Too much fuel, not enough air.

Targan

Targan

New Member
I have a grubee slant head 66cc engine with an NT carb, and an expansion chamber with that silver silencer thing on the end. Basically my bike boggs and has almost no power, it is VERY jerky and will not reach top speed. This all happened out of no where too. I cleaned my carb and adjusted my needle to the leanest possible setting. I also cleaned my filter and tried running with it off as well. My plug still comes out black, oily, and wet. It seems like not enough air is reaching the engine. I tried running with the expansion chamber completely off for a couple of minutes and no difference (except now I'm deaf lol). My spark plug sparks just fine. I am out of ideas.:-||
 
what's your fuel mixture? with regular crappy oil it should be 24:1 for break in, and 36:1 afterca few tanks.

running without a pipe will heat the motor up like crazy, so thats not a good idea.
 
The engine has about 300-400 miles on it already. I was running 32:1 when the bogging started. I thought it was a too much oil issue at first so I drained it then added a 40:1 mix. Nothing changed. I have done all the textbook inspections. Everything is clean, I get fuel (too much), spark, and air (not enough it seems). I moved the needle clip in the carb to the leanest setting (nothing changed), then to the richest setting (bike wouldn't even start), then back to the leanest. The bike origanally ran on the middle clip setting just fine for a week or 2 when I installed the NT carb. Any use of choke and the bike dies which tells me it's an air issue.

*Side note*
This same issue happened on my old CNS carb (never found out why. The CNS carb ran fine for 3 months straight). I changed it out for this new NT carb, it ran well for 2 weeks, then BLAM, bogging badly again.
 
It sounds like you moved the clip the wrong way. When moving the clip UPWARD the needle drops down leaning your fuel . Another thing , once your plug has gone black it won't come back to a lighter color. You'll have get a fresh plug . If you have leaned it to the TOP natch and plug is still running black then its time for you to JET DOWN . I mit be wrong but , as I recall most It's come with a .70 jet. So you'll be needing a .68 jet IF I'M CORRECT ABOUT THE STOCK JET SIZE. SICKBIKEPARTS sell single NT jet reasonably priced and then a response on shipping well let's just say the rocketshipper's.
 
I would also suggest checking the float needle to make sure it's working and not causing an overflow problem. THis could also dump too much fuel into the cylinder.
fatdaddy.
 
If the bike was running good then started with this "bogging" thing I doubt you're looking at a jet size problem. Something else is responsible. You say the same thing happened with the CNS carburetor and now the NT. They both ran good then started acting up.
If it was jet size the problem wouldn't just appear after a few miles.

I concur with fatdaddy in that you might have a float or float valve problem that is allowing too much fuel in the bowl. Are you using an in-line fuel filter? Possibly the float valve is not closing due to trash in the seat.
Are you using fresh gasoline? 2 cycle mix has a short 'shelf life' and should only be stored for a few weeks. Old mix won't perform as well as a fresh batch.

What plug gap are you running. .024 to .028 is a good ball park place to start.

Also keep in mind that the needle clip position only effects fuel flow at or below 3/4 throttle. Above that, up to WOT the main jet determines fuel/air mix.

Tom
 
2door said:
If the bike was running good then started with this "bogging" thing I doubt you're looking at a jet size problem. Something else is responsible. You say the same thing happened with the CNS carburetor and now the NT. They both ran good then started acting up.
If it was jet size the problem wouldn't just appear after a few miles.

I concur with fatdaddy in that you might have a float or float valve problem that is allowing too much fuel in the bowl. Are you using an in-line fuel filter? Possibly the float valve is not closing due to trash in the seat.
Are you using fresh gasoline? 2 cycle mix has a short 'shelf life' and should only be stored for a few weeks. Old mix won't perform as well as a fresh batch.

What plug gap are you running. .024 to .028 is a good ball park place to start.

Also keep in mind that the needle clip position only effects fuel flow at or below 3/4 throttle. Above that, up to WOT the main jet determines fuel/air mix.

Tom
Click to expand...

