won't start, need some troubleshooting

[artmaker]

Hi all,

I need some help.

Two stroke, 80cc, memorial day it ran, but ran rough when I slowed and tried to speed up again. Got home, left it in neutral, tried fiddling with throttle, it speeds up fine. High rpm fine. Exhaust was blue, no backfireing, no sputtering. So shut it off.

Tried again in about 20 min only it would not start at all. Died as soon as I put it in neutral.


So some forum hopping, and a talk with my mechanic, rings was his first though. Sure enough we pulled the piston and one of the rings was in pieces. The other warn thin.

So... today I had them put the new rings on. Cleaned all the parts, replaced head and lower gasket (jug? I forgot the name of that one, but it's replaced.)
Also bought a new plug. Didn't need one but what the ****.

It still won't start.
It's got spark.
It's got plenty of compression.
No fire.
And both my mechanics are left scratching their heads.

What else could it be?

 

[Bikeguy Joe]

Obvious, but is it getting fuel?

Once I pushed a 750 Honda for a mile on the freeway before I decided to check the fuel.

It was out.

 

[artmaker]

Yup they checked. He pulled the brand spanking new plug out and sniffed. Said it's getting fuel.

Also... while I'm huffing and peddling, trying to turn the motor over, I can turn the throttle and it will try to rev. SO must be getting fuel. But it wont' start up and stay running and wont' pull the bike. They are stumped.

 

[2door]

You said the engine has "plenty of compression". How did you confirm this? A compression gage should be used and it should give you at least 100psi, or better.

If the piston ring was broken it might have gouged the cylinder walls bad enough that you don't have sufficient compression. If the cylinder was damaged I hope whoever installed the new rings didn't try to hone out the scratches. That will only make things worse.

Tom

 

[artmaker]

NO gage, they simply supported the bike so the rear wheel was off the ground and tried to peddle. Plenty of force needed. Mechanic said if there was a lack of compression it would be easy to move. Besides when I tried to peddle start it, it was harder than before.

The cylinder seemed fine. It was "glazed" and he used some heavy grade sand paper to scuff the inside.

the guy was practically raised on a motorcycle. This isn't the first motor he's fiddled with. When he says the cylinder is fine, I believe him.

 

[artmaker]

I'm wondering.... He was telling me how much better a four stroke would be. But that they don't put out as much power. Rather than throw parts at this, I wonder if an engine upgrade wouldn't be a better idea? Any thoughts? Here is a picture of my bike when it was brand new. http://artmakersworlds.com/testing/Bike/Bike1REPLACED.jpg

And I'm no lightweight. The 80cc two stroke got me up the hills around here. It struggles but does the job. Gotta have at least as much power. (more would be better.0

 

[bigbutterbean]

since your bike has gears, you could install a shift kit. sick bike parts sells two stroke and four stroke shift kits, so whether you are able to get your current engine working or decide to switch to a 4 stroke, a shift kit is an option. a shift kit allows the engine to use the bicycle's drivetrain, so as you shift through the gears on your rear wheel, you will achieve different gear ratios with your engine, some gears better for speed, others for torque. something to think about.

 

[Bikeguy Joe]

Still gotta get it running...

 

[artmaker]

since your bike has gears, you could install a shift kit. sick bike parts sells two stroke and four stroke shift kits, so whether you are able to get your current engine working or decide to switch to a 4 stroke, a shift kit is an option. a shift kit allows the engine to use the bicycle's drivetrain, so as you shift through the gears on your rear wheel, you will achieve different gear ratios with your engine, some gears better for speed, others for torque. something to think about.

Yea... maybe someday. Actually I was considering putting this bike up for sale (after it's running right again.) And upgrading. But just a thought at this point. Too many other things going on.

The latest working theory on why it won't start is the plug cap. I finally found another mechanic willing to look at it. But... darn bike wont' fit in the back of my SUV. And I don't have a rack that fits this car. Just blew 200.00 fixing the AC on my car and the guy said he'd come by if he can. Then... he said he started out with these same kinds of two stroke motors and thinks he knows what the problem is. Plug cap. Or something in that box it goes to. He said he can fix the one I have. That cap does wiggle and it didn't when the bike was new so my bet is he's right.
Now the cap is only 4.00 but the whole assembly is more like 16. So will wait till he can look. I could just replace both if I have to. I MIGHT be able to talk my neighbor into taking me too. He's got a pick up. Or.... I did buy a rack for my former car. That actually might work on my husbands car. Hmmmm I'll have to go see.

So that's where I stand on that. Still not running at the moment.

As for gears, well it does just fine as it is. I'm very happy tooling around at about 22mph. got it up to 42 when I first got it and that's just hair raising! (not to mention the teeth rattling ride.)

 

[maurtis]

It very well might be a faulty spark plug cap making an intermittent connection, they are junk. Mine fell apart in pieces before I even got the motor completely installed. I ordered an upgraded wire and cap from Al.Fisherman here on the forums, the wire core is much larger than stock and the rajah plug cap looks old school and I looooove it. Positive click onto the plug, and no boot to get in the way so I know it is completely attached.

Here is a comparison picture I took of the wire along side the wire that came with my Jaguar CDI (Al's wire is the thicker one):

Hopefully the mechanic did not hose the new cylinder by attacking it with sandpaper. From what I have read, honing a nikasil lined cylinder can be very tricky.

Also, did he have the magneto magnet off at any point? I read that they can be installed backwards. Or maybe check the woodruff key on the magnet, if it sheered you can still get spark but the timing will be off and cause the engine to not fire.

On the gas front, you can always squirt some starter fluid or carb cleaner into the intake.