REALLY stumped by this......

I must be missing something....... Ive replaced the full ignition system in my series 3 2.25 engine. New Battery, Solenoid, Coil, Dizzy and leads (Dizzy is points) New spark plugs and recently new carburettor. Will she start???? NO WAY! Just turning over and over, not fireing. Theres a spark at the plugs but they seem dry! Fuels getting up to the carb. Ive a feeling its a timing issue, I dont have a strobe etc, I used the olf TDC (Top dead centre) mark, which although may not be that accurate Ide thought I might have got a cough or two out of her? She has run prior to this renewing being carried out so I dont suspect anything really serious. Can anyone tell me why petrol isnt getting to the plugs, cant be blocked carb as is brand new? Could a valve be sticking??? Will probably take her to garage as Ive been trying to sort this for a while but have always prefered to do repairs myself. Any advice???

check tappets , manifold gaskets ,remember the two manifolds shouldnt be tightened together till fastened to head ,new carb is quite likely to be faulty ,blocked or float level wrong etc

Ok so get some one to keep there foot down on the throttle and then
Chuck a cap full of fuel down the carb let the throttle go again
And the try and start if she fires and try's to run its looking like the
Carb I would say

If its timing I have before when stuck loosened the dizzy and while
Twisted it as someone else has cranked the engine to get it to cough
Your nearer to the right timing than you were before just keep
Hands away from the ht leads grip the bottom on the dizzy to turn it

Also have you checked that fuel is getting to the carb ie pump working ok ?
Has it got fuel ? Don't laugh I have fallen for that one !!!

Will try all that tomorrow thanks and report back!

PS its not the pump plenty of fuel getting up to the carb. tested by disconecting the feed pipe turned ignition and good supply! So thats one thing crossed off

Well each thing crossed off gets you one step closer !!

I came across a problem on my 2.5na, it would tow start but not start off the key. But evrthing checked ok.

It turned out when ignition was on everything worked ok. When thhe key was turned to start position, engine would crank over, but the power supply was shut to my fuel solenoid.

Could it be your engine is cranking but the power to fuel pump and coil is being shut down? Easy test, put a lightbulb in thhe circuit and see if it turns off whilst cranking.

Have you for the plug leads on in the right order are you sure the dissy's not 180 degrees out?

I had issues like this once and just plugged the king lead straight to #1 plug and adjusted dissy until it tried to fire then tried each of the four holes on the dizzy in turn until I found the right one then put plugs on in firing order anti-clockwise.

The number one dissy hole should be the one that point roughly in the south-east corner of the distributor when viewed from the bonnet front i.e. one nearest #1 plug then 3, 4, 2 going anti-clockwise.

However if anybody has done anything with the dissy drive gear (i.e. replaced cams) then it could be anywhere!

Check the points are deffo opening and closing and that the gap hasn't closed up

Silly me... just re-read and your getting a spark

JTlandyboy said:

PS its not the pump plenty of fuel getting up to the carb. tested by disconecting the feed pipe turned ignition and good supply! So thats one thing crossed off

Click to expand...

Are your plugs wet tho ?

It can get to the carb and a blocked jet ruins that idea straight up ...

A good squirt of carb cleaner or Easy Start down the carb throat with someone else cranking it and stomping on the throttle always tests if your getting some sort of spark under compression situations. On 2-strokes you could never rely on a spark tested by earthing to the block while cranking. Could be different in this application but a weak ignition system could still fail to fire an engine under combustion chamber conditions perhaps?

As Dominic Beesley said firing order could be the issue as well; easy to put the leads back in the wrong order and make sure you ID #1 cylinder on the dizzy by lining up TDC compression stroke on number #1 cylinder (front of the engine). If you timed it on the exhaust stroke that would stuff it up as well! Been there...........

All is good again! I must confess to doing a perculiar dance once she fired up on the turn of the key this morning!
Bit of a silly mistake really, she wasnt fireing up previously because the TDC point was not the TDC stroke thats the compression stroke. So obviously no compression, spark, petrol = nadder! What a plonker! Soon as we got her TDC compression stroke she fired first turn! Is stalling now when you let her idle but think thats the new carb ajustment?
Thanks everyone......sometimes its the simplist of things eh.......