TGB Delivery won't start after engine swap

[ozmatt]

Hi there,

I have a delivery 50 which suffered a collapsed crank shafter bearing, so I managed to pick up a replacement engine from a TGB 303RS. From what I have read these engines are pretty much the same (they look identical to me except for the rear wheel shaft being different lengths)

So I swapped the engines over and connected everything up correctly and no go. It won't start or even attempt to start. I have checked the following:

• Checked spark plug for spark - spark present
• Checked compression by holding hand over the spark plug hole - Finger gets popped off
• Checked fuel flow - fuel line is full and bottom of float has fuel in it

Really not sure what else to check? I have put the old engine back on a number of times and it starts fine so there isn't anything wrong with the carb and fuel lines or spark.

Could it be a timing issue or something? ie the spark is going off at the wrong time and therefor not igniting?

any suggestions would be great, i'm going crazy over here (and sick of catching the train to work each day)

cheers, Matt

[ozmatt]

oh, I also sprayed some fuel into where the spark plugs goes but still no start.... and then tried some "start ya bastard" spray into the air intake and also the spark plug hole and still nothing 

[harry]

its not good to spray  fuel or liquid dynamite in the plug
hole. it strips the oil from the piston,cylinder wall & rings.

 if it doesn't fire with a hot shot in the air box and you have spark;
 
there is a electronic lockout for the cdi and it shorts it out to ground.
its the brake switch  , try holding in the right side lever.

if battery is low it will turn over the motor  but there is not enough
left   over to make a strong spark.

on cdi 2 strokes there is no way to adjust spark advance
like on older scooters or mopeds that have points.

yes,the cdi stays but
spark is generated by the stator and that is getting swapped with engine.
 
oilyhans

 

[ozmatt]

I put the old engine back in this morning and it started straight away. Same spark plug, carb etc. I then put the new engine back in connected it all up and nope, no start just it cranking   I double checked the pressure on the intake manifold on both engines and they seem the same. Not sure what else to check. I ensured both brakes were engaged

Is there anything specific on the engine that would stop it from starting?  I'm just about ready to give up

Cheers

[harry]

i assume  you have no history on that motor ?
was it running when you got it?

 the only thing that would put you out of time would be a sheared key
on the flywheel , it happens but very rarely.

to test~ go buy a led test light at radio shack
 and remove the plug put the led on ;ground the black side to the battery
or good chassis ground,
turn on the key. slowly turn the motor over with a wrench, you should
see the light go on ;stop turning the motor and check the piston is at the top of the stroke.

without the light check the piston's max stroke height and compare the two,
best if you use a caliper with a depth gauge to get an exact reading.

or you can just remove the fan shroud & fan, pull the flywheel and look
but you need a special tool for removal.

oilyhans