• Hi Guest!
    You can help ensure that British Car Forum (BCF) continues to provide a great place to engage in the British car hobby! If you find BCF a beneficial community, please consider supporting our efforts with a subscription.
    There are some perks with a member upgrade!
    **Upgrade Now**
    (PS: Subscribers don't see this gawd-aweful banner
Tips
Tips

Midget backfire at intake side...

Share this page

K

karls59tr

Obi Wan
Country flag
Offline
Hello Spridget forum I'm visiting from the Triumph forum. A friend of mine is having some issues getting his Midget running after being off the road for a couple years. He put fresh gas in the tank,checked the timing and went over the ignition system and cleaned out the carbs. He says the engine idles good but when you step on the gas there is a backfire. We are thinking it's a fuel problem? He did say he had to give the fuel pump a rap to get it going so it's probably the contacts in the pump. I have a spare pump he could try if that's the actual problem Anybody had similar symptoms with their Midget and know what to check next? Any ideas most appreciated.
 
Backfire thru carb is usually a quick lean condition.
maybe one carb has a plugged jet or stuck float.
 
Yes- as SD Bugeye said you are running lean on (at least) one carb
Try pulling the choke when you are giving it gas and if it improves then it is tune time but if it doesn't help then one carb is probably fuel blocked
BillM
 
Thanks for your responses. That narrows it down to what to look for. I'll post again after we get a chance to work on the Midget again. :eagerness:
 
That sounds like a classic symptom of not having oil or too thin oil in the dashpots. And that's the easy thing to check too.
 
There is little to add to the above. However, when checking the carbs, don't assume fuel getting to the carbs is the same as fuel getting into the carbs. If these are HS2s, after the engine backfires, immediately stop the engine. Remove the float bowl lids and check the fuel level in each bowl. The fuel should fill between 1/2 and 2/3 of the bowl. Lower fuel level can be a poorly adjusted float or a stuck/blocked float valve.

Since the car sat for a couple of years there may be gum built up in the float valve. This can be cleaned out with spray carb cleaner. Likewise, the goo from old fuel can build up in the jet. Use the spray straw from carb cleaner and clean out the jet. Make sure the carb cleaner is coming up/out into the float bowl while you spray into the jet.

Finally, if the car sat in a damp place for a while, with the dashpots removed check that the pistons in each carb can be lifted easily and fall freely using a finger through the carb throat. Any binding or sticky behavior should be addressed by cleaning the piston and the vacuum chamber.
 
Replace the coil. It's always the coil. And if it's not, you now have a fresh spare coil for when it's not the coil next time.
 
Coils do fail, but nowhere near as often as people say they do. It is very unusual for a coil to fail from "just sitting" like this car has been for a couple of years.

Most threads where people report a failed coil also included statements that a dozen other parts were changed at the same time. That makes it impossible to say what part was at fault.

If you decide to replace the coil, change it alone and see if the car runs better. Don't change it and a whole bunch of other parts at the same time.
 
Back
Top