Anecdote trouvée sur le site anglais bbs;
Le type note un défaut de vibrations moteur, il poset une demande le 02/11/2009.
Consillé, il va dans tous les sens possibles avec un brin de recul, et finalement, le
25/10/2010, c' est gagné. La cause: un jet de SU remplacé en neuf non approprié
( 0.1" au lieu de 0.09" )
Pour le puristes ou amateurs de langue de Shaekespire je joins le lien, il y a eu 102
échanges entre les intervenants pour solutionner de petit probléme!
http://www2.mgcars.org.uk/cgi-bin/gen5? ... 1513822846
Cdt.
Posted 02 November 2009 at 21:51:38 UK time
H J Adler, Victoria, Australia
Hi All,
My first time on this BBS.
I have a 1967 or there abouts MGB roadster, that was supposedly restored to 95% concourse standard. 10 months on and I'm still trying to complete it.
After having solved a myriad of problems I am now stuck with this one, at about 1500 RPM the engine shakes, with sideways displacement of about 1 1/2 inches (~40mm) , this is standing still, ie not driving. Higher revs stop the large shaking but there is still a vibration apparent, felt through the body of the car. Lower revs, ~ 1000 rpm the engine runs reasonably smooth, about what you would expect at a fast idle.
Details
Engine is 5 bearing, cast November 1965.
New coil
New 123 distributor (old distributor does the same shaking)
New plugs and leads
New jets and needles in the carbys
New float valves and level set correctly
New ECCO fuel pump and pressure regulator, set to 2 psi
Fuel filter fitted
I've had the head off and found that the engine has been recently rebored to 60 thou oversize.
Found that the PCV valve was missing some of its works, removed it and connected the ports on the carbys for crankcase ventilation.
Resealed all ports on the inlet manifold.
I currently have the timing cover off to check that the camshaft is correctly timed, it is.
The only things I can think of that might explain this shaking is a very hot camshaft or massive unbalance in the engine.
Any suggestions very appreciated.
Herb
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Posted 25 January 2010 at 00:41:43 UK time
Herb Adler, Victoria, Australia
Hi All,
Just come back from swapping that 0.1" jet for the correct one. I took my trusty 2.2mm drill bit with and checked the supplier's stock of jets, all were OK. Just my luck to get the one that was off.
Previously I said I would use one of the old ones, but the one with the 0.09 hole was of a fabricated construction, ie an aluminium tube with a brass plug in the end, drilled to 0.09". Unfortunately it was so worn (3 thou under, compared to the new one, and when you consider that the min clearance of the needle to the jet is something like 1/2 thou) that I couldn't centre it so the the piston didn't jam. It was OK until the choke linkage was connected and then the side pressure offset it.
Now to go and install.
Paul H.
Your comment about the rotor to cap alignment not changing with centrifugal advance is correct for a mechanical dizzy, but for an all electronic one, like the 123, it isn't. These dizzys don't have any mechanical advance, it is calculated from the engine rpm and the spark is fired earlier in the rotational period, ie with the rotor more advanced.
Herb
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Posted 25 January 2010 at 18:32:40 UK time
Herb Adler, Victoria, Australia
Hi All
SUCCESS SUCCESS SUCCESS!!!!!!
It works. I could almost balance that proverbial penny on it now, at 1500rpm.
Thank you all for your suggestions and moral support. It helps to have a "mate" to talk to and occasionally a shoulder to cry on.
