Runs great and fast, no idle!

[Cellerx]

Hey guys, i just bought a motorized bike off of my boss, he doesnt use it anymore and it runs great, only problem i have come across is it wont idle. If i pull the clutch while its running i have to keep giving it gas to keep it going. Iv been fiddling with the idle screw turning it tighter to no avial, any ideas on how to get it to idle?. Also when i went to go buy it, he told me to just use striaght octane gas with no oil mixture? Hes been using it like that for a while and said its fine, i was like nahh, and got rid of that gas and i used a 40:1 ratio and it actually runs faster now, not sure if i should lower that ratio, i used truefuel 40:1 premix for 2 strokes. Again it runs really well, just wont idle. All replys appricated!!

 

[crassius]

top end may be damaged from lack of oil, but usually when the idle screw goes all the way in with no idle, then it needs to have the needle dropped down a bit leaner

 

[Cellerx]

top end may be damaged from lack of oil, but usually when the idle screw goes all the way in with no idle, then it needs to have the needle dropped down a bit leaner

When will i see the effects of the damage to the top end? And i havent tightened it all the way, just as tight as my hand allows me, but which needle are you talking about? Sorry ima nooby

 

[Cellerx]

Anyone know anything?

 

[60weight]

Cellerx,how bout pics...Is it 2 stroke or 4 stroke?

 

[2door]

Cellerx,how bout pics...Is it 2 stroke or 4 stroke?

Because it has a manual clutch we're assuming this is a 2 stroke engine. Depending on how long your boss ran the engine without oil I'm guessing you're going to find some damage to the cylinder walls, piston, rings and bearings. Crankshaft seals would also suffer from lack of lubrication.

My guess is you have a major air leak somewhere in the intake circuit or crankshaft seals. A high idle speed is a symptom of excess air entering the engine.

Tom

 

[Cellerx]

Cellerx,how bout pics...Is it 2 stroke or 4 stroke?

Its a 2 stroke

 

[exokinetic]

I have to agree with 2 door on this one.

Sounds like a massive air leak, requiring the throttle to be high enough to deliver enough fuel to account for the excess air.

I imagine making the idle circuit richer (lowering the clip position, and thus raising the needle) will improve the situation, but it won't solve the leak if that is indeed the problem.

If there is an air leak, it needs to be addressed as it will eventually lead to a siezed piston, or a fat hole in the piston dome.


Running without oil is pretty much disaterous to a 2 stroke engine. I am amazed it still runs at all.

If I knew an engine had been run for any period of time with NO OIL I would do a complete disassembly and inspection of all parts.

What kind of reading does the top end achieve on a compression gauge?

Is there signs of oil making it past the crank seals since you started running it with oil (you would notice black liquid -oil- pooling up in either magneto housing, the clutch housing, or both. This would indicate a definite leak at the crank seal, and a potential source of an air leak)

Do the bearings look smooth or pitted? Do they roll smoothly, or do they grind?

Same questions for the surface the bearings roll on.

Is the cylinder wall smooth? Does it have pits, scrapes, gouges, or flaking chrome?

Is the piston skirt smooth? Does it have scrapes, gouges, vertical smearing, signs of excessive blow-by?

Are the ring end gaps within an acceptable range?

Do you notice any metal shavings accumulating anywhere in the engine?


All told, I would be extremely suspect on ALL of these things if a 2 stroker was run with NO OIL at all.

Modern 2 strokes have an oil injection system with a separate oil reservoir that you fill, and can run lower premix ratios like 40:1, 50:1, 100:1. SOME of these can be run with no oil IN THE FUEL, because the injection system takes care of all the oiling needs.

Our engine is an ANTIQUE. It was one of the FIRST 2 stroke engines ever developed.

It loves oil. IF YOU JET FOR IT I highly recommend running more oil in your premix in the future.

I would not run anything less then 32:1 in this type of engine.

My race engines live on 16:1, but they also spend 80% of their run time above 7000 RPM's, frequently hitting, and sustain 10,000+ RPM's. They are also disassembled and inspected after every race.

You probably don't run it this hard, just as an example.

 

[Cellerx]

Just road it around for a little bit, starts up fast and runs super good, better than the one i built, but once i pull the clutch to try to idle, it just kills the engine unless i keep applying some throttle, also my kill switch doesnt work, idk if something might have happend between the kill switch and clutch, but in all honeslty it runs good, i dont even need to go to hard on the throttle to keep a decent speed. Tho idling is pretty useful

 

[exokinetic]

Sounds like an air leak somewhere.

That will cause the engine to run fine everywhere but idle, it also limits the effectiveness of the idle speed screw.

If you would try to lower the clip position on the needle we could see if that helps the idle situation.


It could also be some part of the ignition system.

The spark plug wire on the standard CDI is actually pretty decent, but the boot is suspect, I would replace the boot with a quality MSD, Denso, Bosch, Accel, etc. NON-RESISTOR boot.

