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Author Topic: EFI Bighorn  (Read 15359 times)

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Offline 2T Institute

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EFI Bighorn
« Reply #15 on: September 30, 2012, 11:13:40 PM »
I wonder if anyone has ever considered using crank porkchops (i.e. not full round wheels) as a rotary valve mechanism instead of hanging that extra disk off one side of the crank?

Model car/boat/plane engines use that sort of a system. One system used on the Exactweld 250 was to use discs on both sides of the engine, with the timing staggered produced works type HP in the day. Disc is by far the best induction system, as it is not throttle dependent, reeds don't open unless the throttle is open.Kim Newcombe (RIP) went oh so close to winning the world 250cc road race title with a converted Koing boat engine. Moving the disc valve to the rear of the engine creates drive issues, which has traditionaly been a bevel drive or belt.
I've got a 1979 Gilera 125 MX with rotary valve induction in my collection, it looks like a Maico with a straight axle fork. If I'm not mistaken MZ pioneered disk intake valve technology in the 50's and when key people defected to the west this design made it's way to Japan (and your Bighorn - gotta love the name!).

 The Can Am's Rotax engine has an interesting history. Rotax began in Dresdan, Germany and was purchased by Fichtel and Sachs in 1932, whereupon production was transferred to Austria. In 1970 the company was sold to Bombardier of Canada and I've been told the rotary valved engines were already on the drawing board at this point.

IIRC there is a 79 or 80 KTM 125 disc valve  I was chasing a Gilera engine for road racing until the rules were changed to have a 82 cut off then got a hold of Rotax 124 engines, which are basicaly the Can Am 125 aircooled bottom end with an external water pump and a Rotax 256 cylinder. Easy 36-38HP ;)  Any pics of the Gilera they are a nice bike
« Last Edit: December 31, 1969, 04:00:00 PM by ' »

Offline Uniflow

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EFI Bighorn
« Reply #16 on: October 01, 2012, 12:13:45 AM »
That McCulloch with the chambers looks like a seizure waiting to happen. These engines are still used today in gyrocopters. These engines were only ever supposed to be drone engines for military shooting practise, short life.
I have to agree with 2T, there is nothing like a rotary valve to offer unrestricted induction access to the crank case. Just needs a little control is all.
« Last Edit: December 31, 1969, 04:00:00 PM by ' »

Offline TMKIWI

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EFI Bighorn
« Reply #17 on: October 01, 2012, 05:40:50 AM »
Kim Newcombe (RIP) went oh so close to winning the world 250cc road race title with a converted Koing boat engine. 

You mean the 500cc Champs. ;)
« Last Edit: December 31, 1969, 04:00:00 PM by ' »
If you don't fall off you are not going hard enough

Offline 2T Institute

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EFI Bighorn
« Reply #18 on: October 01, 2012, 12:28:35 PM »
Yes something didn't look right and it's KONIG too  :-[
« Last Edit: December 31, 1969, 04:00:00 PM by ' »

Offline Uniflow

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EFI Bighorn
« Reply #19 on: October 02, 2012, 08:06:56 PM »
Just found another problem. When the voltage goes below six or seven volts ( old battery ), the Ignitec has been defaulting to some fourstroke program! Keeps looking for a cam sensor, no spark. I've changed the default to the program I use now. There is a charging system so when the engine is running, no problem it's just if the voltage drops when starting. This system should now be able to run with just a capacitor.
« Last Edit: December 31, 1969, 04:00:00 PM by ' »

Offline SachsGS

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EFI Bighorn
« Reply #20 on: October 03, 2012, 04:01:39 PM »
My Gilera is identical to this: www.bringatrailer.com/2011/11/01/1979-gilera-125-cr/

The Gilera is unusual in that it does not have primary kick.That long travel centre axle fork is different as well and produces some strange handling characteristics. The motor has zero bottom end and is very strong in the top end for it's era. ;D
« Last Edit: December 31, 1969, 04:00:00 PM by ' »

Offline 2T Institute

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EFI Bighorn
« Reply #21 on: October 04, 2012, 02:44:17 PM »
Just change the disc timing then............................................................
« Last Edit: December 31, 1969, 04:00:00 PM by ' »

