Back- and Mis- firing issues...

Post by **alex_holden** » Thu Mar 15, 2007 9:30 pm

You can't overfill it - if you put too much in it just overflows into the carb and burns up in the engine. Perhaps the oil has solidified?

Post by **jackkelleher** » Thu Mar 15, 2007 9:42 pm

I just replaced it! And even the old stuff was less than a year old. Well, I'm mystified. Nothing seems to be getting in the way, but it is quite stiff... Actually, it gets progressively harder. The first time after a pause of ten-odd minutes it's easy to lift the piston, and with every successive lift it gets harder until it's prettymuch impossible.

Post by **bmcecosse** » Thu Mar 15, 2007 9:46 pm

Sounds like something is blocked - but try it with the damper rod unscrewed - to see if the piston can actually move freely. The wobbly needle is an 'improvement' that was fitted on later carbs to stop the needle binding up in the jet. Minors never had them - so it must have a later carb fitted.

Post by **jackkelleher** » Thu Mar 15, 2007 9:50 pm

Really? Oh. It has a late (but still Minor) air filter, and seems fairly standard. I did notice a slight difference in the float style and float chamber lid, but they were negligible details... Does it make much difference?

Post by **Packedup** » Thu Mar 15, 2007 9:53 pm

jackkelleher wrote:Well, the needle is straight, but it moves considerably within its housing. With the tightening screw fully tightened, there is a play of about two millimetres in every direction. I have dismantled and rebuilt two or three different carbs (I have a whole load lying around) and none of them have had this.

If you've got teh spring biased needle arrangement then this is perfectly normal - Loosen the screw and remove the needle and collar. If there's a spring pushed over the end of the needle then you have got the springy one. If not, then you may well have a serious problem!

Post by **jackkelleher** » Thu Mar 15, 2007 9:59 pm

I'll try that, thanks.
So, I tried the piston with the damper removed and it worked fine. Replaced the damper and it was almost immoveable.

Post by **Willie** » Fri Mar 16, 2007 5:30 pm

If the piston will not rise freely with the damper fitted with NO oil in it then the problem is mechanical friction. If it is only too stiff with oil in it then examine the end of the damper. There should be a brass collar which is retained by a split washer and which is free to move up and down by at least 1/8". If it is not free to move then check that someone
hasn't added washers which prevent it moving which is essential to allow the oil to pass through the damper valve.

Post by **bmcecosse** » Fri Mar 16, 2007 7:50 pm

The springy needles came in later than the Minor - must be a carb from a Mini. But that's ok - they are better carbs! Try the very thinest of oils in the carb damper - it must move to the top of the stroke, although there should be a steady resistance.

Post by **jackkelleher** » Fri Mar 16, 2007 9:51 pm

Thanks, people. I'll try all this stuff. Is there a "done" way to thin oil? Or do I just procure some thinner stuff?
While spending a couple of hours under my car with a rag and some degreasant, proving to myself that the gearbox is indeed silver and not black, and the engine is still green lower down (affirmative on both counts) I found something very interesting: There is no gasket between the'box and engine!

Is this normal? I'm fairly sure it's not. It might explain the nice steady (but fortunately slow) oil leak from that general environ... Am I right in thinking that this means removing the engine to fit a new gasket?

Big job for me without any damn decent tools out here!
Also luckily discovered that screws on the timing cover were coming undone, now safely done up once more...

Post by **Willie** » Fri Mar 16, 2007 10:07 pm

There is no gasket between the engine and gearbox. The thickness of the oil in the damper will not be the cause of your problem, it is ok to use engine oil.

Post by **jackkelleher** » Fri Mar 16, 2007 10:21 pm

My god, that's a relief. One less problem...
So, what would be the cause of this? I checked, and there are no extra washers, and it moved fine without oil in it.

Post by **Willie** » Fri Mar 16, 2007 11:14 pm

I am having Trouble posting answers on here Jack, keep getting invalid
session

Post by **jackkelleher** » Fri Mar 16, 2007 11:27 pm

Oh yeah, I had that problem the other day. Don't worry, I'm happy to wait.

Post by **Willie** » Sat Mar 17, 2007 7:42 am

I am not familiar with the spring loaded needle type of carb but wonder if that stops the 'soft plop' when the piston hits the bottom. You may be
misinterpreting the pressure needed to lift the piston as it should need a steady pressure as you are forcing the oil through the damper valve.
Unless you are putting treacle in there i would suggest that you try the car with no oil in there. Normally this would make it undriveable since it
would stall whenever you tried to accelerate.

Post by **Packedup** » Sat Mar 17, 2007 10:09 am

Willie wrote:I am not familiar with the spring loaded needle type of carb but wonder if that stops the 'soft plop' when the piston hits the bottom.

Nope, it's just a very weak spring that leans the needle very gently to one side when the piston/ dashpot is removed. It's nothing like strong enough to cause enough friction to mess with the rise and fall of teh piston, there should still be a quiet metallic clunk (or "plop") when the piston is raised and let go.

Post by **bmcecosse** » Sat Mar 17, 2007 10:55 am

There's no gasket - the oil will be easing pat the rear scroll seal on the crankshaft - made worse by any crankcase pressure. Best to use what we would call 3 in 1 oil - it's a thin domestic oil sold in little tins for door hinges etc. Probably get something like that in the Dollar shop!

Post by **jackkelleher** » Sat Mar 17, 2007 5:24 pm

Oh, yes, I know the stuff. All right, I'll get some. Thanks, people...

Post by **Willie** » Sun Mar 18, 2007 10:57 am

Jack, did some checking re the damper and you should check the following. starting from the bottom you have the spring clip, then the brass barrel which should have the champhered end downwards. Then you have a floating brass washer. THIS WASHER MUST BE FITTED WITH THE CHAMPHERED SIDE OF THE HOLE UPWARDS. If it is fitted the wrong way up then the gap through which the oil can pass is reduced thus causing more severe damping than intended.

Post by **bmcecosse** » Sun Mar 18, 2007 11:20 am

Interesting - never known one to be taken apart - but obviously it's possible. I do know there are different amounts of 'free travel' rods available - and Special Tuning specified 90 thou dampers for use on the Works Rally Minis.

Post by **jackkelleher** » Sun Mar 18, 2007 2:54 pm

Interesting; well, since I have a mini carb in place I could fit one of those if the urge took me couldn't I...Hmmm.
Well, I'll check the damper washer/clip order at the next opportunity, but unfortunately my parents want to go out just now. I think it's all correct, though, from cursory examinations in the past- but we shall see.
By the way, does it matter that when the piston is removed, the spring mechanism means that the needle points off to one side? It's pulled straight when it fits into the jet...

Morris Minor Owners Club

Back- and Mis- firing issues...

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damper

damper

Re: damper

damper