Billet cylinder head

I got you guys talking now, didn't I?
One thing that has become more obvious to me during the latest process is that commenting existing solutions/designs is far more easy than trying to figure the whole thing it out from scratch.

First of all: I am stunned by the quality of the preparations of the simultaneous 5-axis control program and machining of Mossbergs Mekaniska!

@Bushie:
I do not know the volume of the combustion chamber in the head. It requires manual grinding to be completed and measured. I put the valves 2-3mm up in the head, not to make the combustion chamber too flat, because that will kill the swirl at TDC. Other than that, I would probably be able to produce synthetic diamonds if not increasing the volume. :wink:
As for the cooling passages, I have not experienced any misfit with my cases.

@Popup:
There is one theory saying that you will get a better use of the exhaust pulses, if they are kept as one big pulse and not divided into separate pipes. Maybe large cylinders give away pulses that are strong enough, even if being split into separate pipe, whereas the 450´s might not. I have no experience of my own supporting this theory. Instead I kept the OEM position, to make it possible to fit any after market exhaust system straight on.

@Taffy:
Thanks for the cheering! I believe pistons grew once people understood how to design to obtain a good combustion with large diameter pistons. That made it possible fx Ducati 1198 to go to 106mm and reduce stroke but still get the required cylinder volume. I also believe that in order to get a good midrange (4-7k), with only one cylinder you will need some "leverage" to the crank. I think that with 2 cylinders or more, you can keep a fair midrange (and acceleration) with smaller stroke, because the cylinders will cooperate. As for the 450´s, revving is more interesting which requires a smaller stroke not to get obscene piston velocities. But that's only my humble unscientific ideas. I think my new design will work pretty well up to 105mm. Above that you will need even larger valves and lift and ports and-and-and...

To whom it might concern:
If critizing others work gets you off, then fire away! I will not deny you that pleasure!
If you think you are being constructive, you might have opened the hatch 2 months ago!

Now, this is still just a shiny piece of aluminum. There are more work to do before we know what laptimes it can make possible.

spanner said:

Sorry Dr C I think you my have misunderstood my attempt at humour
was in no way meant as criticism.
Love your work!

Cheers spanner

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Absolutely no offence taken, Spanner! Not by you or anyone else! Honestly!
It just strikes me how much more easy it is to have an opinion once there is a reference established. Forming your own idea/opinion out of "nothing" is much more complicated. It least it works that way for me.

I get it now, Spanner!

BERGBRO said:

Yo DR_C bro..... I've been wondering why a 250 chassis and not a 125 (looks like a bit of space left over in 250) then I thinks maybe something to do with rear wheel/tyre size. Could be tricky trying to lay down all that torque through a bicycle sized tyre of a 125? Or maybe you are more comfortable on a more substantial frame (I prefer the feel of bigger bikes to little ones, little ones seem flimsey).
You have obviously put a lot of thought into this project so Im thinking it wasn't because thats what you had kicking around in the back shed.
I am not in any way critisizing you (your work is brilliant from my point of view) its just that somebody once told me physics sez the smallest lightest bike (all things being equal) should have the highest apex speed (although I used to make a point of passing him around corners on my bigger bike).
By the way... whats the top speed of your machine? Must be one of the fastest singles around? Purely a guees from me 230km/h+

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Yo Berg bro! Yes, you are right about this being thought through! At first I was very close to building a Minimono (125-style). I thought that as the Husaberg 650 was only 1kg heavier than a 450-japcrap, I could run a 650 in it without tuning so much. Then I started to project the build. At the time no one was building Minimono´s on 125-chassies. Everyone was going towards steel tube chassies with 125-dimensions. Tigcraft, GRC, NWS and others were offering chassies for a sum of money. The 125 rear wheel has 3 pins connecting the rear sprocket to the rim. So there was an obvious need for a cush drive. PVM offered special 125-wheels for Minimono purpose with cush drive. So all was do-able but it summed up well over 15000€ for the complete bike, back in 2003. At the same time fellow racers had terrible problems getting the chassie builders to deliver in time, to the contracted cost and with expected quality. On top of that I wasn't sure that 180cm, 77kg deadmeat would be able to utilize the high corner speed that Minimono was making possible. So, I decided to buy a Honda RS250 (with extra wheels) and sold the engine. Fabricated engine mounts, cush drive, air box, modified the fuel tank, etc. Cost was down to perhaps 6000€, I was in total control of all fabrication and supply and familiar with the charasteristics of the 250. From purschase of the chassie, the bike was completed to the first race of the season, 3 months later! Thanks to my lovely and understanding wife!

On tracks with high speed corners (Spa, Assen, Hockenheim, Donington fx), a Minimono can be very competitive. You can keep the high speed up and utilize that awesome corner speed. On the small club-racing tracks we are racing in the Nordic Cup, you will need more "grunt" to get out of the tight low speed corners, making a Supermono with 65+ RWHP a better weapon.

In the european Supermono Cup there are Pami BMW´s or Happeck Yamaha´s with 720-740cc and over 80RWHP... With my current engine I'm loosing a bike length on a short straight compared to one of those bikes, with 644cc...

I have no speedometer, but 220km/h seems possible with the existing engine. I will have to get back to you once the new bits are tuned together!

Hello again, friends!
Lot of things have come in the way of me finishing the DOHC-project, but now I have managed to put in some hours. Today I got the engine, with the DOHC-head, fitted in the frame. I had to cut some in the frame and weld, but now fits! Tomorrow I will manufacture tools to adjust the cam timing and something to hold the ignition pickup sensor in place. I will stick it through the hole in the flywheel cover for the cables.

Davo said:

Hey Dr C, is the second hole to the right for the Camshaft Position Sensor? Looks about 18mm diameter with a 5~6mm threaded hole to suit the Honeywell Hall Effect Sensor.

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Yes, it is! I just made a steel insert in the alu chain sprocket for the sensor to be happy. Tomorrow I will time the camshafts. I have not decided what LC to adjust them to for the first test. Somewhere around 115 degrees I think. The 13,9:1 piston will add so much mid range I think I will need to go up with LC (and back off with ignition advance) to make it go "zing" as well. I'll keep you guys posted. After so many hours it is finally close to the first start. Very exiting!

Gentlemen!
Finally it has come to the first fire! The fuel injection was challenging, but finally it came alive! Fun to see the injector working "live" according to map, rev and throttle opening! Now the work begins with adjusting intake, exhaust and mapping it up.

bushmechanic said:

Its alive!

excellent Dr_C :cheers: :cheers: :cheers:

can we get some sound clips ? I keep cliking on the picture but its silent! I would use a bigger hammer on the mouse but im afraid to spill my beer on the firecrackers :lol:

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The cost effectiveness comparison with investing in beer and fire crackers, caught you, did'nt it?

OK, Bushie, this one is for you: http://www.youtube.com/watch?v=wQoPtR7LPco

Scary close to David Attenborough.