Revs fine with no load, Boggs when clutch engaged.

kdaddy1980

kdaddy1980

New Member
:-|| ive got a 66cc grubee Skyhawk kit. its got 400 miles on it. its been running great. it started losing power gradually and I found the air filter was getting clogged with oil. I sprayed it with some brake cleaner and compressed air and it worked fine. the other day I took it on a long ride and it ran fine but noticed a small power drop,(usually goes about 22-23 mph) but was struggling to get to 18 mph. so I figured the air filter clogged again so I took it off and still same problem. I did a test run after it cooled off and the thing wouldn't go past 14 mph. it runs decent with the clutch disengaged but its a dog engaged and will hardly move at all.

1. I replaced the spark plug
2. I checked and adjusted the clutch
3. adjusted the clutch arm (pulled the cable about 1/4" tighter)
4. checked the magneto
5. checked the wiring to the cdi
6. took the head off and checked the piston and cylinder
7. drained the fuel and replaced with new oil gas mix about 25:1
8. checked vacuum on carb (seems to be pulling a good deal of air)


there was a small nick and some thin scratches at the top of the cylinder (about 1/8" from the top) the head gasket didn't seem to be leaking. piston moved up and down freely and smooth.

I took the carb bowl off and looked inside everything seemed ok and clean. I checked the choke and throttle operation and they both seemed ok.

my exhaust baffle had fell off so I made a new one out of sheet metal, I thought it might have been clogged so I took it off, and still same issue.

I thought the choke cable might have been sticking so I checked it and that was ok.
could the cdi be going out? I figured since it runs good with clutch out it was ok
could it be the carb? also thought it was ok since it runs good with the clutch out.

clutch problem? it engages and disengages fine too.

I cant seem to figure out why I have no power.
any info would be appreciated, got to get this dog back on the road again

.drn2
 
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I assume since you have Grubee you have CNS carb, but which version? The one with the red plastic air filter is known for clogging, the foam insert gets loaded with blowback from the carb and chokes out your air, so you need to remove and clean the foam insert thoroughly and regularly (I recommend changing to a cone style high flow air filter and this problem will go away). Also there are 3 jets in the CNS, the main jet, the idle jet and the enrichment jet (choke). The idle jet is very small and clogs easily, you need to make SURE ALL the jets are clean. Finally, you should check the fuel filter in the petcock and make sure it isn't clogged, best just to remove that bogus filter and run and in-line filter instead. '
Also, contrary to advise from the manual, the 16:1 break in mix is WAY too much oil. I like to break in with 1st gallon 20:1, 2nd gallon 24:1, then 32:1 from there on. If you have 400+ miles on the motor with a break-in mix then I would move right over to 32:1 fuel mix and stick to it (quality standard 2-stroke oil, air cooled type, NOT marine type)
Thats a bunch of general stuff off the top of my head....
PS and make sure your head is still torqued down properly.....
 
sounds like it might be going lean, so check air leaks & fuel flow

if not that, check for clogged muffler, or something rubbing on chain/rear tire
 
What does the plug look like?
If it is pretty white you may have an air leak, it could be the intake manifold, carb gasket, or the motor seals.

If you have the new CNS carb with the blue cone air filter don't clean it with solvent, drop it in a bucket of Dawn dish detergent and hot water, let it soak awhile, swirl it around, rinse it off and let it dry.
 
Have you checked the drivetrain? Your wheel could possibly cause symptoms like this if the bearings are seizing or something else is going wrong in the rear.
 
MitchP said:
Yes it's an NT in the video, but a plug chop told me that I'm too lean. Fixed the low speed bog. May need to go higher(?) on the c clip.
Click to expand...
Higher on the clip means the needle is farther down in the jet, hence leaner, move the clip down to bring the needle up for a richer mix.
 
good news guys, I figured out what was wrong with my low power problem. it was the MUFFLER!...from running too much oil in my gas! the catalytic converter material got hopelessly caked up with oil and soot. finally just clogging the whole exhaust flow. I figured it out by taking the muffler completely off and running it up the street. I don't advise this because the motor seemed to rev out of control, but boy did it have some power lol I was screamin down the street. .wee. so what I ended up doing is cutting about 2 1/2 inch section from the end of the muffler. inside was another pipe that had a welded endpiece with holes in the side for the exhaust and the bolt for the baffle. I cut that straight off and there was the clogged up converter. it had a small, spoke sized hole in the center, I stuck a spoke though it and out came a little chunk of carbon buildup, that helped a little but not enough. so what I ended up doing is taking a 5/16 drill bit and drilling straight through the converter material. it worked like a charm. I put my homemade baffle back on it and I was back in business. its been running great ever since this mod. hope this helps if anyone else has had a problem like this.
 
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when mixing the oil, the chart on the bottle says 16:1 then the next one is 32:1, how do you get and even 20:1 and 24:1 mix? im havin a hard time breaking it down.
 
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