Aero 50-High Cold Idle but dies when hot!

Trying to get your Spree/Elite to run, or run better? Post your questions here.

Moderator: Moderator

Post Reply
bajarocks
Noob
Noob
Posts: 5
Joined: Mon Sep 09, 2013 1:34 am
Location: Portland

Aero 50-High Cold Idle but dies when hot!

Post by bajarocks »

So i bought a 1986 Honda Aero 50 that had been sitting for many years and after cleaning the carb, putting a new air filter in and cleaning up everything else, it seems to work well except for how it idles. When I first start it up, the engine starts to rev, coughs, and keeps doing this until it maintains what would probably be an engine speed at 20 mph. When I adjust the idle speed down it drops to a normal idle, and then as it warms up it slowly drops until it dies. What could be causing this?
User avatar
motormike
Moderator
Moderator
Posts: 5488
Joined: Wed Dec 29, 2010 10:58 pm
Location: Glasgow, KY

Re: Aero 50-High Cold Idle but dies when hot!

Post by motormike »

My guess (at this point) is a pilot jet still not open, causing it to stall at idle after the bystarter has warmed up and closed the enrichening circuit.
Not sure about the initial fast idling...check for vacuum leaks as a first line of attack.
The idle stop screw may be set too fast for the initial setting after the cleaning.
Often times several cleanings are required to achieve a fully operational carburetor...even for seasoned veterans of the 50cc tuning world.
G'luck and report your progress... :hi:
RideRed
<Gyro S><MB5><Honda Navi><Helix><Sym Wolf><Yamaha Razz><Honda CH150 Deluxe>
"Live Large - Ride Small"
bfowler
Elite
Elite
Posts: 509
Joined: Sun Oct 21, 2012 6:37 pm
Location: Hawaii/San Francisco

Re: Aero 50-High Cold Idle but dies when hot!

Post by bfowler »

Don't quote me on this. But I've read a couple of posts that talk of extremely high revs on start up and the cause of it was a carb slide put in backwards. Check to see if you put the carb slide in correctly.
bajarocks
Noob
Noob
Posts: 5
Joined: Mon Sep 09, 2013 1:34 am
Location: Portland

Re: Aero 50-High Cold Idle but dies when hot!

Post by bajarocks »

Update- I cleaned the carb again and didn't see any obvious issues. I made sure the air box was seated well but didn't really formally check for vacuum leaks. I put it back together and had the same situation. It revs pretty high when it first starts but after about a minute it settles down to normal. Is this just the bystarter giving it extra fuel and I've just been paying too much attention to it?
User avatar
swimmingfree
CBR1000RR
CBR1000RR
Posts: 3357
Joined: Tue Jun 14, 2011 12:28 pm
Location: mich.

Re: Aero 50-High Cold Idle but dies when hot!

Post by swimmingfree »

yes my scooter dose 2500 rpm when i starte it cold and after it worm up it drop down to around 2000 rpm ..
swimmingfree
handicap (dyslexia)
looking for
se50 crank...

SpreJunk 87elite in a spree body
ruckus variator , 3.5 tire , 1500 drive face spring , a 64 bbk ,
8 gram rollers, stock carb , after market air filter and 105 jet
eliteguy50
CBR1000RR
CBR1000RR
Posts: 4219
Joined: Thu Mar 05, 2009 9:02 pm
Location: Iowa, USA

Re: Aero 50-High Cold Idle but dies when hot!

Post by eliteguy50 »

Don't set your keel screw until the engine is is at operating temp.
motormike wrote:Errands become adventures.
bajarocks
Noob
Noob
Posts: 5
Joined: Mon Sep 09, 2013 1:34 am
Location: Portland

Re: Aero 50-High Cold Idle but dies when hot!

Post by bajarocks »

I had gotten it running for a while, but had electrical problems that looked like a mouse chewing on the wires. I fixed up all of the exposed wires, but had issues starting it again. I cleaned the carburetor again, but now I can't get it to hold an idle again. The only time I can get it to steady out is with both the idle mixture and speed screws all the way in and the bystarter unplugged. If any of these change, it slowly dies out and can only be kept up with the throttle. I feel like I've cleaned out the carb quite well but this is sounding a lot like a clogged jet. What should I do from here?
User avatar
motormike
Moderator
Moderator
Posts: 5488
Joined: Wed Dec 29, 2010 10:58 pm
Location: Glasgow, KY

Re: Aero 50-High Cold Idle but dies when hot!

Post by motormike »

You're right, it does sound like the pilot is still plugged...But not necessarily... :confused:
Could also be the passages that flow air through the pilot circuit, which includes the idle mixture screw.
When you clean the carb, did you remove that particular screw, along with all the other jets and screws. It must be done.
Fuel delivery from tank to float bowl is still a possible problem.
Petcock issues can affect that.
Don't give up.... :wink:
I think your symptoms are pointing primarily at a bad bystarter.
I would do the cold bystarter test to confirm.
If the bystarter fails to close after warming up, it will allow too much fuel into the engine and throttling is the only way to keep it from dying.
Here's the cold bystarter test:
A. remove bystarter
B. measure length of brass metering needle from base of bystarter to tip of needle
C. Connect one wire to the + side of a 12 volt battery..either wire
D. Connect the other wire to the - side of battery
E. allow 5 minutes at least and re-measure
F. needle length should increase by 1/4 to 3/8 inches.
RideRed
<Gyro S><MB5><Honda Navi><Helix><Sym Wolf><Yamaha Razz><Honda CH150 Deluxe>
"Live Large - Ride Small"
User avatar
paulpauly7
CB900F
CB900F
Posts: 1945
Joined: Tue Feb 21, 2012 6:57 pm
Location: nz

Re: Aero 50-High Cold Idle but dies when hot!

