KymcoForum.com
General => Technical | How To => Topic started by: MN_Scoot on June 12, 2014, 12:09:25 AM
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I solved my last stalling problem when I realized the carb had loosened from the intake. Tightened it up again and it ran great for about a week.
Now, I have the same symptoms, even though the clamp is now tight. Everything runs great for about the first 3-4 miles. Then, I can feel it start to lose power and if I approach a stop light, it dies as I'm slowing down. I can always get it started again by holding the throttle open all the way like you would for a flooded engine. Could the engine be flooding itself as I drive?
It often seems to happen on straight-aways with full throttle (after the first 3-4 miles). Not sure if this is a red herring, but it also doesn't seem to happen at night when it's slightly cooler.
I somewhat suspect the choke needs to be replaced since the problem is somewhat sporadic. -it also won't start in the morning without me holding the throttle open a bit for the first 2 minutes before it will idle on its own.
This problem developed after the following maintenance completed a month ago:
cleaned carb/jets (added new gasket and o rings)
adjusted valves
new fuel filter
new air filter
new spark plug
adjusted idle to rpm spec in manual
Appreciate the help!
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It does sound like the choke is sticking part way open. Not enough for a cold start but enough to make running difficult. Pull it out and check it. It MUST move at least 4mm.
OR it could be cracks in the rubber boot that attaches the carb to the intake manifold. That would create an air leak, and lean running. The throttle being held wide open will allow more fuel thru the main jet allowing it to start.
An easy way to tell is pull the spark plug, and see if it is black or white.
Black for a bad choke, and white for a leaking boot.
Could be a few more things like a bad float level but I suspect these first.
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ok, yeah, I read somewhere else about checking the choke, but I didn't know what "checking" entails. I've seen mentions of checking distance and electrical resistance, but didn't exactly understand how to go about doing it.
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Automatic Enricher Operation (10x Speed) : Choke Bypass Bystarter (http://www.youtube.com/watch?v=O2qRVOkfdaY#ws)
You pull it out of the carb. (two tiny phillips screws, and a C shaped retainer).
Leave it plugged into the harness, and turn on the key. It takes about 90 seconds to 2 minutes to fully extend (4mm minimum). If it is not moving verify there is 12 volts across the yellow, and green wires.
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Perfect, thanks Zombie. …I almost felt inappropriate watching that clip at work. :-\
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Yeah... It got me too. Ive never seen anything grow that fast. (Zombie curse)
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I solved my last stalling problem when I realized the carb had loosened from the intake. Tightened it up again and it ran great for about a week.
Now, I have the same symptoms, even though the clamp is now tight.
The answer is so simple, you'll fall off your chair. All qmb139 engines have the same problem. The intake manifold has an O-ring between the manifold and the head. The stock O-rings are cheap neoprene and they go flat from the temperature. The result is a tiny air-leak, and your scoot won't start or idle properly. Replace the O-ring. If you live in a big city, look for Viton (heat resistant) O-rings at an industrial supply shop. Cost: maybe $1 You'll have to replace the O-rings every 5000 miles or so forever, so buy several at a time.
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The answer is so simple, you'll fall off your chair. All qmb139 engines have the same problem. The intake manifold has an O-ring between the manifold and the head. The stock O-rings are cheap neoprene and they go flat from the temperature. The result is a tiny air-leak, and your scoot won't start or idle properly. Replace the O-ring. If you live in a big city, look for Viton (heat resistant) O-rings at an industrial supply shop. Cost: maybe $1 You'll have to replace the O-rings every 5000 miles or so forever, so buy several at a time.
Hmmm, I'm about at 8,000, so I will give that a try as well. Thanks.
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Check that "bako-lite" spacer for cracks, and warping. Also check the rubber manifold when you have it off. They all eventually crack/leak.
I have a link to an aluminium spacer, and a cure for the sh** manifold if you find they are an issue.
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Check that "bako-lite" spacer for cracks, and warping. Also check the rubber manifold when you have it off. They all eventually crack/leak.
I have a link to an aluminium spacer, and a cure for the sh** manifold if you find they are an issue.
