6 replies to this topic

[Angus 850]

I am new to the Mini Forum. I have searched for my problem but I Have not be able to understand the problem.
I have an early Mini 850 that has not been used for a few years. The engine starts ok but lacks power on the roads. I was eliminating possible problems and I checked the plugs. After running the car for 15 minutes, I was surprised to see they were wet, not sure if it is water or fuel. I put a tissue in all four cylinders through the spark plug holes and the cylinders are slightly damp. Not really wet but not dry. The tissue was slightly marked.
I don't think it is the cylinder head gasket because I have done a compression check and all four cylinders are between 130-140.
The points are set up correctly, coil is new. The timing has been set up correctly.
The carb is in good condition. I am not sure if it is the original carb, it has a su hs4 fitted, not sure if it should be a hs2.
Any help or advice would be greatly appreciated

[carbon]

Angus,

 

If your 850 was built before 1974 it should be fitted with HS2 carb, and after this date the HS4 was used.

 

Damp plugs after 15 minutes running could be fuel, if it has not been run for couple of years. Some suggestions:

- drain petrol tank and refill with fresh fuel

- put in-line petrol filter just before the carb

 

The filter is to stop any rust getting stuck under the float chamber needle valve, this causes engine to run rich. You can get cheap clear plastic in-line filters for about a quid, that's all you need.

[dklawson]

In addition to the advice above, remove the float bowl lid and clean out the float valve.  Examine the tip of the float valve looking for witness marks.  If any are present, fit a new float valve and set the float level height as described in the service manual.  As Carbon said, if there is dirt in the carb's float valve seat or if the valve tip is worn, fuel can leak by and cause a rich mixture... to the point of the cylinder being wet at idle.  

 

The filters I use most often are the ones that used to be common on air cooled VWs.  Bought on eBay they are quite inexpensive and being translucent you can see when they are loading up and need to be replaced.

 

[Angus 850]

Thanks for that. It could well be the old fuel. I will fit a fuel filter.
Will changing the old spark plugs leads help?

[Stevie W]

Hi,

 

I suspect Doug & Carbon are probably on the right track with over an rich mixture due to flooding. Is there any black sooty smoke from the exhaust? This will also indicate a rich mixture and may account for the lack of performance on the road. Does the engine revs freely or does it sound choked up?

 

Changing the plug leads and distributor cap for new would probably be worth doing too if everything else on the ignition side has been well set-up.   

 

Cheers, Steve.

Edited by Stevie W, 21 December 2015 - 12:57 PM.

[Angus 850]

Hi,
 
I suspect Doug & Carbon are probably on the right track with over an rich mixture due to flooding. Is there any black sooty smoke from the exhaust? This will also indicate a rich mixture and may account for the lack of performance on the road. Does the engine revs freely or does it sound choked up?
 
Changing the plug leads and distributor cap for new would probably be worth doing too if everything else on the ignition side has been well set-up.   
 
Cheers, Steve.

Thanks Steve, it does seem to be running rich, some black smoke coming from the exhaust.
The engine seems to be choked up, not really running freely. I have set up the timing using static timing, I don't have a rev counter to be able to use my timing light accurately. It seems to run better when I turn the distributor clockwise until the points are just about to open on cylinder 1 but it revs too much even when the carb idle screw is undone to the minimum.
The exhaust back box was replaced recently. I fitted a 1275 back box that I had in my garage. Could this create any problems?

Edited by Angus 850, 21 December 2015 - 05:27 PM.

[Stevie W]

Hi Angus,

 

I can't imagine the 1275 rear box would make any difference. I would concentrate on the mixture issue with the good advice from Doug & Carbon!!

 

Cheers, Steve