Hello, I'm kinda newb, and posted in the 1st gear the other week...
Anecdote, then question...
Well, when I got my Mini about a month ago, one of the instructions I was given was to keep oil and water in her and she'd be fine. I was slightly concerned to find out there was the nastiest rusty water *ever* in the radiator, so I've just gotten done with a radiator flush and fill (then flush again and again...) and that done, I turn my attention to the fact that she's been having a bit of a rough idle, and coming back from 4xxx RPM she seems to pop a bit. Misfire? Time to replace the sparkplugs? Check the timing? Dist. cap? Anyone have any thoughts? She's got 38xxx miles on the engine and she was built from the chassis-up in 94. Probably time to change the plugs anyway.
Also, has anyone done a change of the sparkplugs and is it difficult? Are there any traps I should watch out for?
Oh, and as I posted in the 1st. gear, thanks to all who've posted in the classic talk - chances are I put your advice to good use when researching/ buying my Mini. If you're reading this and haven't seen picts, sheck out my gallery.
Thanks in advance, and if anyone's in St. Louis, chances are we'll wind up meeting at one of the local events!
LatOr!

 

Swapping plugs on a classic Mini is about a simple a task as you'll ever do under a bonnet. Just make sure you either label your plug leads or only remove 1 at a time.
I removed 1 to get the number off it, then drove the MINI to Autozone and had them do a cross-match on the part number to a plug brand that they actually carry (no Champion in this part of the US), took home my new Bosch platinum plugs, gapped them and installed them. About 30 mins if you don't include driving time.
My wife's favourite part was when the bimbo behind the counter at Autozone told me she couldn't help me cause Austin wasn't in their system. I replied, "I just want spark plugs, not the whole engine." She went and got the (also female) manager who did a lookup and got me the plugs I needed.

 

based solely on my experiences with my '79 (1275, HIF-6 w/K&N cone, LCB, PlayMini exh')

a bit of a rough idle, and coming back from 4xxx RPM she seems to pop a bit. Misfire? Time to replace the sparkplugs? Check the timing? Dist. cap?

Well, you are starting in the right place - always be sure the ignition is solid b4 you mess with anything else. Based on age, swapping the plugs ain't a bad idea, but it isn't where I'd start. First I'd pull one plug and check it for signs. What's the color? Ideally you want a light tan or 'bisquet'. If it is burned/charred, or oily - you have other work to do. I'd pull each plug one at a time and check for fouling - you might want to check the gap. Heck, be sure each cyl' has the same plug! And that the plugs are the right ones!

But if they are the right ones - and a bisq' color I doubt I'd change 'em. To change or pull is easy btw - just get the proper spark plug socket and be sure you don't cross thread 'em. Agro's suggestion of 1 at a time so you don't cross the wires is right on (I label the wires 1,2,3,4 with a sharpie)

I'd be sure my timing was right on tho ... plenty of folks back off the timing to get rid of ping when they run cheaper gas. Run high test - better than 90 octane - and the factory spec is 12 degrees b4 top dead center with vacuum assist disconnected, engine warm and idling (working from memory tho so check me...I use the Heritage CD's to get these #'s, but for ref they have always agreed with Haynes) I spent a lot of time chasing stuff when I couldn't get a smooth idle below 1500, and had occasional run-on at shut down....all went away when I got the timing set right.

new cap? Does it look old; is it cracked? Usually the problem you'll have with the cap will be moisture related. Other possible ignition issues would be the coil or the condensor .... or the plug wires themselves. What do they look like? They can break down over time (factory Miata wires would crap out at 30,000 miles. I didn't believe this on Miata.net until I changed mine. WOW - better ones lasted longer but now I know)

When the engine is slowing you say it pops....is it misfire or an exhaust burble? I get a burble on mine too. This is not necessarily bad. I had A LOT of burble at idle 'til I found a vacuum leak in my intake manifold (an emissions line removed but poorly plugged). When plugged right, burble went way down....still there if I engine brake. From the pic's it looks like you have other than stock exhaust - I do to. The free flow exhaust can be a source of burble because of less back pressure.

I'd look at timing, condition of plugs & wires, and condition of all vacuum lines for signs or cracking/leaks. If ya wanna change the plugs - just be sure you set the gap properly. They probably won't come out of the box right.

