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Dave

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Mk 5 Carb issue

Started by Philmein, 17 May 2024 at 16:05

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Philmein

Hi..appreciate thoughts on an issue I have with my mk 5..starts but runs on the right cylinder only..If I rev it and push down the choke button halfway on the left carb that cylinder fires up!
Thinking its fuel issues ive checked flow from the tank, cleaned the carb out but to no avail..any thoughts please?

Thanks

alistair

check yer compression and valve clearances

oldtimer

#2
I have the same problem on my Mk 1 it runs on the left and when I choke the right it fires up . I swoped the carbs over and the same carb will not run without half choke . i ve had them autrasonic cleaned ive checked valve clearances to no avail . all the jets and everything is identical in both carbs so it must be a fuel issue but it beats me . I did put this same question on the forum about two months ago but no answers to the problem yet . if ya find out what the problem is let me know and I will do likewise.


Oldtimer's previous topic - 'Carb trouble'


Link added - Dave, 19May2024

Philmein

Compression is same on both cyls at approx 100psi ..
valves checked and fine..

Please chip in if anyone can give advice..Thanks


Philmein

#4
Quote from: oldtimer on 18 May 2024 at 11:57
I have the same problem on my Mk 1 it runs on the left and when I choke the right it fires up . I swoped the carbs over and the same carb will not run without half choke . i ve had them autrasonic cleaned ive checked valve clearances to no avail . all the jets and everything is identical in both carbs so it must be a fuel issue but it beats me . I did put this same question on the forum about two months ago but no answers to the problem yet . if ya find out what the problem is let me know and I will do likewise.

Will do!!


Quote fixed - Dave, 19May2024

eddie

Check out the magneto. With the points cover removed, see if the points plate can be lifted (even if only a few thou). If it can, then the armature bearing is probably loose in the end plate, causing one cylinder to run retarded of the other. With the end plate removed, you will find the bearing is smaller than it's housing - this is intentional as the bearing should be in a paper cage to prevent the armature from earthing out through the bearing tracks, causing them to etch away prematurely. When replacing the paper cage, a light smear of 24 hour Araldite on the cage, between the bearing and it's housing helps to provide extra support for the bearing. (Obviously, leave the magneto for 24 hours before using it - to allow the Araldite to fully cure).

  Regards,
                Eddie.