Club 80-90 Forums

New 2.1 motor fitted along with my old 1.9 carb and ancillaries. When I came to time it up when running, my timing gun was bust so did it static and then 'by ear'. Since borrowing a gun I cant seem to time it up! The marks are about 30 degrees to the left of the mark and when I try to get them close it runs horribly then dies. The motor has Mv pistons and barrels with a dj bottom end and new heads. Is there something Im missing? Can't stop scratching my head!

Did you keep your DG distributor? Is the vacuum line disconnected?

Hi, yes I kept the dg distributer and disconnect and plug the vacuum hoses. I do have a dizzy for the 2.1 but was advised to reuse the dg one which is suites to the carb.

So you can get it running nicely by ear, but the timing light shows it to be 30 degrees advanced, without the vacuum advance connected. Strange. When you did it by ear, was it running well? I wonder if some secondary effect, like an air leak, might be causing it to die when timed by the gun. I know my DJ doesn't sound great when timed at low rpm without the vacuum attached. When the vacuum is reattached the timing advances by 12-16 degrees, the revs pick up and it runs more smoothly.

I don't know which distributor the MV should have. The DJ, being higher compression, doesn't like a huge maximum advance, so the DJ distributor is better for the engine than the DG distributor. But I'd guess that the lower compression of the MV pistons will mean that the DG distributor might be a better choice than it is for the DJ.

By ear it seems to tick along nicely but on the road there is slight hesitation, I can feel its not quite right. Just a bit puzzling? I read somewhere about MV motors being timed up at 3000rpm and I think with the advance connected but I could be mistaken ! An air leak is a possible cause but I'm suspecting not as it will die immediately once the vacuum tube is disconnected.

Mine is a DJ on a DG dizzi with a DG unmodified carb, but I run it on LPG. It times up perfectly and I run it at 10 BTDC for best results. Even on petrol with super unleaded, no pinking. But those KBS tappets are a pain. Are you using the right plug lead to trigger your light?

We'll, stronger things have happened! I'm using number 1. Interesting that your motor is timed at 10 degrees, everything I've read says to time at 5 with this engine and carb combination? Thanks for the info though.

T3BUS wrote: Interesting that your motor is timed at 10 degrees, everything I've read says to time at 5 with this engine and carb combination? Thanks for the info though.

Mine's timed at 5 btdc (2.1 DJ, new Pierburg carb and the original DG dizzy) ... you loose some power but gain longevity, mine was set up that way by Aidan Talbot and that's good enough for me. If you are running predominantly on LPG then 5 btdc is the best way as you don't need to find super-plus unleaded for the occasional run between the gas stations.

Ian

Thinking aloud - if the engine dies at idle without the vacuum advance connected, I wonder if your idle mixture is a bit lean. At low revs and without the vacuum advance these engines don't run very nicely, and something like an air leak or a weak mixture might be enough to tip it over the edge and mean that yours won't idle. If the mixture screw was set correctly for your DG, maybe it needs to be wound out (anti-clockwise) a fraction to allow a little more fuel to pass to suit the bigger engine.

CJH wrote: If the mixture screw was set correctly for your DG, maybe it needs to be wound out (anti-clockwise) a fraction to allow a little more fuel to pass to suit the bigger engine.

The carb was never touched to run our DG carb on a DJ engine, nor have I ever heard of one requiring adjustment.

Ian

That might depend how accurate/borderline the screw setting was on the DG. My own DG carb needed a touch more fuel at idle when I fitted it to my DJ. But if the screw had already been one or two turns further out when fitted to the DG it would have been fine on both.