34 replies to this topic

[crackfoo]

Hi, 

 

First time owner of a classic mini! Rupert was off the road for 11+ years until recently. I took it to a shop to get the needful done and the running and legal. Basically there are no shops around here that can deal effectively with carb'd engines. The few dynos (rolling roads) around here, won't even entertain taking on a carb'd car to have tuned. So professional resources  are limited. 

 

I've read a lot of the posts here and other places about tuning the carbs and I suspect there is some issues with the existing setup. The front carb when it hit the shop was completely plugged up with old gas. Was taken apart and cleaned up and reassembled. The problem I have is when I'm casually motoring around town.  Often on take off (unless I really come on to it) it gets quite boggy and I have to back off the gas and kinda tap on the gas to pull it through smooth again, until the next gear. Most times it will be fine if I reaaally take it easy but it's hard to baby it around. On the other hand, I can't really go around tearing the wheels off it all the time.

 

I've seen quite a few suggestion, to leave the carbs alone until you've checked the electrics! I think that might be the majority of the issue as the shop did balance and set the carbs up as best the could, and those standard checks seem to be in order (piston left) etc... There are a couple items I'm not sure about how the car would behave:

 

The vacuum spigot is blocked  (blocked_vacuum.jpg) off and it looks like my distributor doesn't have a vac advance anyway. What effect would that have?

 

The brass pipes that come off the carbs (carb_overview.JPG) at an angle, have a single hose attached between them? Is that proper? Is that breathing into each other?

 

The shop check the points, rotor arm, clean them up etc... and said the timing was set but would that be true on for idle? 

 

I'm thinking perhaps I should just get a new electronic distributor as the one on there looks to be in general, rough shape...  (coil_dizzy.JPG)

 

Some engine info:

 

Engine Type, 12h A Series (MiniSpeed)

Size: 1380cc (73.94mm Bore)

Pistons: Hepolite

Cam: 276

Clutch: AP Racing Clutch Kit

Flywheel - Pre-Verto

Timing Gear: Duplex

Carbs: Twin 1.5” SU HS4 w/ AAA needles

Filters: K&N Cone

Distributor: Aldon Yellow?

 

 

Any advice/suggestions would be great.

 

Paul

Attached Files

•  blocked_vacuum.jpg   54.4K   11 downloads
•  carb_overview.JPG   77.35K   25 downloads
•  coil_dizzy.JPG   79.93K   8 downloads

Edited by crackfoo, 03 December 2014 - 04:28 AM.

[Spider]

These sort of problems can be very hard to resolve properly from behind a keyboard, however it maybe worth checking some basics.

 

Your carbs are twin HS4's.

 

The 'bogginess' you experience when taking off could be a leaning of the mixture under accelleration. If you undo the Black Plastic thumbcaps on the top of each carb, the 'space' within should be filled to within about 20 mm of the top with Engine Oil (though there are many Oil Used, that would be a starting point), this may help with that problem. It would also be worthwhile checking for vacuum leaks around the carbs and manifold.

 

You may also find much useful information here;-

 

http://sucarb.co.uk/...ion-adjustments

[crackfoo]

yeah, I know these problems are tricky troubleshooting this way. The dashpots have about that much oil in them, but it does seem really thick, but it's clear, perhaps cause it's pretty cold here now? Getting into the 0C to -5C ranges and soon colder. Some suggest ATF? Putting them back they seemed quite resistant but I think that might be from the oil trying to get displaced. Should they be pretty firm to re-insert?

 

Thanks for the link.

 

Cheers

[Spider]

Maybe try some thinner oil, but I don't think that would be the problem as when the car does get warmed up, the carbs do get some considerable warmth from the exhaust, however, with ambient air temps around those numbers, I'd say the mixture getting in to the cylinders isn't attomising properly and maybe either a richer needle(s) and/ or setting the mixture richer maybe what's needed.

 

Also, what altitude above sea level are you at?

[KernowCooper]

Use the lifting pins built into the carb body if the engine stalls the carb is to weak if the engine revs up and stays there its to rich, it should rev slightly and resettle, only do this though when the rest of the engine tune been done.  revove the filters and use a small hose and slip it into the carb mouth in front the slide and listen to ensure both carbs are pulling the same amount of air, adjust as required.

