How much choke?

[jojax64]

Without getting too technical, I was wondering just how long would you expect to leave your choke cable out, starting from cold at this time of year?
My original standard 1098 carb/air filter seemed to be pretty good. Not much choke required, and the car ran very smoothly after a short period of time (a couple of minutes). However, when I came to changing the plugs, they were a very dirty sooty black in colour. The car did actually over-run at switch off once during hot weather.

Since I recently fitted my brand new carb and K&N filter, I find that I need to use far more choke than before. When I check the plugs, they are still black, so I'm loathe to make the mixture any richer.
I suppose I just became accustomed to running rich with my original set up, so I just wondered, how long would you say was "normal" to have to leave the choke cable out in your personal experience?

Thanks guys.

[rayofleamington]

I'm not sure that there is a 'normal'. I've had a lot of different Minors and they all liked differnet amounts and duration of choke. Most of it is probably to do with the carb setup / carb wear. Other factors will affect it too (including how much carbon deposits are in the head - changing the compression ratio).

Generally I push it in after about half a mile anyway (to save fuel) but some will need the choke pulled on again at junctions for up to 2 miles and others were fine without choke after 30 secoonds of running.

[Willie]

I assume that you know that fitting a KandN filter will weaken the mixture
unless you fit a suitable needle? My 1098, set up by using the carb lifting
pin and confirmed by using a Colourtune plug, needs little choke to start from
cold and less than half a mile to be ok without choke.

[jojax64]

Yep.
I had to richen the mixture quite a lot. I used the lift pin method, and the engine speed increases a little when I push it. I reckoned I had it pretty well set, but the plugs are still black.
Is this colourtune plug still available?

[chrisd87]

Sounds like you've enriched the mixture too much - maybe take it back a flat or two and then re-check the plugs.

Colourtune is still available from Gunson's:

http://www.gunson.co.uk/item.aspx?item=1822&cat=439

[bmcecosse]

You don't need a colourtune - the lift pin tells all. To be honest - it's also possible to hear when the idle is just right. Too weak and it stumbles, too rich and it's 'splashy'. The filter makes no odds at idle - there was always plenty of air getting in through the old filter at idle - it's when running hard that the new filter has less resistance - so you 'may' need a different needle. But all needles are virtually the same at idle - the first 1/4" or so is almost always the same thickness.

[jojax64]

"Colourtune is still available from Gunson's:"

Yes, but is it available in the "old" plug size? Probably used for modern applications with smaller plugs nowadays.........

[Onne]

no it is available. Plenty of modern cars still use proper spark plugs

[paul.kissick]

u can also get them at frostauto restorations.

[jojax64]

"so you 'may' need a different needle"

Gawd, I'm even more confused now. Where would I source such a needle?
(My brain hurts........ )

[chrisd87]

The Mini places will probably sell you different needles. There is a computer programme (winSU?) that tells you which one you need, I think.

[Onne]

I found one here
http://www.beavispits.co.uk/winsu/winsu.html

[KirstMin]

If you've changed your set up then you are more than likely going to need to change the needle. I have had to change mine twice now: once when i changed the exhaust/carb/mani/filter and a second time when I changed the head. Its a bit of a black art to get it spot and usually requires a rolling road but winsu will put you in the right range of needle.

For your info, my car needs the choke for quite a while as the heated bit of the inlet manifold is bypassed. On a cold day it can take a while to get going but she gets there in the end. The guy who tuned it said this would happen.

[Cam]

If you have JUST changed your air filter then you might well be OK with your current needle. If you have changed your manifold and outlet too and are driving around at full throttle then a needle change will be required if it feels like it's running out of power at high RPM.

For information. My 1098 needs little choke and then can be pushed in after about 1/2 mile too. My 1380 needs much more choke and has to be kept out for longer.

[jojax64]

Naa,
Had enough farting about. I've gone back to original and the car is running much better.........this is my second attempt fitting an aftermarket filter, just a load of hassle.
I'm sure that the more technically gifted have no problem tuning high-flow filters, but I've had enough......time to give somebody else a shot.
Sod it.

http://cgi.ebay.co.uk/ws/eBayISAPI.dll? ... 4628752030

[Willie]

A lot less induction roar too!

[jojax64]

I notice now that 2 plugs are brown in colour, the other 2 are brown/black. Why would the colour be different for each cylindar?

[chrisd87]

The inner 2 cylinders tend to be slightly leaner than the outer two - I just adjust the mixture very gradually until all four plugs are as close to the 'tan brown' colour as possible. I think this is probably due to the manifold design but no doubt there's somebody who can explain properly on here.

[minor_hickup]

I personally don't think its worth changing the filter unless you're prepared to mess about with needles. I only put a pancake style filter on mine and it was running lean as a reult at any throttle opening, so i enrichened the mixture at idle ever so slightly. But then it was running rich at idle and lean at full throttle. Put the old filter on and everything is grand!

[bigginger]

I've just had to do a LOT of engine work because of the same problem, it having resulted in a piston melting/breaking up - dropping dead, really. I think the general consensus was that it's due to pistons 2&3 sharing one inlet port, so blame Sir A. Well, if he'd designed the engine (I can't remember ) it would be his fault...