BUILDING A NEW 750 RACE BIKE.

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Fast Eddie and SteveA nicely summarized some important points to a rational approach to building a performance road race motorcycle. I am a firm believer in the priorities of building a bike which are: first, make it handle, second, make it stop, and third, make it go. In the real world, if one has the budget it all gets done together at once, otherwise with a prioritized mix. As stated by me earlier, going down the path of a phased crank for this build is not good (for a variety of reasons including waste of time and resources) but given that you have committed to this path I suggest the following:

With the 500 cc ultra short stroke, it began life as a 360 degree phased with a Steve Maney crank. We then converted to a 180 degree crank with a center bearing. That is when the cam and cam drive problems began.

I cannot visualize the phasing of the crank to phasing of the cam lobes loading and unloading so I suggest that if you have not done so, do so. I am pretty sure that both center lobes will be loaded together at some point in time. You may want to consider a middle bearing support for the cam as it will likely break. We broke a few and opted for the center bearing and that problem solved. Phasing the crank away from 360 degrees causes loading on the cam that Norton never dreamed of. Furthermore, the valve spring seat pressure and spring rates will likely be significantly greater than stock and inertial loads from opening valves will be way up there if you have plans to rev this engine. As a benchmark, say your stock engine redline is 7,000 rpm and you anticipate the shorter stroke will allow at least 8,500 rpm redline; 8500^2/7000^2 = 148% of the inertial loads at 7000 rpm.

We broke cam chain adjusters and cam chains so installed an all gear drive cam. No more cam chain or cam chain adjuster failures!

We split crank timing pinions. You may want to consider fabricating a timing pinion of better material than what the factory used.

A center bearing for the cam will help but there are oh so many other unpleasant surprises. One only needs to use their imagination when any one of these failures occured. It is not a matter of purchasing and installing part but more like fabricating, custom fitting.

I am going to assume you are not in your youth (age wise at least). Do you want to spend time building and rebuilding or building the bike and then riding it with high reliable so you can build your riding skills?

Lecture mode off.

Suggest center bearing for cam, better cam chain adjuster or replace with gear drive and sort out the crank pinion problem. Elsewhere on this forum you can read about someone (Comnoz?) seeking to get a better pinion made but I don't think it was done.
 
Many thanks gents for much appreciated, and I am sure hard earned experience, advise!
I may very well take them into consideration.
Would you have any pictures/data from that centre cam bearing ? And the rest of the mods
you did ?
Now, I am so far ito this engine that it will be hurting to abandon the principles laid down.
Starting on a second unit is a good idea. Will look for the necessary funds and should they be there
a way to sneak them out from the prying eyes of .. you know.
Now, let me ask you for opinions on engine lubrication oils! Mineral, Synthetic, Vegetable or a mix
of them. Brands & viscosity and so on. I have learnt as much from the last few days on this blog
that I am now seeking opinions BEFORE I decide on my choice.
 
moppedog said:
Many thanks gents for much appreciated, and I am sure hard earned experience, advise!
I may very well take them into consideration.
Would you have any pictures/data from that centre cam bearing ? And the rest of the mods
you did ?
Now, I am so far ito this engine that it will be hurting to abandon the principles laid down.
Starting on a second unit is a good idea. Will look for the necessary funds and should they be there
a way to sneak them out from the prying eyes of .. you know.
Now, let me ask you for opinions on engine lubrication oils! Mineral, Synthetic, Vegetable or a mix
of them. Brands & viscosity and so on. I have learnt as much from the last few days on this blog
that I am now seeking opinions BEFORE I decide on my choice.
Click to expand...

Oh dear, you shouldn't have done this, oil debates will now take over this entire thread!

Here's my input:

Some while ago, whilst racing Triumphs and Nourish engined bikes, I was using Castrol fully synthetic. Dave Nourish and other 'old boys' were all adamant that I should use R.

So I contacted Castrol, as I was already using Castrol, they had nothing the 'sell' and could be honest. They said that R has the highest film strength and lubricity of any oil. Period.

But, when too cold, its like treacle. When too hot, the molecular structure breaks down (permanently, the old is shot). It also absorbs moisture and doesn't last long. According to Castrol it should be drained after each meeting and stored in an airtight container and should be changed very frequently, like after 2 meetings.

Anyway, I ran it in my 500 Nourish and 900 Nourished Triumph. The Nourish engine used to make so much mechanical noise when started, it really made me cringe at the thought of what was going inside!

The Triumph was worse, the oil pressure gauge needle moved around like the tacho needle when blipping the throttle... But backwards, pressure dropped as revs rose. The pump just didn't seem able to draw oil fast enough to maintain pressure when cold.

Both ran fine when warm.

So, it seemed to me that with R, cold starts with treacle will damage your engine and a hot engine could damage your oil, which will damage your engine!

