Wideline 650 project

Jim, I built a 650ss from bits into a slimline a year or two ago. I bought the engine as rebuilt, good, except they may have forgotten to overhaul the big end arrangement. Tell you about that and confirm when we get time to strip it down.

I'm using the low pressure oil system and it seems OK in the 132 miles completed but may change to the high pressure system with scrolled rocker spindles as I have all the parts. All this depends on what is found during the strip down. I'll return to that thread when it happens.

As for the carb: What is wrong with the 30mm single Amal Mk 1? Apart from the knocking this bike goes really well and I'm looking forward to having it back to health again. BTW, the MK 1 Amal is the cheapest option too.

Hi James,

I built a broadly similar engine for my 1960 slimline 99, I went for the single 930 Mk1 with No3 slide and 260 main jet, and the high pressure rocker feed with plain, (not scrolled) spindles, I had to fit a needle valve into the rocker feed line to stop it from flooding the rocker box. It has the 650SS cam with flat base tappets in a 1958 type 99 barrel with cut outs in the spigots to clear the rods, I fitted a superblend main bearing on the drive side, and a full-complement ball-race (M306) on the timing. I used the long pushrods and short stem valves, the oil pump is Commando with the six start worm. I have done approximately 15,000 miles on this without any real problems until I overheated it recently and a valve guide came loose, my fault for going too weak (no.4 slide) trying to combat plug fouling with modern fuel, the combination of parts gave a lovely torquey engine which sounded great on standard 99 pipes. It will be back on the road as soon as I sort the head out.

Good Luck!

I would recommend using the 6 start drive with those type of conrods. The Commando oil pump has a higher capacity then the standard 99 item but once the engine oil gets warm the pressure will drop fast. When cold the timing cover release valve will take can of any excess pressure.

I agree with Phil. Stick to the 6 start gear on the oil pump. That will still be fine with a low pressure feed to the rockers off the oil return line.

Could also block the "squirt holes" in the rods.

Sorry to disagree Gordon, if scrolled rockr shafts were ok, with the higher pressure oil system, why would Norton have bothered to change them?

I could be wrong here, but shouldn't the high pressure rocker feed have plain shafts to prevent over-oiling? One thing I have never been troubled with is wear on the rockers with the low pressure system so it can't be that bad.Happy to be corrected.

I always thought the scrolled rocker spindles were to prevent over oiling, Gordon. I have plain ones on my low pressure system.

Be good to know the official line for my 650 strip down.

Previously neil_wyatt wrote:

I always thought the scrolled rocker spindles were to prevent over oiling, Gordon. I have plain ones on my low pressure system.

Be good to know the official line for my 650 strip down.

Haha, there's no "official line" for anything involving Nortons. There are as many opinions as there are variables. Engineering knowledge and experience help to separate nonsense from good advice. Both can be found liberally on here.

BTW I have run bikes over the years with high capacity pumps and feeding scrolled rockers from the return without problems.

Previously neil_wyatt wrote:

I always thought the scrolled rocker spindles were to prevent over oiling, Gordon. I have plain ones on my low pressure system.

Be good to know the official line for my 650 strip down.

No, the scrolled rocker spindles are for the standard low-pressure system from the return line, this is how our bikes came from the factory, the plain unscrolled spindles are for the high pressure system to prevent over-oiling, even with these fitted, I had to put a needle valve in the feed line and gag it down until it stopped smoking, when I found a setting I liked I locked it off, but whether or not it was really worth the trouble of converting it, I couldn't really say.

I have the feeling that some people are getting a little confused with regard to how the two systems. (low & high pressure) work and the fact that you can mix and match to some extent.

In chronological order there were basically 3 versions of the rocker feed system for the heavy Twins (& some of the lightweights). Anything pre-1961 would have the standard oil pump with a 3 start worm and drive. The feed to the rockers coming off the return oil pipe between the pump and the tank. This was known as the low pressure rocker feed system.

With the arrival of the 650 Manxman, a bigger capacity pump was used to handle the larger journals of this engine. This pump was usually stamped with a letter 'S' by the timing cover outlet. But this bike still used the low pressure rocker feed.

Problems with oil starved pistons and big ends, on the 650 motor, resulted in several important decisions. First, conrods with bleed holes were fitted to spray the cylinder bores. The larger capacity oil pump was up to the job until the oil got hot and thin and then the pressure would drop fast. The cure for this was to fit a 6 start worm and drive to the oil pump. So at a stroke the oil pump was now pushing out loads of oil, at great pressure, but the rocker feed was still low pressure from the old return pipe. Meanwhile, at the top end of the engine, someone noticed that the SS head was not coping too well in the rocker department. Possibly due to the SS camshaft, chunkier springs, scrolled spindles and the higher load now hitting all the bits.

So the next move, at the end of 1965, was to introduce plain spindles fed directly off the oil pump itself, via the timing cover. Hence the term of high pressure feed.

Now it is possible to mix and match a bit with the combinations. The higher capacity oil pump will go on any engine and will certainly be of help to the earlier versions. Adding the 6 start worm & drive is a must if you are the owner of a 650 or Atlas. Any excess pressure, in the system will be dumped by the timing cover release valve.

On any of the engines, if you go for a pressure feed to the rockers then you must fit plain rocker spindles. Plus, do not fit old worn out rockers that have seen better days in the company of scrolled spindles. Otherwise, they will let the oil pass through and flood the cylinder head.

You can fit plain spindles to the earlier cylinder heads and feed them from a smaller oil pump or one with a 3 start worm & drive.