Classic Mini Engine Parts
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 Posted: Jul 10, 2020 03:53PM
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one last update:

 

after narrowing it down to most likely a carburator-related issue, i took it down to Heritage for a look-see to see what they would say. Larry, who has been ever-patient with me and my questions, took a look and noticed that the linkage between my twin carbs was activating them slightly off of each other, and that the fast idle cam wasn't even touching the screw on one of them when the other was being activated. he recommended that before doing any major adjustments, i balance the carbs against each other, adjust my idle, and align the linkage to the carbs.

spent the last couple hours futzing with it and putting it all back together, and i can say that the car is running much more smoothly now! i might invest in a proper manometer to balance the carbs more accurately (i used the rubber tubing method described in the haynes manual) but it certainly is noticeably better than it was.

next up i will probably want to tweak my idle/fast-idle speeds, as i couldn't quite get that locked in... idle seemed a bit fast, but if i lowered it down any more the car would stall out after a little while again. are there any general tips for getting that dialed in?

 Posted: Jul 5, 2020 01:30PM
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Wanted to post an update that I've cleaned and re oiled my air filters as well as changed my spark plugs with no noticeable effects. Next up will be vacuum leaks, engine timing, and carb adjustment.

Thanks again to everyone assisting!

 Posted: Jun 30, 2020 10:59AM
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CA
The reasom I asked about vacuum-assisted brakes is that they use a port on the carb. If the connecting hose is leaking, your car will run lean. Deeper in, the vacuum actuates a diaphragm that provides the assist. If the diaphragm is old, it may be leaking. I don't have that so cannot advise further.

A simple test would be to remove the brake vacuum hose from the carb and cap the port. Go for a careful test drive away from hill and traffic and see if the engine is better. Be aware you will have to really stand on the brakes without the assist - hence no hills or traffic. If you don't feel any difference in the brakes, the booster may not be working anyway.

.

"Hang on a minute lads....I've got a great idea."

 Posted: Jun 30, 2020 07:22AM
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it is my first mini, and first classic car. purchased in december, it was already very nicely restored so i was starting from a good place and have only had to do minor maintenance thus far.

i checked the dashpots and they seemed to have enough oil. i honestly can't tell about whether the air filter is clean, it looks greyish but i'm not sure what color it was to begin with. probably wouldn't hurt to hit it with the air hose while i'm under there and see what comes off, and replace it if it's pretty bad.

i do have a brake vacuum servo (i think it has another name but i'm blanking on it so i had to look it up in my hayne's ), do you think that it could be related? while i was letting the car idle with the hood up, i noticed what sounded like a hissing sound, so anything that moves air will likely be my next place to look.

i have been thinking about getting new plugs since the issue began, but have put it off because they seemed to be fine (although they are gapped rather larger than the manual says but have been since i got the car). but for the price, i might as well just do it and see if anything happens.

 Posted: Jun 30, 2020 05:51AM
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US
Install a new set of spark Plugs - yours are probably fouled out from the bad running + idling around alot.
  Freshen those before you start making other changes .  Foulded plugs stumble easily and chase missfires.



NGK - BPR6ES -  Part number 7131 at your local parts store.

 Posted: Jun 30, 2020 03:02AM
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CA
You said you are new here. Welcome!
How long have you owned this car? Are you relatively new to owning classic Minis?
(My suggestions are based on the assumption you are new to Minis.)

Assuming you have a SU carb, before changing any carb settings, have you checked the dashpot oil in the carb? A  gradual decrease in performance is often caused by low or absent oil.

If your carb is a SU HS type, it will have a little fuel bowl hung on the side of it. You can remove the cover and inspect for dirt. On the underside of the lid is a float valve - be very gentle with it, being careful not to change its settings.

Is your air filter clean and properly seated?

Are there any vacuum leaks? Do you have vacuum-assisted brakes and are the vacuum hoses in good condition and properly connected?

.

"Hang on a minute lads....I've got a great idea."

 Posted: Jun 29, 2020 04:36PM
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well the new coil seems to have resolved the tachometer issues, and the engine stalling at idle, but the rough running seems to still be there. so at this point i'm probably going to have to chase down carburetor adjustments and cleaning and check for leaks, as you all have recommended. hopefully i don't leave the car inoperable for too long.

thanks to everyone helping here, i purchased the car as a way to force myself to learn my way around an engine bay and i'm enjoying every minute of troubleshooting. i'll update as i find out more!

 Posted: Jun 29, 2020 03:04PM
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US
It could be electrical but it sounds more like a vacuum leak to me. Check that the carb and intake manifold fasteners are tight. You can also run a bit of water over the intake manifold joints while the engine is idling to see if it will stumble. Air leaks in the connections of the breather control valve or the brake booster can cause problems.