Yeah, would definitely like to see links for future reference. Thanks.
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On this page, there's two different gaskets, an O-ring and the entire intake all claiming to be for QMB139 engines. I didn't think we needed that grey or black gasket...
http://www.partsforscooters.com/151-7-Carb-Gasket (http://www.partsforscooters.com/151-7-Carb-Gasket)
Are there different versions of QMB139 engines?
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The one you linked I THINK is the OEM plastic type. Its hard to tell from the Pict.
This is the one I use on all the conversion engines I build...
http://www.racingplanetusa.com/intake-manifold-spacer-naraku-flow-aluminum-milled-139qmbqma-p-5390-1.html?cPath=7534&sessID=2642caa5d879b95abc6dce8485fff653#.U5-1XtTbzl8 (http://www.racingplanetusa.com/intake-manifold-spacer-naraku-flow-aluminum-milled-139qmbqma-p-5390-1.html?cPath=7534&sessID=2642caa5d879b95abc6dce8485fff653#.U5-1XtTbzl8)
Sucks it has to be from RP of all places...
Start a dealer account under whatever company name you want. You don't need the TAX ID number because you will be paying sales tax on every purchase. It makes the parts like 40% off for most items. Electronics have less of a discount.
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Check that "bako-lite" spacer for cracks, and warping. Also check the rubber manifold when you have it off. They all eventually crack/leak.
I have a link to an aluminium spacer, and a cure for the sh** manifold if you find they are an issue.
Thanks for all the info Zombie. Going to open it up again tonight. You think intake cracks will be immediately obvious or can they be hidden?
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You'll see it. That spacer usually comes out in pieces. If it is whole, and nothing obviously wrong I would take a piece of 100 grit sandpaper, and use a flat surface to block sand it. That will show/correct if it is warped.
Two new O rings, ans a little Indian Shellac will seal it up. Don't use that RTV crap.
Also check real close on the rubber intake for cracks. That is the next weak link.
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Two new O rings, ans a little Indian Shellac will seal it up. Don't use that RTV crap.
Also check real close on the rubber intake for cracks. That is the next weak link.
I didn't even think of a sealant…I looked that stuff up and it said it's for low temp applications (350 max). That area won't exceed that?
Also, do you put the sealant on both sides of the spacer? Do you put it over the seated o-ring as well or just a little around it?
Appreciate all the help. Hopefully someday I'll send it the other direction, but I clearly have a lot of Jedi training to go!
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I just use a bit on my fingers, and smear it on the O rings. It sort of glues them in place during assembly.
The Temp. thing don't matter. What happens is if it is tooo hot for the sealant it liquefies which is actually what you want. I use it for everything on all types of engines.
Don't worry about Paying it forward/backward. Just post up some random sh**, and people will believe anything you say.
Thats how I got 10K posts....
https://www.youtube.com/watch?v=ObiSnfUNqvw (https://www.youtube.com/watch?v=ObiSnfUNqvw)
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I just use a bit on my fingers, and smear it on the O rings. It sort of glues them in place during assembly.
The Temp. thing don't matter. What happens is if it is tooo hot for the sealant it liquefies which is actually what you want. I use it for everything on all types of engines.
Don't worry about Paying it forward/backward. Just post up some random sh**, and people will believe anything you say.
Thats how I got 10K posts....
https://www.youtube.com/watch?v=ObiSnfUNqvw (https://www.youtube.com/watch?v=ObiSnfUNqvw)
Thanks man, for the feedback and for that very touching music video. sniff sniff. ;D
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LOL. I forgot I posted that.
This is much more appropriate...
https://www.youtube.com/watch?v=Vk2xM_YuP2o (https://www.youtube.com/watch?v=Vk2xM_YuP2o)
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Ugh! This problem is going to be the end of me.
Over the weekend, I took off the intake, lightly sanded the spacer, put in new o-rings in the spacer and intake and went to a friends house about 20 miles away. Thought everything was great until about mile 15, I hit a hill and it started doing the lose power and stall out thing (I usually feel a slight surge or two while this happens). I let it sit for a minute os so, did the full throttle start (as you would for flooded engines) and it started up again. It again stalled out 2 more times in the last 5 miles.
