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Cylinders 2&3 Look Like Nothing Is Going On?


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#1 YeOld&Gold

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Posted 11 June 2021 - 06:46 PM

To keep it short I've just picked up my self a colortune 500 of eBay and it's a neat bit of kit as it took no time at all adjusting the air fuel mix.

Just out of curiosity I thought I'd see what the other cylinders are doing and in doing so something doesn't seem right with cylinders 2&3. 1&4 have a nice blue burn to them with a touch of orange as I think running a tad on the rich side seems Ideal from what I read up on so far.

2&3 have next to nothing going on, the spark seems brighter than the burn.

Things I've done so far and not in any order which could be the issue it's self to be fair

- Points gap (new points & condenser)
- Timing as best as it can get as the previous owner bent the toothed tab completely out of whack
-Tappets set at .12 thou across the board
- Full carb Tear down and clean, not check the needle though
- Fuel filter added inline


The engine is completely stock, 998cc ,it's an SU carb fitted

Other things pockets of information ive found on here before joining is carbs can favour sides, I need to buy a compression tester, could be burnt values and a few other bits, will have a look at my book marks on Chrome to find the thread it had loads on it.

All in all though it drives well and doesn't seem to be under powered will sit a 50mph even got to 60 at one point on a commute to work.

Any ideas on what it could be or if it's normal for a mini would be good the hear

Cheers for having a read through

Edited by YeOld&Gold, 11 June 2021 - 10:59 PM.


#2 Coalhod

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Posted 11 June 2021 - 07:36 PM

Possible air leak at #2 and #3?  This can be checked by squirting carb cleaner around the intake manifold area and note if there is a rise in rpm's.  Compression test a good idea also for possible head gasket leak in that area.



#3 YeOld&Gold

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Posted 11 June 2021 - 08:18 PM

Will pick up some more carb cleaner this weekend and give it a go.

I did have the exhaust manifold and inlet of just the other day getting to the fuel pump and noticed the alloy spacer block to my carb has loads of cutting marks both sides, quite deep to with gaskets either side. Didn't think anything of it but could be the issue now you mentioned a possible leak.

#4 bpirie1000

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Posted 11 June 2021 - 08:31 PM

Did you switch the plugs about see if thatchanges anything?

Clean the dizzy cap?

#5 YeOld&Gold

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Posted 11 June 2021 - 08:58 PM

Points & condenser are new gap set to .15 thou at TDC on compression cylinder 1 , dizzy cap is new, HT leads are new all working as i can see a nice spark when using the colortune plug, firing order seems to be fine 1-3-4-2, plugs swapping doesn't change anything.

 

All replace over the past month  

 

Is posting short videos a thing on this forum? 



#6 sonscar

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Posted 11 June 2021 - 10:03 PM

Air leak is unlikely as 1&2 share the same port and3&4 share the other,though not impossible.The inner and outer ports receive different mixtures tho I forget how,outside richer?What you see could be normal.60 should be no effort at all.Steve..

#7 Steam

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Posted 12 June 2021 - 07:24 AM

Is it actually misfiring or are you chasing ghosts in the colourtune tool.
Personally I have not much time for colourtune, too many variables.

#8 Ethel

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Posted 12 June 2021 - 08:37 AM

To an extent it's just the way A Series are made. It's the siamese ports: 1 immediately follows 2 & 3 follows 4, so the inner cylinders have a free run on the inlets, while the outer cylinders have to snatch them off their twins. It creates many quirks, like charge robbing, fuel flow bias...

 

What you get at idle can be different to what you get under load when there's less manifold vacuum & less induction overlap - measured in time, rather than degrees.*

 

Vizard wrote an article about rigging up a d-i-y colortune dyno with axle stands & your brakes.  :unsure: Taking your front wheels off was probably the most critical part!

 

* My uneducated guess - at idle, the pressure drop across the throttle is acting 1 part carb to 2 parts refrigerator. The petrol is dropping out of the mix and inertia favours the straighter path to the outer cylinders as it streams along the manifold walls.



#9 Chris1275gt

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Posted 12 June 2021 - 09:09 AM

At idle mine has slightly different colours on the outer cylinders. Give each cylinder a 10 second blip at 2000 revs and see what each is doing mine are all the same colour. Exhaust colour is fine plugs look perfect and mot man is happy and it runs well. What Ethel says is sensible.

#10 YeOld&Gold

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Posted 13 June 2021 - 09:32 AM

Could be chasing ghosts but I've got no experience with minis other than being able to take it apart then re assembly

I've fired her up today let it warm up then give her a 10 second throttle blip and still not much going on.

There is a compression kit on its way to me today, Currently have the engine in bits any ways as it needs sprucing up

Picture of the plugs see if anyone picks up on something

Edited by YeOld&Gold, 13 June 2021 - 12:18 PM.


#11 YeOld&Gold

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Posted 13 June 2021 - 09:36 AM

4 3 2 1 in order

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#12 Ethel

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Posted 13 June 2021 - 11:12 AM

Hard to say, if it's not run under load it won't really get hot enough to burn off any accumulated carbon. Where you can se past the carbon they look ok, 2 looks a little oily, but wouldn't say it's excessive on the strength of that photo.

 

It could just be damp with fuel because that's where the engine stopped - another A Series quirk



#13 sonscar

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Posted 13 June 2021 - 11:55 AM

Rest assured that if you only had two cylinders working you would know,however if the head gasket was only passing slightly at the moment?Compression check would be reassuring.Good luck,Steve..

#14 YeOld&Gold

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Posted 13 June 2021 - 12:27 PM

Thanks for all the input really appreciate it,

I've got some new gaskets on order for a number of things, head gasket is one of them. To be fair if I'm chasing something that's nothing and just a mini thing like a few have mentioned.

More information and experience, also checking the inner parts along the way would be reassuring that driving it isn't going to be an issue.

#15 YeOld&Gold

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Posted 19 June 2021 - 06:56 PM

Very delayed reply i do apologize,

 

So after doing a lot of cleaning up in the engine bay and still tons more to do, finally got around to compression testing.

 

Cylinders 4 160 psi 

                3 50 psi

                2 40 psi

                1 165 psi 

 

looking like Something internal and hoping nothing to bad has happen, going to start dismantling it some more will keep you all posted.






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