Poor response at low speed - Must flutter throttle to get moving

[bastardbiker]

Wow!

Before I get into my request for guidance, I'd like to say thank you all for participating in the discussion and making it easy to get information about these scooters. The internet really fulfills its potential in places like this. Keep it up, and I'm happy to be here to contribute whatever usefulness I'm able to.


I purchased an Agility 50 a few weeks ago used but almost didn't go through with it because it had been obviously sitting in the weather so long, and just kinda looked like crap. I had gotten him down to 200 before seeing it in person. I offered $140 and after some hesitation we made the deal. At that price and condition, I was hesitant to even expect it to start at all. It is a 2007 model though, with less than 3k miles on it... Not too shabby when they are selling slightly newer models of the EXACT same scooter in the shop up the street for 1900... 0_0

Here are the problems with it: When we got it, it wouldn't start and I knew the carb we just dinked, full of varnish and junk. It sure was. The kick starter is stuck too and will only move with an insane amount of force. I plan on taking the cover off and seeing what the hell is going on down there... It was covered in stupid stickers and filth. The unpainted plastic parts have been partially bleached by the harsh ultraviolet light of the sun. Going to dye them later. Other than that, the thing seemed to be in decent condition. How bad could it be, right?

In our spare time my friend (who helped me pick it up) and I have been working on the carburetor, cleaning it multiple times. Before the last cleaning, it would idle roughly. Upon dis-assembly, we saw that the pilot jet was clogged again. We tried to get everything looking spotless and after putting her back together again, she idles very well when warm, and will even reach a top speed of around 37-38 mph indicated on flat ground which seems pretty good to me. The CDI epoxy thing has not been cut into yet wither.

The problem is, it is very difficult to get the thing moving from a stop (moreso when cold). When the bike is cold, you have to flutter the throttle a couple of times to get the engine to rev a bit before you give it hard gas. If you try to give it full throttle when the scooter is cold, even at a modest rate of twisting, it will bog down and die.

Once the bike warms up, you can pretty much open the throttle wide open from a stop and it will verrrrry slowwwwly increase RPMs and the bike will crawl forward until the engine RPM starts to move up significantly and get decent acceleration. If I continue to flutter the throttle when warm, I can pull away from a stop faster.

If I flutter the throttle and get the revs up to a moderate level (but not wide open), then let off the throttle, it kind of hangs and returns to normal idle levels quite slowly.


So, in short: Lack of power at low speed. Engine RPMs hang after releasing throttle from modest revving. Idle seems normal. At 25 mph speed or higher, performance seems normal. Top speed is surprisingly high.

My guess is: lack of fuel? I noticed there are a couple of bolts missing on the air cleaner cover... grrr. Think there might be a leak there causing a lean state?

The problem is steady and not intermittent.



And hey, as an aside, what can you guys tell me about switching to a slightly beefier carb on this bike? Something with a manual choke instead of the wacky auto-bystarter? Any tips on how to set that up, or carb models to look for?


Thanks so much for all your help everyone! 

[bastardbiker]

Also, I'm thinking that the crazy cut-off valve contraption mentioned in the service manual might be clogged up with gummy varnish. I think it's sort of under the floorboard near the engine. It has vaccum lines going to it. Should I just replace all my lines too? What are the stock diameters for the hoses... is that printed in the service manual somewhere? Could anyone tell me what the function of this device is, and how it might be tested and/or cleaned?

Thanks again 

[axy]

Also, I'm thinking that the crazy cut-off valve contraption mentioned in the service manual might be clogged up with gummy varnish. I think it's sort of under the floorboard near the engine. It has vaccum lines going to it. Should I just replace all my lines too? What are the stock diameters for the hoses... is that printed in the service manual somewhere? Could anyone tell me what the function of this device is, and how it might be tested and/or cleaned?

Thanks again 

I might enter the business of service manual distribution.
Send me your email by private message.

[glopezz05]

check your variator and weights.  might be worn. 

also, look up the Seafoam thread here...  a couple tanks of gas, each with a cap full of seafoam, may help clear out your fuel system.

good luck.

[blue]

sounds like you almost have it . maybe a better cleaning of all lines and gas tank too or the gas filter put new one in. and maybe a good valve adjustment. if your looking for a new carb try A slder carb one like you see on the 50 dirt bikes they work good. but then you are talking re jeting and a new kind of air filter. also your throtle cable maybe sticking some wear.

[Hoolander2]

My experience has been if there is varnish in the carb then there's going to be varnish in everything else in the fuel delivery system from the gas tank through the hoses, shut off valve, filter, -- everything.  Just cleaning the carb won't do the most good because varnish keeps disolving off upstream and getting to the carb and that'll go on for a long time.  I would agree that if you can keep it running, some tankfuls of seafoam or similar could be the cure.  If you want a really good fast fix though, clean everything. 

Anyway, you've done it some good already.  Keep at it.   

[sparko]

http://www.stadiumyamaha.com/pages/parts/viewbybrand/73/Kymco.aspx

I would start here and see if the fuel system can be helped. or just take everything and clean it. if you pull off the fuel line and the pressure is good when you apply vacuum then the fuel system is ok, as is the fuel cock and the strainer. that strainer is probably full of gunk. or just put a new in-line filter in from the auto parts store.

[Hoolander2]

Oh yes, as to your question about lean condition, the symptom of "hanging" before returning to idle does sound like that.  Look for small air leaks downstream of the carb too. Maybe as simple as a loose clamp or bolt on the intake.  Or as hidden as a bad gasket or missing o-ring in the carb. 

[sticlistul]

The problem is, it is very difficult to get the thing moving from a stop (moreso when cold). When the bike is cold, you have to flutter the throttle a couple of times to get the engine to rev a bit before you give it hard gas. If you try to give it full throttle when the scooter is cold, even at a modest rate of twisting, it will bog down and die.

Sounds like we have the same problem ... but I have it just at first 500 m-1 km max ... or just for 5 min of worming the engine ... after that all is good . I have that problem since I opened the carb for cleaning ... I just don't know what i'v messed up ... maybe the floating thing ?  I don't know what can it be ...

[sidthesloth]

I can't see how old this thread is, but have you checked the diaphragm and slide for correct operation, sounds like the slide might be slow to move.

[greagle]

Picking up some Seafoam tomorrow, I have heard it to many times not to on these boards.  Thanks guys, I am having get up and go situation as well, will post back if it helps or even if it doesn't --> Thanks.