 

Thanks for the advice. I'll check the condition of the plugs b/4 anything else. The wires look ok, the dist. cap looks good... I'll look for a vacuum leak in my intake manifold - if only now I knew where that was, what it looked like , or even what exactly it does... I'm not a big engine guy, I'm more into the electronics - wiring, relays, stereo, etc.
Coming from 4xxx RPM in neutral it really sounds to me like it doesn't fire for a fraction of a sec. and then starts firing again after a pop (several times in a row.) Kinda like an old bi-plane stalling out. And at idle it rhythemicly tries to die out, then catches up.
Looks like I'm going to get a spark plug socket first, then see what there is to see. After that, I guess I'll get a light gun to check timing. (gotta figure out how to do that one, too...)
I'm running premium gas right now. The first tankfulls after I got her I didn't notice this, and those were on cheaper gas. Maybe I'm running too high an octaine. I didn't think you could do that. Or I can set the timing where it belongs.
How tough is changing the timing? The Haynes manual does give descriptions of how to do it... Anyway, it's a learning process. The worst thing would be that my "toy" car wouldn't run for a week until the part that I broke came in... And that's at the absolute worst.
I'll post back and let'cha know what I find out, when I find out.
Thanks!

 

see https://www.northamericanmotoring.co...ghlight=timing

 

NGK-BP6ES plugs

Can't tell if wires are good by looking at them...nor cap....

Use only premium, you can't buy too high octane at the pump

Cheap parts, easy to find and replace. After 30K -replace

If you have points, I'd suggest changing to a PERTRONIX IGNITOR ignition and matching 3ohm coil.

 

BTW, your SU may have a spring loaded valve on the throttle plate that may cause your problem. The plate can be replaced with a solid one (joecurto.com).

check out M.A.D.M.E.N. who are hq'd in your area http://members.***.net/mininews/

They will be more than willing to help you out!

 

Actually to keep one of these beasts happy you need

a) Auto motive repair skills and a decent tool box (and a reference manual or two)

b) a healthy checkbook and a mechanic who understands British engineering

c) a local club with a and part 2 of b

d) better yet, a healthy mix of all the above.

"just keep oil and water in it" .... well, that hasn't been my experience.

 

Well, I changed out the plugs, even though the old ones didn't look too bad... and the result is that the "popping" is gone. Running quite strongly at lower RPMs. Idle is still a little rough wavering between 700 and 1000 RPM. At least it doesn't dip into the 500's like it was doing and making me think it was going to die at the stoplight. There's still tweaking to be done with timing and the dist. cap. And I'm going to check the vacuum line...
Of course all of this is put on hold during the 100 degree weather (check local listings.) So, I'll probably pick it back up next week or so...
BTW does anyone know what the max RPM of the engine should be. I've only owned little Japanese made high revving cars, so 6,500 - 7 is what I tend to consider redline. Not that I'm planning on maxing out the 1275 engine every gear, but the power band of most engines is near top RPM - and mine seems like it doesn't want to go much over 4,000. That kinda makes me think (from what I've been reading) vac. line and/or timing. Well, time and tinkering around will tell...
Oh, and the "to keep a classic Mini happy" -That's awesome!
I've got some if not most of that, with myself bringing the skills to the table. Experience, on the other hand, would be nice but I'll pick that up along the way... Thanks all, and I'll post back next week as to progress.
"
Actually to keep one of these beasts happy you need
a) Auto motive repair skills and a decent tool box (and a reference manual or two)
b) a healthy checkbook and a mechanic who understands British engineering
c) a local club with a and part 2 of b
d) better yet, a healthy mix of all the above."

 

I've wondered the same thing - what's the redline. I haven't found that in Haynes or the CDs tho. Since the didn't typically come with a tach, I guess you just go by ear!

Found this on Mini Mania: Racers typically use anywhere between 7000-9000, mostly 7500-8500

but that racer engines. Does that apply to all?

I run mine conservatively, but am curious what the top end is so I can gauge 'how conservative' I am.

My mechanic does note tho that these engines, like your ricers, like high RPM...that's where the power is.

 

Well, mine's got a tach, and it shows in the 6500 range "redline." I'm just not gettin' anywhere near it.
Also, today I've been reading about needles in the SU Carb. Pretty neat read. Wouldn't mind playing around with it... After I check everything else.
http://www.team.net/www/morgan/tech/tuning.html
enjoy!

 

u r learning fast my friend

google SU CARB and search every site deeply. Many say that you can't do squat wrt an SU unless you have the car on a rdyno, with a gas ****' hooked up and a handfull of needles..... if you want some pages, PM me.

