Honda Gyro starts and stalls after about 10 seconds

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dfgtye
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Honda Gyro starts and stalls after about 10 seconds

Post by dfgtye »

Just picked up a 1985 Gyro S in pretty good shape but not running. Has been sitting for a number of years and the guy I bought it from never had it running. Heres the issue. I have compression , spark and fuel. The engine will start right up when the starter is engaged and run for about 3-10 seconds then stall. If you give it any throttle it stalls. Acting as if it has no gas. I have rebuilt the carb (wasn't actually to dirty). I've rebuilt about 100 carbs so ok with this. Every oriface is clear and clean. The float is working good. The gas line is clean. I cleaned the petcock. Ran gas through the tank and lines to flush. Then put in new gas. The fuel flows good, and the bowl is full. After a stall, I pulled the carb and checked the bowl. Full. Also re-cleaned carb with compressed air. Clean. Re - installed, and same issue. New plug and new air filter. So to recap--clean carb,new plug,new air cleaned, fresh gas, unobstructed fuel line,compression good,spark, charged battery, easy start--but will not stay running or take any throttle. Anyone ever have this issue? When you pull the plug after a stall it is wet. Possible weak spark. The spark is blue. Any idea how to check this or if it is something else that I am missing? Thanks.
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Re: Honda Gyro starts and stalls after about 10 seconds

Post by deuce217 »

What is the plug gapped at? Current compression PSI?
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Re: Honda Gyro starts and stalls after about 10 seconds

Post by motormike »

I own a 1985 TG50M Gyro. I also have owned 2-'84 gyros, and 2-'86 gyros.
I do all my own repair work.
I am 60 years old.
The scenario you describe has been common to me.
I find that the bystarter is in good working order, which makes cold-starting easy.
The sudden stopping of the motor occurs when the FUEL in the BYSTARTER "well" has been depleted, and fails to re-fill quickly enough to maintain running.
Even after cleaning a carburetor several times, it can be found that not all passages are as open as first thought.
With the case of my '85 Gyro, the tiny orifice that connects the float bowl to the bystarter "well" was only partially open.The motor would start good when cold, then die after a few seconds.
It would re-start after a few seconds, but not immediately after die-ing.
The problem was eliminated once cleaned the orifice that feeds the bystarter "well"
The orifice being only partially open would feed fuel to the "well" too slowly to maintain running.
Hope you find that this is also the status of your carburetor and another careful cleaning will eliminate the problem.
I would also take particular care to ensure that the "idle jet" is fully open, as that too will cause motor to die when throttle is introduced....g'luck... :urban:

EDIT: I suggest that the spark is fine and not likely to cause the symptoms described.
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Re: Honda Gyro starts and stalls after about 10 seconds

Post by dfgtye »

motomike--your description sounds exactly like what is happening to me. Except that I cant give it any throttle. I would think that i could still give it throttle and it should speed up. My understanding is that when the throttle opens, it blocks the flow from the bystarter chamber. I'll look at the carb again(easy enough to take off ), but i checked that passage last night, sprayed cab cleaner through the hole and compressed air. Seemed free. Perhaps i'll run a soft wire through it. Thanks. I'll see what happens.
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Re: Honda Gyro starts and stalls after about 10 seconds

Post by dfgtye »

Ok. Got home. Pulled carb again. Cleaned everything again. Ran a wire though the bystarter holes. Very clean. Started again and ran for 30 seconds. Stalled out same as before as if out of gas.
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Re: Honda Gyro starts and stalls after about 10 seconds

Post by motormike »

The next logical explanation is the idle jet being clogged which results in being unable to throttle.
I'm sure you have already verified the idle circuit to be flowing good.
Slow fuel delivery from tank to bowl still a possibility.
Possible too is the holes along the emulsification tube being clogged, reducing throttle response.
The tube I mean is the one above the main jet. (#2 in the parts fiche).
Sounds as if you are chasing a mystery problem, but seems most likely to still be in the carb.
Main jet size is #75.
O-ring on manifold surfaces might be too old to seal good ?

