G'day all,

I took the mini for the first ever (well first in the 10 years+ I've had it) drive today on a yet to be opened road. It seemed to be tuned sweetly when parked at home, revs very well no back fire, but today when driving it back fired like nothingelse, it seems to backfiring from carby.

Can anyone give me any clues on what I need to do?

Cheers
Mark

If it is a backfire (up the intake through the air filters) You may need to check you timing again as timing which is too far advanced can ignite the mixture while the inlet valve is still open.

If it is an afterfire (down the exhaust pipe) it may be that the mixture is incorrect (too rich and not burning fully) or too lean (not igniting in the cylinder but burning in the hot exhaust). This also can be caused by a delayed ignition, so again check your timing .

Also helps to check your points, plugs and leads (check gap and dwell) to see they are all in good condition after such a long time.

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SooperDooperMiniCooperExpertEngineering

All garage work involves equal measures of enthusiasm, ingenuity and a fair degree of irresponsibility.

Thanks for the quick reply!

So first check will be the timing, I'll have a look at it tomorrow arvo and see how i go. shame though, I thought it was pretty sweet since it was reving smoothly when just sitting there...

Cheers

When exactly does it back fire, straight away when accelerating, when going up hill, after accelerating 10-15 seconds. Just thinking it maybe carb related, i.e. lean mixture (blockage), sticky carb piston, weak fuel pump etc

it did it pretty much straight away, as soon as i was accelerating with just a little load (pretty flat run), now I think about it (im not 100% sure as i was heaps excited to finally be driving after 10 years) it would get a burst and be pulling much better with no backfire?? but then poped and crackled all the way driving up the next stretch.

I just went out and had a squiz under the bonnet to see if anything stood out as different and noticed there is something leaking out the bottom of the carby, it from bottom of the black pipe bit close to the firewall, is this the bottom of the jet??

Heres a pic:

That is the bottom of the jet. It would be a good idea to hit that with some carby cleaner to get it clean so you can try and work out if it originates from a crack in the jet and hose or otherwise.

After such a long time you may also need to check the rest of the fuel hoses for cracks in the rubber if it has degraded. Don't forget under the rear as well.

Is the fuel in the tank new?

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SooperDooperMiniCooperExpertEngineering

All garage work involves equal measures of enthusiasm, ingenuity and a fair degree of irresponsibility.

Thanks Mick, really appreciate your help, will clean it up and see if i can see it leaking tomorrow arvo.

Yep, fuel is only a few weeks old and all rubber hoses are new.

Cheers,
Mark

Ive been itchin to get home from work all day, but ended up running late from work and now going out for a few beers, so I only had 15min spare to go have a look it.

Would you believe it, it might have simply been a loose dash pot cap causing the backfiring, as i spotted it loose so tightened it up and then kicked her in the guts, gave one quick pop straight away and then revved sweet as for a while. but didnt get a chance to take it for a run, fingers crossed it was just this...

still need to sort out the leak though,

Check the points gap, when they close right up weird things happen.. as I found out years ago with my 1310S.
After binning the points and going electronic I've not looked back!
It is now the 21st century...

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DrMini- 1970 wasaMatic 1360, Mk1S crank, 86.6HP (ATW) =~125 @ crank, 45 Dellorto (38 chokes), RE282 sprint cam, 1.5 rockers, 11.0:1 C/R.