Engine Trouble Will not Idle, At All!

Lloyde

New Member
Local time
5:25 AM
Joined
Mar 26, 2016
Messages
25
So here are the circumstances that lead to the problem. Just before it started getting real cold last year I was riding my bike and got the engine to run like normal, then about a 1/2 mile from my house I look down to adjust the Air Intake to get more air and run a little smother. As I am looking down my engine gives a POP, and I see the Cylinder Head jump up at me and the engine dies. I do the safe thing and turn around, when I get back home I remove the bots holding the Cylinder Head and find it is is 2 pieces! (see pic) As I have come to understand this is actually a somewhat common occurrence.

After doing research (and waiting for it to get warm again); I ordered a new head and CDI coil, cleaned the piston, cleaned/gaped the spark, and a couple other things

I got the new parts and could not test them for months because it got to cold and snowy/icy. But now it is warm and I was testing the other day. It took a couple minuets but it did start again, yet it did not sound like it used to. When I got to a stop sign I had pulled in the Clutch, released the Throttle to make sure my phone was still in my pocket, and the engine DIES!

I jump off the bike and poke around it with a questioning look, I jump back on and start moving again it starts back up, but the silly thing Will Not Idle, and it takes a while to get started each time.

New (?) problem, trying to start the engine it will sometimes Backfire (?), not sure if that is the right description, but a small white poof of air will sometimes come out of the Air Filter on the Carb.

Any help with this is much appreciated
 

Attachments

  • 1917148_1013635175360836_5741528608680018191_n.jpg
    1917148_1013635175360836_5741528608680018191_n.jpg
    56.7 KB · Views: 194
  • 12910133_1074671039257249_1815775740_n.jpg
    12910133_1074671039257249_1815775740_n.jpg
    87.4 KB · Views: 224
The obvious place to start is to keep tightening the idle screw on the carb until you can find the magic place where the engine will hold an idle.

If the idle screw has no effect then you have a different problem. Could be a fuel line issue, maybe a bad float in the carb, etc.
 
Did you check the new head for flatness? Most can use a little clean up. I tape a piece of sand paper to a flat glass and sand the head surface in a circular motion, its surprising how untrue a head can be. I do this to the cylinder and head before I ever install the engine. All heads are not the same, some have squish bands and some don't. The former runs a lot more efficient.
 
Did you check the new head for flatness? Most can use a little clean up. I tape a piece of sand paper to a flat glass and sand the head surface in a circular motion, its surprising how untrue a head can be. I do this to the cylinder and head before I ever install the engine. All heads are not the same, some have squish bands and some don't. The former runs a lot more efficient.

Hmm, now that you mention it the new head did have a couple of indents on the area that should seal onto the Cylinder Head. I'll have to try the sandpaper trick, what grit sandpaper did you use?

If the idle screw has no effect then you have a different problem. Could be a fuel line issue, maybe a bad float in the carb, etc.

No fuel line issue, the Carb works perfectly (other than that odd puff of air thing), and I tried the Idle Screw already. All the way in, and out.
 
Hmm, now that you mention it the new head did have a couple of indents on the area that should seal onto the Cylinder Head. I'll have to try the sandpaper trick, what grit sandpaper did you use?



No fuel line issue, the Carb works perfectly (other than that odd puff of air thing), and I tried the Idle Screw already. All the way in, and out.
I resurfaced mine with what sandpaper was available at the time. IT was 600 grit and it worked nicely. Definitely not to rough and the finish was very smooth in my opinion. I also made a new gasket out of gasket material as I heard you should not reuse the aluminum head gasket. It's really quite simple to do.
 
I start with around 200 grit then go to at least 400, the 600 would be good and smooth. You can also do a compression check, anything between 80 to 120 psi for a stock engine.
 
hey, the engine is backfiring. I know it is because I can smell fuel in the puffs of air coming out of the Carb now. Do I need new jets, seals, or what?
 
Try moving the clip down a notch on the needle, I had one nt that would not idle with the clip in the top slot. Either the needle was too long or the jet was under sized, moving the clip down a notch let me adjust the idle with the screw. What you are seeing is blow back coming from the carb, since these engines don't have reed valves that seal after the fuel is drawn down in the crankcase some will blow back when the piston cycles.
 
There is a LOT of blow back, as in I can feel it moving my pants as I try to get the bike started.

I moved the clip on the needle down one notch (it is now on the bottom notch), and it is puffing a lot worse so I may move it up to the second notch.

If it is the jet then I am thinking of getting a jet kit (
http://www.gasbike.net/products/5mm-nt-carburetor-jet-kit )

I currently have a 36T Sprocket on right now getting a Max of around 24mph. I can't entirely say why, but I think it was going faster with the 44t Sprocket that the engine comes with. Pain in the Arse to put on, but as far as I can tell completely worth it.
 
A couple of questions, have you checked the head for flatness? If you can feel the compression leaking between the cylinder and head that's a big problem. Have you turned the head 180° ? Sometimes the head will seal better, if the plug wire is long enough its worth a try. Once you get the head sealed you can tune the carb.
 
Back
Top