|
|
Post by zakonzakon on Jun 25, 2018 2:41:32 GMT -5
What can cause sputtering at wot? Is happens every few seconds, the scoot is holding the speed but it sputters
|
|
|
|
Post by 90GTVert on Jun 25, 2018 6:00:18 GMT -5
 The main jet may be wrong, usually rich for sputtering. Could be an ignition issue. Loose connection, a component going bad, or weak spark. Use an adjustable gap or HEI tester to see if the spark will jump a big gap. If you don't have either of those, take an old spark plug and bend/cut the ground strap all the way back or off. That makes a big gap tester for the spark to jump. Doesn't even have to be a plug for the engine since it's just used as a tester. It should be able to jump the gap consistently and still be white/blue/violet in color.
|
|
|
|
Post by humanshield on Jun 25, 2018 7:53:23 GMT -5
The post above is the best. But may I also suggest.......
Have you altered your intake in ANY way? (removed anything, cut anything, changed it in any way)
Reason being, I had a similar issue and eventually I found it was due to changing air pressure at the intake and the fact that I had removed part of the intake tube and so when I was at full speed, the engine would gain and lose power as the wind whipped across the intake inlet. But this was more an irritating intermittent loss of power.....not so much a sputtering.
If you mean actually "sputtering", that might be something totally different and more related to Vert's post above.
|
|
|
|
Post by zakonzakon on Jun 25, 2018 14:15:24 GMT -5
The main jet may be wrong, usually rich for sputtering. Could be an ignition issue. Loose connection, a component going bad, or weak spark. Use an adjustable gap or HEI tester to see if the spark will jump a big gap. If you don't have either of those, take an old spark plug and bend/cut the ground strap all the way back or off. That makes a big gap tester for the spark to jump. Doesn't even have to be a plug for the engine since it's just used as a tester. It should be able to jump the gap consistently and still be white/blue/violet in color. Thank you, I tried to lower the needle by one groove, and the sputter is gone, what does that mean,am I running to rich? Should I use smaller jet? |
|
|
|
Post by scooterted on Jun 25, 2018 16:16:37 GMT -5
Lowering the needle (said a different way, moving the clip toward the top of the needle). Leans mixture, typically at part throttle. I would try several smaller jets. Youll likely find some power. Dont go too lean, as thats even worse. 90gtvert has an excellent tuning guide here www.49ccscoot.com/faq/carbtune.html |
|
|
|
Post by GrumpyUnk on Jun 26, 2018 13:05:11 GMT -5
I would have suspected fuel flow problem. Not quite enough flow to keep up with demand, engine sputters, fuel continues to fill float bowl, enough fuel and the level rises a few mm, and then the mix is good to go again.
Semi-proof is leaning out the mix. Leaner mixture demands less fuel, all the time, as resulting by lowering the needle. Lower needle narrows the circle around the needle, between the needle and the I.D. of the jet/emulsion tube. Raising needle widens the circle, or gap, allowing more fuel to flow for a given vacuum level(height of the slide changes with vacuum). Slide moves against spring with linear pressure(more or less), so X.Xmm/Hg vacuum produces UU.Umm of movement of the slide. Narrow needle(moved up) flows more fuel. etc.
tom
|
|
