998 running a AAC needle and K&N cone. Carb was rebuilt back in June. I find the car runs better with the choke even once warmed up. Without the choke the car hesitates under throttle, and power seems greatly reduced.

I don't think its fuel pump since it idles fine without choke... I am thinking vacuum leak / wrong needle?

What's the best way to search for vacuum leaks??

 

Get a little tank of propane with a needle valve **** on the end (such as a brazing torch), then attach a length of rubber hose, like surgical tubing. Run the car with the choke off. Let the propane flow out of the end of your tube, slowly, and point it at various locations around your intake system. When your RPM increases, it's because it's sucking propane in from the leak. There's your hole.

You can do the same thing spraying carb cleaner, or starting fluid, but it's less accurate. And starting fluid is the devil and will destroy your car and if you have any starting fluid lying around you should throw it in the nearest trash can.

 

Absolutely best way to find a leak is a smoke device:

http://www.popularmechanics.com/cars...-a-vacuum-leak

Can't help on the needle.

 

how much choke? Reason I ask is a properly working SU carb in a Mini only engages 'fast idle' for the first 1/3 of the choke pull {ref - owner's manual}. . . so unless you are pulling it about 1/2 I suspect something else is going on. Where is your idle set btw . . . what RPM? Do you know where your timing is set? Does the vac' advance on the dizzy work? (do you have and know how to use a timing light?)

I'm not sure - and this is little more than an educated guess - but it sounds to me like the wrong needle. Remember that the 'running mixture' for the SU carb is determined by the needle. The mix settings on the carb are only applicable for idle aka the starting point. When you pull the choke manually (far enuf) you make the mix richer across the range by shifting the postion of the jet to a different point on the needle to begin with. (ref SU Carburetters Tuning Tips & Techniques, Wade, Brooklands Books, 1994)

Now when you change from a standard air cleaner to a cone type like the K&N it is generally accepted that the increased air flow is going to require a different needle to send more fuel to the extra air (maintaining the same ratio) .... this suggests to me that you need a needle change. In the UK you'd head to a Mini savy shop with a rolling road (dyno) and they would play with needles (educated guesses) to achieve the best mix/performance. Not easily done here in the US. (altho if you live near Va Beach, ABACUS Racing is a place I'd recommend you visit . . .)

If it were me, I'd start by calling Seven and seeing if I could talk to a tech. Of course I buy from them so they might be a wee bit more receptive to the time expenditure .... but if you start by saying I want to buy some parts, beginning with a needle but I'm not sure what I need . . . .

I'd tell you what I run with a K&N, but I have a different carb and a different displacement and different manifolds . . . so I'm not sure what I run matters much.

As far as the vac' leaks..... assuming your car has had all the de-tox stuff removed you don't have a bunch of vac' lines running around; so there aren't that many places for a vac leak to occur. Primarily you'd be looking around the intake manifold and the places where vac lines would be running out from. When I got my car, one of these capped take-offs had a deteriorated plug allowing a significant loss of vac at the manifold . . . . something to look at.

 

you need to adjust the carb and set it up properly..................there is a large brass nut under the carb tighten this all the way in and then 3 flats back out this will a good place to start then start your engine and test run it if still not sorted try 1 flat at a time this will richen you mixture.....