Post by paulpauly7 »

clean the tank and petcock filter .Replace the fuel lines with new ones
86 Nifty Fifty (spree)
ZX disk brake
Kitico 120kmh speedo
AF18 ZX ported
Polini corsa
Malossi crank
CTmani
24mmOKO
40pilot118main
Scorpion pipe
8.44 to 1
Michelin s1
71.3mph
92 yz125, 94 crm250
User avatar
Wheelman-111
Moderator
Moderator
Posts: 11319
Joined: Wed Oct 22, 2008 5:09 pm
Location: Deepinnaharta, Texas

Re: Aero 50-High Cold Idle but dies when hot!

Post by Wheelman-111 »

Greetings:

Does a successful bystarter electromechanical test guarantee the circuit in the Carb will close when it heats up? Not if the socket is full of resin. Just a thought.
Wheelman-111
Most of my money is spent on scooterparts. The rest is just wasted.
"ISO": '03 Vespa ET4 Malossi187 74MPH
Flash 9: 2001 Elite SR Contesta 72 ZX Tran, 9:1 Gears, Stock Airbox/Carb/Pipe 58.8 MPH
Punkin: 2010 Vespa/Malossi S78, 61MPH
bajarocks
Noob
Noob
Posts: 5
Joined: Mon Sep 09, 2013 1:34 am
Location: Portland

Re: Aero 50-High Cold Idle but dies when hot!

Post by bajarocks »

I checked the bystarter like you said and it seems to be working. I cleaned the carb again and this time took out the idle speed and mixture screws and cleaned them as well. I put it back together and it ran better, but if I let it idle for a minute or two it would slowly start to die again and needed the throttle to keep the revs up. Changing the idle speed and mixture screws didn't seem to affect it much. Any more thoughts?
bajarocks
Noob
Noob
Posts: 5
Joined: Mon Sep 09, 2013 1:34 am
Location: Portland

Re: Aero 50-High Cold Idle but dies when hot!

Post by bajarocks »

Would it be worth it to just buy a $30 knockoff carb on ebay? I've cleaned this carburetor at least 4 times and it seems like nothing is really curing the issue...
User avatar
paulpauly7
CB900F
CB900F
Posts: 1945
Joined: Tue Feb 21, 2012 6:57 pm
Location: nz

Re: Aero 50-High Cold Idle but dies when hot!

Post by paulpauly7 »

low compression could cause your issue
86 Nifty Fifty (spree)
ZX disk brake
Kitico 120kmh speedo
AF18 ZX ported
Polini corsa
Malossi crank
CTmani
24mmOKO
40pilot118main
Scorpion pipe
8.44 to 1
Michelin s1
71.3mph
92 yz125, 94 crm250
User avatar
S4Patrick
Elite
Elite
Posts: 625
Joined: Sat Sep 11, 2010 10:29 pm
Location: TheMotorCity
Contact:

Re: Aero 50-High Cold Idle but dies when hot!

Post by S4Patrick »

It's definitely your pilot circuit on the carb. It's the skinny brass tube that's within the carb when you remove the lower bowl. When you remove the lower bowl, at the center of the carb is the main jet circuit, and mounted parallel to the main jet tube is the brass pilot circuit. Soak the carb over night or even longer (of course removing the float valve, all rubber o-rings, and screws first) in a carb cleaner and then blow compressed air through it thereafter. You might even need to run a thin-guage piano wire through the brass pilot too (which will test your nerves).

As Pauly said, check your fuel tank & petcock valve (silver valve that screws into the lower porting on the fuel tank) for contamination. Clean the fuel tank thoroughly and blow out the petcock valve (unfortunately by mouth) and replace both the vacuum line and fuel lines leading from the petock valve to both the silver intake pipe & carb. There's a fuel filter up in the tank that you should pull out & clean when you remove the petcock valve (be careful not to lose the little 0-ring that's on the fuel filter).

Hope this helps.... :2thumbs:
'87 Aero 50 STOCK (only 350miles)
'87 Aero (AF16 Corsa-PG-Short-OKO24mm-8.44)
'86 Aero (AF16 Corsa-SEF Black-OKO21mm-8.44)
'98 Live Dio ZX - 50th Anniversary Edition 68cc
'92 Super Dio ZX - AF18 Corsa

Visit: http://www.airtoolsforless.com
treekiller
BMX
BMX
Posts: 39
Joined: Fri Sep 06, 2013 11:15 pm
Location: United States

Re: Aero 50-High Cold Idle but dies when hot!

Post by treekiller »

My Chineese Knockoff kehin does this since day one. I tune it where is does not want to take off on warm-up and stalls when warm, tune it for warm running then while warmup it wants to jump off the stand. My soloution is going to be to use my old Dellorto from another build Manual choke and all.

Despite Perfect plug chops IT's a lot easier to tune when the weather is warmer. which makes me think I'm still jetted rich so some 50:1 premix and a little more needle seems to have broadened my tuning window, while I wait for my manifold to come in from Racing planet.
Post Reply