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Post by sweden on Sept 6, 2011 8:39:38 GMT -5
Hi,
Well, I have had a pretty good summer of riding, sorted my bogging and other issues out in spring and have really been enjoying my scooter and having rides out.
The other day I rode into town for an appointment and the scoot was running as well as it has been but when I came out of the appointment, I started the scooter just fine, I got onto ride off and when I opened the throttle it just died down, it doesn't pick up and die down, it just dies!
I have plenty of petrol in the tank, I have cleaned the air filter and none of that has helped, I did notice today when I went to try it again that I could wind the a/f screw all the way to the right and it didn't cut out. I have a glass fuel filter and I can see that is filling.
Anyone have any idea what is going on here, I didn't go over any bumps, drop the scoot it just started happening after running fine.
I have the 139 qmb engine.
Any ideas or help, as always, greatly appreciated........I should be an expert by now!!!
Thanks folks.
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Post by Pony66 on Sept 6, 2011 8:50:26 GMT -5
Many people will say go right to a valve adjustment. It needs to be set at first and a good thing to check every 1000 miles or so.
I had the same symptoms once due to a clogged main jet in the carb. Another scooter I accidentally made a small hole in the diaphram on top of the carb. They would idle all day but die if you hit the throttle.
Black fuel lines will degrade from the inside out. A bit of rubber melts, comes loose and travels to the carb. It gets sucked into the main jet and when the bike cools, it hardens into a blockage. So people drive somewhere and come out to a scooter that suddenly wont run.
And it could be the valve lash is too tight. You drive somewhere and the valve gets hot and expands. The valve sticks and next time you cannot get it to start. But you said it starts and idles fine so I would clean the carb first.
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Post by sweden on Sept 6, 2011 9:06:12 GMT -5
Hi pony66, I did check the diaphram and it was seated fine with no tears. so I eliminated that. I will whip the carb off and check the jets. I lashed the valves in the spring (late spring as it doesn't really reach spring in sweden until early May) so I don't think it will be them.....just yet......or? The thing that is stumping me is that I can wind the AF screw all the way in without the tickover changing?  ?? I'll do that carb tomorrow and report back, thanks for the reply.  |
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Post by Beachy on Sept 6, 2011 12:11:40 GMT -5
Swede, also check your spark plug or better yet swap it with a new one.
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Post by relaxinrob on Sept 6, 2011 19:51:07 GMT -5
sounds like too much air is getting to the carb. airbox cracked??
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Post by mainepeace on Sept 6, 2011 20:01:36 GMT -5
The valves can loosen (or even tighten) up even with a recent setting. It depends on how careful you were when setting the valve lash the last time. If you don't tighten the nut enough it can work it's way loose. Also, if you don't re-check the lash AFTER everything is tightened down again it may be set improperly. As you tighten the nut the retaining bolt is compressed slightly, loosening the lash by up to .001", depending on how much you torque it. Also, the "feel" of the gauge, or how loosely it will move is subjective, so when one person sets the lash to .004" it may actually be .0045" to someone else.
Greg
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Post by sweden on Sept 7, 2011 6:51:57 GMT -5
Thanks for all the suggestions guys, I will whip the plug out and check it, although that was new in the spring too, but I will take a look.
I was thinking it must be too much air getting in as I could wind the af screw all the way in but nothing visible on the box, so I will check the rubber tube between the carb and airbox.
I will also check the valves, but I have done them several times and been bitten by not checking them afterwards before so I always check after resetting, but you are right they could have worked loose.
It is a very rainy day here today and I don't have any covered space to work in, but as soon as I get onto it, I will report back.
Once again, thanks for taking the time to reply to my post.
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Post by keetarider on Sept 7, 2011 11:55:22 GMT -5
No rpm response from an adjustment of the A/F mix screw, often times indicates clogged jets.
You can also screw it too far out and loose the o-ring or spring placement. Screw it in too far not good either.
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Post by sweden on Sept 8, 2011 4:17:43 GMT -5
Hi folks,
Well, I took the air box off and checked for cracks, leaks and there was nothing obvious,.
I removed the carb and cleaned the jest but once again they were visibly clear, I blew them all out, along with all the other ports and put the bike back together.
I pulled the plug and it was dry fouled, sooty, so I cleaned that up and replaced it....this suggest running rich on fuel, which would back up the theory of an air leak.
Anyway, the bike runs much better with slight bogging at WOT, so I guess my next step is to redo my valves...right?
As always, thanks for the help, I really appreciate that there is a forum and folks like you out there.
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Post by sweden on Sept 8, 2011 6:32:55 GMT -5
Just been out on the bike to the shops and it is back at dying with acceleration........again!!!!  |
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Post by Beachy on Sept 8, 2011 10:30:46 GMT -5
Swede, do you have a spare spark plug? It's worth a shot, they do foul pretty easily and can cause those symptoms. I can buy NGK's here at the auto parts store for $2.50, I'm sure they're more in Sweden, but you should keep a spare just for troubleshooting purposes.
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Post by mainepeace on Sept 8, 2011 22:34:58 GMT -5
I buy spark plugs 20 at a time. Can never have enough spark plugs. But then I go through that many a week.
Greg
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Post by nhaven on Sept 8, 2011 23:07:44 GMT -5
Sweden, did you check the ignition coil where the spark plug terminal plugs into. I had the same problem as yours about a month ago. Turned out that part of the coil was bad/loose. Got a new coil and problem solved.
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Post by sweden on Sept 9, 2011 2:36:16 GMT -5
$2.50 for a spark plug...wow! I paid 69 krona which is about £6.50 (sorry, being English I always convert to sterling first) so that is about 10 dollars!!!
