Hi all.
Got a couple of niggling little probs with my mini.
At 2500 to 3000 rpm with a steady throttle, she almost sounds like she’s missing or something.
If I bury or lift of the foot she is all good.
If I try to gradually increase throttle, it slightly increases the problem until the throttle is open enough, and then smoothes out and I’m accelerating away cleanly.
I’ve had this issue for some time now and in that time I’ve,
Changed to electronic ignition,
replaced the distributer under the electronic ignition (reco’d from the shed),
changed from 1½ su to 45weber,
changed fuel filter,
changed from std barrel to hi output ignition coil,
replaced wire from battery to starter and solenoid,
leads and dizzy cap are new and good ones.
Oh, and a different fuel pump. Not the std su type unit. But not a solid state pump ether.

During the gradual installation of these mods.
The issue has reduced from, regularly fouling plugs through being a ning nong to tune.
To a mild annoyance that I fear will create some other problem further down the track.
The reduction in severity of the problem (I recon) has come predominantly through the Weber and electronic ignition being installed.
I’m of the mind that this problem was more than likely hidden under the carby and ignition being iffy,
and now that she is starting to run quite nicely, this has come more to light.
Or alternatively,
the dramas I was having with su and ignition were caused by this and now that I have improved their quality I’m left with the original problem.

I’m starting to think I might be over thinking this.

Now once upon a time she was a 64 850, But that was long before I got her.
She is currently running a 998 mtr with an 1100 crank and 1¾ lcb .
I bought the mtr as a recently recoed 2nd hander.
So the internals are entirely unknown to me.

Anyone got any ideas?
Valve related? Perhaps a better fuel pump?

I know.

What would cause a flutter at a specific point in the mid rev range?

After all that I recon that’s the question.

Thanks for thinking.

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One Lill-Red 1100
A project morris van
One rusty assed delux shell
and a clubby van

warm camshaft?
out of tune?
tappets?
wrong plugs?
plug gap?
the list can go on more...

_________________
Miniworx Centre 0883741299
Sooperdooperminicooperexpertengineering
Online BMW Mini Shop

Sounds like carby to me,to lean or rich..I had the same problem with su's ,,but after changing mixture and eventually needles...fixed the problem..air leaks with make them rough s well....Thats my 2 cents worth but someone on here should be able to help you

A flutter sounds like pinking (often called pinging). Usually caused by too low an octane or ignition too far advanced. Causes incomplete combustion.

You could try retarding the ignition a little and see if it goes away.

Also try 98 octane and see if that makes it go away. If you use 98 already and have fouling plugs then I am guessing you are using Optimax. I switched to BP and Mobil 98 and it cured my plug problems. Got this tip from Graham Russell who told me that when running engines on his dyno with Optimax he has to change the plugs every 10 minutes.

Pete

It concerns me that you still have this problem after changing from an SU to a Weber. I have a very similar problem but it is down to the SU not being 100% set up.

It may be time to visit a Dyno and see if the problem is fuel related or ignition related, other wise you may be scratching your head for a while.

When was the last time you had the head off Might be all coked up and running on the deposits

_________________
"Show me the Mini!"

My money is on camshaft.

It's to do with the inlet and exhaust overlap.

From memory Adrian Flynn built your engine and it doesn't have a standard camshaft.

Ok . Thanks so far guys.
In responce to the messages so far.
I had the weber fitted and tuned at kent town auto. When he ran it on the dyno the only thing he picked up was valve bounce at the higher end of the rev range.
So i'm reluctant to blame tuning.
Could valve bounce occur in the middle of the rev range and then occur latter as well? but it dosn't sound like valve bounce. If im corect, and when i have heard what i would call valve bounce, It sounds like someone mashing the gearbox.

brickworx
I've wonderd about the cam before. Is there an easy way of identifying it without removing it?
I'm sure the plugs are corect, I didn't gap them prior to fitting, but would that cause a localised prob? Or one across the whole rev range?
There is a small amount of ticking noise at idle but it isnt what i would call tappety.

peterw..
nah, more of a miss than a pink i think. I do run on 98 from bp and i also run flashlube for lead replacement.

Anto..
yea was originaly set up on a dyno

willy..
Nah the 1275 that was in it was to smokey. has been changed to a second hand unit from blair athol. But thats interesting info for the rebuild of that one.

9YaTaH..
umm... never. i've been trying really hard to avoid that. I really hate with a passion the manifold nuts on mini's. Plus when the carb was fitted, the mech put on fancy star shaped nuts and i havent found a spanner or socket for them yet. he said they made it heaps easyer to get on and off. Ha. not if ya dont have the spanner it dont.

_________________
One Lill-Red 1100
A project morris van
One rusty assed delux shell
and a clubby van

You want be able to check the cam unless yo pull it out and maybe best to ask the builder

regarding to plug gap...does that mean you just pulled them out of the box and put them in....they should be gapped around 13ish not noing the cam you have...i'd check them could be the problem

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Stop Licking the Dog...I Don't Care Who Started It

spark plugs with wrong gap will cause problems
I suggest a full tune...
start at the start, end at the end. don't just try bits of a tune.
we may be able to identify a warm cam, buts specs we won't know while it's in an engine.
after all that's done, maybe run up on a different dyno and check mixtures

_________________
Miniworx Centre 0883741299
Sooperdooperminicooperexpertengineering
Online BMW Mini Shop