The CDI itself can be flaky if you got a bad unit, swap it with one that idles good on another bike.

All of the Magneto's I have gotten from just about every vendor (I've tried alot of 'em, 12v Magnetos, stock Magnetos, Screaming Roo Magnetos) have proven to be super flaky. Try to swap one from a bike that is idleing good.

The spark plug could be on its way out, try a new one, they are super cheap.

 

[Cellerx]

Um no there is no dripping of oil anywhere, no shavings, the engine is clean, the carb looks a little dirty might have to clean the inside of it, idk how to attach pics from my phone will attach some when i get to a computer

 

[Cellerx]

Sounds like an air leak somewhere.

That will cause the engine to run fine everywhere but idle, it also limits the effectiveness of the idle speed screw.

If you would try to lower the clip position on the needle we could see if that helps the idle situation.


It could also be some part of the ignition system.

The spark plug wire on the standard CDI is actually pretty decent, but the boot is suspect, I would replace the boot with a quality MSD, Denso, Bosch, Accel, etc. NON-RESISTOR boot.

The CDI itself can be flaky if you got a bad unit, swap it with one that idles good on another bike.

All of the Magneto's I have gotten from just about every vendor (I've tried alot of 'em, 12v Magnetos, stock Magnetos, Screaming Roo Magnetos) have proven to be super flaky. Try to swap one from a bike that is idleing good.

The spark plug could be on its way out, try a new one, they are super cheap.

How do i lower the clip position? A video or a pic so i can see what clip or needle we are taking about

 

[exokinetic]

For sure!

This is where you will find the needle, with the aforementioned clip:

Where the throttle cable goes into the carb, there is a cap that threads onto the Carb body (seen in the above pic)

After unthreading that cap, the throttle Slide(the round gray bit with the needle sticking out of it), the "jet neddle" (the needles official name) and the return spring come out.

Compress the return spring by pressing the slide up against the threaded cap and with a little persuasion the throttle cable end will protrude out the bottom of the slide, and you will be able to pull it out of its slot in the slide, and then remove the slide from the throttle cable, so you can access the jet needle.

Example:

Now that you have the needle out by itself, you will notice multiple grooves the c-clip (referred to by everyone as "the clip") can be placed in.

The higher the groove the clip is placed in, the lower the needle ends up in the "needle jet" (this is the brass well that the needle goes into, the Main Jet is threaded into the bottom of this well, the well is referred to as the "needle jet")

The lower the "jet needle" is inside the "needle jet" the leaner the Carb mixture is from idle to 3/4 throttle position. The Main Jet controls the mix from 3/4 to wide open.

We think you are lean at idle.

We would like you to lower your clip one position (making things richer) and report back the result.

I would also recommend trying all the available clip positions, to see witch one gives the best throttle response.

If you find going richer on the clip solves the idle issue, but hurt wide open throttle performance, that would indicate you need a leaner Main Jet.

All of the adjustments in the Carb overlap slightly, so changing one effects all the others, it's all about finding balance.

 

[Tyler6357]

Never run any engine without oil, your boss is a moron.

 

[Cellerx]

Alright ill go down on that jet needle tomorrow morning, should i keep the idle screw truned all the way clockwise?

 

[Tyler6357]

Yes, leave it in all the way and see if it will idle without giving it any throttle. If it revs high turn the idle screw out until its at a low setting but still won't die.

 

[crassius]

don't worry about air leak until you know more

the needle is inside the slide, and can be lowered by moving the clip up closer to the top - this is a good thing to be checked first because it can easily be changed back if it doesn't help

another thing that may be happening is that your clutch isn't adjusted properly and is dragging your motor to a stop

search the board here for info & pics about both these things

 

[exokinetic]

another thing that may be happening is that your clutch isn't adjusted properly and is dragging your motor to a stop

Good idea Crassius, it could totally be this.

 

[Cellerx]

Just tried to adjust the jet needle, i took the cap off the carm and pushed the springs back, i couldnt find or see any c clip on the jet needle, i ended up juat putting it back together and saying screw it, the bike runs fine as is, its not hars to start up so its not that bad of an issue if it shuts off if i disengage the clutch. Also i realised itll only shut off once i get to a slow speed, if i keep pedling while disengaged, it wont shut off

 

[exokinetic]

Probably your clutch is dragging.

When you "disengage" the clutch, it is still rubbing against the pucks. It will still run if your are still pedaling at speed, but as soon as wheel speed drops too far below engine speed, the friction bogs down the engine until it dies.

In a nutshell, with the bike stopped and idling there is too much drag from the clutch for the engine to run. The clutch is not disengaging far enough.

If you keep the throttle open when stopped (or going slow), you give the engine enough fuel to overcome the drag and it will still run. Close the throttle and the drag is too much. The engine dies.


If you are interested in knowing how to adjust the clutch post back here, I would be happy to write up a guide.