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Re: Honda Gyro starts and stalls after about 10 seconds

Post by wentwest »

What do you think about the idea that it's not starving, it's choking. Maybe not enough air getting through the filter? Did you squeeze out the oil really well? Maybe the float is too high? With what you have done it seems like it's a mixture problem, and you are reporting a wet plug. Are you using the oil pump or premix, or both? Maybe too much oil?
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Re: Honda Gyro starts and stalls after about 10 seconds

Post by dfgtye »

Carb is completely clean. Float level good. Does not over flow. Checked the flow with hose disconected and into a bottle. Good on both reserve and on. Same result with or without air filter installed. And tried it with the oil mix line attached to the intake and detached and the oil mix hole plugged. Checked the seal for leaks at the carb to manifold and manifold to engine.
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Re: Honda Gyro starts and stalls after about 10 seconds

Post by dfgtye »

Ok. Tracking it down. Bystarter has continuity. Took the bystarter off and held my finger over the hole. Idled good and throttle works. Ran out of time. Something with the bystarter circuit. Getting closer.
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Re: Honda Gyro starts and stalls after about 10 seconds

Post by MPDano »

Did you resolve your issue, I know it's an old thread but always best to chime in once in awhile to give status for those that search the threads to get some troubleshooting tips.
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Re: Honda Gyro starts and stalls after about 10 seconds

Post by motormike »

MPDano wrote: Tue Nov 10, 2020 9:38 am Did you resolve your issue, I know it's an old thread but always best to chime in once in awhile to give status for those that search the threads to get some troubleshooting tips.
The OP has never returned since the previous post. It's been 7 years and he's gone.
If you have a similar problem, we'd be happy to help you....motor
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Re: Honda Gyro starts and stalls after about 10 seconds

Post by MPDano »

motormike wrote: Fri Nov 13, 2020 10:14 am
MPDano wrote: Tue Nov 10, 2020 9:38 am Did you resolve your issue, I know it's an old thread but always best to chime in once in awhile to give status for those that search the threads to get some troubleshooting tips.
The OP has never returned since the previous post. It's been 7 years and he's gone.
If you have a similar problem, we'd be happy to help you....motor
Thanks Mike. Been working off and on, on my 1984 project. Rebuilt the top end and cleaned the carb. After reading the thread, I'm going to make sure bystarter orifice is well cleaned. Also, since I'm taking the carb off, going to check my reeds and replace the oil pump o-ring. My symptoms is very hard start. Got 100 psi compression with throttle wide open but someone mentioned this is due to rings not fully seated yet as well as maybe the reed/oil pump o-ring. FYI, once I did get it started, I did do some varying RPM runs with no load (wheels off among other things, lol).

Maybe you have more helpful input to share.

Much Thanks.
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Re: Honda Gyro starts and stalls after about 10 seconds

Post by Volvo850R »

Try to crack the gas cap open
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Re: Honda Gyro starts and stalls after about 10 seconds

Post by MPDano »

Volvo850R wrote: Mon Nov 30, 2020 6:22 am Try to crack the gas cap open
It's not hooked up to the tank yet, using a temp fuel source.
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Re: Honda Gyro starts and stalls after about 10 seconds

Post by dkevin »

I have an 86 Spree that exhibits the same symptoms. It will cold start and run for 5-10 seconds, then die. It will not immediately restart but if it sits for 1-3 minutes, it will start and run the same. The carb has not been replaced or disassembled. The air filter is clean. I have replaced the bystarter with new (reads 8.6 ohms) and the engine is delivering fuel to the carb. I removed the lower bowl screw and cranked the starter..the fuel ran out. I pulled the plug to inspect it...it was soaked in fuel and had a lot of debris around the tip. I am trying to visualize what might be going on here and I am open to possible courses of action from this point onward. Thank you for your help!
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