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Keeping Spree Elite Aero 50cc and Gyro Alive!
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PostPosted: Thu May 10, 2018 8:09 pm 
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I recently acquired a Suzuki FA50 in decent shape and not running. Got it running within five minutes of getting it home. The problem is that it doesn’t go past 18 mph. It will not rev high and stumbles between 3/4 and full throttle. Full throttle makes the revs actually lower from 3/4 throttle. It idles perfect btw. I have put a brand new carb in (cleaned the stock one but was still convinced it was a carb problem which it wasn’t), ran full tank of gas with seafoam through it, opened up the head to check for score marks of possible piston ring damage and it was perfectly fine, checked fuel lines and the fuel cap to make sure there is no vapor lock or shortage of fuel, changed transmission oil, checked for air leaks anywhere and everywhere possible by spraying wd40 while it was running, and changed spark plug. I cannot figure this out and am reaching out to you guys as a last ditch effort before getting rid of her.


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PostPosted: Thu May 10, 2018 9:15 pm 
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Sounds like its getting choked out somewhere since full throttle is where the issue occurs. Possible airbox restriction with a crappy filter cutting off airflow. Maybe a gummed up exhaust not allowing gases to escape at full bore. Possible fuel delivery restriction not allowing the needed fuel at wot...like petcock, fuel filter, fuel line, etc..

Im assuming that youve removed the airbox and looked into the carb venturi and confirmed the slide is fully open while you twist the throttle. Possible issue with the throttle cable being too long, stretched or simply needs an adjustment if possible.

Dont sell it...keep at it and you’ll find your gremlin eventually.

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PostPosted: Thu May 10, 2018 10:07 pm 
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Thanks for the motivation I need it lol but I forgot to mention the previous owner did buy a new air filter but I might try my high flow air filter that I don’t use for my elite and maybe try to tune that. I also checked the exhaust which the previous owner bought “new” or in other words new to him but it was pretty dang spotless from just looking inside and ran the same with the exhaust off (just a slight bit louder). Has anyone heard of someone who’s had a petcock clog?


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PostPosted: Thu May 10, 2018 11:24 pm 
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Ive had a petcock go bad in couple different ways. No flow, constant flow and the ever frustrating (and toughest to diagnose) intermittent flow. Ive never had restricted or partial flow but its not impossible. A dirty fuel filter would create the situation you describe..also a gummed up (or kinked/damaged) fuel line.

How old is the fuel? Check compression?

You’ll only fail if you stop trying. Keep going.

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PostPosted: Fri May 11, 2018 9:47 am 
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Fuel starvation, it will normally go to top speed immediately, then stumble down.

You're describing a lean carb at 3/4 to WOT. You need to check the condition of the main jet and emulsifier tube. I'm betting one or both are partially clogged, or main jet's not correct for the application.

Other things to check are clogged exhaust and over-oiled intake filter (wring it out with clean paper towel until you can't get any more oil out.)

Also check condition of plug cap. On most, you can unscrew the cap, trim 1/4" from end of wire, and screw back on. I've had this create goofy issues in past.

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PostPosted: Fri May 11, 2018 11:39 am 
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Meatball wrote:
Ive had a petcock go bad in couple different ways. No flow, constant flow and the ever frustrating (and toughest to diagnose) intermittent flow. Ive never had restricted or partial flow but its not impossible. A dirty fuel filter would create the situation you describe..also a gummed up (or kinked/damaged) fuel line.

How old is the fuel? Check compression?

You’ll only fail if you stop trying. Keep going.


I dumped the fuel when I got it and have ran about one and a half fresh tanks through it. I have heard that some gas tanks sometimes have a fuel filter at the very bottom of the tank have you heard of one of those being on a moped?


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PostPosted: Fri May 11, 2018 11:53 am 
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noiseguy wrote:
Fuel starvation, it will normally go to top speed immediately, then stumble down.

You're describing a lean carb at 3/4 to WOT. You need to check the condition of the main jet and emulsifier tube. I'm betting one or both are partially clogged, or main jet's not correct for the application.

