Spark Plug Issues
- Thread starter Alson
- Start date
AussieSteve
Active Member
With a larger gap, it's harder for the CDI to produce a strong spark, but more of the spark is in contact with the mixture.
A smaller gap results in a stronger spark, but less spark/mixture contact area.
It's a balance between the two.
A 0.024", (0.6mm), gap seems to work pretty well with these engines. Some guys that use the white wire for lighting, (which draws power from the ignition winding), set the plug gap at 0.020", (0.5mm), to compensate for the weaker spark.
0.036", (0.9mm), is a very large gap. These CDIs aren't very strong, so a smaller gap would definitely be better than that.
A smaller gap results in a stronger spark, but less spark/mixture contact area.
It's a balance between the two.
A 0.024", (0.6mm), gap seems to work pretty well with these engines. Some guys that use the white wire for lighting, (which draws power from the ignition winding), set the plug gap at 0.020", (0.5mm), to compensate for the weaker spark.
0.036", (0.9mm), is a very large gap. These CDIs aren't very strong, so a smaller gap would definitely be better than that.
changing gap and better plug
My engine sputters, I moved the C-clip up, then lost power. So I put it back, got a lot of power, but still sputters when I dont give it throtel. Im was told to go with a better plug NGK B6HS but try a B5 first it might take care of the sputter, is what I was told, I'll see
My engine sputters, I moved the C-clip up, then lost power. So I put it back, got a lot of power, but still sputters when I dont give it throtel. Im was told to go with a better plug NGK B6HS but try a B5 first it might take care of the sputter, is what I was told, I'll see
AussieSteve
Active Member
Not real sure what you mean by 'sputter'. Missing? Only at idle?
Still, if you're using the stock plug, that could well be the problem. Fit the B6HS and see how it goes. (I never even fitted the stock plug after reading the recommendations here.)
A better air filter isn't a bad idea, but that won't be causing the problem. These engines can be tuned pretty well with the stock one.
Run the B6HS for a bit, then pull it out and check the colour for an overall indication of your mixture.
Engine still sputters
I put a NGK B6 in and it seems the same, I took my air cover off and seen oil in the filter, its spitting oil and gas back in the air filter. I moved the c-clip to lean it but lost a lot of loaer but it didnt sputter like it did, so I put back to second from top it sputters when I dont give it throttel, but when I give it throuttel it runs real good. No idea how to fix it, any sugestions would be apprecheated
I put a NGK B6 in and it seems the same, I took my air cover off and seen oil in the filter, its spitting oil and gas back in the air filter. I moved the c-clip to lean it but lost a lot of loaer but it didnt sputter like it did, so I put back to second from top it sputters when I dont give it throttel, but when I give it throuttel it runs real good. No idea how to fix it, any sugestions would be apprecheated
AussieSteve
Active Member
It's perfectly normal for these engines to blow a little fuel/oil back out of the carb. They're what's known as a 'port scavenged' engine. There is no reed valve or other means of stopping some mixture being blown back as the piston drops, before the intake port is blocked by the piston. Some mixture is also blown out the exhaust during the cycle. (That's the purpose of an expansion chamber. The tuned length provides a reflected pulse from the rear of the chamber that pushes the mix back into the combustion chamber.)
Odd that it's only real rich only at idle and not through a bit more of the rev range.
Usually, if mid-throttle mixture is OK, these things idle surprisingly well, considering the carb has no idle circuit.
Maybe the float level is set too high. It should be set at 21mm. The procedure for checking is described in NT Carb Tuning Basics.
There isn't any fuel in the float, is there?
Have you removed and cleaned the carb with compressed air? Might be a bit of c r a p in the float needle seat, although that would usually affect more of the rev range.
Odd that it's only real rich only at idle and not through a bit more of the rev range.
Usually, if mid-throttle mixture is OK, these things idle surprisingly well, considering the carb has no idle circuit.
Maybe the float level is set too high. It should be set at 21mm. The procedure for checking is described in NT Carb Tuning Basics.
There isn't any fuel in the float, is there?
Have you removed and cleaned the carb with compressed air? Might be a bit of c r a p in the float needle seat, although that would usually affect more of the rev range.
AussieSteve
Active Member
No, it wasn't the clearest. I got a bit of glare from the flash.
With the carb upside-down and gasket removed, measure from the gasket seating face to the highest part of the float. Should be 21mm.
I saw your post in 'NT Carb Tuning Basics'. Hopefully the other carb will work properly. Then you know it was the float level.
Good luck.
With the carb upside-down and gasket removed, measure from the gasket seating face to the highest part of the float. Should be 21mm.
I saw your post in 'NT Carb Tuning Basics'. Hopefully the other carb will work properly. Then you know it was the float level.
Good luck.