Section D.6
CARBURETTER
Dismantling
(l) Unscrew the plug and withdraw the piston damper.
(2) Take out the two suction chamber securing screws,
lift off the suction chamber and withdrarv the
piston and jet needle.
(3) Disconnectth e rod from the bottom of thej et, and
the nylon feed tube from the base of the floatchamber;
pull out the jet and tube.
(4) Unscrew and remove the jet adjusting nut and the
spring.
(5) Unscrew the jet bearing locking nut.
(6) Removet he float-chambesr ecuringb olt and the
float-chamber.
(7) Take out three screws and lift off the top of the
float chamber; withdraw the float.
(8) Screwo ut the needlev alvea ssembly.
Inspecting
(9) Note the condition of the needle valve and seating;
fit a new needle and seating if necessary.
(10) If the jet needle is bent or otherwise damaged,
withdraw the locking screw in the piston and fit a
new needle. Push the needle in until the shoulder is
flush with the lower face of the piston.
(11) Cleana nd dry the piston assemblyl;u bricatet he
piston rod only with thin oil.
Reassembling
Rcverse the dismantling instructions and centre the
jet.
Jet centring
(12) Screw the jet adjusting nut up as far as possible,
lift the piston with the lifting pin and allow it to
drop; it should drop freely onto the bridge with a
soft metallic click. Repeat with the adjusting nut
screwed fully down. If the piston does not fall
freely in either of the tests, proceed as follows.
(13) Carry out instructions (3) and (4) above.
(14) Refit the adjusting nut without the spring and
screw it up as far as possible.
(15) Slacken the jet bearing lock nut until the bearing
can be turned with the fingers.
(16) Remove the piston damper and press the piston
down onto the bridge. Tighten the lock nut.
(17) Lift the piston and note whether it falls freely;
f'ully lower the adjusting nut and check again. If
the second check produces a sharper click than the
first, repeat the centring.
(18) Refit the parts that have been removed, pour thin
oil into the hollow rod of the piston damper to
within .5 in. (12.7 mm.) of the top of the rod.
MINI. Issue1 . 4908
Fig. D.6
The carburetter adjusting screws
Jet adjusting nut. 4. Jet locking nut.
Throttle adjusting screw. 5. Float+hamber bolt.
Fast-idle adjustment screw. 6. Jet link securing screw.
Adjustrnents
Slow running
(19) Turn the throttle adjusting screvr as necessary.
Mixture
(20) Run the engine until it is at its normal temperature.
(21) Disconnectth e chokec able.
(22) Unscrew the throttle adjusting screw until the
throttle is fully closed and then screw it up about
one turn.
(23) Hold the jet up against the adusting nut and then
turn the nut until the engine runs smoothly without
missing or hunting.
(24) Raise the piston about 3l in. (1 mm.). If there is a
momentary increase in speed the adjustment is
correct; if the engine stops the mixture is too weak;
and if it continuesto increasee venw hent he piston
is raised f, in. (7 mm.) the mixture is too rich.
(25) Adjust the idling speed as required.
(26) Set the fast idling screw so that there is a clearance
of about ft in. (.4 mm.) between the cam and the
end of the screw when the engine is warm and
idling with closed throttle. Alteration may be
needed after the mixture has been adjusted. Reconnect
the choke cable.
(27) Fuel starvation or flooding may be caused by an
incorrect float level. To check the level, insert a
$ in. (8 mm.) bar between the lip of the floatchamber
and the hinged lever. Adjust by bending
the lever where the curved portion meets the shank.
On carburettersf itted with a nylon float use a test
bar of { in. (3.18 mm.) diameter.

 

Wow, thanks for posting that information on the carb. I don't need it now, but I definitely will in the future.

Jeff

 

Thanks for all the posts. I can answer some of the questions... From my SU tuning book and what I found on some UK forums, the AAC should never have been fit to an auto 998. Something to do with fixed needles being used on the Autos? The needle I should use to get a slightly richer mix is a AUD1267 (M1 Fixed needle). So that's on its way, it was cheap enough to give a shot even though it may not be the issue.

I do have a timing light, I have never used one. I do know when the carb was rebuilt he followed the procedure listed out above. But he had to back out the brass nut a lot to get the car to run right. I know when he showed me the timing with the light, the arrows lined up... but not sure that means TDC or there was some advancement?

As for the Choke... It runs better the more you pull it out. Though once I get out about 1/2 way it feels like the choke cable is essentially giving throttle to the car. Meaning I can accelerate up to 20mph with the choke out all the way and cruise around like that.

I'll be checking for leaks this weekend, and I'll adjust the carb as outlined. When you say back out the nut 3 flats, that means rotating three revolutions? or three flat sides of the nut?

 

"As for the Choke... It runs better the more you pull it out. Though once I get out about 1/2 way it feels like the choke cable is essentially giving throttle to the car. Meaning I can accelerate up to 20mph with the choke out all the way and cruise around like that"


That's because it is causing the car to "idle" at a higher rpm. My car does the same if I were to do that, although after only a few seconds after I start the car, I need to put the choke in 3/4 to 1/2 the way in. If I have the choke all the way out it floods the engine.

