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Offline Uniflow

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YZ 250 EFI
« on: January 31, 2013, 04:42:01 AM »
If you will remember around Christmas time I made a pattern for a drum type throttle body

Here are four castings I've had done, they have been heat treated to T6.

These only turned up today, so I'll have to get to machining them next week or so. One of these is for the YZ 250 EFI project the rest are spares.
« Last Edit: December 31, 1969, 04:00:00 PM by ' »

Offline citabjockey

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YZ 250 EFI
« Reply #1 on: January 31, 2013, 05:03:51 AM »
Watching with keen interest!

« Last Edit: December 31, 1969, 04:00:00 PM by ' »
Yamaha CT3, RT3, MX125, SC500, Toy Prius, Diesel F250 (it all balances out)

Offline eprovenzano

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YZ 250 EFI
« Reply #2 on: January 31, 2013, 01:42:53 PM »
« Last Edit: December 31, 1969, 04:00:00 PM by ' »
Eric Provenzano
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Sold 1991 KDX 200... fun play bike
Sold 1999 KX250
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Sold but never forgotten 1974 Honda Elsinore CR250M
Sold 1974 Honda Elsinore CR125

Offline SachsGS

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YZ 250 EFI
« Reply #3 on: January 31, 2013, 03:41:56 PM »
Lots of detail please! ;D
« Last Edit: December 31, 1969, 04:00:00 PM by ' »

Offline yota

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YZ 250 EFI
« Reply #4 on: January 31, 2013, 03:44:34 PM »
looks like a valve body for an underground water sytem. :-X
« Last Edit: December 31, 1969, 04:00:00 PM by ' »

Offline jimaras Greece

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YZ 250 EFI
« Reply #5 on: January 31, 2013, 05:53:50 PM »
any news about the projekt?
« Last Edit: December 31, 1969, 04:00:00 PM by ' »

Offline Uniflow

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YZ 250 EFI
« Reply #6 on: January 31, 2013, 09:15:33 PM »
Yes certainly I will keep you informed. It has been a bit of a slow process, finding time, work has been very busy and after hours is being soaked up with the Kawasaki Bighorn. It's always had a problem with leaning out when trail ridden??? Why, and yet a five lap VMX no problem? With ethanol there is a certain amount of extra fuel needed as the engine gets hotter but this is way leaner. I fitted a external temperature gauge to a head stud and ran it up in the workshop for about fifteen minutes to check the readings are the same ( as the computer ), suddenly lean condition appears and low voltage warning on the computer. The alternator it seems has enough grunt to keep the battery charged above  five to six thousand but below that the charge is negative, it's only a small battery. I'm getting the stator rewound to be more efficient at lower rpm's. I know just keep it pinned :D
BTW Lozza, part of the reason the bighorn kicks sideways is the rear wheel is moving 10mm side to side!! I need to replace the bronze swing arm bush with an aluminium bronze bush, much harder.

The fuel pump is the problem as it draws just over four amps all the time, even when the engine is idleing. It is a standard car HP pump so delivers way more flow than needed. I'll need to find something a little smaller for the YZ project. Fourstroke MX bike pumps look very similar to mine, big and heavy. That's just a waste of energy!! The YZ project flywheel and stator are late model rare earth magnet type, this will help, smaller too.
« Last Edit: December 31, 1969, 04:00:00 PM by ' »

Offline Stusmoke

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YZ 250 EFI
« Reply #7 on: January 31, 2013, 09:41:57 PM »
« Last Edit: December 31, 1969, 04:00:00 PM by ' »

YZ 250 EFI
« Reply #8 on: January 31, 2013, 11:33:11 PM »
The throttlebody is the easy part.  Management is what makes everyone give up.

What are you using for management?  Microsquirt? 
« Last Edit: December 31, 1969, 04:00:00 PM by ' »

Offline cnrcpla

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YZ 250 EFI
« Reply #9 on: January 31, 2013, 11:44:53 PM »
Definitely very interested in this!
« Last Edit: December 31, 1969, 04:00:00 PM by ' »

Offline Uniflow

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YZ 250 EFI
« Reply #10 on: February 01, 2013, 06:41:17 AM »
I'll be using the Link, same as my Bighorn, it works well. Link are releasing a special version for the two stroke ( from my input ) middle of the year. At last!!!
Just found a smaller pump today 2 amps usage and still an external type.
I'm not quite sure if it is apparent but I've got two YZ projects on the go. One is the standard YZ250 converted to EFI ( for the local Yamaha dealer).
The other in the YZ250F frame with my own 360 engine,  cases are cast and machined to suit the YZF frame so no cutting is required. This engine has vairable rotary valve, blade type power valve, reverse rotating crank and reverse cylinder. This engine will uses the vairable valve casing as the throttle, driven from the link computer ( throttle by wire ). Much better engine control!
Cut the first engine case pattern today in the CNC. I will be using castings.
« Last Edit: December 31, 1969, 04:00:00 PM by ' »

Offline 2T Institute

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YZ 250 EFI
« Reply #11 on: February 01, 2013, 06:44:35 AM »
You reckon you would have ever thought of using the variable disc for a throttle valve? Things like that is what Frits is bloody brilliant at..
« Last Edit: December 31, 1969, 04:00:00 PM by ' »

Offline Uniflow

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YZ 250 EFI
« Reply #12 on: February 01, 2013, 07:15:55 AM »
Yes, I told Wobbly ( over a year ago ), Wobbly told Frits, now Frits is telling me! The circle of life :D
Although Frits did suggest moving both sides of the port. I hadn't thought of that.
« Last Edit: December 31, 1969, 04:00:00 PM by ' »

Offline Uniflow

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YZ 250 EFI
« Reply #13 on: February 01, 2013, 08:03:46 AM »


Machined up one casting today, just need to build the drum now. This will be shelled by the CNC, 2mm wall to make it light. Little hole is for oil line if needed. Lug on the back will be machined to accept the TPS. Drum runs on ball bearings nothing touches the wall. This is for the YZ250 project.
« Last Edit: December 31, 1969, 04:00:00 PM by ' »

Offline Uniflow

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YZ 250 EFI
« Reply #14 on: February 01, 2013, 08:08:34 AM »


Here is the first pattern to be roughed out, engine will be using a YZ250 clutch and gearbox.
This is the YZ360 VRV project.
« Last Edit: December 31, 1969, 04:00:00 PM by ' »