16-06-2023, 04:17 PM
Hi
Some more possibilities:
Engine very tight. Unlikely as it would affect idle and you would notice on the starting handle.
Exhaust system blocked. Rare but not impossible.
Intake air blockage. With no air filter and such simple manifolding this is almost unheard of.
Accuspark not advancing timing with revs. I believe 'bob weight' style advance is still used internally. A strobe light and marks on the camshaft pulley is the way to check. Insufficient advance is unlikely to cause backfiring though.
Low tension supply to Accuspark insufficient. Check Ignition switch, wiring and grounding, including distributor to engine block.
Fuel flow insufficient
From the details given, I think restricted fuel supply the most likely, especially if the tank and pipes have been unused during the overhaul. Can you blow back down the pump input pipe into the tank and feel airflow ? In desparation can you try a temporary gravity feed with a small (e.g. lawnmower) tank ?
As usual, I am prepared to be proved wrong !
Some more possibilities:
Engine very tight. Unlikely as it would affect idle and you would notice on the starting handle.
Exhaust system blocked. Rare but not impossible.
Intake air blockage. With no air filter and such simple manifolding this is almost unheard of.
Accuspark not advancing timing with revs. I believe 'bob weight' style advance is still used internally. A strobe light and marks on the camshaft pulley is the way to check. Insufficient advance is unlikely to cause backfiring though.
Low tension supply to Accuspark insufficient. Check Ignition switch, wiring and grounding, including distributor to engine block.
Fuel flow insufficient
From the details given, I think restricted fuel supply the most likely, especially if the tank and pipes have been unused during the overhaul. Can you blow back down the pump input pipe into the tank and feel airflow ? In desparation can you try a temporary gravity feed with a small (e.g. lawnmower) tank ?
As usual, I am prepared to be proved wrong !