920 engine build waffle (2016)

Fast Eddie said:

Chris / Steve, if there are hardly any Norton’s, and fewer big triples, what’s the main contenders these days?

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No, point is the classic 1300 class itself is in decline.

In F750 there are triples, a couple of Weslakes, the odd Yamaha 4, Suzuki 3 and Honda 4, and the occasional Norton....in 1300s there are a handful of triples and a couple of big Weslakes and maybe a Norton! Probably 7 or 8 bikes on a classic 1300 grid this year.

The races these classes run in are dominated by '80s post classic Japanese bikes....really for me it is rather too much like it was in the late '70s continually riding against bikes with 50% more power, and these days some of them over 40 years younger! Guess I should be happy not to finish last!

Thankfully BHR has a class for up to '72 750s, as does French VMA and Belgian CRMB, a decent field of '70s 750s twins alone back in August with the odd 70s Honda 4.

In my own mind part of the downfall is people being seduced into bigger capacities, thereby disipating the interest and increasing the cost.

That and the fact that UK CRMC continues it's march toward being a post classic race club......OK, I have ridden post classic too, but I didn't expect the classics to fade at the rate they have done this year.

Brooking 850 said:

Steve A , mine is not on methanol, was on avgas, now trying 50/50 avgas/91 unleaded. There a lot of guys using methanol in my class.
Once my dyno is finished I will be doing runs on different fuels to see what comes out the best.
It is way easier buying fuel at the pump on the way to race meetings than having to borrow a fuel card and head out to the airport before each round.
Regards Mike

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I have found it much easier just running pump fuel. Some Avgas might help. But again, I will need access to a dyno to set it up. Methanol isn't legal at CRMC, or appropriate for most classes at BHR, certainly a no no in France and Belgium.

For those who are OCD enough to remember such trivia, a while back, I dyno’d a Maney 2:1 system on the Trident Hunter.

First time I tried it I had a JS#1 cam, 10.5:1 CR, JS pistons and rods, 35mm FCRs. The Maney system wanted to run weaker than the peashooters, and give 5bhp gain, and this gain was from the mid range right through to peak. I was well impressed. Nevertheless, I still ran the peashooter set up on the road due to noise and pillion ability.

The second time I tried it was after I fitted the Comnoz re-worked head. This head work gave a 9bhp increase and huge increases from around 3k upwards. I was staggered by this huge increase. He also put a slightly tighter radius on the BSA followers, which, in theory, sacrificed a little peak HP for more mid range.

This time, much to my negative surprise, the Maney system gave almost no improvement, it had a very little peak gain and a small mid range loss, but hardly anything in it.

In the 920 motor I’m gonna be running at around 10.5:1 CR and still having a tight squish thanks to the slightly dished JS pistons. It’ll have the Comnoz head (with opened up squish band) and the same FCRs. I’ll be running the 86c/12c Webcam, which is similar to a 2S and Maney cam.

So, I’m hoping that the cam will allow the Maney style exhaust (one of Mikes) to work ‘properly’ this time.

We’ll have to wait n’ see.

Hi all

Steve Maney has my pistons & barrels to work on. So my 750 will be out next season. I will be selecting which CRMC events I enter & will see you in Belgium Steve.
Mike, Steve Maney always advised me to run 50/50 avgas Super unleaded. Best of both worlds protection & go. Like Steve I have now changed to pump fuel, with lower compression ratios. The run to the airport was getting a bit fraught!
Must say when I started in 501 unlimited it was mainly triples, 8 valve Bonnies & Weslakes, also Bonnies & Commandos. The odds were a Laverda SFC, a lone Rickman BSA A65, a couple of big bore XS650 Yamahas & a raft of BMW's some of them with very big bores! People race what they loved in the day. Most now want to press a button (plus have reliability, not to mention low repair costs) so we race mixed classes. As Al said to me last season, whats the point of being outbraked in corners by triple disc bikes, with more rubber, that block you on the way out, yet can run with you on the straights.
Its a shame as the crescendo of noise a pack of big bore bikes make leaving the grid is jaw dropping, to be in that pack is wonderful beyond belief.

