Bystarter Failure?

skipper20 · Post by **skipper20** » Mon Oct 06, 2014 7:14 pm

On a carbureted scooter, what are the main symptoms of a carburetor bystarter going bad? TIA,

Bill in Seattle
'09 150 Blackjack
'12 170i Italia

jrsjr · Post by **jrsjr** » Mon Oct 06, 2014 7:42 pm

Allow me to point you to the classic thread on this topic, Bystarters 101, by our very own charlie55.

skipper20 · Post by **skipper20** » Mon Oct 06, 2014 10:29 pm

jrsjr wrote:Allow me to point you to the classic thread on this topic, Bystarters 101, by our very own charlie55.

I remember the write-up now and it was a very good one. I even contributed to it with an input on my '86 Honda Elite 150's difficulty with cold weather starts. What's missing though is a recommended test or tests to isolate the problem, i.e. bad heater, plunger, needle or? So, any thoughts on a possible test procedure?

Bill in Seattle

charlie55 · Post by **charlie55** » Tue Oct 07, 2014 12:49 am

I checked the Buddy service manual here on MB, and I can't seem to find any bystarter test procedures specific to the brand. (Or any at all for that matter.) So here's the generic procedure:

1. Find the bystarter's electrical connector and separate the two halves.

2. Connect an ohmeter to the two wires going to the bystarter and test the resistance. Since there's no documentation on what's "normal", I can't provide much assistance in that regard. For a Helix, the norm is between 2.8Ω and 5.2Ω at 68° F. However, the wiring diagram for the Buddy shows that there's an external resistor between the bystarter and ground. The Helix doesn't have one. So, I don't know what the individual (bystarter) or total (bystarter + external resistor) resistance should be. Perhaps someone more familiar with Buddies can help out.

3. Connect a voltmeter to the other part of the connector and start the engine. From the Buddy wiring diagram, I'm pretty sure that it's AC. With the engine running, you should see voltage. I'm gonna guess and say that it's somewhere in the range of 12 volts AC.

4. If this were a Helix, the next step would be to remove the bystarter from the carburetor and inspect it to see that the plunger is retracted and free of corrosion, gummy deposits, etc. If everything is OK, then the bystarter would be connected to a 12V source (a battery is OK since the heating coil doesn't care if it's AC or DC). After a while, the bystarter will heat up and you can see whether or not the plunger has extended. As said before, though, your bystarter has an external resistor, so connecting it directly to an external voltage source without that resistor in series could damage it. If I had to guess, I'd do the following (with the engine cold):

- Reconnect the bystarter's wiring.
- Remove the bystarter's retaining clamp and separate the bystarter from the carburetor. At this point you can do the visual inspection for retraction and crud build-up.
- Re-seat the bystarter into the carb and clamp it.
- Start your engine and let it warm up fully.
- Stop the engine and quickly remove the bystarter as before and see if the plunger has extended.

That's about as specific as I can be without access to a "better than Chinglish" service manual to refer to.

ucandoit · Post by **ucandoit** » Tue Oct 07, 2014 2:50 am

Charlie---My buddy 125 carb. floods, chronically. I notice gas in the air box, poor gas mileage, poor running; am working on diagnosing this problem. Anyway, I cleaned the entire carb. but could not get the screw off holding the "bystarter" (I call it "enricher") off. I was afraid I was damaging it. So, I didn't remove the enricher. The dealer said the enricher is either on or off, which I don't quite understand. Your method of testing it makes sense, if I could get it off.

My question is: if my enricher/bystarter is on all the time, would that cause the carb. to flood & leak gas into the air box?

My other question is, how can I tell if my float is adjustable. I so want to know if the float fills too high. Thank you.

charlie55 · Post by **charlie55** » Tue Oct 07, 2014 4:35 am

ucandoit wrote:Charlie---My buddy 125 carb. floods, chronically. I notice gas in the air box, poor gas mileage, poor running; am working on diagnosing this problem. Anyway, I cleaned the entire carb. but could not get the screw off holding the "bystarter" (I call it "enricher") off. I was afraid I was damaging it. So, I didn't remove the enricher. The dealer said the enricher is either on or off, which I don't quite understand. Your method of testing it makes sense, if I could get it off.

My question is: if my enricher/bystarter is on all the time, would that cause the carb. to flood & leak gas into the air box?

My other question is, how can I tell if my float is adjustable. I so want to know if the float fills too high. Thank you.

Well, let's define "on" and "off". Electrically, a properly-functioning bystarter is always "on" whenever the engine is running because there's current flowing through it. It's only "off" when the engine isn't running. That's the electrical viewpoint. From a functional viewpoint, on and off have a different meaning. The bystarter is on when its internal heater hasn't warmed it to the point where its plunger extends to shut off the extra fuel needed for cold starts. Likewise, it's off once the plunger has extended and blocked the extra fuel passage.

In so far as the flooding, it's not dependent upon the bystarter or any of the other fuel passages for that matter. They're merely tubes, and the only reason they'll overflow is if the fuel level in the carb's bowl is too high. So, it's a pretty sure bet that there's a problem with your float, float needle, or the petcock (which is really a vacuum-driven valve if I remember correctly).

The "adjustability" of the float is usually determined by the material used in the tang. The tang is the part that bears against the float needle and forces it into the closed position as the float rises. Adjustable floats usually have metallic tangs (mainly brass) that can be bent towards or away from the float pin so as to change the level at which it cuts off the fuel. If you bend the tang towards the pin, the fuel supply cuts off earlier (at a lower level). The opposite is true if you bend the tang away from the float pin. Non-adjustable floats are usually molded from a single piece of plastic and do no have a "bendable" metallic tang.

skipper20 · Post by **skipper20** » Tue Oct 07, 2014 5:21 am

charlie55 wrote:As said before, though, your bystarter has an external resistor, so connecting it directly to an external voltage source without that resistor in series could damage it. If I had to guess, I'd do the following (with the engine cold):

- Reconnect the bystarter's wiring.
- Remove the bystarter's retaining clamp and separate the bystarter from the carburetor. At this point you can do the visual inspection for retraction and crud build-up.
- Re-seat the bystarter into the carb and clamp it.
- Start your engine and let it warm up fully.
- Stop the engine and quickly remove the bystarter as before and see if the plunger has extended.

That's about as specific as I can be without access to a "better than Chinglish" service manual to refer to.

Thanks. That last part definitely helps. I'll let you know how the test goes.

Bill in Seattle