Sluggish Then Dead 80 cc Motor

[AussieSteve]

Sorry, we got off-track with the oil ratio. That is definitely not the problem.
Stick with your current ratio, it's fine.

Best way to test for spark is with the clutch out. Lay the plug on the head as described, then lift the rear of the bike and spin the wheel forwards.
(You might need a helper. A centre-stand is great for this, or if you have a side-stand you can lean the bike over so that the wheel is off the ground.)

Otherwise, with the clutch disengaged, (pulled in), remove the magneto cover and use a drill with a socket to spin the motor.

Don't be too concerned, it won't be too hard to sort this out.
Keep us informed.

 

[wrightmor]

second reply here, lost my post

Just a quick note of sincere thanks for all your helpful suggestions. As you probably have been able to discern, I am not a mechanic nor do I even play one on tv. I am just a guy that got lucky and managed to put my bike together and It worked - too good to start with. Went from stand still to a little dot in wife's vision as she was going to photo my maiden ride. Carb part put in backward. 0 to 35 in 5 seconds.

I do intend to replace plug and cable assembly just as soon as I can purchase the parts this week. Hope I can find them at the local Mopeds and More shop. Might have to mailorder.

 

[AussieSteve]

No worries, glad to help. I have heaps of spare time these days.

Try your local mower shop as well. The cap is irrelevant - any type will fit. The main thing is to get a plug lead the right size for the CDI. I think it's 7mm, but I'd advise you to measure your's.
Note that some plug caps need the little screw cap on the plug, whereas with others such as the standard cap the plug's screw-cap must be removed.

 

[wrightmor]

I'm back on the road.

The good news is the bike is running. I replaced the spark plug cap. It now buttons down and snaps to lock on to top of plug.

The bad news is it's idling a bit fast and still skips on the road. The idle is rough.
Also, I think somehow I have messed my muffler up. seems louder now. The plug looked like it was very hot at the base of the porcelain and maybe a little damp or at least discolored

But I had a fairly long ride. Just not sure why the idle is so rough. nor how I could have messed up my muffler.

Another good news story, though, is I think I fixed a squeak I've had in the clutch ever since the original install. The clutch engaged even while I was rolling the bike (motor not running) to garage. So I pulled out pliers and readjusted clutch cable. did one more quick ride and no squeak.

 

[AussieSteve]

The bad news is it's idling a bit fast and still skips on the road. The idle is rough.
Also, I think somehow I have messed my muffler up. seems louder now. The plug looked like it was very hot at the base of the porcelain and maybe a little damp or at least discolored

Check that the screw in the end of your muffler is tight. Also check the exhaust mounting nuts for tightness and the exhaust gasket visibly for signs of leaks. That would make it louder.

It sounds like your fuel/air mixture is a bit lean. That would cause a fast, rough idle and overheating.
First, what colour is the spark plug? It should be a tan colour. Black and oily indicates a rich mixture and grey or whitish indicates a lean mix.
If it is lean, the most common cause is an air leak where the carb attaches to the inlet tube. Some sealant in the joint during assembly will fix that. You only need a tiny bit. Better still is to get an 'O' ring that just fits into the carb opening such that when the carb is pushed onto the intake, the end of the inlet seals against the 'O' ring. Best of all is to buy an alloy inlet tube and file an 'O' ring groove as close to the end as possible. That's what I did. See NT carby/inlet leaks - a reliable solution

Have you adjusted the idle screw to try to slow the idle? (That's the screw on the LHS of the carb.) Screw it out to decrease the idle or in to increase.
Did you fit a new spark plug? (NGK B6HS)

 

[wrightmor]

tried to replace plug but could not find proper equivalent. He sold me a little midget type that is totally swallowed up by the cap. I bought it in case the new cap was not sufficient to get me started. When bike started w/o the new plug, I decided to wait and find a plug closer to recommended. The vendor said the little plug works great on motor bikes but still I am skeptical. May have to order the plug.

I hate to sound dumb but color of plug? You did mean to take the plug out and look at gap area, right? I can see discoloration aound the bottom of porcelain w/o taking it out.

Muffler screw. I looked up at bottom of muffler and saw the "guts" of the apparatus surrounded or encased in the hollow shell of the muffler body. Dead center of this 'gut' was a screw hole (I can see threads) but no screw. Would putting a screw in make a difference or was the missing (if there is a missing) screw holding something else together. I told you I'm not a mechanic.

I haven't tried adjusting the carb screw yet. I did that when I first got the bike because I didn't have idle at all. Never got the idle that way. turning made no diff. I called the place I bought it from and he suggested adjusting the top of the carb where the cable goes in (to raise or lower it thereby causing more or less gas to carb). That got me my idle and it has worked great for couple of years now. I will try adjusting the screw this weekend.

Carb reseat? Should I try this your were saying. If so I'll prob go the permatex route at least this first time.

 

[AussieSteve]

These things are a real learning curve, aren't they?

You shouldn't need to order in a spark plug.
Be skeptical - the vendor doesn't know what he's talking about. All motorbikes take different plugs, designed for different amounts of heat transfer and a particular thread length and overall reach, among other things.
The best suitable plug for these engines is an NGK B6HS. They're sold by most auto-accessory shops.

Yep, when I refer to plug colour, I'm talking about the colour in the gap area and on the porcelain tip, when the plug is removed. There's a pic showing the right plug colour several posts into this thread,
NT Carb Tuning Basics , as well as a little more info on NT carbs.

There are a couple of different muffler types. Mine has an end-cap that is held on by that screw. With either type, if the screw is missing it will be noisier because some exhaust gas bypasses the baffles and escapes directly out that hole. The end-cap and would fall out if the screw fell out of mine.

The idle screw is the best way to set the idle, rather than by tightening the cable. The problem with using the cable is that it's always under pressure and so the idle will rise when you turn the handlebars. It's best to have about 2-3mm slack in the throttle cable, to allow for this.

Virtually all[i/] NT carbs leak at the point where they join to the intake tube, making them hard to tune. Any sealing method is OK.

I think I've covered everything.
Have fun.

 

[cabinfever1977]

Your muffler is missing the end cap and the screw that holds it on, it is much louder without this cap.

 

[AussieSteve]

You're most probably right. I pictured only the screw missing, but that wouldn't make it very much louder. And as I said, mine would fall apart almost immediately without the screw.

wrightmor, the end cap, (which includes a short length of pipe that extends back into the muffler), is probably somewhere by the side of the road where you were riding when it got louder. Most likely flattened. You'll probably need to buy a new muffler in this case.

 

[wrightmor]

muffler gone

Y'all are both right. Muffler is shot. I have ridden several passes over my roads and didn't see it.
I did get new plug. Made no difference. It is drivable. Just sluggish, especially when I try to throttle more. When I throttle it tends to cut back. If I slow down on throttle then re-throttle it will somtimes pick up the speed like it should but that doesn't last.
I noticed when I got home from last ride there was a constant stream of bubbles going up my clear plastic gas line. the bubbles lasted about 4-5 minutes. When it stopped I wiggled the line down toward the carb and more bubbles appeared. Maybe this is normal. I just never noticed it before. I think when I wiggled it it let air in from the bottom of the tube where it slides onto the carb.

Am I doing damage to bike riding it when it is responding like this? It rides ok and rides fairly fast but is slightly erratic. I tried adjusting the screw for idle. It works but I noticed when I had it about right (so I thot) and tried to pull up the choke to kill the motor, the choke actually served to reve motor.

I am getting a new muffler soon. Should I try to re-fuel with fresh gas and oil mixture?