brace, one of those too. The only thing holding the carb on is the two bands pictured. And they don't seem to want to tighten any further.

Since the carb is coming off again in a week or so, I'll check the float level with a caliper to be sure it's dead on spec.

 

Find or make a support bracket or you'll be doing this all again in a few weeks.

 

Thanks TwiZted - I ordered the O rings and new clamps, but forgot about the support bracket...

The parts manual indicates HD part 29018-71A bracket pictured is what I need for my '75 FXE. However I do not have the factory stock air cleaner, it is aftermarket, a smaller round one.

Anyone know if this bracket bolts to the carb ear vs. a separate mounting spot on the factory air cleaner? If its the carb ear I'm good, don't have to make anything or swap anything.