Great response, thank you. I have checked the carb and cleaned it out, as well as using fresh gas. Spark plug gap is .026. I am using an inline fuel filter too. I called a guy who repairs these bikes and said something about it being piston rings? I'm good with the basics but I'm not very knowledgable about the actual engine. He said the piston rings probably need replacement. Literally everything on my bike is 100% good to go, working, and clean, EXCEPT the engine. I have not looked into that because I don't know what to do or how to work on them. The engine is VERY oily inside and out. I repeat: I am using a 40:1 ratio.
 
I forgot to mention that starving the bike of fuel did not seem to help either. I tried running with the petcock off, stayed jerky until it died. Tried draining the float, stayed jerky until it died. It helped somewhat, but not enough to label the float as the problem.
 
This might sound silly, and it wouldn't apply to the CNS carb but have you checked to make sure the choke plate is fully open and isn't vibrating closed?

Tom
 
2door said:
This might sound silly, and it wouldn't apply to the CNS carb but have you checked to make sure the choke plate is fully open and isn't vibrating closed?

Tom[/QUOTE
been there, done that. riding along just great then all of a sudden the thing starts running like crap. Check petcock, Check plug wire, look in tank, Make sure I got gas. SMOKE a CIG and think about it.Notice choke lever, OPEN CHOKE, START BIKE, continue my ride feeling a little foolish.
Darned 2 stroke vibration and loose choke levers.
fatdaddy.
Click to expand...
 
2door said:
This might sound silly, and it wouldn't apply to the CNS carb but have you checked to make sure the choke plate is fully open and isn't vibrating closed?

Tom
Click to expand...

Unfortunately it's solid as a rock. Open as can be. Any replies about the piston rings being the issue? I still have no idea what they do or where they are. Guy i called said they were probably the issue, but i want to fix it myself since I'm broke.
 
its possible you cracked a ring, but normally that will destroy your piston, jug, and possibly everything else.

in short, theres two rings set into grooves around the piston. they expand to form a seal which gives you compression.

if you blew a ring, normally the parts fly around inside and gouge up the cylinder walls, crack your ports, chew up bearings, and all sorts of other nasty stuff.

and it's pretty obvious. it wouldn't just run rich. unless you got really lucky and the chunks blew out your exhaust before causing damage.

you can pull the head off and look for grooves in the cylinder walls.

on old cars the rings wear down eventually causing low compression, oil loss, etc, but our engines don't normally last long enough for that to happen. it's usually a catastrophic breakdown.
 
Targan said:
Unfortunately it's solid as a rock. Open as can be. Any replies about the piston rings being the issue? I still have no idea what they do or where they are. Guy i called said they were probably the issue, but i want to fix it myself since I'm broke.
Click to expand...

I think the rings would have to be REAL bad to not let the engine at least POP a little. Perhaps GONE and laying in the lower case. Otherwise it should at least ACT like it wants to start and go pop pop once in a while. I guess yer gonna hafta pull the cylinder and check. or just do a compression test.
fatdaddy.
 
A lot of auto part stores have a loan-a-tool program, were you put down a deposit use the tool, return it and get your deposit back on the spot. That's what I did @ Auto Zone .
 
Hey guys, so both my piston rings were broken. They stayed inside of the grooves "lucky me. I ordered new ones. I never installed these before, is there a special process or trick to do?
 
first, grow your thumbnails a bit long for spreading the new rings over the piston (there is a tool for this if you're going to do it a lot)
 
When it comes time to install the new rings you'll need to be very careful and not break them. They aren't made of rubber and will only stretch so far to go over the piston. Go slow and carefully work them on in a circular motion into the ring grooves.

There are ring gap alignment pins in the piston ring grooves. The gaps of the rings must align with those pins or the rings can not be compressed enough to slide back into the cylinder bore. Lubricate everything, rings, piston and cylinder with whatever oil you use in your fuel mix before reassembly.

My concern is that if you had broken rings that there is damage to the cylinder walls. It would be rare that the rings would break when the engine is running and there not be damage to the cylinder. Inspect the cylinder walls for gouges. A damaged cylinder will not allow the new rings to seal and you'll be back to square one and will have wasted you money and time buying new piston rings.

Tom
 
Oh, just remembered - last time I saw a set of broken rings, I pushed a small magnet on a piece of flexible plastic around the bottom of the case - found some tiny pieces of ring
 
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