Now that it is colder, I keep the choke out a clothes pin width out to let the fuel run slightly richer since the air is now thinner.

 

Thanks. I think you mean colder air is more dense, thus you need more fuel. But I got the point.

I talked to someone (via email) over at SU. He confirmed that AAC is a proper needle for a standard 998cc setup with a manual but not an Auto. So I think I might be on the right track with the change in needle.

I'll also be checking the timing, and the A/F mixture this weekend. Thanks!

 

So I got a chance to tinker last night. I decided to check the timing on the car. Having read my haynes, watched a video or two, I felt pretty prepped. Once I got the car to idle without choke (to get a true idle with low rpms) I was shocked to see the timing mark not even on the scale. My guess is around 24 degrees BTDC. I was shocked the car would even run.

I wasn't sure where the plate was to loosen the distributor to rotate at first, and I realized that it was loose enough that I could rotate the distributor without much effort. This would explain why it was originally 8 BTDC when I got the car back from the "Mini Expert" and why now it was so far off.

I rotated the Dizzy back and got it to 8 degrees. The car was smooth at idle, revved up nicely. Took it for a spin, and starting losing power immediately. I got it almost home before it died with one wheel on the driveway and the rest in the street. I could not get the car to start again... After unsucessfully trying to push the car up the driveway, I loosened the Dizzy advanced the timing a bit and the car started right up.

At that point, I just parked it for the night, and will look at today. My question is: why would the car idle smooth, rev well, and then loose power when driven, and then not start. I was able to start the car a couple times at 8 BTDC before taking it for a spin with no issues... Second, what does it mean if my car needs more than 8 degrees of advancement to run well?

 

Never Never Never play with the fuel system until you are 150% sure the ignition is spot on . . . .

as you were playing with the dist' was the line for rthe vac' advance connected? Usually when setting the timing the book values are for the vac' advance disconnected and plugged. The once you have the timing set to the right value you'd reconnect the vac advance line (the very small tube running from some vacume source on the motor - varies by model and maybe different on an automatic tranny - and connects the the silver vacuum unit on the side of the dist'.} the function of this is to change the advance as motor speed increases.... In a worst case the vac' advance could be broken . . .

Given that you already found something loose in the ignition, I'd be checking the points. If they were improperly installed it is possible they have shifted in the dist' and the gap could be way off and the plate could even be moving. None of this would be good. Time to read up about changing the points and setting their gap. Not much more difficult than doing the timing (but don't drop the little screws .... esp not into the distributor . . .ouch)

For sake of discussion - one can change the timing if dealing with a pre-ignition issue. Back in the early 70's when lead was removed from gas and the octane rating started dropping like a rock, it was a trick to adjust the timing to get rid of the knock or ping created in high compression engines from the lower octane fuels cooking off b4 the spark would happen.

 

I see your still having problems..............try this....
1) remove rocker cover.......and spark plugs and dizzy cap....
2) put in 4th gear and pull car forward untill NOs:1 and 2 valves (piston closest to rad) are rocking this is NO: 1 firing firing stroke...
3) look at dizzy and see where rotar arm is pointing and pop a dot of white paint opp on block....
4)now replace dizzy cap and see if NO:1 lead is opp dot.........if nor loosen clamp and turn dizzy untill NO:1 lead is opp dot and retighten clamp....
5) refit rocker cover and spark plugs and test............Your timing should be near spot on.......Good luck

 

these cars do try your patience... A week or so ago I installed a new needle on the car. I think it was an M1. After talking to a few different companies the consensus was that it was a good starting point for my Auto 998. I put in the new needle and I was shocked at how well the car ran without any further tuning. It started right up, I didn't need the choke once the car started even when super cold.

I adjusted the A/F mix as described and readjusted the timing. The engine was humming. I took it for a spin last night and the car was just perfect. I took out on the main road to go fill the tank up and got on it a little bit. It kicked down, the revs were building and nearing when I expected the car to upshift, then nothing. I lost all power. I got it to a sidestreet. I could not get it restarted. I checked all the wires/plugs, dizzy, etc. It would crank but would not start.

