Motor kit stopped running all of a sudden.

[funderb]

Hello,

So I'm new here, and am already posing problems...
I have been running the Daemonbikes "80cc" 2 stroke for a couple months,
and its been running perfectly.

I was riding today, immediately following a carb cleanout, only about 2 miles for a test run.
and as I pull up to the apartment, all of a sudden, the motor stops running.

Right now I have no explanation.

Here are the symptoms:

Upon attempt to start:
Engine turns over and goes putputputputput....
but you can feel its only being dragged along by my fat butt.

Upon evaluation:

Spark - Visible in the day time

Compression - Just under 150psi (149 abouts...)

Fuel delivery - All lines open, Carb sprays fuel/oil mist out the throat when the engine is turning over.
Carb- All seals tight, fuel ports open and clear.

Piston- also stays wet with fuel.

> removed head to inspect, piston clean, cylinder walls clean, no scoring.

Right now I'm running 16-1 fuel mix. It had been running great up until this point.

(Mods- Opened up intake ports a little, exhaust port a little. Got top speed up to 35.)

I'm thinking of replacing the stock slide carb with a "Racing" carb. Mostly in hopes that it isn't so...
crude....


Anyone know what the deal is? I'm stumped.

 

[Snogcel]

Hello!
You might try a new spark plug - I've had the experience of the plug appearing to fire OK when hanging out in the open air, but refusing to fire under compression. It may not fix it, and if it doesn't, at least you've eliminated one more easy thing.
Good Luck!

 

[funderb]

I've tried two, one just began returning no spark at all.... so I think its the CDI that quit on me.

First plug was stock, it lights up, but only at fairly high rpm.
Second was a bosch platinum 2pt plug that used to light up no problem.
doesn't light at all any more.
Does that sound like the CDI or the mags? (or, mag...)

 

[bairdco]

if you're getting an intermittent spark, start by tracing the system backwards.

is your plug wire tight on the plug?

is the plug wire tight where it enters the CDI? (it threads onto a screw, sometimes it comes loose or loses it's connection.)

are your wiring connections tight? did the kill switch wire ground out?

basic troubleshooting will get rid of all the little variables before you start suspecting it's the CDI or Magneto.

 

[funderb]

All righty. I'll go on a gas run as soon as I have a moment to myself.
For now i'll be driving. Diesels are so much easier to care for.

 

[funderb]

Update: New CDI came in friday, and I also got new gas, at 32-1, as recommended. First I tried out just the new gas, and got a couple putts... then nothing. Then the new CDI went on and wham! first rotation startup. I also down/upgraded to a 34T cog, giving me a cruising speed of 28-30mph, top speed of 35.5 on the flats. I don't mind pumping the pedals a couple times to get going from a stop.
Good to be riding again.

on another note, I'm about to do a search, but who's done little carburetor scoops for these things?

 

[bairdco]

i've built my own air cleaners, which are mostly open except for the sponge element. my bikes run better with more airflow, but if you're looking for a "ram air" effect, these bikes just don't go fast enough to utilize it.

glad to hear it's running again.

 

[funderb]

We'll see i suppose, its less looking for ram air, than flipping the cleaner over to get it out of that hot oily eddy that builds up behind the engine when its moving, than adding a rain hut. Any extra pressure, however small, can't hurt too bad, right?

 

[bairdco]

yup. i figured the same thing. the carb doesn't get any fresh air crammed in there like that, so i just got it out of there completely

 

[funderb]

Dang chang, thats a pretty one. I love that classic frame too. Mine's an ugly duckling, on a spray painted schwinn skyliner. (but hey, she moves.) If I had a camera that was worth a dang I'd post pictures.
Here's a crappy photo:

Here's the first iteration, with a front wheel far too nice to leave one it. When I ride my regular road or mountain bikes i am surprised at how much effort it takes...

 

[Black_Moons]

Heh, I totaly looked into ram air effect, Unfortualy its like 0.1psi at 90mph, 0.5psi at 170mph...Something along those lines And its a square of the speed effect too, So at 30mph its gonna be like 0.01psi, Not even worthwhile trying.

The 'Cold air' part however is worth a few % if you can signifigantly change the temp.

 

[Goat Herder]

I had a bike like yours Funderb. There was never any room for a filter. I finally used a ho-made housing and cable tied about four layers of panty hose that thing breathed good then. There are a lot of ways to go about it.