GT750 reed intake idea's

[ja-moo]

It is easier to make peak HP without reeds, as any obstruction in the intake tract is going to reduce hp. But there are trade offs that can actually make a lesser hp bike faster than a higher hp motor.......

[tz375]

And if the motor needs a lot of intake time area to make HP, a Reed motor with on demand timing will potentially make more HP than a piston ported motor. If transfer timing or exhaust time are are the restriction, reeds won't help. Yamaha supposedly found that on a fully developed reed motor they could make up to 30% more power than the piston ported equivalent.

[Suzukidave]

yeah .. yeah .. i love the sound of 30% more HP

[ja-moo]

And if the motor needs a lot of intake time area to make HP, a Reed motor with on demand timing will potentially make more HP than a piston ported motor. If transfer timing or exhaust time are are the restriction, reeds won't help. Yamaha supposedly found that on a fully developed reed motor they could make up to 30% more power than the piston ported equivalent.

What time frame did they find that kind of HP?

[tz375]

That would be back in the early seventies.

A well designed reed assembly does not restrict power output. It did take a long time for manufacturers to work out what works and even A.G.Bell had some issues as to optimal reed and port shapes. And of course there's more to it than just dimensions. Modern reeds may not produce the sort of power we'd like to see if the rest of the ports and pipe don't act the way they are supposed to.

In our computer modeling of a GT750 with reeds, the highest we saw was 168hp IIRC, but that had ports that just physically could not be put into that block, but why let the facts get in the way. And it was really hard to get a reed combo to beat a piston ported motor, but that's another story.

Of course, fool computers can't tell when you lie to them. They'll never catch on.....

In the real world, I think Kevin has the record at 120 ish at the rear wheel.

[ja-moo]

That would be back in the early seventies.

I was thinking later 70's as the 750 TZ's certainly made more HP than the H2R's, but nothing close to 30%.

[tz375]

TZ750 - average early 700 made about 90hp and later 750's made around 100 at the rear wheel - which was awesome for the time. Works OW's supposedly made from 120-140

On a 350, the 750 top end makes it so easy to ride that it's like a mild street bike compared to a 350G with 6 transfer ports per pot. A 350 non reed motor made more HP than a reed 750 (the point you made earlier), but a 350G with reeds supposedly makes more than either and teh OWs had that configuration - reeds and 9 ports per pot.

Maybe I should add reeds to my MOTRAC 350G barrels and scare myself even more... Or maybe not.

[Gene]

This is an interesting thread. Searching around on the net brought up a guy who modifies 2 strokes for reed valves. The 250 Hodaka housings and 6 petal reed seem similar to the project thread. At $300 per housing it would get spendy.

http://richstaylordporting.com/products.html" onclick="window.open(this.href);return false;

[Suzukidave]

Looking for thoughts on this idea , today looking at piston sets both 2 and 4 stroke i see so many 4 stroke sets with almost no skirt . With a reed intake controled engine do you think it would be a good idea to machine off the skirt the same way as these short skirted 4 stroke pistons instead of cutting windows in them ? Maybe leave a bit more on the thrust sides but on the sides cut them up close to the wrist pin area ?

[ja-moo]

Not a gread idea, 4 strokes don't have holes in the cylinders. The old race Yammi's had a huge cresent cut in the back skirt, and the pistons lasted one race.

[Suzukidave]

John , you think its a problem with the pistons rocking in the cylinder ? or what do you feel would be the reason for the quick wear out ?

[ja-moo]

John , you think its a problem with the pistons rocking in the cylinder ? or what do you feel would be the reason for the quick wear out ?

Mostly piston rock Dave.

[Suzukidave]

Any update's John ?

[tz375]

How much HP is that reed motor of your making Dave?

I hope you are making more progress than i am...

[Suzukidave]

uh