Sounded like it wasn't getting any fuel. I had to get it towed (last 5 drives, 2 tows). I am thinking a snapped throttle cable maybe? Any other thoughts? Need to get it fixed soon, since the tow truck clipped a stack stone retaining wall we have and took that out, the wife is on a rampage to get rid of Me or the Mini (not sure which one yet

 

sounding, I know, like a broken record ... are you SURE the electrics are right? What you describe sounds to me like your ignition suddenly cut out. No spark equals no zoom zoom. You "checked" the plugs et al. What does that mean? Hold a plug wire to the block, just barely not touching, and crank the engine. Does the spark jump to the block? If no you know where to start looking.

If you have spark - a broken throttle cable would be easy to spot. Look at the linkage on the carb while someone mashes the pedal. Movement: yes = cable OK. p.s. IF the cable was broken, you should have been able to use 'fast idle' mode on the choke. Remember that the first 1/3 to 1/2 (depending on adjustment) of the choke pull on the SU does nothing about choke, it just raises the idle. I can get my RPMs over 3000 with just the choke cable - folks have limped home this way. You absolutel should have been able to start this way if the problem was linkage.

When you crank and crank with no start, do you eventually smell fuel? If no, then maybe you are not 'passing gas'. If spark and the cable and linkage is good here's a wild thought: if you didn't get that new needle in correctly, maybe it has come loose and fallen down into the orifice and is blocking all flow thru the carb . . .

 

Good points as always. I did have spark from the plugs when I cranked. The tow truck guy was cranking while I checked.

I did not get a chance to check throttle cable, but using the choke did not help me get the car started. I know with the new needle the car was starting without choke... so probably not this now that I think about it.

Your wild thought actually makes a lot of sense, because I was not smelling any gas. Great place for me to start looking at least.

 

still having probs what cc is your engine and is it a standard engine with no mods at all...............if modified then you will have to List whats been done to it so we have some clues as to whats what...........IE head, cam, carb, and exhaust.....sounds like jetting and needle problem.....

 

Sorry guys, forgot to update you all. I got a chance to work on this over the holiday weekend... the needle had fallen. I don't know any of the proper terms for what I am about to describe, so bare with me.

I was told by Minisport in the UK that an Auto 998cc has a "fixed" needle and that the M1 needle was a good place for me to start. The car had an AAC "floating" needle. I got the new needle and compared it with the AAC I had and there were obvious differences in the needle. The AAC had, what I can only describe as a top hat on the end of the needle. Essentially a lip that sits on the screw on the carb and keeps the needle in place. It also had a spring on top of this. The M1 needle being a fixed needle did not have any such mounting. It was just a straight needle.

From some random posts on a UK site back in '07 someone ran into the same issue. There is supposed to be some mounting hardware for the auto version of the carb to use these needles (or at least that was my understanding from the thread). The solution he was given was to remove the mounting parts from another needle and use on the new needle.

So that's what I did, I was able to pry off the top part of the needle and put it on the new needle. Unfortunately I did not clamp down hard enough on that, and thus the needle slipped and fell into the hole -- no fuel to the engine. So the fix was easy, clamp down the mounting part to the needle better, reinstall. And like magic the car is running great.

I also replaced the vacuum advance hose, as I did find a tiny crack. Now I was able to get the timing just right. 10 degrees BTDC (it didn't like 8 as much, maybe because of the richer needle?).

Anyways, hope that makes sense. And maybe I am completely off and all new needles are just straight needles without the mount up top. But based on my google searches that's my understanding.

 

here's a wild thought: if you didn't get that new needle in correctly, maybe it has come loose and fallen down into the orifice and is blocking all flow thru the carb . . .

Sorry guys, forgot to update you all. I got a chance to work on this over the holiday weekend... the needle had fallen. I don't know any of the proper terms for what I am about to describe, so bare with me.

You're welcome . . .

 

"Your wild thought actually makes a lot of sense, because I was not smelling any gas. Great place for me to start looking"

You were right. Thanks!

 

still not said what state of std or modded in any way...........

 

I agree 120%

with what ever that says

cuz he's from 'over there'

 

I mean is the engine bog standard 998cc as left the factory.........or modded IE head cam exhaust and carb all these make a difference in setting up