Kelley

"If you can afford the car, you can afford the manual..."

 Posted: Jun 29, 2020 05:29AM
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US
As Ian said in his first post, the tach behavior indicates you have a problem with the low-tension side of the ignition system.  It may be the coil, it may be the condenser.  It could also be the points but probably not if the gap is right.

Also as was suggested above, borrow a 12V (standard, non-ballast) coil and install it as a test.  If the problem goes away, buy a replacement coil.  If the problem persists, re-install your old coil and fit a new condenser and points.  

Always start with tests and if you begin buying parts to swap, buy the cheap ones first and only change one thing at a time.

Doug L.
 Posted: Jun 28, 2020 11:03PM
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Coils is coils .. to misquote an old TV ad.  Actually there are 2 types .... ballasted or not.  Surely you know someone with an old car or truck that has a coil (of the correct voltage) that you could borrow for 10 minutes?

Cheers, Ian

 Posted: Jun 28, 2020 03:53PM
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all great suggestions, thanks to everyone! i have a timing light but i'm not sure if the leads are long enough to reach into the car for a road test,  i definitely want to check and make sure i'm getting regular spark at each plug. i know they look healthy enough but that doesn't mean that an individual one isn't misfiring every once in a while.

luckily i'm local to a great shop (heritage garage) so i'll give them a ring on monday about a new coil... i didn't realize it could test fine on the bench and still be a problem. and if it's not the issue, then it wasn't too expensive and at least i'll have a spare in the garage

before this, the car was running very smoothly, then this started to crop up little by little. it's been progressing slowly, so i'm not too concerned, but it's noticeable enough now that i want to take care of it sooner rather than later.

 Posted: Jun 28, 2020 03:26PM
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I shudder to think what parts get purchased without knowing if it’s fuel or spark.  

 Posted: Jun 28, 2020 11:56AM
 Edited:  Jun 28, 2020 11:56AM
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Distributor Doctor in the UK is a good source for quality ignition parts, condensers and points.  Not that expensive but good stuff.  Only drawback is the time involved for shipping from England.

 

"To catch one, you need one"....John Cooper

 Posted: Jun 28, 2020 10:19AM
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US

 

Don't start changing a bunch of parts guessing. You'll never know what the issue was. Start with the coil as suggested, and a condenser is cheap. Buy a good brand product.  If you don't have a shop manual, get one for your car. It has all kinds of troubleshooting info and test info along with the regular mechanical repairs.

What was your car running like before this started?

 Posted: Jun 27, 2020 08:43PM
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I fixed a similar problem with a new condenser. Then fixed it even better with Pertronix electronic ignition.

 Posted: Jun 27, 2020 07:52PM
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Install new plugs, maybe change the brand and/or heat range. NGK BP6ES or BPR6ES are the most popular. I've found Champions to be useless.

 Posted: Jun 27, 2020 06:40PM
 Edited:  Jun 27, 2020 06:44PM
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If you have a timing light, hook it up, run it inside the car so you can see it flashing, go for a drive and see if missed flashes coincide with misfires or not. Works really well to decide if it’s a fuel or spark issue. Start with the coil wire if normal, move on the each cylinder wire.

 Posted: Jun 27, 2020 04:20PM
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I would be suspicious of the coil.  Try to borrow one: a known good one is better for testing than a new off the shelf..

The tacho is a dead giveaway that you have an ignition issue.  IME you can't really do a useful coil test.  My Father-in-law used to run an autoelec shop and they chased a bad running problem I had with an old Volvo.  They tested the coil and everything else.  We changed computers and all sorts of stuff.  Eventually they decided to chuck in an old coil that was laying around and voila!  Problem solved...

Your problem could be hiding in lots of places but the coil is good place to start (@ zero cost if you can borrow one from a mate or local shop

Cheers, Ian

 Posted: Jun 27, 2020 03:57PM
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howdy, brand new here but wanted to get some input about an issue i'm having. my 66 austin cooper S is getting a bit rough, usually when driving at a steady pace between 2k and 4k RPM. feeling is just generally juddery/jumpy, not as obvious as a regular misfire but similar. also it will often stall when idling at a stoplight, though i can avoid this by giving it a little more juice with the throttle or pulling out the choke enough to give it a higher idle.

initially i thought it might be electrical, as my tachometer is also acting a bit funny (jumpy/glitchy in those ranges) but i've checked my spark plugs, dizzy points, and ignition coil resistance and they're all well and good as far as i can tell.

is it time to tear apart my carbs and give them a good once-over? can i avoid this by putting some Sea Foam in the tank? i've been avoiding this because it's beyond my comfort level, but i've got to start somewhere i suppose.

thanks in advance!