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Offline Uniflow

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YZ 250 EFI
« Reply #255 on: September 03, 2013, 10:20:05 AM »


Wayne Blackwood, right, with his YZ250EFI and some other guy hanging around we couldn't get rid of!

« Last Edit: December 31, 1969, 04:00:00 PM by ' »

Offline Jeram

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« Reply #256 on: September 03, 2013, 11:06:05 AM »

There is quite some arguement that 2ts will go to more oversquare engines, especially with such techs as DFI, as the fuel component of the charge, will be less dependent on the 'whole engine' concept.

I disagree with the idea that a DFI two stroke would require an over-square engine configuration. Its still a two stroke, it still relies on crank case induction and exhaust scavenging, just like almost all other DFI two strokes (with boats being the exception).

However a DFI trapping valve two stroke would probably make good use of a short stroke as it does not need the long stroke for additional exhaust time area.
« Last Edit: December 31, 1969, 04:00:00 PM by ' »

Offline bearorso

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« Reply #257 on: September 05, 2013, 08:04:27 AM »

There is quite some arguement that 2ts will go to more oversquare engines, especially with such techs as DFI, as the fuel component of the charge, will be less dependent on the 'whole engine' concept.

I disagree with the idea that a DFI two stroke would require an over-square engine configuration. Its still a two stroke, it still relies on crank case induction and exhaust scavenging, just like almost all other DFI two strokes (with boats being the exception).

However a DFI trapping valve two stroke would probably make good use of a short stroke as it does not need the long stroke for additional exhaust time area.


Disagree all you want young fellow.

As I wrote "There is quite some arguement that 2ts will go to more oversquare engines, especially with such techs as DFI". Therefore, there will be disagreements.

I don't believe there is a need for 2ts in Motorcycles to go that route - chasing revs to get HP, as naturally aspirated 4ts do. That's through my own, perhaps 'old timers' viewpoint, on what I want from a 2t.

2ts can keep relatively long strokes, whilst doing battle with 4ts.  Simple maths / time calculations show that 4ts "big bang advantage", so to speak, is gradually being negated by the revs they must go for, for power to compete against a 2t, at least for now. Though, Moto 3 rules (well, the max. bore rule of 81mm - shared with Moto 3 - is a somewhat of a 'control' in Moto GP) , are keeping a cap on revs.

But, as I wrote, there have been, and will remain to be, quite a varied opinion on what bore / stroke ratio is 'optimum'.

One Engineers "Optimum", will be anothers "Dud".

I gave the Evinrude dimensions as an example of what has been done, with a certain, pretty successful application of DFI  2 strokes.

I'll have to have a squizz at what the 2t Snowmobiles tend to use. It may be comparable to the
Outboards, as they may be more of a 'steady state' engine than a Motorcycle Engine ( but, I'd think, less so than an Outboard) would be. It, of course, may not be comparable, at all.
« Last Edit: December 31, 1969, 04:00:00 PM by ' »

Offline Jeram

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« Reply #258 on: September 05, 2013, 08:55:43 AM »

There is quite some arguement that 2ts will go to more oversquare engines, especially with such techs as DFI, as the fuel component of the charge, will be less dependent on the 'whole engine' concept.

I disagree with the idea that a DFI two stroke would require an over-square engine configuration. Its still a two stroke, it still relies on crank case induction and exhaust scavenging, just like almost all other DFI two strokes (with boats being the exception).

However a DFI trapping valve two stroke would probably make good use of a short stroke as it does not need the long stroke for additional exhaust time area.


Disagree all you want young fellow.

As I wrote "There is quite some arguement that 2ts will go to more oversquare engines, especially with such techs as DFI". Therefore, there will be disagreements.

I don't believe there is a need for 2ts in Motorcycles to go that route - chasing revs to get HP, as naturally aspirated 4ts do. That's through my own, perhaps 'old timers' viewpoint, on what I want from a 2t.

2ts can keep relatively long strokes, whilst doing battle with 4ts.  Simple maths / time calculations show that 4ts "big bang advantage", so to speak, is gradually being negated by the revs they must go for, for power to compete against a 2t, at least for now. Though, Moto 3 rules (well, the max. bore rule of 81mm - shared with Moto 3 - is a somewhat of a 'control' in Moto GP) , are keeping a cap on revs.

But, as I wrote, there have been, and will remain to be, quite a varied opinion on what bore / stroke ratio is 'optimum'.

One Engineers "Optimum", will be anothers "Dud".

I gave the Evinrude dimensions as an example of what has been done, with a certain, pretty successful application of DFI  2 strokes.

I'll have to have a squizz at what the 2t Snowmobiles tend to use. It may be comparable to the
Outboards, as they may be more of a 'steady state' engine than a Motorcycle Engine ( but, I'd think, less so than an Outboard) would be. It, of course, may not be comparable, at all.

The 2T snowmobiles have a large bore/short stroke configuration, but the main point is that the bore/stroke rations did not change when the bikes went from carbied to EFI and then to DFI. The DFI two strokes did not alter their bore/stroke ration when they swapped from carbied to DFI either.