Hopeful of doing a bit more next season.

all the best Chris

Chris, I found that super unleaded (the Shell version is my preference, V Power I think they call it) with Silkolene Pro Boost octane booster could handle anything I ever tried it in, inc the big 8 valve Dresda. No airport runs required !

Mike , wouldn't it be easier in NZ to just run the BP ULTRA 98 readily available at an extreme price , it adds up quickly in a V8 landrover

Hi Eddie

I once got a rollicking when I asked about octane boosters after the big motor had gone bang. Told they were illegal! I just wanted to prolong the life of my Commando that would have run on 5 star leaded back in the day. I was told to detune it until it ran on unleaded!
Funny thing is, when I got the North out to play it came with octane booster. Richard Peckett advises nothing else! I had a walk round the paddock to speak to other triple racers & found they all ran octagon booster. All my Commandos do now.

Chris

Yes I have been advised that with the methanol 650 I have, it may well run just as well on pump fuel if the CR isnt there to take advantage of the methanol.
I wont know until I know whats in the motor as it is heresay at the moment. CR I mean
Splatt, once the dyno is finished , I will be doing fuel tests so I know for sure if I have made big losses(orgains) or no change at all with change of fuels.
That is a few months away.
Regards Mike

Fast Eddie said:

Goodness gracious... you are quite right sir. It is indeed maths.

I shall go and stand in the corridor....

In my usual spot...!

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While you are out there in the corridor, you can also consider your misuse of the word wasted.

Bugger!

I thought I’d got away with that !

Way back in a different life (circa 1990) i raced an F2 sidecar with a TZ350 engine installed. To obtain high octane fuel i mixed acetone in the ratio 7 :1 with the available four star petrol, Put half a gallon of acetone in an empty jerry can and topped it up with three and a half gallons of four star on our way to the race meeting. Beauty of it is it dosent colour the fuel blue like mixing avgas with the petrol. And it was a ton cheaper than any proprietary octane booster! Never had any detonation problems on our way to winning our local club championship.

Fast Eddie said:

Well, a bit of an update guys.snipped


This is the head that Sir Comstock did for me earlier this year, it gave awesome results on the dyno and I intend to use it as is on the 920 build (with the squish band opened out to suit the 81mm bore of course) :

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Please come in from the corridor now. Did this head start life as an RH10 or an RH4?

Charlie

The head is a RH10 Charlie.

So, just when you’d all forgotten about my long in the tooth 920 waffle...

Ok, if we’re honest, none of us like being wrong. So, amongst others who slanderously threw the same accusations at me, Glen said way back in post #11 that I should get a TTI box for the 920. Well, after being in denial for quite some time, I basically have to come clean and say, yeah Glen, you were right!

Here’s pics of my new Heavy Duty 5 speed box. They’re a bit utilitarian in appearance out of the box, but a wire brush and scotchbrite pads have brought it up nicely I think:


It’s still only ‘rough cast’ but it looks nice I reckon...


With a little luck, I’ll have this motor sorted before petrol runs out.

More updates to follow...

Fine piece of machinery there Nigel.
Now you are free to make all the Norton HP you can muster!

Glen

Indeed Glen... and therein lies the (current) plan !

I think it was Sun Tzu who said ‘no plan survives contact with the enemy’... well this build has been its own bloody enemy!

The plan has had a few twists and turns along the way, often the case with long projects I find. Actually, part of the reason this 920 has taken so long is that the current 850 motor is just such a peach. The JS#1 cam and high comp pistons, with Comnoz head job and FCRs on Matts manifold just gel so well! It has to be close to perfection as a street motor, well, to my mind at least.

And at 65 rwhp it certainly ain’t bad on power.

But, as it’s such a peach, I’ve kinda concluded that I don’t want to cannibalise it for the 920.

So the plan now is to leave it as a whole lump.

And that kinda free’s me up as to how I might approach the 920, and, long story short, I wanna build something hot!

I think I have a plan...

But will it survive contact...?

More later...

Wish I’d not put 2016 in the title

Fast Eddie said:

Wish I’d not put 2016 in the title

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Don't worry, if you hadn't, we would have reminded you

Billet cases perhaps Nigel?

Not quite Mike, I’ve already got Maney cases, crank and barrel that I’m sticking with. Also sticking with the JS rods and pistons mentioned earlier in this thread.