Hitchcocks Forum

Does anyone know what plug I should be running in a pre- 55 350 Bullet? (Lucas M01 magneto fitted)

B6ES NGK is what I had in mine with no issue.

Cheers Simon, Was it fine for both Town and A road use? I used to have to change my ural plugs from l=L81 to L82 back in the day....
Another thing about these older engines, - the exhaust stub is different, were the exhausts "push over" , or "push in" ?

Zippy, you need to be more specific than pre-55! The heads changed from push over stub to push in sometime in 1954-5, probably fairly early but I don't have the parts book to hand at the moment. As to plugs, I had a conversation with a plug expert at The Spark Plug Company when sorting plugs for my magneto Interceptor and he recommended Iridium ones. If you're lucky you might find a grade that suits the Bullet that is not a Resistor type (it probably won't be an NGK, mine are NDs,) but he said that the benefit of running an Iridium in an old design oily engine like ours will still outweigh the small disadvantage of losing a little spark through the resistor. You can follow the rebuild of my Ebay bargain (!) 1955 350 Bullet in the Royal Enfield Magazine, free to view at greenlane.biz HTH, REgards, Mark

No resistor in a B6ES as far as I am aware, I had the same one in the old bullet for the last seven years with no problem. Its true you don't want to use a resistor cap or carbon/nylon HT leads as you'll overload the armature windings. I put a B7ES in the bitsa because it is higher compression and tended to pink a bit after a fast run (this is before the ally barrel) but both this and the older styled 51 Bullet took the same plug and both are mag ignition. A good idea is to give them a smaller plug gap than the usual 025" I generally set mine at 015" which makes starting easy and doesn't seem to affect fast running.

Thanks both, - I'm ahead with the plug cap and HT lead,. I put old fashioned copper core lead on, and a resisterless black rubber cap. I will try the smaller gap idea too, - but I'm a bit off that stage yet. The bottom end still needs attention. Also I'm going to have to come up with something creative to get my high level exhaust to fit into/over the exhaust port in the older head....

I've used a B6ES in a 350 Bullet with Lucas SR1 magneto for years without problem.

I did it by welding a sleeve over the end of the header that fit on to the exhaust spigot. I cut a couple of clamping slots into it with a fine cutting disk and had the whole thing re chromed. If you don't want to go to the expense of re caroming you can braze the sleeve on. The pipe won't stay shinny forever and someone with a skilled torch hand can do it with minimal chrome damage.

Yes, was thinking something similar, but maybe using a stainless sleeving piece and brazed.

But will the brazing stand the exhaust temp, being so close to the port????