Aero 80 revived, but now another problem ...

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Aero 80 revived, but now another problem ...

Post by MogyDad » Sat Jan 05, 2019 8:39 pm

Following a repeated and more thorough carb cleaning, my long-term stored Aero 80 was running great! Had the air screw and idle adjusted well. Did some cosmetic improvements and fixed some minor mechanical issues. Figuring snow would be coming soon, I prepared it for a few months storage - filled the tank and added Sta-Bil.

Took it for a quick spin to work the stabilizer into the system. Thought I would see how fast it might go so I opened the throttle and quickly accelerated to 25-30. Suddenly, the engine started cutting out, lost acceleration power, smoked considerably and chugged to a stop. It didn't stall, but had no power to engage the clutch and continued to smoke more significantly than usual. Got back to the garage and function seemed to return to normal. Turned around and went back up the drive only to have the symptoms return almost immediately.

I let the bike sit for a few hours and attempted a restart. It started, but with the same symptoms. Engine ran, smoked excessively and would not rev up beyond a inconsistent idle. I drained the fuel tank and the carb and added fresh gas. Wanted to ensure the Sta-Bil was not a factor. Primed the carb and restarted the engine. No improvement.

Any suggestions?

Thanks!

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Re: Aero 80 revived, but now another problem ...

Post by bonesv » Sat Jan 05, 2019 11:39 pm

What "minor" mechanical "issues" did you fix?
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Re: Aero 80 revived, but now another problem ...

Post by MogyDad » Sun Jan 06, 2019 6:48 am

Repaired a cracked left front turn signal housing mount. When that was disassembled, noted that the wires to the turn signal were bare thanks to a hungry rodent. Sucessfully replaced them. All other wires were in good condition. Doubtful anything I did related to repairs / cosmetic improvements would contribute to this problem.

Initially I suspected the Sta-Bil as potentially the problem. I added one ounce to a full tank and then thinking about it later, recalled that I may have already put some in it a few days earlier - probably one ounce then as well.

It's been a long time since I owned a 2 cycle bike - like 1973 - but remember often having spark plug fouling issues. Do you think the extra Sta-Bil has fouled the plug? Something is creating a lot of excessive smoke.

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Re: Aero 80 revived, but now another problem ...

Post by bonesv » Sun Jan 06, 2019 2:59 pm

Yea I thought you meant an issue related to mechanical as in powerplant related. Doubtful that wiring would be related to excess smoke. Maybe you mixed in an ounce of oil by accident? By all means, change out the spark plug with an NGK - my favorite brand..... :love:
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Re: Aero 80 revived, but now another problem ...

Post by MogyDad » Sun Jan 06, 2019 3:27 pm

Just fired it up and got it running. Tried tweaking the air mixture and found it ran best with screw all the way in. Took it down the road and it died.

I now strongly suspect fuel starvation. Probably a bad fuel valve. The diaphragm was stuck shut when I first started working on it, so perhaps it’s still an issue. The carb drain only produced about an ounce or less of gas, and the other symptoms seem to point to an intermittent fuel supply. Runs OK at idle but not under load. Once the bowl empties it misses, bogs down or shuts off. The excess smoke could indicate lots of oil, but not enough gas. Anyway... ordered a replacement fuel valve so will see if that solves the problem.

And... the scooter already has a new NKG spark plug!

Thanks!

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Re: Aero 80 revived, but now another problem ...

Post by bonesv » Sun Jan 06, 2019 6:30 pm

There should also be a filter in the fuel line if not then it’s inside the tank just above the valve. Pull it out to clean it but if you ordered a new valve from a Honda dealer it should come with a new one. The vacuum valve will only pull fuel when vacuum is applied. Or could be leak in the vac line? I don’t recall hearing about a fuel valve that was stuck closed unless it was trashed and full of rust.
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Re: Aero 80 revived, but now another problem ...

Post by MogyDad » Mon Jan 07, 2019 10:23 am

I'm now pretty certain that the root of my problem is an intermittent malfunction of the petcock. Initially, the petcock diaphragm was stuck preventing the flow of fuel. I was able to release it ... at least partially, to obtain flow. Testing it with a small syringe for vacuum it produced fuel.
This morning I thought maybe a vacuum leak was at fault. Using the syringe for vacuum it started easily, but quickly ran lean. I pulled the line of the carb only to discover a very modest drip of fuel. Even though the syringe had earlier produced sufficient vacuum for full flow, it wasn't any more. Putting a hard suction on the tube created a full flow.

It's doubtful the manifold vacuum produces the suction I had to apply to gain full fuel flow. The new petcock will narrow this issue (if it persists) to a vacuum leak.

Thanks for your assistance!

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Re: Aero 80 revived, but now another problem ...

Post by MogyDad » Sun Jan 13, 2019 2:07 pm

Swapped out the petcock with a new one. Verified it was working. Started engine and allowed it to warm up. Once it was warm and idled down, the problems returned - engine continued to slow to the point of stalling, and the only way to keep it running was by working the the throttle. However, eventually it stalls.

