Engine Trouble All put together. I just can't start it. [ spark fluids ]



I have just put together my 48CC motor and all appears to be well. I have two problems. It won't start when I release the clutch and the more I twist the throttle the worse it seems to be. Also how much play should the chain have. If I have it tight it comes off the cog on the rear wheel. But if it is loose enough not to come off it seems too loose and hits the chain guard. I am new to this and I am busting to get motoring.

Do you have spark? Also..Did you taper the rear sprocket before installing? Let us know...Thanks..
It won't start with a full choke, especially on a new engine.
Use choke to get a good prime in carb and then move choke to 1/2 way.

Check spark plug gap. Not unusual for plug tip to get smashed into center electrode when in the box being shipped from China to USA and eventually to your home.

Throw away that stock factory kill switch and replace it with a quality one that won't fail. I have had 4 switches (factory) fail and prevented me from starting because they were stuck.

You have to find the sweet spot on the throttle and occasionally on the choke on a new engine/first start situation for it to fire. I usually vary both while pedalling down a hill to keep speed up.

You may also want to squirt some starter fluid into the foam airfilter assembly just before you pedal to start (act quickly, since this stuff evaporates quickly)

Chain should have about 1/2 inch slack in it. If tension is not consistent, your sprocket is out of round and not centered properly.
i never use the choke to start it, the engine is so small that it needs air, i only use it to shut it off. starting fluid wont work either because it goes into the crankcase first and by then it has already dissipated... choke off, petal up to about 6 to 8mph and release the clutch and petal for your life and eventually itll kick over :D

Uh? Starter fluid doesn't disappear..the crankcase is sealed in two stroke engines and it will eventually find itself into the combustion chamber to be ignited. It works well for new engines and is an easy way to rule out ignition problems. If the engine won't fire on starter fluid (ether) than you have an electrical issue. If it fires on ether but won't stay running then you know you have a fuel delivery issue.

As for choke? I do not understand what size of engine has to do with choke or need for air (air requireements). All engines regardless of size need about 14 parts air to 1 part fuel for the mixture to ignite. However, a cold engine needs a mixture that is richer than the usual 14:1 (stochiometric ratio)..a choke is an easy way to achieve that mixture and start a cold engine. Our chokes do not completely block off airflow..just partially...most of the engines do better on partial choke but my newest one surprised me and will run on full choke.
Wont start

Starter fluid may blow your engine. Take the kill switch completely off and get it running before installing. Check to make sure you have a spark. Take the kill switch completely off and get it running before installing. The kill switch. Use full choke, and full throttle. You will probably never read this because you are probably off rideing. Make sure you get that chain issure straightened out before you mess something up. I always want to just take off as soon as I make a bike. Rode rash hurts.
Trouble Starting

I had the same problem last year when I bought my first motor kit and installed it. I noticed I was getting spark maybe one time spark per who knows how many rotations of the engine. After much talking with the guy who sold me the kit, I sent my CDI in and had it checked out. It got sent back to me and it had checked out OK.

So I installed the CDI again. Still no start. I was about to get a refund from the guy I bought it from but I decided to try one more thing. I popped the magneto cover off of the left side of the engine. When I went out to try it again I had a vehicle pull me (don't worry, I was very safe. I was on an airport flightline!) and I noticed whenever I popped the clutch, that spinning thing inside of the magneto wouldn't move very much at all. Then I stopped and pushed in on it and then turned it about 10 times with my finger. The next time I went out to try it, it worked!

No more problems.
Welcome to MBc. as far as the chain goes...1/2" to 3/4" play between cogs is standard around these parts.
learn to use the search (upper left hand cormer of these pages). i entered "chain tension" picked the 'search for all terms' option and got 43 hits.
Happy :mrgreen:
Twist the throttle and it gets worst. Mine did the same thing when I put it together. What I found was the Intake manifold had a vacum leak. Make sure it's tight and the carb, if you have to make a new gasket for it. I used a roll of gasket maker from auto store.
Hello again. A previous poster said that starter fluid may blow your engine? I wish to point out that is highly unlikely. Starter fluid is very safe to use in gas engines. Its use in diesel engines is another issue since diesels don't have a throttle to restrict airflow and can "run away" with ether use.