Offline Uniflow

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EFI Bighorn
« Reply #22 on: October 05, 2012, 10:08:38 PM »
Vary the valve timing, sliding disc housing, best of both worlds.
« Last Edit: December 31, 1969, 04:00:00 PM by ' »

Offline Uniflow

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EFI Bighorn
« Reply #23 on: October 05, 2012, 10:28:44 PM »
First round of the VMX yesterday. The Bighorn foot peg broke off in the practice, lucky I found a farmer down the road with a welder. So a DNS for the first race. I've been having a lot of trouble with the off idle to approx 1/8 ish throttle. I made some last minute change's to the program the night before ( not tested ). What a difference! Easily the fastest in a straight line in pre 75, and pulls so much better than it ever has from the bottom of the rev's through to 8600. Still might need a little more advance down low or perhaps a little more compression or perhaps just some new rings. Gearbox is standard F9, so having a wide power spread is a good thing. F81M close ratio gearbox would be nice to have but they are almost unobtainium now. I will look at making some gears up, is anyone else interested in an F81M gearbox? If I find some pictures of the racing I'll post them.
« Last Edit: December 31, 1969, 04:00:00 PM by ' »

Offline 2T Institute

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EFI Bighorn
« Reply #24 on: October 05, 2012, 11:02:20 PM »
I have a good gear gutter here Neil but I'm not the bloke with the 5 axis either  ;D. I would be keen on some gears, I'll email you a exel file that takes the guess work out of it.Biggest benefit will be from a pipe as that pipe looks to short to me.
« Last Edit: December 31, 1969, 04:00:00 PM by ' »

Offline Uniflow

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EFI Bighorn
« Reply #25 on: October 06, 2012, 01:24:52 AM »
I've been talking about making these gears for a while with Harry Klemm but work just keeps getting in the way. We have a gear hobb here, just need the time to machine out some blanks. Will make them from EN39B high quality case hardening steel. We make all our aviation gearbox gears out of this material. The chamber on the F9 is a FMF with a little added in the middle, nothing too special. I'm sure a proper chamber would work much better.
« Last Edit: December 31, 1969, 04:00:00 PM by ' »

Offline citabjockey

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EFI Bighorn
« Reply #26 on: October 06, 2012, 04:28:28 AM »
In your class are you racing against Maico radials? And your FI "Hornet" is speeder down the straights?

Sounds like you made some great progress on the maps!

First round of the VMX yesterday. The Bighorn foot peg broke off in the practice, lucky I found a farmer down the road with a welder. So a DNS for the first race. I've been having a lot of trouble with the off idle to approx 1/8 ish throttle. I made some last minute change's to the program the night before ( not tested ). What a difference! Easily the fastest in a straight line in pre 75, and pulls so much better than it ever has from the bottom of the rev's through to 8600. Still might need a little more advance down low or perhaps a little more compression or perhaps just some new rings. Gearbox is standard F9, so having a wide power spread is a good thing. F81M close ratio gearbox would be nice to have but they are almost unobtainium now. I will look at making some gears up, is anyone else interested in an F81M gearbox? If I find some pictures of the racing I'll post them.
« Last Edit: December 31, 1969, 04:00:00 PM by ' »
Yamaha CT3, RT3, MX125, SC500, Toy Prius, Diesel F250 (it all balances out)

Offline Uniflow

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EFI Bighorn
« Reply #27 on: October 06, 2012, 09:42:24 AM »





No Maico's racing. The biggest problem with this bike is the lump on it. I need to be way fitter, I can hardly hang on to it after only a few laps, not the bikes fault.
« Last Edit: December 31, 1969, 04:00:00 PM by ' »

Offline 2T Institute

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EFI Bighorn
« Reply #28 on: October 06, 2012, 10:20:27 AM »
Have yet to see many off the shelf aftermarket pipes with correct proportions on them.You could add a 50-70mm straight section at the header for better pull off the bottom.
« Last Edit: December 31, 1969, 04:00:00 PM by ' »

Offline SachsGS

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EFI Bighorn
« Reply #29 on: October 06, 2012, 04:53:01 PM »
Hound number 77 till he sells you that Can Am. ;D
« Last Edit: December 31, 1969, 04:00:00 PM by ' »