hardleydavidson Posted June 30, 2014 Posted June 30, 2014 Hi,I've been having running issues for a while now (as I posted previously) and now it's got to the point where I am completely gazumped.The problem:50cc 4-stroke.Bike starts on the choke then dies. Repat this 3 or 4 times and it starts and ticks over. Put it into first and it dies. repeat this about 2 times and it starts and can pull away in first albeit sluggishly. It'll get me to the end of the road and either slow down and die or die when the bike stops. It won't start again for a minute or so then it starts and will get me about the same distance again before dying.What I have tried so far (bear in mind some of these may be irrelevant and tried trough desperation). Checked the spark plugChecked compressionChanged the air filterCleaned the carbChecked the jetsChecked the linesChecked the petcockChecked the fuel filterChanged the fuelChanged the OilInstalled new batteryChecked the chain tensionChecked the tyre pressureAdjusted the mix screwAdjusted the idleChecked for leaksChecked exhaustKicked it a few timesSworn at it several timesPushed it lots Now I'm far from being an expert but I get the feeling that it's just running on the fuel from the carb bowl which would indicate that the fuel flow to the carb isn't fast enough. This makes no sense as I've blasted the float valve hole, the fuel line and the petcock with compressed air and the are all clear and fuel flows freely out of the carb if you take the bowl off. The plug is white indicating that it's starved of fuel which would make sense if the bowl runs dry.Now it could have been a vacuum issue but I ran it without the cap seal and still had the same issue.It's now driving me insane, I will have to stop four or five times just to get home from work.Anyone have any ideas?????? Quote
acting_strange Posted June 30, 2014 Posted June 30, 2014 You may need to check the float level...also it could be sticking....take the carb off and make sure... Quote
eastanglianbiker Posted June 30, 2014 Posted June 30, 2014 also is it a vacuum type fuel tap?as that might have hole in hose from engine to fuel tap Quote
hardleydavidson Posted June 30, 2014 Author Posted June 30, 2014 Float is ok, checked it yesterday, moves freely. Float level is right too.Fuel tap is gravity fed and screws straight in to the tank.I'm wondering could it be valve clearances causing not enough suction through the carb to draw the fuel up??? Quote
Mr Fro Posted June 30, 2014 Posted June 30, 2014 Doubt it'll be the valves if the compression is okay.Have you checked the fuel level? Just because the float level is right doesn't always mean the fuel level in the carb bowl is correct.There should be a nipple on the bottom of the carb with a drain screw and also a mark on the side of the carb as a reference point. Connect up a bit of clear tube to the nipple and tape the other end to the side of the carb. Open the fuel tap then the drain screw until fuel starts to fill the tube. Try not to wiggle the tube as it might give you a false reading.Measure the distance from the reference point to the fuel level and see what it's like in comparison to the manual.You can also get the engine running and see whether the fuel level is stable or if it fluctuates.Oh, how did you measure the float - with the valve closed but before the float compresses the spring?Also, sorry if I'm, telling you how to suck eggs! Got to add that I've just read the manual and it's bloody hilarious! Quote
hardleydavidson Posted June 30, 2014 Author Posted June 30, 2014 I used the very pigeon english manual which said to measure the distance between the top of the float and the top of the bowl chamber, didn't mention springs.I'm going to try that pipe idea although I'm not sure it has any markings on the outside, the carb is a pz19There just doesn't seem to be any earthly reason that fuel wouldn't get into the carb. Also, if it starts ok but then dies does it indicate a slow fuel flow rather than a low level on the bowl from an incorrect float?? Does the float maintain the fuel level?? Another thing to add would be it seems to get a bit better the longer I ride it, a half hour jaunt and it's almost ok. Stop for five minutes and it's back to the stop/start/stop shinnanigans. Quote
Mr Fro Posted June 30, 2014 Posted June 30, 2014 I've had a rummage around and can't find anything about a fuel level reference on your carb but I did find a reasonable how-to guide (I'm very busy at work today )http://www.allthingsmoto.com/forums/f-15/how-set-your-motorcycle-carburetor-float-level-more-commentary-13608The end of the first post is the bit that you need although I wouldn't measure the distance with the carb upside down as it'll compress the spring that's in the needle (you can't see it but it's in there!) I hold mine so the float is off of the needle and slowly rotate it until the float tang touches the needle and makes it close without pushing in the little pin that sticks out of the top of it (if that makes sense).If your problem gets better as it warms up it really does sound like a lean condition so if you measure it again and find it to be right, you might want to raise it (make the gap between the carb and float bowl smaller) by 1mm and see how it goes. Maybe double check the screw on the side while you're there too. Quote
hardleydavidson Posted June 30, 2014 Author Posted June 30, 2014 Nice one, I'll give it a go tonight Quote
hardleydavidson Posted July 2, 2014 Author Posted July 2, 2014 OK, the carb doesn't have any external markings and the fuel defintitely flows freely in to the carb. I've adjusted the float by 1-2mm and that seems to be a little better. One thing I noticed, which I really should kick myself about is that the throttle needle was set one notch above the middle. I've moved it to one notch below and now have much more power but I'm still having the stop start issue.New carb?? Quote
Stu Posted July 2, 2014 Posted July 2, 2014 sounds like you have messed with the pilot jet too much to me set it to stock setting if you havent already and go from there also check for air leaks around the inlet rubber Quote
hardleydavidson Posted July 2, 2014 Author Posted July 2, 2014 It's already set at stock.Have tried 1/4 - 1/2 turn out, still no joy. Quote
Grumpy Old Git Posted July 2, 2014 Posted July 2, 2014 Have you tried adjusting the mixture screw? You should be able to peak the revs at tickover. Quote
Mr Fro Posted July 2, 2014 Posted July 2, 2014 It's already set at stock.Have tried 1/4 - 1/2 turn out, still no joy.Do you mean and extra 1/4 -1/2 turns out? I can't find the link now but I think I read that it's supposed to be ~2 turns out... Quote
hardleydavidson Posted July 7, 2014 Author Posted July 7, 2014 No 1/2 - 1/4 from stockHaving said that I've made a huge improvement. Have re-set the valve clearances as at TDC the intake valve had no play at all and that's with a cold engine. Have adjusted the throttle needle down another notch and one full turn in on the mix screw.Now the bike starts and idles without dying. Still had the dying issue this morning when I got to the end of the road but the bike didn't feel sluggish like before. Admittedly I dodn't have the choke on but the whole thing feels a lot better.The proof will be on the way home as it's mostly uphill. Quote
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