engine problem

[ed1380]

So I got an engine for free.
I cleaned it up and it still wouldn't start. (yep I broke a ring and stripped a bolt)
my dad took it apart and cleaned everything, and it still didn't work

it has a spark that'll jump 3/8 of an inch, great compression(we put in a thinned head gasket), and we use starting fluid so the carb aint that inportant.

it doesn't start no matter what we do
we think someone messed up the timings(cams)

is teh spark really supposed to hit twice per cycle
once at TDC when compressing and once when done expelling exhaust

this for reference and this for pics


@robert- why did you close the other thread?
do you really hate me that much

 

[kibble]

On these small engines the spark fires every time the magnet on the flywheel goes past the magneto. So yes it would be twice. You should be able to fix the timings, if that's what the problem is, by looking at the gears or chain or whatever yours has and they should have some sort of marking as to where their initial position should be.

BTW, robert hates me too. He closed my other thread as well.
(Just kidding)

 

[ed1380]

On these small engines the spark fires every time the magnet on the flywheel goes past the magneto. So yes it would be twice. You should be able to fix the timings, if that's what the problem is, by looking at the gears or chain or whatever yours has and they should have some sort of marking as to where their initial position should be.

BTW, robert hates me too. He closed my other thread as well.
(Just kidding)

yeah I saw that , but at least he gav you a reason.

so it should go off twice?

 

[kibble]

If there's nothing between the spark plug and the magneto to control when the spark goes off, then yes, It'll go off every time the flywheel turns once. That's how my engine is.

 

[RobertD]

So I got an engine for free.


@robert- why did you close the other thread?
do you really hate me that much

hee hee, no offense. When threads start wandering it's not a bad idea to start another one. I miss a lot of stuff on other forums b/c I just see the title, but the actual discussion has gone to another direction (that I might be interested in!)


about the engine -- so it's got spark but you can't get it to fire, at all? Could be someone didn't re-assemble correctly. Take the side of the engine off, position the piston at top dead center, and look at the tiny little dots (one on crank, one on cam). They should align.

 

[2or3wheels]

If the timing is correct the carb may be not adjusted and what not, Otherwise before you do all that check the compression you need 80 PSI for a weak motor for it to run.

 

[RobertD]

also, if the gaskets are bad / the carb isn't tight, you're going to have a vacuum leak and it won't run properly. Should run with starter fluid, just won't keep running...

 

[ed1380]

we redid the timings. turns out it was 3 teeth off.
now it'll start on starting fluid and sputter for a second.

now I need a starting assembly, and the diaphram for the carb.

 

[RobertD]

and a gasket... especially if you pick up the engine by the tank/carb, you're going to loosen that connection and have problems running.

Why do you think it's the diaphram?

 

[ed1380]

I took apart the carb to clean it, and the diaphram is still. (unmovable stiff)
the little valve flaps had a bunch of crap on them, but I cleaned that out.
I'm going to a small engine repair shop today, so we'll see if I can get some stuff

 

[ed1380]

I got the diaphram. it'll work for a few seconds if you periodicly spray starting fluid.
we put gas in the tank, and when it got primed and it started flowing, then engine started to backfire.
(backfire is when it makes the engine rotate backward?)

What comperssion should it give?
what could be wrong? we matched teh dimples.

 

[mikeandike]

mabe theres too much compression so the fuel preignites itself before the spark plug fires and the piston isnt at the top?

 

[ed1380]

it turns out the key broke. we made another one, and it broke too

 

[ed1380]

we thought they broke cause we were using the flywheel to start it, so we got a starting clutch for it, and after the first pull it broke.

could it be the super compression we have going?

 

[RobertD]

sounds bizarre... I guess it could be that.

 

[ed1380]

IT"S ALIVE
Well not any more. the carb is clogged up.

the problem was that teh flywheel nut wasn't on tight enough.

now it has a steel key, is on extra strength thread locker, and is tightened with a foot long adjustable wrench to the point of no return. (quite litteraly)

drives pretty good too.
not bad for a 3hp tiller engine

how tight is teh chain supposed to be

 

[RobertD]

the chain should have no more than 1" of up and down movement IMO.

 

[ed1380]

its about that.
heres a vid
http://www.youtube.com/watch?v=5c0l-avPCt0

 

[RobertD]

if it falls off, it's too loose.

 

[ed1380]

me and my dad spent a whole day trying to mount the engne so the chain was tight.
in teh end we got rid of a link