52 norton dommie running fault

[ozzylowe]

Dear All,

Can I pick your brains on the following running fault

My recently acquired 52 Dominator runs well on one cylinder at tickover, with the odd pop from the other side.  As you increase revs. the other pot fires more and more until at half/two thirds throttle both are running together.

The 'good' cylinder shows 100 psi on first kick, the bad one only 80/85 which sometimes takes two or three kicks to achieve, so I'm thinking rings, but the whole think has been apart with the previous owner (now sadly passed away).  He was an experienced engineer, and recently fitted a new oil pump and an unleaded cylinder head, so i'm assumng he wouldn't have put it back together with a duff 'ring (unless one got damaged without notice on re-assembly)

New plugs, and no it doesn't help if i swap them over, and the bad side does show a good spark.

Others tell me it's an ignition fault, but as it's single points, i'm assuming if there no problem with one side, can't be timing, and as it runs fine higher up the leads etc must be okay.

Before i pull the head off any other ideas would be grategully received.

Thanks in advance

Chris
ozzylowe

[L.A.B.]

If one cylinder is struggling to make 80/85 psi and the other makes 100 psi fairly easily then I would think there is a reason to investigate anyway as the readings should be within 10% of each other.
Try squirting some thick oil into the low-reading cylinder so that it gets onto the rings, then do the compression test again. If the reading is higher then the rings could be the problem, if the reading is about the same as before then possibly a valve is leaking?

[lsdt]

Hi Chris,
Is that photo taken at Holka Hall Museum? sure looks like Tommy's van in the background. If it is, there's a lot of folk in Cumbria will help you.
Dave

[ozzylowe]

Yes, i,ve got no room at home so it's on display in the old garage there.  On the previous point, the comp. is a little better with oil in the bore, and the valve clearances were well out when i first got it, but there pretty close now (access is tight with the tank on) But it's had a cylinder head overhaul (at the cylinder head shop) converting to unleaded and bigger valves, so i'm assuming they've been lapped in correctly, but it may be time to take the top end off and have a look.  Will check valve clearances again first.

On a different subject can anyone tell me who does the oil shut off valves? It dropped 2 pints into the sump in the 3 weeks it's been stood recently!

thanks ozzy

[lsdt]

Chris,
RGM sell a check valve, but first try the pistons on top dead before laying the Norton up, it sometimes helps.
Dave