The Mega-Horn

[Jeram]

My new project.

was going to call it the Yama-saki-aris but it was a bit too long so were just coining the term 'Megahorn' for it; a Bighorn on steroids.



should have it mounted up in the next month

[L.B.]

Um.....wtf is it?
Big 2s single?

[Jeram]

The only type big bore disc valve single ever made, and then adapt it to run a late model liquid cooled cylinder from Polaris.

should hopefully have a wonderful torque curve starting at 35 ft lbs at idle and then linearly working its way up from there until signing off at 9000rpm.

[JonW]

Sounds interesting Jeram, interested to see the build progress

[2TInstitute]

Decide to incorporate some late Aprilia GP features like watercooled crankcases. Should be a barrel of laughs. The old Big Horn trail bike has to be one of the most under rated engines ever built. AHRAMA regular Dave Crussel rides the Scott Clough tuned big horn and everywhere except Daytona is it match for the period 350's and 500's.

Will be nice to hear the sound of a 44mm Mikuni

[Jeram]

Decide to incorporate some late Aprilia GP features like watercooled crankcases. Should be a barrel of laughs. The old Big Horn trail bike has to be one of the most under rated engines ever built. AHRAMA regular Dave Crussel rides the Scott Clough tuned big horn and everywhere except Daytona is it match for the period 350's and 500's.

Will be nice to hear the sound of a 44mm Mikuni

Lozza, you should see this bottom end, its built like a nuclear bunker. eg:the gears are even beefier than a suzuki gsx1100, and better design too (straight cut gear).

I think it can handle everything were going to throw at it.

[Jeram]

CR500 primary



Bighorn Primary

[Jeram]

little bit of progress since I finished my 2nd last uni semester last week.

engine is fully apart and ready to be modified and then rebuilt.

Im also getting a little closer to finding the right engine position in the frame, once Im happy with it I will start making the mounts.






Kudo's to who ever can guess how this enormous flywheel weighs (in oz).

[Jeram]

my cases also have baked on mud, oil and gasket sealant on them from the seventies.

whats the best method to get this off?

Oven cleaner (caustic soda) ?

vapour blasting?

etc.

[EPApolice]

Vapour blast them, I can give you the number of a guy that does a great job and cheap. He just did a YL1 motor for me that was the worst I ever saw it came back like new.

[Jeram]

yeah shoot me his details please, how much do you think itd be to get a crank case done (single cylinder left/right side)?

[EPApolice]

I will PM you his details.

[Jeram]

slowly accumulating parts

[2TInstitute]

Might have to move those engine mounts further up the frame, would make a better job of it

[Jeram]

I was just going to mount the engine via the bottom front mount, using two M12 high tensile turnbuckles, as its straight under the frame mount.

but you think it definitely needs moving forward to mount at the front?
If I was going to do that, Id just take it to MCR and get them to move it forward but also extend the mount so that it reaches the motor mount.

If thats the case then Ill leave the engine mounts till later in the year and instead will concentrate on getting bits for the motor and more rolling chassis parts.

actually, your dead right with needing to move the mounts, because on the other side of the motor the engine mount is in the way of the carb