Hi all,

On and off since i got the BOC it's infrequently not wanted to stop when i turn off the ignition. As i said, it's only very infrequently but it's still quite concerning when it happens!

So sometimes when i turn off the ignition, the whole car shakes for a second or so and goes "chunk-a-chunk" and sounds like the engines gonna jump out of the bay!

There seems to be no regularity to it, and no particular reason like temperature or driving style...

Any ideas? Seems strange to me. I know i need to change the stabiliser bushes, but surely that's not the issue.

Thanx heaps, guys!

over-run! its usually caused by one or more of the following:
* Lean Fueling
* Timing out
* Carbon build up in chambers

um...thats all i can think of, give it a nice tune up and see what happens, its real embarising when you have a girl in the car

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speed costs....how fast do you want to go...

Over-run, eh? Hmmmmmmmm...

I only had it serviced 1000 miles ago and tuning was SPOT ON PERFECT (I was actually standing next to my mechanic as he checked it). It's also been happening before the service, so...

I've heard of this carbon build up before. Anything i can do about that?

And what do you mean by lean-fuelling?

Thanx for ur help, jbeenz!

I used to have a XC Fairmont 302 that used to over run (sometimes for minutes) due to the carbon build up, I solved it with 2 bottles of Nulon cylinder head / fuel system (?) cleaner into the petrol tank.

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One should never skimp on the zip ties.

(over-run, running on etc)
(i hope its lean feul not rich that causes this somtimes )
the lean feuling means that the mixture of air/fuel going in has too much air, and not enough petrol, the mixture can be adjusted fairly easily.

no from memory the brittish open classic is a 998cc? the combustion chambers in the smallbore motors have 'peeks' between the valves, carbon can build up on these peeks and get hot to the point where it 'glows" this hotspot ignites feul after the ignition is turned off, causing run-on. This can be fixed by removing the head and cleaning up the chambers, alot of people tend to grind the peeks down a little(or alot) to stop this from happening.

Your mechanic should be able to help either way, id tend to look at timing and fuel befor having the head off!

hope ive helped

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speed costs....how fast do you want to go...

Just stall it in gear when you turn the ignition off...

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Lillee - 1969 Morris Mini K

hehehe, a true mini owner!

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speed costs....how fast do you want to go...

Thanx for that one!



How realistic is this option? Cos to be honest i have no idea about removing heads and peeks and the like!

Oh, and jbeenz, the BOC is a 1275...

feul system/head cleaner may be an option, but i would tend to check other things first, as the 1275 peaks are no AS likley to carbon up, somtimes it can also be solved by driving it to within an inch of its life (you do not want to do this if it is lean...you may run it out of life )

id tend to get the mixture checked and also have it checked for vacume leaks arround the manifold area, and tighten up the manifold bolts. and have the timing reset. somone else should shed some more light soon, this is all i can think of at the moment.

nice looking car by the way!

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speed costs....how fast do you want to go...

Thanx, jbeenz!

And all help and comments are greatly appreciated...

Hullo,

I have a new head with new valves, new ports, no carbonisation, running ultimate 98 and my car runs on. Stall it! i do, so does the doc, it won't hurt it if you time it just right (when the revs are just about to die you release the clutch).

Cheers

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Lillee - 1969 Morris Mini K

68Delux is right, you wont hurt it by doing this, and from experiance, you do get very very good at timing it just right

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speed costs....how fast do you want to go...

Could fuel type be a problem? I know there are a lot of opinions on suppliers on here, but could that realisitcally be an issue?

It could be but unlikely. if you are running high octane (which you probably should anyway).

The doc reckons it's a sign that your timing is correct



Indeed! It's almost second nature to me now in fact it's probably worste letting it run on and it could/is spinning backwards when it runs on...

In reality you can probably spend money and time fixing it with an anti run on valve bla bla but I'm too cheap and too lazy

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Lillee - 1969 Morris Mini K

I think it is actually caused by running rich, not lean. running rich covers the combustion chambers in carbon and also puffs a fair bit of carbon out the exhaust

My car was running very rich - was using 10L/100km - and after tuning it up and leaning it out it no longer over-runs. I haven't driven it in summer yet though.



I don't think it is running backwards. A 4-stroke engine cannot run backwards because the inlet and exhaust effectively get swapped over and it doesn't get a fuel supply. It may be possible with fuel injection though

at 600rpm the engine will be doing 20 compression strokes per second, and it would take a small amount of time for the engine to actually stop turning (mostly because of flywheel inertia). if it fired while it was still turning then the engine would continue to turn in the same direction, and could continue to do this as long as it is firing (as with the falcon speedy mentioned)

The only way the engine could turn backwards is if the engine stops while if it is half-way through a compression stroke but still fires. In this case the engine may turn backwards a little bit even if it doesn't fire.