6 replies to this topic

[petehuws]

Hello folks, I've had my mini (S-pack 1275 RSP) garaged for some months & took it out for a spin recently, the performance was very poor; to cut a long story short when I done some troubleshooting I found that I couldn't balance the carbs correctly, carb #2 (cyl 3&4) seemed fine albeit running slightly rich, the air pull through the carb-balancer & throat was strong with a good reading, however I couldn't get any reading with carb #1 and there was virtually no air pull.
Thinking I may of had a blown head gasket I done a compression test across all 4 cylinders dry then wet =
Dry 1=185 2=190 3=195 4=200
Wet 1=200 2=205 3=210 4=220
My question is would you agree with those readings that the cylinder head gasket looks OK?
I'll remove the carbs & inlet this weekend replacing gaskets there incase of air leakage.

Many thanks

Edited by petehuws, 09 October 2014 - 09:31 PM.

[carbon]

Those compression readings look fairly consistent, pretty much what you would expect.

 

Does not indicate a head gasket problem to me.

[nicklouse]

Check you valve clearances. If there is differences that might give you a clue.

[petehuws]

Guys thanks very much..
I'll check these out...
Many thanks

[Cooperman]

1. Set the tickover to about 1200 rpm warm

2. Undo the linkages joining the two carbs so that each operates independently by moving the individual carb throttle lever.

3. Set the mixture for each carb by lifting the little button under each carb body so that the engine speeds up slightly then settles back to tick-over when each lifter button is raised.

4. Use the carb balancer to set each carb to suck the same at the selected tick-over revs using the slow running screw.

5. Connect the linkage to make both carbs work exactly together.

Edited by Cooperman, 09 October 2014 - 10:14 PM.

[petehuws]

Thanks all & Cooperman. I had checked, & made some slight adjustments to the valve clearances so maybe I mucked something up there, & I tried balancing the carbs exactly as Cooperman describes which led me to think air was being drawn in other than the Carb. I have some time tomorrow morning so will post back my findings. Kind regards

Edited by petehuws, 10 October 2014 - 09:07 AM.

[Cooperman]

Is there an air leak into the carb after the butterfly? Some carbs had a vac take off and if this has previously been blanked off and has become 'un-blanked' it could cause this. I've seen it before and it then did exactly what you have described.

Or is ther a slight air leak between carb & manifold?