 

Funny, there weren't any dynos about to tune these cars for over 40 years ago, somehow they ran on the street and got raced okay.....a little knowledge, skill and patience will get it sussed out.

 

I've been looking at a few of the sites about how to tune SUs. They say to get it "right" you need an exhaust analyzer, but I spend several hours yesterday trying to find one for sale online to no avail.
Anyone have a source for something like this?

 

spent some time looking around and least exp' I found was $250!

That's not inexpensive in my book either. Bt I'll keep looking.

BUT, consider this. My local speed shop (who happens to collect Healy's so Knows SU's), will give me 3 'pulls' on their DYNO for $** ... a lot less than $250....and this hookup is a standard part of the tuning session. So I could try 3 setup's for that plus the cost of the needles....

WRT to the "don't need no stinkin' rolling road" comment. UR right, and the link provided even speaks to that. The anecdote is seeing some racers with a handful of needles and asking how they knew? We don't, we just keep changing and see what happens. That was ART. Unfortunately, we've tried to apply science.

 

Righto!

Like putting a silver saddle on a jackass....hahaha

 

So how the hell do I determine exactly which SU carb I have?

 

Oh yes, been there...... Especially sice I knew I didn't have the stock carb for the car ( doesn't have the original engine either).

I picked up a copy of "SU caruretters

 

I have the Haynes "SU Carburettors" in front of me. None of the pretty pictures exactly match what I see on the car. I know for a fact that it's a non-original engine.
I know that I REALLY need to lean the mixture, but I can't for the life of me work out where the mixture adjustment is!

 

Okay, wild guess...since your car's a 90's you prolly have an HIF SU similar to above. That one is 1 3/4" throat diameter (HIF6/44). They also come 1 1/2" diameter (HIF4/38). But they adjust the same.

Fuel mixture screw is in the hole below the small brass pipe (gas inlet) in the lower left corner of the second picture. Clockwise to enrich/cc to lean.

Idle ajust screw is on the right side above the linkage levers shown at bottom right of the first pic. Down inside the casting next to the right side of the dashpot.

Initial settings:

Idle:
Idle screw 1 1/2 turns after first contact.

Mixture:
Remove dashpot (dome on top of carb)
Careful with needle.
Turn the mixture screw until the jet tube is flush with the top of the jet guide in carb body. Now turn 2 turns clockwise.
Reassemble.

Start, warm motor, readjust - this is where you need a tachometer & CO exhaust gas analyzer.

 

OMG.... it appears that what he "should have"

AIN'T

what he DOES have ....


What was it that Gomer said ......

 

The carb looks like this:

 

I think these pictures will help you identify your SU as an HS

and from what you told me about the # of holes for mounting to the intake manifold, I'm guessing a 1 1/4" HS-2

http://www.minisport.com/classic-min...-products.html

 

It may be a HS4 1 1/2" SU, but still the same function. This is a waxstat carb. The jet tube has a adapter on it that varies the mixture when hot. These can be problematic. Good news is you can buy a kit to convert it to a regular jet from www.joecurto.com.

Put light oil in dashpot piston. 3 in 1 oil, 20W, or similar. To 1/2" below top of hollow piston rod.

Idle adjust:
Photo #2 about 4 o'clock position down in hole, next to dashpot retaining screw

initial setting- unscrew until it is just touching its stop and the throttle is closed. Then turn 1 1/2 turns open.

Mixture adjust:
hex nut under carb, spring loaded. turn in (clockwise frm underneath) to lean, turn out (counterclockwise) to enrichen

1. remove dashpot & piston
2. disconnect mixture control wire
3. screw adjusting nut up until jet is flush with the bridge of the carburretor
4. refit dashpot & piston, check the piston falls freely on the bridge when the lifting pin is released. Piston lifting pipn is at about 11 o'clock looking from above the carb just under the daspot mounting flange. In photo #1, it'd be under by the air cleaner, under where the screw for the dashpot is.
5. turn the adjusting nut down 2 turns (on non-tamperproof carbs, 3 turns on tamperproof carbs)

Start engine and set desired idle speed.
Turn the jet up or down to obtain the fastest idle speed consistent with even running
Reset idle speed
Lift the piston via piston lifting pin (or small screwdriver 1/16")

• if idle increases & stays higher, its too rich - lean out
• if idle stumbles , its too lean - enrichen
• if idle momentarily increases then returns to idle - just right.
• Reconnect mixture control wire

 

Minimad - THAT's the info I was looking for. Thanks.