Pre heating the oil before pouring it into the bike, and running an oil cooler would solve these, but it seemed like a lot of messing around to me!

Long story short, after checking out many different oils, I now use Red line motorcycle oil. With Red line you must use their specific motorcycle oil in order to ensure it has high zinc etc additives.

If I were still racing, I would use their dedicated racing oil.

There are of course many people running R very successfully and who absolutely swear by it. There are many other good synthetic oils out there that people swear by too.
 
moppedog said:
Now, let me ask you for opinions on engine lubrication oils! Mineral, Synthetic, Vegetable or a mix
of them. Brands & viscosity and so on. I have learnt as much from the last few days on this blog
that I am now seeking opinions BEFORE I decide on my choice.
Click to expand...

Pour a whiskey and a coffee and read/watch ...

another-point-view-oils-ect-t25019.html
 
Fast Eddie said:
So, it seemed to me that with R, cold starts with treacle will damage your engine and a hot engine could damage your oil, which will damage your engine!
Click to expand...

Did you personally notice any actual damage from running Castrol R 40 - cold or hot?
 
jseng1 said:
Fast Eddie said:
So, it seemed to me that with R, cold starts with treacle will damage your engine and a hot engine could damage your oil, which will damage your engine!
Click to expand...

Did you personally notice any actual damage from running Castrol R 40 - cold or hot?
Click to expand...

On the 900 Nourish / Triumph I changed it out to synthetic ASAP after seeing the oil gauge incident. The 900 also ran very, very hot in this early incarnation, so I thought this engine to be at risk from both the cold start and high temp (note this was using a Triumph plunger pump though, which are hardly the best. I later went to a rotary pump and an oil cooler which solved the very hot running issue).

In the 500 Nourish engine, which has Norton copy oil pumps if I recall correctly, didn't suffer the same horrible oil pressure drop situation. It may have sounded like a bag of spanners on start up, but I got into the habit of squirting oil around inside the rocker boxes and down the pushrod tubes before starting and being uber gentle warming it up. These engines in 500cc format don't run terribly hot either, so it seemed to 'fit within the parameters' of running R. I kept it on R and no, there was very little wear on this engine, that regularly revved to 8750 rpm. It went on to two new owners, who continued to run it on R.

I did however, change the oil very frequently, meaning after every second one day meeting, or after each two day meeting.

I believe what Castrol told me. That R is still the best racing oil, provided it is kept in a certain temperature range and changed very frequently. The 500 fitted that criteria, the 900 didn't.

Also regarding the requirement of frequent changes, it is fairly well documented the R was part of the reason for Vincent's failure to achieve their 24hr record targets at Montlhery in 1952, the combined effect of the crowded roller big end design being at its limit and R breaking down caused the big ends to fail. 24hrs is a lot of run time, and was presumably too much for the R!
 
Hello gents!
Many thanks for opinions/advise! Still, I ask myself how Castrol, Silkolene, Morris et cetera
can stay in business producing castor oils, and still very few of the Norton community seem
to use them ?? Are they all for the speedway freaks ? How about pre-heating the R oil to e.g.
75 degrees C before filling it in the oil tank, run the race and then drain it and toss it?
There must be something here that Castrol et cetera know and that we miss. Otherwise they
would not produce their R oils. Or is this just the wrong forum? Maybe I need to switch to
ACCESS JAWA or similar ???
 
moppedog said:
.........How about pre-heating the R oil to e.g.
75 degrees C before filling it in the oil tank, run the race and then drain it and toss it?
Click to expand...

Believe me, you won't want to do that at a modern race meeting where the circuit will chase you for environmental damage....

And, imagine that you arrive Friday and want to do noise tests, in the limited time available, noise tests are best done with a warm engine..... Now you have two more days of this....

And you will want to keep your oil warm for practice, and each race, you may have two each day, some hours apart.....

Basic practicality Ulf.....there really is enough to do at a race meeting.....
 
moppedog said:
Hello gents!
Many thanks for opinions/advise! Still, I ask myself how Castrol, Silkolene, Morris et cetera
can stay in business producing castor oils, and still very few of the Norton community seem
to use them ?? Are they all for the speedway freaks ? How about pre-heating the R oil to e.g.
75 degrees C before filling it in the oil tank, run the race and then drain it and toss it?
There must be something here that Castrol et cetera know and that we miss. Otherwise they
would not produce their R oils. Or is this just the wrong forum? Maybe I need to switch to
ACCESS JAWA or similar ???
Click to expand...

Yes you can pre-heat the oil, I mentioned that in my post. I never did this.

