Mornin' all - first time poster, so go easy on me. I'm the proud owner as of last spring of a 1983 Sportster, with S&S carb (I think the super "E"), just hit the bike's first 10 grand marker a couple days ago.

I gave my buddy an oil change, adjusted the chain tension to spec (chain and sprocket only had 1 or 200 miles on 'em when I bought it, so practically new), and went on my merry way to test how he'd handle on longer trips. I'd only, up until this point, tooled around on backroads with it - only just got my license a couple weeks ago, so the highways are now at my disposal.

Okay, enough fiddlefaddle; I took a 45-50 mile journey to me gram's, no problems. Took a fifteen minute break to warm up my bones, and then filled up and went home. Must have been about five miles from home, when I noticed the bike seemed to be maybe backfiring a little bit, bogging down, slowing down, not firing - unless I really leaned on the throttle. Mind you, I'm keeping the bike at a pretty constant 3500-4000'ish RPM's for the ride home, all highway.

Figured since it's not a constant problem, and only happened after a long ride, must be a heating issue. Double-checked my plug gap (new NGK plugs in it, maybe 200 miles on them), all OK. So, where to go from here?

Could the type of oil I used be causing an overheat? Mine was getting grimy, and all I had immediately available was pennzoil SAE 20-50. Couldn't get my hands on a filter yet, either - but changed the oil anyway, figuring it couldn't do any harm.

Any other suggestions are welcome, as well. I do plan on taking the hike to my 'local' dealership to stock up on a handful of filters, and nab the proper oil type, etc. either way. Much obliged, cheers.

- Al

 

A few questions for yah. One when you say backfiring where exactly was it backfiring from? The pipes or the carb? And when you say overheat, do you mean your pipes were red hot?

I would say it sounds as though this is what happened. It didn't overheat but started to run really rich.

I would first pull your plugs on the bike and examine what they look like. Are they a really tan color from running lean or are they a very black souty color from running rich?

Start with easy stuff first. If you have the ability, check compression on both cylinders, plug readings, fuel delivery, and spark.

 

Check your intake for air leaks, long rides vibrate stuff loose sometimes.

 

I'd also check your ignition timing - sometimes the screws that hold the plate in it's spot like to vibrate loose

 

I should probably add that I've ridden the bike since then on short trips (less than fifteen miles), and it's been acting beautifully (including a couple trips on the highway, etc.)

When I say overheating, I say it loosely. I'm really just deducing things - it isn't a problem which always happens, nor is it RPM sensitive, or speed sensitive. I definitely had fuel in the tank, and definitely have the ability to deliver enough fuel to the bike to get him up to eighty without a problem. I've thought about checking to make sure the fuel filter screen isn't full of anything scary - though I personally doubt it will be. So, as dangerous as this is, me wondering if it's an overheating problem comes from me using logic to see what factors could have changed to make the bike act strangely.

I've already inspected the plugs, and they don't appear to be abnormal at all. Very tiny bit of black in the threads, but the contacts on the plug look fine. I don't think anything has vibrated loose, since the bike is running just fine still. I'm continually going over things, though, so I'll just push checking the intake and timing up a notch. Almost did the timing last night, actually - just couldn't find my light anywhere! Hope someone didn't think it was junk and tossed it on me.

That's probably the extent of what I'm able to do presently with the tools I possess. I've suspected for some time that my jets are too big on my carb, causing the bike to run a little rich (the set of plugs the bike came with were FOUL, but they were also gapped WAY too small). As far as actually tuning the carb, though, I'm fairly certain I've got it tuned decent. I'm no professional, I'm a hackjob garage mechanic - but, I learn a little bit every day, and read up on / tinkered with that carb enough to feel good about how it's set up.

Thanks for the replies all - I'll keep yer posted on anything that changes, etc. I think I may take another long run with the bike to see if the problem reoccurs, try to glean a little more information on the topic.

- Al

 

On cast iron sportsters use only 50wt motorcycle oil!! If you live in places like AZ use 60 wt

 

Straight 50? Huh. Manual called for 20-50 for 20-90 degree environments, if memory serves me right.

So I should snag 3 quarts of Harley Davidson's finest 50 when I ride down to grab my oil filters then?

 

20 -50 wt for evo sports straight wts for cast iron sports I use to run 70 wt in my knucklehead when I lived in SE PA

 

yep 60 w for my 84

 

I forgot I posted this thread - it's been a year and a half now!

Ironhead has been treating my nicely overall. Last season ended short, with the hitachi generator failing on me. Replaced a couple months ago with a cycle electric, new battery, and I was back on the road about two months ago.

And so I'm back to wondering about overheating...

I have troubles with it on longer rides; after cranking 3500 rpm's down the highway to/from work, it doesn't fire right towards the end of the journey. Actually, when it gives me this hesitation / misfire problem, if I pull the clutch in it'll actually stall out. However, if I run it slow after this point, it'll idle again without stalling. Plugs aren't fouled, seem to be possibly indicative of running hot / lean.

Believe it or not, still haven't checked the timing on this. Picked up a light yesterday, and I'm going to adjust tomorrow. But also - I'm running the S&S E carb. Flipping through my Hayne's, I see something in here about a VOEC (vacuum operated electric switch) for the timing advance being attached to the carb. Where is this thing? I don't see, at first glance, anything like this attached to my carb. And hey, since we're on the topic - the "choke" on that S&S never has worked for me. Any troubleshooting tips?

Thinking of trying to run some colder plugs, and I've got to replace the front rockerbox gasket.


- Al