The bore/stroke rations remained constant because gas flow dynamics and power characteristics do not care how and when the fuel enters the engine, only that its there and dispersed in time for ignition to occur ;)

So therefore I can only assume, and rightly so, that the bore/stroke will stay constant for two stroke motorcycles regardless of the fuel delivery type.
« Last Edit: December 31, 1969, 04:00:00 PM by ' »

Offline citabjockey

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YZ 250 EFI
« Reply #259 on: September 05, 2013, 03:11:28 PM »
I would think EFI (and DFI) would give engineers more freedom to work with other engine parameters. If a really oversquare piston would be prone to hot spots and pinging at specific throttle settings and RPM ranges it may be easier to compensate with the computers than it would be on a carb. So one would expect EFI/DFI engines to push the envelope in this regard (ratios further away from 1.0 than we are use to seeing). Maybe.
« Last Edit: December 31, 1969, 04:00:00 PM by ' »
Yamaha CT3, RT3, MX125, SC500, Toy Prius, Diesel F250 (it all balances out)

Offline georgemicra

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YZ 250 EFI
« Reply #260 on: September 18, 2013, 11:33:10 PM »
It might be possible to set up the ecu as a virtual V engine and use 3 injectors (2 transfer and 1 intake port) and run the 2 from one driver of say right side of V engine and the intake injector from another driver of the left side of virtual V setup. Then you have to play with the V degrees in order to adjust the injector groups timing.  :D
« Last Edit: December 31, 1969, 04:00:00 PM by ' »

Offline Uniflow

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YZ 250 EFI
« Reply #261 on: September 19, 2013, 03:50:50 AM »
I thought I was using an Ignitech EFI ( ordered through Wobbly ) but it appears they might be no more! Wobbly's ordered is now five months old and no news. Not even contact from Emails. They have taken the money for the order. Unfortunate as it seemed like it might have been a good unit.
We will stick to the LINK ecu at the moment, we now have total control over injection timing.

This is totally off subject but my own YZ now has a Rekluse clutch in it, with a left handle bar rear brake. Foot brake is totally gone ( for old people with a worn out right hip ). It's a bit like a mountain bike with both leavers on the handle bars operating front and rear brake. Much better entry to the corner control. 
« Last Edit: December 31, 1969, 04:00:00 PM by ' »

Offline Jeram

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« Reply #262 on: September 19, 2013, 06:14:07 AM »
I thought I was using an Ignitech EFI ( ordered through Wobbly ) but it appears they might be no more! Wobbly's ordered is now five months old and no news. Not even contact from Emails. They have taken the money for the order. Unfortunate as it seemed like it might have been a good unit.
We will stick to the LINK ecu at the moment, we now have total control over injection timing.

This is totally off subject but my own YZ now has a Rekluse clutch in it, with a left handle bar rear brake. Foot brake is totally gone ( for old people with a worn out right hip ). It's a bit like a mountain bike with both leavers on the handle bars operating front and rear brake. Much better entry to the corner control.

That's very disappointing!

Ignitechs quality was lacking in a big way over the last 2 years, I've had numerous faults and very poor customer support. So its not suprising that theyve gone belly up. (I dont know whether they have or not, but what your saying doesnt sound good)


« Last Edit: December 31, 1969, 04:00:00 PM by ' »

Offline georgemicra

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YZ 250 EFI
« Reply #263 on: September 19, 2013, 12:15:38 PM »
There is a new brand to me that makes an ecu with many features and good price. I tried to send a message to uniflow but is seems that there is a problem and I cannot send a message.
« Last Edit: December 31, 1969, 04:00:00 PM by ' »

Offline lauterbacher

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YZ 250 EFI
« Reply #264 on: September 19, 2013, 01:33:22 PM »
Post your link for him on the Board.it can't be any worse thing than people saying come and check out my bike porn.
« Last Edit: December 31, 1969, 04:00:00 PM by ' »

Offline rsmith

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Re: YZ 250 EFI
« Reply #265 on: February 27, 2017, 05:27:41 PM »
Anyone know how to get in contact with Uniflow?  He doesn't have an e-mail address listed with the board.

I would like to let him know that I was able to recover this thread and see what happened with this project.

--Ron.

Offline Coop

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Re: YZ 250 EFI
« Reply #266 on: February 28, 2017, 03:38:21 PM »
Maybe GerbilGronk on youtube who posted his videos for him has a way to contact him?
- Mike - Don't take life so seriously, nobody gets out alive.

Offline citabjockey

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Re: YZ 250 EFI
« Reply #267 on: February 28, 2017, 11:04:35 PM »
Hi is on this forum: https://www.kiwibiker.co.nz  as username flettner. You might try to contact him that way.
Yamaha CT3, RT3, MX125, SC500, Toy Prius, Diesel F250 (it all balances out)

Offline Flettner

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Re: YZ 250 EFI
« Reply #268 on: March 03, 2017, 04:47:08 PM »
I'm here, just not so often these days. Thought this TSM had died, nothing seemed to be happening. Fire away.

Offline rsmith

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Re: YZ 250 EFI
« Reply #269 on: March 03, 2017, 07:14:31 PM »
I'm here, just not so often these days. Thought this TSM had died, nothing seemed to be happening. Fire away.


It did die actually, Charles wasn't doing backups so I had to go to some somewhat extraordinary means to recover it.

This topic about the EFI YZ project is how I found the site way back when. Uniflow says in there somewhere that he was using this site to document the project and so I wanted to let him know that I had gotten it back.

So is Flettner Uniflow? or do you know how to get a hold of Uniflow?

Thanks for checking in either way, we are working on generating more traffic here to hopefully get the discussions flowing again.

--Ron.

--Ron.