 

Here are the BL Special Tuning needles

 

Twin H4 1.5" Special Tuning

Engine Size

Needle Std.

Needle Rich

Needle Lean

Spring Type

850 and 1071 S Competition

MME

-

-

Blue

997 Cooper with thermo jets

MME

-

-

Blue

998 Modified Head

AO

-

-

Blue

970 Cooper S Competition

CP4

-

-

Blue

1275 Cooper S Competition

BG

-

-

Blue

 

Below you can see the BG is richer than the AAA worth a couple of needles to try, obviously readjust the carbs after fitment

 

BG = Yellow

Attached Files

•  aaa v BG.png   85.41K   13 downloads

Edited by KernowCooper, 03 December 2014 - 12:54 PM.

[crackfoo]

I think I may try thinner oil anyway. The day I checked them it was a warmer day and seemed thick.

 

I get the impression that it is already running rich as there seems to always be a smell of gas and my gas milage is pretty terrible. I'm at nearly the highest point in the city which is only ~100m above sea level. When I go to work, it's on the water front, so only a few meters then.

[crackfoo]

Use the lifting pins built into the carb body if the engine stalls the carb is to weak if the engine revs up and stays there its to rich, it should rev slightly and resettle, only do this though when the rest of the engine tune been done.  revove the filters and use a small hose and slip it into the carb mouth in front the slide and listen to ensure both carbs are pulling the same amount of air, adjust as required.

 

 

I did that as a check when it came back from the shop and the engine behaves as I would expect with the piston test, but I did do it with the filters off... and I haven't done the hose/air test... I'll try those tomorrow but you say only when the rest of the engine has been tuned. Do you mean the electrics? 

[KernowCooper]

Timing and a engine tune, tappets etc.

[crackfoo]

Timing and a engine tune, tappets etc.

 

Right ok. Haven't explored the tappets yet, thats uncharted territory for me so far.

 

You suggest a BG? That's quite a different curve than the AAA which Minispeed fits with the engine... I am willing to try some different needles though as the shop I had it in said it could use some.

 

Any thoughts on the vacuum? I think the car was originally destine for a track which a vacuum wouldn't have been needed. I'm looking to use it as a road car, would it be worth getting a dizzy with one?

[crackfoo]

 remove the filters and use a small hose and slip it into the carb mouth in front the slide and listen to ensure both carbs are pulling the same amount of air, adjust as required.

 

A uni-syn will accomplish this test correct? I just got mine in the mail today...

[KernowCooper]

Yes mate if you have a vacuum balancer then fine, if your car is used on the road a vacuum unit is a must it will drive better on a light throttle with more torque and return more mpg.

[crackfoo]

Yes mate if you have a vacuum balancer then fine, if your car is used on the road a vacuum unit is a must it will drive better on a light throttle with more torque and return more mpg.

 

Ok good. Will put the uni-syn to the test tomorrow just to see where it's at.

 

I figured as much with the vacuum as I'm really only seeing some problems when I'm casually getting around town. With the engine mods I have, am I restricted to only a yellow aldon dizzy w/ vacuum (I think they exisit) or are there other dizzies that would fit the bill? I would like to move to an electric ign anyway so hoping I can find an alternative here in Canada.

[KernowCooper]

The Aldon Yellow is a very good distributor and I have one in my 1330 (95bhp) 276 cam with a vacuum advance, if you want electronic then either fit the Aldon Igniter which I have in mine or use a Powersparks/Accuspark/Britpart unit in yours £30. Lots here run one of those and they are reliable.

 

Another distributor even the electronic wont have the correct curve, I would just get a Vac Advance Unit from Aldon for yours and a electronic trigger. The FAQs Electrical has a step by step on how to fit one which I did last year.

[minilee94]

Hs4 is abit small for a 1380 you need a hiff carb or weber

[crackfoo]

Hs4 is abit small for a 1380 you need a hiff carb or weber

 

 

Twin HS4 even?