I was pretty much convinced it was a fuel starvation issue originating from a bad petcock or possibly a vacuum leak preventing the petcock from opening. Don't think so any more. Using a larger and bigger syringe to create and maintain suction on the vacuum line, was able to maintain fuel flow even after the engine died. Also was able to detect decent vacuum draw on the manifold nipple with my finger. The engine would surge and then fall as I covered and uncovered the nipple. Note the nipple was capped during the initial warm up and while I attempted to find any vacuum leaks with carb spray.

So ... Do I still have a carb issue - its been off and cleaned twice - but perhaps still not clean enough? Am I missing something else I should try?

Thanks!

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Re: Aero 80 revived, but now another problem ...

Post by Wheelman-111 » Sun Jan 13, 2019 2:42 pm

Greetings:

The Bear had an exhaustive post explaining what I recall was a complicated cold-start enrichening system for the Aero 80. Lots of plumbing as I recall. Your symptoms sound like the engine dies once that system shuts off? If that's the issue, another more thorough carb cleaning is indicated. Another thought I had is that the bowl vent could be obstructed. If so, negative pressure in the bowl prevents fuel from being sucked into the intake stream. Finally the issue could be with the carb float needle not letting enough fuel into the BOWL, even though the fuel flow from the petcock is sufficient. Unless it's a heat-related ELECTRICAL Gremlin - thankfully these are uncommon - it's gotta be one of these things.
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Re: Aero 80 revived, but now another problem ...

Post by MogyDad » Sun Jan 13, 2019 3:17 pm

Thank you for the quick reply!

Here in PA it's snowing ... and a bit cold - even in the garage.

Tomorrow morning I will pull that carb and clean it even more thoroughly, paying particular attention to the details you point out.

"Lots of plumbing" is a pretty accurate comment for that cold start system. It seems to be working as designed, but everything goes south the minute it stops feeding fuel into the carb. Something must still be blocked!

Best regards.

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Re: Aero 80 revived, but now another problem ...

Post by bonesv » Sun Jan 13, 2019 10:33 pm

You must be sure the air/fuel adjustment screw and all related idle circuit passageways are clean and clear. Do this by first viewing a carburetor exploded-view diagram to be able to account for all the individual parts in the circuit and second by using a “carburetor spray cleaner” to verify said circuits are clear. If not able to verify, then use appropriate means to obtain verification of clear passageways. Remove emulsion tube and clean all the pin holes and verify also. It is the tube which the main jet is screwed into. Remove pilot jet as well and clean and verify all the pinholes are clear. Be absolutely sure all vacuum lines and related heat choke tubing is in tact and verify there are no holes or cracks. I would just replace all of them if they are suspected to be the original tubing. Do not replace further related parts(especially with non-oem ebay parts) until you are sure they have failed.
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Re: Aero 80 revived, but now another problem ...

Post by MogyDad » Mon Jan 14, 2019 4:45 pm

Removed, disassembled and thoroughly cleaned carb and components with carb spray, compressor air and visual inspection. Once satisfied all was clear (third cleaning), I reassembled and fired it up. Everything seemed great until the engine warmed up and idled down. As before, unless I worked the throttle continuously, the engine slowed and ultimately stopped.

This time, I added a section of clear fuel tubing at the carb nipple to ensure fuel was flowing through the petcock. It was.

I read through the "Bear" post on creating a manual choke. It sure sounds like I have the same problem he described. Having eliminated everything else I can think of ... its time to try his remedy. It looks like a pretty simple procedure, that can be easily reversed if not effective. Will advise outcome.

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Re: Aero 80 revived, but now another problem ...

Post by MogyDad » Tue Jan 15, 2019 12:45 pm

Picked up some 1/4" fuel line and a cheap shutoff valve (wanted to ensure a solution first) to replicate Bear's manual choke solution. It took about 20 minutes to assemble everything, but once complete, the bike fired right up.

I probably didn't let the fuel enrichment run long enough for a full warm up, but once I got it to settle into a resonable idle, was able to adjust air mix and set the idle. Before venturing out, I let it sit and idle for about five minutes.

After putting the seat back on, I grabbed a coat and took off down the driveway. Now it's about 28 degrees here today, so I only had the stamina for three loops down the street, hitting about 35 mph before I had to hit the brakes. Certainly not a full test ride but enough to convince me that the auto choke was the problem.

Thanks to Bonesv and Wheelman for their expertise and assistance!

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Re: Aero 80 revived, but now another problem ...

Post by Wheelman-111 » Tue Jan 15, 2019 8:06 pm

Greetings:

So glad you got it going. Chilly first rides are the Best!
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Re: Aero 80 revived, but now another problem ...

Post by dr_rock » Fri Jun 14, 2019 11:50 am

How's your scoot running now. That manual choke fix is a life saver on these old Aeros

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