First build - engine is ready but won't start

[Seilon]

Hi guys!

It's my first thread and by the way I wanna say hello to everybody.

But now lets talk about the essential topic.
I built my first engine.
It's a 2 stroke single cylinder engine with 10ccm.
It runns on petrol with 1% oil and has a ignition from a KTM SX 125ccm motocross.

The problem: it doesn't run on it's own
I have to help with the electric drill :wall:
The engine gets fuel, it ignites, its just how it should be but doesnt work.
I guess that the friction is to high because it doesnt run that free.
for video click the following links
[ame]https://www.youtube.com/watch?v=jQ2hAAMgotM[/ame]

with heavy flywheel (~2,2kg)
[ame]https://www.youtube.com/watch?v=EnKRe24u9Kc[/ame]

If anybody has an idea what could be wrong please tell me.

Best regards from Austria
Seilon

 

[canadianhorsepower]

Hi guys!

It's my first thread and by the way I wanna say hello to everybody.

But now lets talk about the essential topic.
I built my first engine.
It's a 2 stroke single cylinder engine with 10ccm.
It runns on petrol with 1% oil and has a ignition from a KTM SX 125ccm motocross.

The problem: it doesn't run on it's own
I have to help with the electric drill :wall:
The engine gets fuel, it ignites, its just how it should be but doesnt work.
I guess that the friction is to high because it doesnt run that free.
for video click the following links
https://www.youtube.com/watch?v=jQ2hAAMgotM

with heavy flywheel (~2,2kg)
https://www.youtube.com/watch?v=EnKRe24u9Kc

If anybody has an idea what could be wrong please tell me.

Best regards from Austria
Seilon

Hi.I
two things 1 not enough compression:wall:
and what you are trying to spin is WAY to Big or hp demanding
for that engine.

My explanation, on your second video with out a spark plug that engine
spins 4 revolution before stopping. With the spark plug on only 3 revolution.

second explanation, on the same video a tow strokes engine will always stop were the exhaust port is close and then will kick back, not yours it stops all over.

you would need a clutch to let that engine generate power Before asking it to work

I'm curious do you have plans for this or Ports timing, or bore and stoke and primary comp ratio

good luck

 

[gus]

I have same problem with ''Firefly" Glow Engine. Poor compression and exhaust port and inlet port position . Fuel flow was another problem. OS Carb mismatch.

Good reason why I went 4 stroke. More work and parts but less problem. I am about to redo Firefly.

 

[popnrattle]

I think it is starving for fuel. with only 10 cc you have got to really rev it to get enough venturi effect to get the fuel pulled in figure a way to restrict the air or open needle enough to make it run rich then back off. I had to incorporate a choke sleeve to make my engine run at slow rpm. hope this helps. later, rt.

https://www.youtube.com/user/popnstart/featured

 

[Seilon]

Hi

I don't think that the compression is the problem. I can adjust that by a thread.
The plan is from Mr Jan Ridders
Pic of the cylinder see attach
Pic of the petrol vapour carburetor see attach

cylinder:
bore: 24mm
stroke: 24mm


@gus
my next engine will be a 4 stroke
I promise

@popnrattle
yes I think you are right
the engine is starving for fuel
the exhaust gases smell as they get burned very hot
how can I improve that?
How does the engine get more fuel with my petrol vapour carburetor?


Thanks for all the helpfull answers!

Best regards
Seilon

 

[t.l.a.r. eng]

Marginal compression, not enough air and fuel mixture, [needs the throttle opened] too much load, incorrect ignition timing.

I noticed it stopped on top dead center, with normal compression this is unlikely to happen.

Probably not just one thing preventing the engine from running on its own, but a combination of problems.

Can you remove the load and run the engine?

 

[Seilon]

compression I think is ok
the ignition also seems to be ok roughly estimated for 1000-2000rpm

the bearing on the crankshaft is the "problem"
then I could remove the magnet of the ignition and it should run much better
BUT if I remove the magnet the ignition will not fire


thanks for the answer!

Seilon

 

[Cogsy]

How sure are you about the ignition timing? Not sure about KTM's but many Jap dirtbikes have built in advance to their CDI's to adjust timing based on RPM. If KTM has the same then the correct position of the magnet may be far from where it appears to need to go.

RXCEL model airplane ignitions have the same feature and can be very difficult to set the timing on a home built model if you don't allow for it. When turned by hand the spark occurs where you expect it but at starting RPM it changes substantially.

 

[V22]

I'm building the same motor at the moment. Your compression is down and it's binding with the plug out. Both are listed by Jan as causes of running problems. Mine turns over one revolution with the plug in when spun by hand - hard to get it to spin 2 revolutions. With the plug out it spins freely 10+ revolutions.

I have not run mine yet but I have a couple of tips:

1 - Use an O-ring around the plug (and rod) to get a good seal and make sure it is tight
2 - Use paper gaskets for both head and flywheel end
3 - Turn the piston until it does not bind (mine has a sweet spot where friction is minimal)
4 - Does your carb bubble if you extend the intake below the fuel line?
5 - I thought this motor was meant to run on Coleman fuel or Shelite?

Mine was low on compression and binding like yours. My piston to bore clearance was perfect at ~0.015mm. Yet compression was low until I did 1 & 2 above. Paper gaskets made a massive difference.

I cranked mine with a drill tonight and you can hear the thump of the compression.

 

[TheMakerBoards]

Hi guys!

It's my first thread and by the way I wanna say hello to everybody.

But now lets talk about the essential topic.
I built my first engine.
It's a 2 stroke single cylinder engine with 10ccm.
It runns on petrol with 1% oil and has a ignition from a KTM SX 125ccm motocross.

The problem: it doesn't run on it's own
I have to help with the electric drill :wall:
The engine gets fuel, it ignites, its just how it should be but doesnt work.
I guess that the friction is to high because it doesnt run that free.
for video click the following links
https://www.youtube.com/watch?v=jQ2hAAMgotM

with heavy flywheel (~2,2kg)
https://www.youtube.com/watch?v=EnKRe24u9Kc

If anybody has an idea what could be wrong please tell me.

Best regards from Austria
Seilon

Hey Seilon, sorry can't be of more help, I'm a complete beginner at making or diagnosing engines. I was just wondering what model engine that was and if you could provide a link to where you found the plans? Or did you design it yourself?

Great job either way. Very sharp machining work. I'm sure you'll get her up and running!

 

[Seilon]

@V22
thank you for your answer
I already use paper gaskets at the cylinder head and the flywheel end
I will try to transplant your tips to my engine

@themakerboards
www.ridders.nu
plans are for free
just write Mr Jan Ridders a nice E-Mail

Best regards
Seilon