I will get another spark plug and try it and check back at the coil too.
Thanks for the tips guys, I'l let you know how it goes.
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Post by norrland on Sept 16, 2011 16:49:47 GMT -5
hi fellow swede and everyone else of course, I have the exact same problem ... no rpm response at all when turning the A/F mix screw, I can turn it all the way in and there´s no rpm difference whatsoever, tomorrow I´m gonna take the carb. down in bits and pieces and see if I can find any solution. plz let me know if you managed to solve this problem, as so will I cheers |
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Post by skuttadawg on Sept 16, 2011 20:56:58 GMT -5
It could be clogged jets if stock there are tiny and clog easy . You could have gas that had water in it . I had that happen to me once , it ran good then sputtered and died . Try to get gas that does not have ethanol in it if you can gt it . Ethanol absorbs water and is a stupid idea to ad to gasoline .Another example of stupid government bs . Installing larger jets helps alot too
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Post by edfr on Sept 16, 2011 21:21:11 GMT -5
Check you Vacumm hose going to the PETCOCK it could be the Petcock is allowing fuel to be SUCKED in through the Vacumm line and would cuase your problem. And that would also be the reason that it does not shut the engine off when you turn the Fuel Ratio screw all the way Clockwise. So it would cause all your symptoms because of the extra fuel being sucked in through the Vacumm line.
Easy enough to test and see if the Petcock is allowing fuel to flow through the Vacumm Line. You could suck on it and get fuel in your mouth, or just take it off and see if it is wet.
Or if you have a kitchen Baster those are the ones with a rubber ball on the end of them to pick up juices from a pan and then squirt it on a turkey in the oven. Good to have one around to also use to squirt gas into the Manifold through the Vacumm line.
Lefty
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Post by rider95 on Sept 16, 2011 23:33:02 GMT -5
thats why we put clear vacum lines on so you can see if your getting gas into your manfold from your pitcock , try taking your plug out and then turn the motor a few times this will pump any gas out then see if it runs better
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Post by norrland on Sept 18, 2011 15:00:48 GMT -5
cant find anything wrong with this carb. everything is according to schoolbook.....I simply give up, gonna order me a new one (none vacuum), dellorto 19mm black edition perhaps, you guys think that 19mm will go well with my setup ?
72cc cylinder + head + race cam
removed plug from air filter
malossi multivar variator
leovince exhaust
malossi sport clutch + bell
+ no restrictions left to remove
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Post by agdcougar on Sept 21, 2011 20:51:21 GMT -5
Check you Vacumm hose going to the PETCOCK it could be the Petcock is allowing fuel to be SUCKED in through the Vacumm line and would cuase your problem. And that would also be the reason that it does not shut the engine off when you turn the Fuel Ratio screw all the way Clockwise. So it would cause all your symptoms because of the extra fuel being sucked in through the Vacumm line. Easy enough to test and see if the Petcock is allowing fuel to flow through the Vacumm Line. You could suck on it and get fuel in your mouth, or just take it off and see if it is wet. Or if you have a kitchen Baster those are the ones with a rubber ball on the end of them to pick up juices from a pan and then squirt it on a turkey in the oven. Good to have one around to also use to squirt gas into the Manifold through the Vacumm line. Lefty Did this ever get resolved? I was going to say, when I first picked up my junk scoot, we discovered the problem when one hose was plugged with a screw and the second went to the petcock valve. After installing the t, she has worked. |
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Post by nougat on Sept 23, 2011 4:16:45 GMT -5
I had exactly this symptom, and it ended up being lean for a combination of reasons, the largest of which was a leaking intake o-ring and bad vacuum hoses. Replaced the o-ring with one from the hardware store. The vac hoses attached to the intake ports were essentially melting and would slide right off, so I replaced that with 3/16" fuel hose.
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Post by norrland on Sept 25, 2011 14:14:51 GMT -5
well I did the petcock test suggested in this post and I didnt get any gas in my mouth, also sprayed starter gas all around the carb to check for air leaks, but nothing,...... anyways I got tired of this vacuum carb and got me a 19mm dellorto black edition....havent had time to install it yet though.
will install it this coming weekend, I can post progress and results if wanted.
cheers for all the replies and help
//Patrick
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Post by sweden on Feb 28, 2012 5:15:57 GMT -5
Hi All, I never got my problem fixed due to the weather getting wet and cold so I just covered up the scoot for the winter. I got myself a new plug today and have had the battery on trickle charge for five days now, so I am hoping to get it together today (now we finally have plus temps and no snow) and am hoping it was a dodgy plus, but I will report back, hopefully with a result!
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Post by terrilee on Feb 28, 2012 10:20:46 GMT -5
vacum, vacum, vacum
but im NOT a mech
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Post by sweden on Mar 1, 2012 7:03:28 GMT -5
OK, I replaced the plug, a kind of bit of wishful thinking, but that made no difference, so I got my old carb (one I replaced a while back that I don't think was faulty) and swapped the diaphragm over, that didn't help, so I took the carb off and replaced the jets with my old ones, tested the petcock with the suck on the carb manifold tube, that was fine, put it back together and after a bit of fiddling with the A/F seems to be running fine now, went for an hours drive, a few flat spot but I think that is down to the A/F adjustment and the fact it is cold and damp today.
Anyway, I am going to put it down to jets being blocked, even though I had cleaned the old ones and they seemed fine....could of course been a sticky petcock and me sucking on it helped unstick it....could that happen?
Anyway, for now we are running again. Cheers for all the tips, as always.
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Post by mainepeace on Mar 1, 2012 13:42:27 GMT -5
The jets could be clear but the passageways blocked. Glad you got it running! Albeit many months later. You're on the homestretch!
Greg
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