Other things to check are clogged exhaust and over-oiled intake filter (wring it out with clean paper towel until you can't get any more oil out.)

Also check condition of plug cap. On most, you can unscrew the cap, trim 1/4" from end of wire, and screw back on. I've had this create goofy issues in past.


The carburetor is new and acts the same exact as the stock one which I cleaned two times so I don’t think it’s clogging anywhere in there (I made sure the emulsifier tube was clean on the stock too). Otherwise the exhaust and intake filter are checked and fine. But my question is, what would be characteristic of if those plug cap wires were junky like you said?


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PostPosted: Fri May 11, 2018 12:24 pm 
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If you're getting lower revs at full throttle than half throttle it's maybe a too rich, or too lean problem at WOT. Did you try to move the needle in the slide up or down? Personally, I'd see what happens without the air filter. Did you check the reed valves?


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PostPosted: Sun May 13, 2018 9:47 pm 
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kingdele wrote:
The carburetor is new and acts the same exact as the stock one which I cleaned two times so I don’t think it’s clogging anywhere in there (I made sure the emulsifier tube was clean on the stock too). Otherwise the exhaust and intake filter are checked and fine. But my question is, what would be characteristic of if those plug cap wires were junky like you said?


Checking the wire would literally be faster than me explaining the possible running issues. Just do it.

"New" carb... new from Yamaha, new Chinese, new to you (used?) You checked the size of the main jet... right? B/c that's one of the things you check on a replacement carb...

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PostPosted: Wed May 16, 2018 7:33 am 
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noiseguy wrote:
kingdele wrote:
The carburetor is new and acts the same exact as the stock one which I cleaned two times so I don’t think it’s clogging anywhere in there (I made sure the emulsifier tube was clean on the stock too). Otherwise the exhaust and intake filter are checked and fine. But my question is, what would be characteristic of if those plug cap wires were junky like you said?


Checking the wire would literally be faster than me explaining the possible running issues. Just do it.

"New" carb... new from Yamaha, new Chinese, new to you (used?) You checked the size of the main jet... right? B/c that's one of the things you check on a replacement carb...


It’s a new carb exactly how I said and yes the main jet is the exact same. I think it’s a Chinese but I looked it over and it’s very well built and they included all the connections and assemblies to replace instead of use the old parts.


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PostPosted: Wed May 16, 2018 1:51 pm 
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Wait... issue followed from old carb to new carb? So that's not the issue then.

Did you check the electric / spark? New plug, etc? It has to be either the electrical system or the exhaust.

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PostPosted: Sat May 19, 2018 7:41 pm 
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noiseguy wrote:
Wait... issue followed from old carb to new carb? So that's not the issue then.

Did you check the electric / spark? New plug, etc? It has to be either the electrical system or the exhaust.


Yes, and I have put in a new plug.


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PostPosted: Sun May 20, 2018 7:46 am 
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Greetings:

Coming late to this, sorry. I don't see that you have performed a compression check anywhere? The condition of the crank seals - one is hidden behind the flywheel, is open to question. If a little weak, it might idle just fine but leak as the pressures rise with higher output conditions.

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PostPosted: Sun May 20, 2018 10:14 pm 
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Wheelman-111 wrote:
Greetings:

Coming late to this, sorry. I don't see that you have performed a compression check anywhere? The condition of the crank seals - one is hidden behind the flywheel, is open to question. If a little weak, it might idle just fine but leak as the pressures rise with higher output conditions.


So by this theory the compression is low but the increased force at full throttle causes a more dramatic drop in power than when using 1/2 throttle in regard to rpms? And yes, I have been meaning to compression test it but I really didn’t think it was that because it idles perfect so I guess I gotta go borrow one (I don’t own a compression tester).


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PostPosted: Tue May 22, 2018 9:21 am 
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I always forget about the bottom end seals... yes those can definitely cause issues if they're worn out. You need to inspect them though... this is bottom end compression and so measuring top end (I don't think) will show the issue. Expect you'll be looking for evidence of oil leak around bottom end seals as the indicator of failure.

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