I have an 83 roadster (sporty) Ironhead. It fires up all right, runs fine for 5 minutes then dies. If I give it a few seconds, then kick it in the guts again it'll run fine, but then only for 10 or 15 seconds. It'll keep doing this until I let it (and me) cool down a bit, then do the whole scenario again.

The charging system doesn't work, but I don't think the battery is at fault because it's not sluggish when I start it. The wiring is a big dodgy mess, I'm going to get the soldering iron and a few rolls of wire and rewire the whole thing.

New plugs, cleaned the earth and battery leads, cleaned the tank and carby, new clean fuel, new mechanical advance unit.

Yes, I know, take it to the shop. But I'm enjoying working on it, it's just my fault finding and diagnosing skills are a bit wanting.

Does anyone have any suggestions, or can point me to a relevant thread on the forum?

 

What was the last repair you did to the bike?

Was this bike stored for over a month or more?

Was the tank full of gas?

Did you add any "stabilizer" to keep the gas from breaking down, which could also cause all the issues you mentioned?

When you say cleaned the carb and tank can you elaborate what you actually did?

The carb ... was it a full tear down? Or did you just remove the air filter and sprayed carb cleaner at it?

How did you "clean" the tank? Did you take off the petcock and clean the filter on it? Any debris on the filter? Did you just rinse it down with the tank still mounted on the bike? OR Did you remove the tank and slosh a cleaner product in it and rinse out the debris. Did you drain it into a clear glass container to be able to see the drained liquid to check for debris?

Starting and stalling in 15 / 20 seconds leads me to believe the float is out of adjustment and the float bowl of the carburetor is not filling correctly with gas. The smallest debris can give a carb trouble. It can hold the valve of the float open and flood the carb, and it can become sticky from bad gas and not open freely like it's supposed to, causing a lot of issues.

I'll check back ...

 

Focus strictly on the carb. That's where your problems lie.

 

Thanks guys, I appreciate the help.

When I ripped the carb off last time it was more to check what was in the bowl. There was a little bit of real fine brown dusty looking stuff (didn't look like rust flakes) but not much more than I've seen in other bowls.

Also, I pulled the tank off, drained it, added a coupla litres of fuel, gave it a good swishing then drained it again. Drained it into a clear container, and it looked clean, even after a couple of days to settle. The fuel filter is clan as a whistle.

I only recently got the bike, and I know it sat for a month at a time, with only 15 minutes ride at a time. The gummy carb sounds more and more like a possibility.

I'll rip the carby off again and give it a good going over.

 

I feel like I'm standing right beside you watching you do all the things I've had to do with my old bike too.

I'm concerned now that the carb jets have a collection of that debris you saw in the bowl and they may be plugged. That gets a bit more complicated when you break open a carb and start removing the jetting before a good wash down. Keep in mind it may be better to use air to blow out debris than just soaking.

I've seen float bowls with debris too but that is a bad sign. It means that from the tank to the carb there's debris being release beyond the tank filter. When there's debris in the bowl it generally tells you your tank filter is not seated correctly to allows sediment from the tank to pass freely into the carb. I just added a little clear plastic inline filter and glad I did. It trapped out even more crud the the filter on the (brand new) petcock missed.

Good job on the tank cleaning and glad to hear you used the clear glass to inspect for debris coming out of the tank. Did you look at the first rinse out, or did you rinse it out several times and then looked to check it?? One way by checking the first rinse out you'd know if there was debris to start with. If you checked after several rinses and now don't see anything that means you did a good job rinsing it out. So I'm just curious if the clear gas was after rinsing, or the very first rinse?

The real fun when you get a used bike is that you generally don't know all it's history and when you have a no start issue you have to rule out so many things it might be.

I hope all this gets you closer to getting your machine running.

 

Ripped the carb right down, cleaned everything and I'm sure there's no crap in it. And, Polarized the generator and I think that fixed the charging issues.

BUT......what is the secret to timing with a strobe?????

Either my head's to big, or my strobe is too small, cos I can't see a timing mark at all. I ordered the special acrylic plug thingo, painted the marks white, but still just see either oil or the reflection of the light. I'm pretty sure I'm bottoming out the plug (it's a tight lil bastard), then backing it off just a touch, but still no bananas.

Is there a special way to hold my tongue or something????

I timed it as per the youtube video, starts and idles fine, but misses a little bit under revs, which leads me to think I need to tweak the timing.

Any thoughts??

 

Yes, the plug gets covered in oil and the mark is impossible to see. I had been adjusting timing on motors for many years and have gotten the feel for it. However the ignition module that I'm using, Crane Hi4E ( no longer available), and many aftermarket models have a timing light that allows for adjust of timing with the light in the ignition module. Some newer systems are small enough that they replace your cam sensor, under the derby cover, with a complete module that takes the place of the sensor and the ignition module.

You should be able to adjust it real close "by ear" to make it run, but you may want a mechanic to do the final adjustment for the best timing.

The aftermarket Ignition Modules (Dayna makes one) actually improve performance of stock bikes by quite a bit. I like the new power curve, the higher range for the RPM limiter, and the ease of timing. The bike is quicker and starts very easy (multi spark feature) with the upgrade. It runs down the road faster, with quicker acceleration.

 

I've seen the electronic gizmos for HD's. They look like a good idea, but to tell the truth I like the idea of the points. It's stupid, I know, to put up with poorer performance and more maintenance when I don't need to, but the thing I like about the old girl is that it's like an old tractor. Vibrates, sounds mechanical, doesn't stop or turn, but it all adds to the experience (I've ridden Jap crotch rockets all my life, and I enjoy the old banger more than than all the other bikes put together). I like the fact it's still mechanical, and would like to try and keep it that way.

I'll play it by ear and see how I go. I found years ago on old cars that the ear works better than the light, I'll have a crack and see where I end up.

 

Still no bananas. Idle's fine, but got 50 yards down the road and she died again. Only way to get it home was to hold the choke on (it's exciting riding a bucking and coughing sporty with one hand)

Ready to give it a good solid kick. Suggestions?

 

Only runs with the choke on is a good clue!

Behind the carb is an intake manifold with clamps, rubber boots, and short "Y" shaped tubular metal connections that attach to the heads .... this is the intake manifold.

As they age, or you mount and dismount a carb the parts can fracture and leak air into the gas air mix coming from the carb. In order to balance that out, putting the choke on to shut off too much air getting through the manifold into the engine will smooth it out. You're running way too rich and will foul plugs out in no time under these conditions.

That would be my next place to inspect.

With the air filter off and out of the way, at an idle you can spray a little carb cleaner at the intake manifold and locate where the leak is. The motor will stall or idle rough if the carb solution is being sucked into a leak. Remember you're NOT spraying it into the carb, but at the manifold and connections behind the carb.

Be cautious and don't spay that cleaner all over your paint or chrome. And don't use a spray that is explosive or highly flammable.


BTW if it idles, and runs the module / points doesn't seem to be the issue.