But I did have a very rigorous cold start pre-oiling procedure. And a very careful, gentle, warming up procedure. And I fitted an oil cooler to prevent the oil from overheating. Drained it after every meeting (probably change it whilst you're at it and add £50 to each race meetings cost). Got a nice digital thermometer probe and checked the oil temp before and after each race, keeping a log to make sure I knew what was going on. Ensure I always switch off rather than risk leaving the motor running slightly too long in the warm up lane, along with the attached worry it would then start properly if the area was not conducive to a bump start, etc.

You can too if you want. But like Steve said, there really are plenty of other things to focus on in a race meeting!

My mentor, Dave Degens, said the racers used to warm up their R on cold mornings on a camping stove. And even put a small stove under the sump of their Manx Norton's to warm up the motor prior to pouring in the warm oil.

I decided that I really, really, had enough to focus on already without doing that!

But, as always, to each his own.

Like mentioned previously, I use Red Line now in my motors, this one: https://www.redlineoil.com/product.aspx?pid=111&pcid=13

If I were still racing, I'd use this (I may use it in my new 920 motor anyway): https://www.redlineoil.com/product.aspx?pid=16&pcid=1
 
Fast Eddie said:
You can too if you want. But like Steve said, there really are plenty of other things to focus on in a race meeting!

My mentor, Dave Degens, said the racers used to warm up their R on cold mornings on a camping stove. And even put a small stove under the sump of their Manx Norton's to warm up the motor prior to pouring in the warm oil.
Click to expand...

Redline as bought in the UK or France is beyond my budget at around £70 a US gallon, not even enough for two oil changes. I have purchased Fuchs Titan at around £50 per 5 litres

I do have one other experience with R40, not my bike, I was offered a ride on a K1000 in Harris modified frame, March '82. The Test day went well, I just had to get on it and ride faster than the other guy trying it. The first meeting was at Castle Combe, which I had never ridden.

The bike would not turn over quick enough to bump start, hardly surprising since it was on the verge of snowing. Eventually it did fire, and blew the sump seals and dumped the sump contents on a very expensive cut slick rear tyre. The owner decided he could get home and get new seals, so off he went, whilst we changed the rear wheel. When he got back we fitted the seals, heated fresh oil over a stove and poured it in, sure enough it fired and we warmed it through, as the last practice session was coming back in from the circuit!

Which left me to plead for a race start, on a circuit I had never even been round on a bicycle....and I had not raced at all since late '79....they were kind to me and put me at the back of about 40 starters, it was a heavy lump, but the bike fired early, and accelerated like a rocket as I climbed on, no clutch starts in those days, so I arrived at the trickiest corner on the track, trying to remember the brake and gear levers were on the wrong side and the gear change upside down....in mid pack on the right hand side of most every one elsewho seemed to be braking harder thann me!, wondering which way the track actually went....open left into tight right was the answer, and if you were too tight into the right, you would be crossing the path of everyone else on the way out! It was all pretty much plain sailing after that.....my second experience with R and perhaps unsurprisingly, I won't use it in a 4 stroke!
 
I used to mount a small propane torch under the motor on cold race mornings just to help it (push) start and this was with petroleum oil.
 
Welcome Moppedog, enjoyed reading, and learning from, your website. Respectful envy here for you and your project. And I wish I could add something but you have thought it out already.
 
Castrol R may need changing often and have gummy problems but it has higher film strength than anything else. I've never used it but Dave Watson switched to it when he had severe cylinder wear with synthetic oil. He rebuilt his 1000cc racebike with different style pistons and castrol R 40 and Gary Thwaites won on it for four years (40 races & beating multis) and never even changed the rings.

Champion Gary Thwaites on 1000cc Nort in middle
BUILDING A NEW 750 RACE BIKE.


the piston skirts after 4 years and 40 races.
BUILDING A NEW 750 RACE BIKE.
 
I have never built a bike that did not leak oil somewhere. Castrol R turns your bike into an instant shit-heap. How can you remove that sticky shit after it has hardened ?
 
acotrel said:
I have never built a bike that did not leak oil somewhere. Castrol R turns your bike into an instant shit-heap. How can you remove that sticky shit after it has hardened ?
Click to expand...

There are a lot of fine speedway bikes and Harley XR 750s running on R that I would never call "shit heaps" and they use the R for a good reason. I've heard that you can remove it from the sump by boiling in antifreeze. Any one try this?
 
My friend has a very nice 350cc ex-works Manx. He took the magnesium crankcases to the vacuublast guy to get the baked-on Castrol R removed. They came back bare of the conversion coating. So he kept them nice and dry and I found somebody who in the aircraft industry who could redo that grey-green coating. The price was, the guy who did the job wanted to see the bike when the rebuild was complete.
 
Has anybody used or have other experience with the FUCHS Castorene R40 ? They call this a castor based synthetic oil but I cannot learn more from Googling about it.
 
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