Going home was fine uphill or whatever for the first 10-15 miles, then it stalled again.
Glad I replaced the o-rings b/c I think they still needed it. Was about to order a new carb, then I read a bunch of forum posts where people stalled after quite a few miles/hills and it keeps pointing to valve adjustment. Sound right?
I just adjusted them about 300 miles ago, so was ruling that out, but maybe I was off a little…used the .04mm feeler gauge.
Any other ideas/things I should check while I'm in there and before I seal it all up again?
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Did you ever check the auto choke?
I have also had a bad petcock that was dumping fuel into the vacuum line. The petcock is like 9 bucks at partsforscooters,com There are a few different ones so be sure to order the correct one
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Did you ever check the auto choke?
I have also had a bad petcock that was dumping fuel into the vacuum line. The petcock is like 9 bucks at partsforscooters,com There are a few different ones so be sure to order the correct one
I tried by just measuring with the ignition turned to on and there was no movement at all for the total 6 minutes. Do I have to hook to the battery directly?
I also could not do the resistance test because I could not get to the choke's plug end without taking off my rear body panels since it was so far tucked back which I didn't have time for that day.
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That may be your entire problem then.
You can order a new choke on ebay or partsforscooters.com It's just a few bucks. Make sure you have 12 volts going to it first... A test light will do because the resistance check wont tell you anything. That pin MUST move 4mm or better otherwise it is constantly flooding. The warmer the engine gets the more the flooding is affecting it.
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That may be your entire problem then.
You can order a new choke on ebay or partsforscooters.com It's just a few bucks. Make sure you have 12 volts going to it first... A test light will do because the resistance check wont tell you anything. That pin MUST move 4mm or better otherwise it is constantly flooding. The warmer the engine gets the more the flooding is affecting it.
Hmm, ok. I just didn't know if only turning the key to "on" was sufficient…read elsewhere that people were hooking the plug of the choke directly to the battery. Do you know if the way I tested would be sufficient? -I assumed testing with the scoot actually running would make gas spurt from the port I just pulled the choke out of. Sorry for the newb questions.
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Just pull out the choke, and turn on the key. IF it is getting power it will move the pin slowly. The only reason to hook it direct to the battery is if there is NO power to the choke, and you need to verify it is working.
Even if it is moving you want to be SURE it moves at least 4mm.
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New pieces to the puzzle...I just opened it up again after letting it sit immediately after the last stall out which happened again at WOT.
The plug was pretty white and the fuel filter was empty. Will check the valves again shortly, but does this rule out a choke problem? I can't get to the choke plug without taking off the body panels...I'm just getting sick of removing and replacing those panels every time something goes wrong :-\
Does the empty fuel filter point to a petcock or vacuum issue?
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To your last question YES.
A white plug means it is running too lean. New guess is either a leaking vacuum line, a bad petcock, or a clogged up fuel screen in the tank. Easiest solution is order a new petcock, and some vacuum tubing.
Pull the screen out of the tank. Be sure it is clean, and replace the petcock, and vacuum line. They are all cheap parts, and you might just find it is a loose or worn thru vacuum line but having the petcock on hand for when it does fail will be a blessing.
I feel your pain on the plastics. One of my bikes has none. I tore them all off for the very reason you stated., and ride it as a bare frame. The second bike I fiberglassed all the plastics together into a one piece shell that simply lifts off. You can do without a lot of the screws that hold yours together, and Zip Ties make for a perfect quick connect system for broken tabs. Just drill matching holes. No one ever see's them if you do it right.
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To your last question YES.
A white plug means it is running too lean. New guess is either a leaking vacuum line, a bad petcock, or a clogged up fuel screen in the tank. Easiest solution is order a new petcock, and some vacuum tubing.
Pull the screen out of the tank. Be sure it is clean, and replace the petcock, and vacuum line. They are all cheap parts, and you might just find it is a loose or worn thru vacuum line but having the petcock on hand for when it does fail will be a blessing.
