My sapphire was fine when I tucked it away last year. It is now back on the road, but when the revs hit 4000 it holds back and coughs and splutters and miss fires. Any ideas?

 

did u try cleaning and gapping the plugs? also is there fresh fuel in it?

 

New plugs, not gapped by me, just off the shelf. New fuel.

 

gaps could be too big causing a missfire on boost id check them

 

Any idea what gaps should be ?

 

Hi m8 mine did this and it was the 3 big wiring multiplug connectors on the bulkhead just above the rocker cover,they were full of oily residue,i just cleaned all 3 out and it was sorted,looks like some people cut the plugs out when reading up on them,worth checking only takes few minutes

 

standard is 0.7mm but you may need it smaller if your running more boost than standard

 

Should be around 0.65mm .

 

Check leads plugs coil ign amp dizzy and rotor for wear to begin with. Chances are its something simple

 

mine did that,it was the threaded terminal that screws onto the top of the plug which the plug lead pushes onto,as you bought new plugs if they had screw tops did you check they were tight?
mine was popping and misfiring as i accelerated and the tops on the plugs were all loose tightened them up ran spot on after,something so simple can make you fear the worst

 

Regapped the new plugs, tightened the earth terminal on the battery and fiddled with the multi plugs behind the engine. Now revs to just over 5000 before it starts missing. Some progress but think I will let Grove Garage take a look tomorrow.