Will not Run

G15 Roy · Post by **G15 Roy** » Mon Jun 14, 2010 8:42 pm

I have recently purchased a 1961 G12 that had been restored by B.D.G. Services from Kent back in 1989.
This bike was never completed and had never been run. I have since changed the mag due to lack of spark but it still will not run. It chuffs when it should puff and puffs when it should chuff.
I have checked all the obvious, i.e. valve timing, valve clearances. It seems to lack some decent compression and after a great deal of head searching it appears that the cam shafts have been fitted back to front. Can you please tell me the correct identification of the cams when in situ. If they are wrong is there a quick fix or does the engine need to be completely stripped to swap the cams over.

Don Madden · Post by **Don Madden** » Mon Jun 14, 2010 9:20 pm

Pull the cap from over the oil distrubutor. If the distributor slot fits onto the tang of the cam, it is the correct exhaust camshaft. To do a similar check of the inlet cam you will have to remove the cap with 4 holes. You should see the end of the cam & it should have a slot, not tang to drive the timed breather used on early twins. If either is wrong, strip the engine completely & check everything. Cheers, Don.

G15 Roy · Post by **G15 Roy** » Mon Jun 14, 2010 9:37 pm

Hi Don Slot in the front cam I have not checked the rear one.

moley · Post by **moley** » Mon Jun 14, 2010 9:47 pm

Apart from the oil distributor bush i dont think it would make a difference to its running. I had a g9 which started and then i stripped it down and the cams were the incorrect way round. cheers

G15 Roy · Post by **G15 Roy** » Mon Jun 14, 2010 10:15 pm

So Can i get this running if so any help on timing?

dave16mct · Post by **dave16mct** » Mon Jun 14, 2010 10:53 pm

You won't have any oil to the rockers if you do get it running. Strip it and change them round.
Cheers Dave.

laxy · Post by **laxy** » Mon Jun 14, 2010 11:56 pm

If you take the camshafts and veiw them end on side by side with the keyways at twelve oclock you can see the cam profiles are mirror images of each other.If your exhaust camshaft is where your inlet camshaft should be and the previous"mechanic"used the dots on the pinions to time the valves then I would say the valve timing is out.
there is only one course of action and that is to split the cases and swap the camshafts over on the bright side at least it will give you the chance to inspect the entire engine internals cos if someones done this who knows what you might find in there

wilko · Post by **wilko** » Tue Jun 15, 2010 12:49 am

Or cheats way is make a new distributor with tang on a lathe and some accurate hand filing. Tsk, tsk!! Although now is the time to machine a groove for an O ring for the filter tunnel when you pull it down.

RogerNorman · Post by **RogerNorman** » Wed Jun 16, 2010 11:46 pm

Roy.Something really easy that you could try is to swap the leads over on the plugs.
I had a mate of mine who could put his hand to virtually anything mechanical but invariably he put the leads on back to front and suffered the same problems that you seem to be experiencing. Worth a try for an easy win if it is the case.

laxy · Post by **laxy** » Thu Jun 17, 2010 12:09 am

If the wrong cylinder was timed then swapping the plug leads would counter act this.A sympton of plug leads being wrong way round is a loud backfire from the silencer when attempting to start.
Either way if the camshafts have been interchanged there is no way of getting oil to the rocker gear.Once the engine is out of the frame its just a case of splitting the cases and swapping the shafts over.There is no need to disturb the crankshaft and centre web or conrods unless of course you want to have a butchers while your in there.