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Feb 27, 2023 20:05:40 GMT
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Gradually getting this Mini back on the road after 12 years
It ran well when taken off the road and the only difference is another cylinder head being fitted
After discovering the distributor is 180 degrees out I set the timing. 12 degrees at 900 rpm idle and 32 at 4000 rpm
It runs quite well but bogs down at around 2500rpm but is good before and after
The car is away getting painted until Wednesday and I'm sat here thinking through what it could be
I think the timing is ok. Could the mixture help?
I don't know what the plugs look like at the moment
Is a flat spot because the engine isn't getting enough fuel at that moment?
Oh It's got 20w50 oil in the dashpot
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I would suggest it's a carb issue or the distributor isn't advancing, if you have timing light you can check the distributor is advancing and also that you are not losing spark as it advances (broken wire to baseplate or cap / rotor arm fault). For the carb check the float level is correct and the bowl not full of crud, that enough fuel is getting through (stick the feed pipe in a jar and turn the ignition on), that the piston rises freely and that the jet is not blocked or worn oval.
Oh and perhaps first of all is is running fresh fuel isn't it?
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Feb 28, 2023 20:51:25 GMT
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When you're driving and experience the flat spot pull the choke out , this will enrichen the mixture, and see if things improve.
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I haven't done much checking as yet and now i've run out of time. It's going on a 80 mile road trip tomorrow so we'll see how it does
It basically drives ok and may even be getting better with more use. It did have a small amount of fuel all those years but i ran some of that out and put a couple of gallons of fresher stuff in before starting. I don't think it's as clean as it could be but at the moment the problem is staying very consistent so i don't 'think' it's a dirty fuel problem. I'll fill it up with new stuff tomorrow but would like to flush the tank out at some point
At the moment it's usable and will do until i think of something else or it deteriorates. I only want to use it a couple of time over the weekend then hopefully next time have it booked in with Mini Sport for a tune up
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When you're driving and experience the flat spot pull the choke out , this will enrichen the mixture, and see if things improve. I tried this and i would say it was inconclusive. It didn't seem to make things much better, maybe just slightly 'different'. If i was to guess i'd say it didn't improve it. I haven't adjusted the mixture and will get the car looked by Mini Sport when i can. I think it's running well enough to make it worth putting on their rollers. They always adjust the needle and it could be something like that it needs |
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SU carbs work on a very basic principle and are probably one of the best ever invented but , a basic understanding of exactly how they work is necessary in diagnosis of faults. Have a look at this video as an expert explains.
Hope this is helpful.
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That was interesting. Thanks
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You said in your other thread that it wouldn't run until you moved the distributor a lot and swapped leads around.
That combined with this new issue of not revving well leads us back to valve timing issues I would say.
If you didn't touch the distributor during the work but have now had to rotate it 180 degrees that ought to be screaming out to you that the camshaft is out of sync with the crankshaft.
It's always difficult to diagnose these sorts of things remotely and like I said before I don't know the a-series engine but from what I can pick out of the different threads I'm still of the view that your valve timing is buggered.
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mk2cossie
Club Retro Rides Member
Posts: 2,946 
Club RR Member Number: 77
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If all they have done is replace the head on a classic mini A series engine, the camshaft timing would not have been touched. As the camshaft is mounted in the engine block...more likely to be leads placed the wrong way around, and valve clearances needing adjustment wouod be my first ports of call  |
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Came back from a 275 mile round trip and it is running better. In normal driving the flat spot isn't very noticeable
It's good enough to use until i can get it tuned
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If all they have done is replace the head on a classic mini A series engine, the camshaft timing would not have been touched. As the camshaft is mounted in the engine block...more likely to be leads placed the wrong way around, and valve clearances needing adjustment would be my first ports of call If it's been standing for 12 years I would go through the the carb isn't as per the video above. Also if it is a 1275 head on a 1000cc engine I'm guessing the compression ratio has dropped so it may need a new needle in the carb . |
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