16 replies to this topic

[77LeylandMini]

Ok. the car has been running like poo for the past 3 weeks now. Feels kind of like driving into a very strong wind, and it stutters on take off-
Things we checked-
Fuel line blockage, fuel filter, cleaned out and rebuilt carb, AAF needle, blue spring, thin oil- thick oil in dash pot, replaced engine driven fuel pump with electric putting out 3-4 psi, ignition timing 12 btdc @ 1000rpm, changed head, changed valves and springs, changed rocker assembly, checked engine timing (chain slack, but timing dead on), sprayed for air leaks, changed head gasket, checked float level (4.0 mm), changed ground strap...... getting expensive....
Now the problem
No matter what we do the engine is running lean- with the choke FULL OUT!!!!! When you tickle the carb it just cuts right off. :'( - so Im thinking mixture is the answer to the car running like a wet fart.
Wierd stuff
Vented oil cap- BUT when the engine idles and the cap is removed the engine idles very rough. Runs better with the line coming from the oil breather to the carb plugged up.
Engine Specs
1275 "A" not A+ bored 30 over to 1310, unleadded head, headers, RC40, K&N filter, Minispares intake manifold, hs4 carb, 123ignition electronic ignition, standard coil, stock cam.

I was talking to an airplane mechanic and he suggested that the cam might be so worn down that the intake is not opening enough. He suggested i open the oil filter and look for metal. He thinks that the mixture is rich as anything but is not being delivered to the cyl. I have had several mini nuts helping me and they are all at a loss as well
P.s. Just tried to raise the float level but there are no washers to remove from under the jet...........................

[77LeylandMini]

dont know if this helps but I thought the level of fuel in the float chamber had to be about level with the jet- in this case it is not, but like I had said the needle can not be raised any more- unless you have some suggestions?

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[dan__wright]

are the breathers all connecte dproperly and airtight or the breather inlet on the carb airtight?

[77LeylandMini]

yes, we checked that last night.....

[Jimmyarm]

If you want to check if the valves are opening just take off the rocker cover and start her up....dont run it for too long like this but it wont do any harm and you can see if all the valves are being pushed down and opening.....

Have you checked the throttle spindle on the carb to check it is not sticking ? and preventing the bronze coloured (cant remeber what it is called!) flap from opening fully ?

Edit; the spark plug leads are all connected correctly arent they ?

My 2p

Jimmy

[minimole]

do you have a dizzy with a vac advance i have found in the past that if my vac advance pipe was not connected the mini ran like C**p. although it seems like you have covered pretty much everything so you have probally either set it up to run without a vac advance or you have already checked this.

also it might be worth check the breather pipes on the carb if you have changed the breather to mini kn type (dont know the proper name) then you will have to block the breather pipe thingy on the carb.

sorry if i am telling you how to suck eggs

[77LeylandMini]

thanks for all the help guys, but unfortunately, the vac advance is properly plugged, as the 123ignition uses computer controled advance, the breather is plugged, tried it unplugged as well, spark plugs are correct, checked the valves, everything is moving, throttle is not stuck.......
HOWEVER!- dont know if it will help at all, but I found that the tube going to the jet has a slight crimp where it enters the jet... Going to try to round up a new one............

[Jammy]

I know parts are hard to get parts over there but have you tried normal ignition? I know 123ignition uses some strange new way to set up the advance curve, are you sure this is correct?

[77LeylandMini]

we used a diff. timing light than the one i have, this one had a dial on the back where you seth the advance you would like to achieve (I think) That light said that the timing was spot on. 12 btdc @ 1000rpm, 24 @ 5000, if I remember correctly from last night.

Just had the car out- 34 flats down from the bridge and.......... LEAN

[Leonard]

that crimped pipe could be restricting flow, making it weak. theres a rubber seal that sits in the hole you put this pipe in (if you have a side float bowl) and if this isnt sitting properly when you do the pipe up it can block/restrict the flow.

[Lomcevac]

Fuel tank breather blocked?

[Sprocket]

Just a thought but is the dashpot spring not usualy red???

[pikey7]

does the water or oil smell of fuel?

Either there is not enough fuel leaving the carb, or the fuel that is there is going somewhere else other than the cylinder.

What about a leakdown and compression test?

[Sprocket]

Like I said, im sure the spring should be red

[Sprocket]

Vented oil cap- BUT when the engine idles and the cap is removed the engine idles very rough. Runs better with the line coming from the oil breather to the carb plugged up.

This could very well be an air leak in the breather system. The mini uses a possative cranckase ventilation system. This pulls a gentle vacuum on the crankase to evacuate any blowby and fuel vapours. if there is a leak in any of the plumming of the breather system it will draw vast amounts of air into the engine as it would if you just disconnected the breather pipe from the carb and left it open. There may be a 'hole' (not litteraly) in the seal of the engine allowing air into the intake of the Engine throught the cranckcase. This will cause lean running. very much like when you remove the oil filler cap, its not sealed but does generate a resistance, also worth noting that these should be replaced on service intervals too.