compression and spark...

jimberlake

jimberlake

0
the new engine won't start at all! Been checking through things and looks like a very weak spark for Some reason I'll get to the bottom of that. I also checked compression...admittedly cold and got 100psi across all cylinders. I know should be around 150 really when warm so dies that seem low or just cause its cold?

thanks

Jim
 
That does seem low but the fact the readings are so even points to something else rather than an engine problem. Is the engine spinning over fast enough with all plugs out and throttle open? or it could simply be the test gauge gone chips:(
Try dribbling a bit of petrol down the carb and see if it will start to determine if it's an ignition or fuel problem first of all.
 
thanks panky...spinning well with plugs out, didnt have the throttle open and choke fully on but spun well still... sure the sparks too weak to fire well...almost fires early on then guess wet plugs stop it all together. Yer maybe the gauge as they are pretty consistent readings...really want to check when warm and the rings are bedded. Thing the fuel good as have a clear filter near the carb that's full. Going to try a coil first and
 
Make sure the carb piston is rising and dropping back with a nice clunk, just remembered about the SU so try holding the piston up, and choke off, as you crank the engine when doing a test so maximum amount of air can get in.
 
thanks guys... Electronic ignition so no condenser... The spark was that weak doubt it would jump anywhere... Was orange and tiny. Hopefully get chance to look today
 
My Lumenition system ruined a couple of coils before I ditched it.:(

Ignition coils are dead easy to check with an inexpensive multimeter.
 
Yer thinking along those lines though the ignition came with the coil so you'd hope was matched. There is slight play in the dizzy too so think I'll get a full kit.

Panky what kit do you have on Yours?

cheers

jim
 
It did make a difference on Ted. Although he usually started fine there was always a little miss and hesitation now and again, the new dizzy was an instant transformation - smoother all round but you soon get used to it:)
 
If you need to test the coil here's how to do it.
A bit long winded but you can skip the first bit.


Not sure if it's the same if you have a ballast resistor coil though.
 
I'd be on the shorts straight away;) Just wait until he starts on about the boring stuff:rolleyes:
 
hi jim
has it run at all since you got it back?
make sure the battery is fully charged as new/ recon engines are really difficult to start,
daft question have you got the firing order right 1 3 4 2
use fresh fuel
once you have definetly got clean petrol at the carb take the plugs out,squirt easy start down the holes.put plugs back in and fire up,it might just encourage it to start
if it does start DONT rev it hard
 
hi Steve...yep was running lovely for a while and slowly got worse with power etc. Finally wouldn't start at all. It does try to after you leave it for a while but doesn't run...i guess the weak spark tries to fire until the plug get wet (removed and covered in petrol) just leaving it until get the new coil and dizzy on so don't wash the bores. It's done about 150 miles upto now.
 
That is partially broke-in then, Jim, considering the compression, you could re-torque the cylinder head nuts, rocker post nuts and re-set the valve clearances.
 
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