ESE's works engine tuner

[jato]

I stand corrected - looking at the previous photo yes i see it. there must be some serious surface speed there at full revs...

[Grumph]

I stand corrected - looking at the previous photo yes i see it. there must be some serious surface speed there at full revs...

OMC outboards of the 60's had silver plated rings in that groove - sprung against the crankcase wall. At least you'd think they would be well lubricated.
And they were seldom called on to go over 4500RPM.

[TZ350]

With an old Suzuki GP125 air cooled cylinder and basic hand tools, how good a port job could you expect.



A drill press worked pretty well at hogging out the B and C transfer ducts. The B port windows were widened and the C port opened up.



Suzuki GP125
27 rwhp for Inlet 140/80 Trans 114 Ex 80 and 70% NF4 pipe.
30 rwhp for Inlet 140/80 Trans 114 Ex 78.5 and 75% NF4 pipe.



NSR MC21 in all its lovelyness.



Suzuki GP fitted with a NSR MC21 Cylinder
28 rwhp for Inlet 140/80 Trans 114 Ex 80 std shape NX4 pipe.
30 rwhp for Inlet 140/80 Trans 114 Ex port roof leveled off NX4 pipe.

Not startlingly different for all its factory lovelyness.

Good old hand porting work compares Ok to the Honda factorys performance sports cylinder.

Just saying, you don't need a lot of flash stuff to get a good enough result .....

[Frits Overmars]

if the centre disc rotates (which it must do,) how much clearence is there between it and the crankcase and why does it have what looks like an "O" ring groove .... surely not?

OMC outboards of the 60's had silver plated rings in that groove - sprung against the crankcase wall.

That's still state of the art - except the silver plating. The radial clearance of the centre disc in the crankcase can be quite liberal; sealing does not depend on it,
but on the clearance of the stationary 'piston ring' in the disc's groove. And that ring settles itself in the crankcase so that it's not pushed left and right anymore.
Wear is not a problem, as the pressure acting on the ring is less than 1% of the pressure acting on a 'real' piston ring, and the local temperature is modest as well.
Here's another picture of the JBB crankshaft.

[jbiplane]

Thanks you guys for valuable comments. I did some computer modeling and realyze that classical V "common finger" good enough and my idea of 90 degree pin offset require more bearing supports on shaft. Smaller torque variation not enough reason then.


Anyone know if intermediate part of jbb crank were one solid part or welding (press fit) of finger and disk?

Finally I am going to make 140cc V with 9500 rpm on max power which should weight below 3000 grammes including fuel injection.
It will be rather long ~4 month project. I think if I will make crancase precisiously then will dont need sealing ring on crankshaft.

[lohring]

This is the crankshaft I built for a 180 degree twin I'm slowly working on.

It will need a balance shaft. The same design will work for a 90 degree twin. It will need more balance weight in any case.

Lohring Miller

[Niels Abildgaard]

Finally I am going to make 140cc V with 9500 rpm on max power which should weight below 3000 grammes including fuel injection.

https://i.imgur.com/9RprD0t.jpg
https://i.imgur.com/n36caso.jpg

What kind of exhaust system?
If the pots are powerfull enough You probably do not need to divide the crankcase volume.

[WilDun]

Probably a very slight gap allowing communication between the (half) chambers wouldn't be a disaster in this case. but then what about the cylinders (axially) overlapping, what sort of arrangement is used to overcome that?
I understand that it all is well proven of course, but was just curious as to how it all works.

Update: Sorry I missed what came after my earlier question about the disc and when I've had my breakfast I'll read it all up!

Ok, so it seems to me that in effect it is really a labyrinth seal with maybe a little touching now and then.

I have heard that if the crankcase cavity is left undivided, (ie with 'V' cylinder arrangement) that the flow into the the lagging cylinder is always compromised - is this true? and of course there is the inevitable loss of pumping pressure for the second cylinder, but some people do seem to believe that this is irrelavent these days!
If I'm wrong, please say so - don't hold back! (it may improve my learning)

[WilDun]

This is the crankshaft I built for a 180 degree twin I'm slowly working on.

