Here is an interesting one for you.

The mini purrs for a while and runs really smooth when it is first running but after a while starts to be a bit harsh. Im not sure if is the engine or gearbox but is this common for mini's?

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Cheers
Alec
1275LS - July 78 - XNFAD18Y/102918

Anyone?

I'm thinking it is the gearbox..

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Cheers
Alec
1275LS - July 78 - XNFAD18Y/102918

Just for interests sake are you using a single row timing chain or a duplex , also what is your breather set up like

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It is a late A series 1275 (12H87UH) so I believe it is a duplex.

The breather is set up as per standard. I replaced the pipework on this not long after I got the car as it had Matt Read style 100% blockage in both of them.

Out of interest, it will idle down to 400 when it is just warm.

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Cheers
Alec
1275LS - July 78 - XNFAD18Y/102918

So duplex timing chain ( maybe ) , breathers OK ( maybe )

Next , do you have twin 1 1/4 SU,s with a swinging needle , also how old is your fuel filter

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Even the late 1275s were just single row chain.
When was the last time the oil was changed? maybe when the oil warms up that has something to do with it.

I'd even wonder if the timing is a fraction out, the car runs okay when cold (choke on running rich?) but with everything up to temp its more sensitive.

Hows the car to drive and through the rev range?

what makes you say it could be the gearbox? normally it'll be obvious that it's one or the other.

how do you describe "harsh"?

It is due for oil so I'll do that this weekend.

Fuel filter.. no idea. Not since Ive had the car. I'll do that with the oil/oil filter.

Generally ok through the range. Not fantastic off the mark but once moving it boosts along quite well for a small car.

I was having a stab with the gearbox comment as I have nio idea and no one was saying anything.. By harsh I mean it just seems to get rougher. I cant really describe it better. Not running rough but feeling rough if that makes sense? If you think of a sewing machine, it runs smooth and quiet with low vibration. When the car gets harsher it gets a bit noisier and the vibrations become a bit more distinct.

I was going to take it to our friendly zombie mechanic a month ago but he decided to take some time off for R&R

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Cheers
Alec
1275LS - July 78 - XNFAD18Y/102918

Well, lets put this scenario together , a dirty fuel filter , an SU with a worn swinging needle , a stretched single timing chain, timing slightly out , breathers need to be checked , tappets need adjusting back to 0.015in

.

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hmm

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Cheers
Alec
1275LS - July 78 - XNFAD18Y/102918

hmm

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Cheers
Alec
1275LS - July 78 - XNFAD18Y/102918

hmm

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Cheers
Alec
1275LS - July 78 - XNFAD18Y/102918

Yep.

So whats the deal with the SU. It is a HS6 by the way.

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Cheers
Alec
1275LS - July 78 - XNFAD18Y/102918

It could also be the ign timing is too advanced- if so it'll tend to run rough, more so when hot.

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DrMini- 1970 wasaMatic 1360, Mk1S crank, 86.6HP (ATW) =~125 @ crank, 45 Dellorto (38 chokes), RE282 sprint cam, 1.5 rockers, 11.0:1 C/R.

Any motor repair workshop with an electronic tune up and diagnosis gear would quickly get to the bottom of the problem. It could an infinite variety of problems from ignition leads, spark plugs, points etc etc.

In this case, rather than a shot gun approach, it would be a wise investment and save you many hours of dead ends and frustration.

I dont know if "TheMiniMan" Matt Read is back up and about after his health set back but he is also in Brisbane and a very good mini mechanic and would also spot your problem very quickly for you.

Mike