I feel your pain on the plastics. One of my bikes has none. I tore them all off for the very reason you stated., and ride it as a bare frame. The second bike I fiberglassed all the plastics together into a one piece shell that simply lifts off. You can do without a lot of the screws that hold yours together, and Zip Ties make for a perfect quick connect system for broken tabs. Just drill matching holes. No one ever see's them if you do it right.
Thanks Zombie,
Will order some parts today. Was hoping to avoid buying a new carburator, but I'm getting so tired of weekly break-downs, I'm thinking of ordering a new carb as well to hopefully be done with this. Pretty soon, I'll have a brand new scoot I built piece by piece! ???
Another puzzle piece, I just disconnected the hose going to the intake at the T and sucked on the end of the T and I couldn't suck air through it.
Couple of follow-up questions to your post...How do you get to/clean the in tank fuel filter you mention? I checked youtube, these forums and the service manual, but couldn't find instructions.
Also, do you need to use that white thread seal tape or anything when attaching a new petcock to avoid leaks?
Thanks again!
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If you can't suck air it is pretty sure but not positive you don't have a vacuum leak. I'd replace the vacuum line anyway. Inside the petcock is a diaphragm that can jam up. Sometimes it jams just enough to partly block fuel, and make for lean running.
When you replace it do NOT use teflon tape. There is a pretty thick rubber washer that seals it up. When you remove the petcock thew washer will usually be stuck in the tank side. Use a tiny screw driver or whatever to pull it out. Same thing for the tank screen. It is pushed up inside the tank. Just pull it down/out w/ whatever tool you have.
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If you can't suck air it is pretty sure but not positive you don't have a vacuum leak. I'd replace the vacuum line anyway. Inside the petcock is a diaphragm that can jam up. Sometimes it jams just enough to partly block fuel, and make for lean running.
When you replace it do NOT use teflon tape. There is a pretty thick rubber washer that seals it up. When you remove the petcock thew washer will usually be stuck in the tank side. Use a tiny screw driver or whatever to pull it out. Same thing for the tank screen. It is pushed up inside the tank. Just pull it down/out w/ whatever tool you have.
Cool, yeah, I will replace all the lines to help rule everything out.
Was looking for new petcocks online. I saw in an older post you recommended partsforscooters.com for petcocks. I looked and they all seem to be in the 150cc pages. This was the closest in resemblance to what I have, but again, in the 150cc pages. Does this looks like it would work for a 50cc Agility? http://www.partsforscooters.com/129-25_Bolt-on_Fuel_Valve (http://www.partsforscooters.com/129-25_Bolt-on_Fuel_Valve)
...Or should I go to the dealer and pay big bucks to be sure it's correct?
Thanks man!
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I have perhaps 6-7 petcocks that don't fit anything. The thread sizes are all different on these stupid things.
QAs I recall I called PFS, and the girl on the line was the biggest help in knowing which one fit.
I think the one you linked is correct. Kymco does NOT use larger petcocks until you get to the 250cc bikes.
Point is I would call, and ask. If there is still a doubt order two, and join the "We have many petcocks" club. (WHMP). Meetings Mon., and Fri. Ramada Inn, Crawfordville.
In case you are interested the Dark Side meetings are Tues., and Thurs. but you have to bring treats. Most of us like cup cakes or Taffy.
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Most bikes won't turn the choke off just by turning the key in. To test reliably take the by starter out and hook up to a battery work alligator clips. Should extend all the way in like a minute or two.
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SOLVED: I readjusted the valves (they were just a little loose so probably a red herring), changed the fuel line and changed the petcock and no more stalling!
To add to the knowledge base, here is the petcock/fuel valve switch that fit my 2007 50cc Agility: http://www.partsforscooters.com/164-93_Bolt-on_FUel_Valve (http://www.partsforscooters.com/164-93_Bolt-on_FUel_Valve)
Thanks again everybody for all the help. Even when I didn't hit the problem, I preemptively replaced some stuff that needed replacing soon.