It will need a balance shaft. The same design will work for a 90 degree twin. It will need more balance weight in any case.
Lohring Miller

So I guess that gives the same piston phasing as a 180deg parallel twin but in boxer twin configuration? - would it justify the added complication and weight of a balance shaft (and crank bobweights)?

[peewee]

Attachment 333428

Suzuki GP100 with an NSR250 cylinder.

Attachment 333422

I have been working on a water cooled exhaust manifold for the Suzuki GP/NSR 110 engine.

Attachment 333423

Chambers is making good progress fitting it all into Av's old NF4 rolling chassis. He is even re cycling the original Honda RS125 NF4 expansion chamber. It will be a fun bike for us to ride.

Attachment 333424

And could be very interesting if Av takes her old NF4 for a spin.

Attachment 333425

Av peddling number 21 up the inside to take the win.

couple years ago i had cr500 with nearly those same timings that was used for racing on sand hills and it had a problem falling off the powerband unless shifted perfect and even then it was a bugger. maybe the pipe or something else was wrong. then again sand can be like riding with the brakes applied. ported a new cylinder with lower timings which worked far better for that kind of racing

[Frits Overmars]

couple years ago i had cr500 with nearly those same timings that was used for racing on sand hills and it had a problem falling off the powerband unless shifted perfect and even then it was a bugger. maybe the pipe or something else was wrong. then again sand can be like riding with the brakes applied. ported a new cylinder with lower timings which worked far better for that kind of racing

Riding in sand requires a broad powerband and a close-ratio gearbox because the rpm-drops during upshifts are far greater than you would expect from just looking at the gear ratios.
With a spinning rear wheel your crankshaft may be doing 8000 rpm but your riding speed may only correspond to 4000 rpm.
During an upshift the spinning stops and after the upshift your crankshaft rpm wil have dropped well below 4000 rpm, where no-one is home, power-wise.
MX-practice is to grab the clutch and send enough torque to the rear wheel to get it spinning again. MX-sidecars with 800cc two-stroke singles are the worst:
some riders cover the whole track in third gear.

[Greg85]

I discovered that making the underside of the transfer ports even with the piston in BDC
was very important: considerably more power, less detonation and far better piston cooling.
We started to have the exhaust ducts CNC machined in 1999 I think.
But first we had to overcome the new fuel regulations in 1998
102 octane had to be used instead of 130 octane.
We expected BIG problems.....
But within a couple of month's we had more power than before!
The compression ratio was lowered from 19,5:1 to 16:1
And the tailpipe restrictor was made 0,25mm bigger.
Then a very serious combustion chamber development was started.
The result was that parallel squish was the best, with a squish height of 0,75mm
Less squish height would give more torque but less revs.
At 0,45 the piston touched the head....
Then a head insert with a much wider squish band (50% of cylinder surface) was tried.
And that proved to be the final touch.
We now had more power than with the 130 octane fuels, and less problems.
The sharp edge between combustion chamber and squish band proved to be very important.
Even a small radius would give 0,5HP less..

hi jan you used a piston domed in the rsa it was doing more power than the conic piston? what squish angle did you have with the piston domed? thanks

[Frits Overmars]

No squish angle Greg, but a squish dome, parallel with the piston dome, as Jan wrote.
I guess you haven't noticed the RSA head drawing that I posted some time ago, so here it is once more.

[Greg85]

No squish angle Greg, but a squish dome, parallel with the piston dome, as Jan wrote.
I guess you haven't noticed the RSA head drawing that I posted some time ago, so here it is once more.

thank you very much for your contribution frits sorry I did not see this post very interesting

[Niels Abildgaard]

Finally I am going to make 140cc V with 9500 rpm on max power which should weight below 3000 grammes including fuel injection.
It will be rather long ~4 month project. I think if I will make crancase precisiously then will dont need sealing ring on crankshaft.

3Kg will be possible.Close at least

http://www.agm-engine.co.uk/agm6060c...ler-p-325.html

And spare parts list

http://www.dle-engines.com/dleg0060.html

I will try and sketch a V-2 crankshaft plus bearing system using these parts.I have quite some already and they are cheap.
Are there any classes for racing where a twincylinder two stroke is wellcome?