ESE's works engine tuner

[wobbly]

Hey Giggle I think you are a little optimistic about the "useability" of the dyno curve.
The problem is that the front side of the curve is very angled upward, makes it look impressive, but the problem is that under racing conditions you will be short shifting all the time to stay in the fat part of the power.
This will inevitably mean low overall gear ratios and this will inevitably defeat the impressive hump of power, as whenever you get into the front side, small openings of throttle will give big increases in power over low changes in rpm.
The exact opposite of what is needed to ride fast.
The perfect rate of change in power is a straight line - so as you open the throttle, you get a linear change in power given.
Doing wheelies off the bottom may be fun, but actually makes it harder to ride fast, as only Pedrosa and Stroud can steer a bike easily with the front off the deck.

[Bert]

few interesting videos:

GP125 cylinder casting by Gnani

http://www.youtube.com/watch?v=I-2rJtnkYq4

http://www.youtube.com/watch?v=Lj4h9...eature=related

http://www.youtube.com/watch?v=A50p3...eature=related

That my friend, is GOLD. nice find...

shame it can't be downloaded; I'd just about put it next to my Britten VHS

[Gigglebutton]

Hey Giggle I think you are a little optimistic about the "useability" of the dyno curve.
The problem is that the front side of the curve is very angled upward, makes it look impressive, but the problem is that under racing conditions you will be short shifting all the time to stay in the fat part of the power.
This will inevitably mean low overall gear ratios and this will inevitably defeat the impressive hump of power, as whenever you get into the front side, small openings of throttle will give big increases in power over low changes in rpm.
The exact opposite of what is needed to ride fast.
The perfect rate of change in power is a straight line - so as you open the throttle, you get a linear change in power given.
Doing wheelies off the bottom may be fun, but actually makes it harder to ride fast, as only Pedrosa and Stroud can steer a bike easily with the front off the deck.

Cheers Wobbly. The more i learn about 2 stroke tuning. the more realize how little i know. If nothing else at least it is a whole lot of fun.

[TZ350]

GP Crank Assembly

The inlet side crank wheel is chamfered at 45deg so its less of an obstruction to the incoming fuel/air mixture.

Attachment 237969

The original GP crank can take a beating and the rod/big-ends handle a lot of abuse and are even better if they have been kitted with later TS/TF rod kits that have slotted rods and silver B/E brgs.

Attachment 237967

But the problem with the original crank is that the piston pin is only 14mm making it hard to get decent pistons. I fitted an original RGV250 rod kit to mine so I could have a 16mm piston pin and therefor a bigger range of pistons to chose from.


Attachment 237966

I got my RGV rod kits by stripping down an old RGV crank, they worked great, I have since found some after market RGV rod kits to not be as good as the originals.

Fitting an RGV250 rod kit meant boring the B/E pin hole out to 22mm and facing off the thrust washer faces and the inside of the crank wheels 1mm for clearance.

Attachment 237971

The balance holes are asymmetricall, one side is bigger than the other, I drilled this hole so that the counter balance was symmetrically even and 100% opposite the bigend. The final balance factor on this crank is 50%. After trying it, I think that 52-55 might be better.

Attachment 237970

The crank was machined down so it had 2mm clearance every where, I am not sure that it helped but the extra crankcase volume and with the programable ignition it seems to have benefited the power spread. Plugging the crank reduced the crankase volume by 25cc, machining down the crank added 50cc to the case volume. Chambers measured the crank in both configurations using the Archimedes principle.

Attachment 237977

Phenolic caged main bearings, Koyo 6205 and 6304 FG C4 max rpm in oil 15-17,000.

The brgs have been fitted so the open side of the cages face the oil feed holes. The phenolic cages are more reliable than the usual riveted cages which can fly apart under the inertial load of quick crank acceleration, like blipping the throttle.

None of the crank work helped much with power but it did improve piston choice and reliability. Chamfering the inlet side crank wheel and changing the balance factor was probably the most helpfull. The original balance factor is about 65% and seems better at 50-55 when running at 10-11,000 rpm.

[Moooools]

That my friend, is GOLD. nice find...

shame it can't be downloaded; I'd just about put it next to my Britten VHS

http://mashable.com/2009/08/13/downl...os-to-desktop/

If it exists it can be fond on the internet...

[Gigglebutton]

i know Dave it kills my RG50 dyno sheet,maybe its a 70,my RG50 made 11hp at 12400 and reved to 14000,and made 6.5hp at 9000,that thing makes 11hp at 9000.

How long ago did you build your Rg? Aren't the Derbie's making 15 plus Hp? Ask why, don't assume

[RMS eng]

How long ago did you build your Rg? Aren't the Derbie's making 15 plus Hp? Ask why, don't assume

i think the derbi 50 s are around 14hp much more than 15hp from a 50 would be hard work at the kart track,ask Dave how much his RG50 makes,fast bike,but Mark on his semi stock Aprilia with maybe 12hp beat all the top 50s and 100s 2 years ago.your looks to be the best for the kart track but the RG50 frame will need work to get the most from it.

[F5 Dave]

He jumped the start!


Gee I thought I'd got over that

[kel]

Mark on his semi stock Aprilia with maybe 12hp

very semi stock as thats approximately 50% more power than off the showroom floor

[Fooman]

The perfect rate of change in power is a straight line - so as you open the throttle, you get a linear change in power given.

Forgive me if I get this wrong, but doesn't that imply a flat torque curve (i.e. engine is operating at peak efficiency all the way through the rev range) as power is the integral wrt frequency of torque.

The new curve may not be perfectly flat, but it is certainly more efficient throughout more of the rev-range (except right at the top), and makes more power overall - the shift points will be lower than the higher-revving motor, but it won't be short shifting for that curve.

Gearing may have to lowered to take advantage of the power wrt to top speed, but the mid range should still be better than the original motor.

Big Bang RG50 anyone? Firing every 2π rather than every, er 360°???

FM

[jasonu]

He jumped the start!


Gee I thought I'd got over that

and you told me off for going on about my crank seal. (which you still owe me for...)

[speedpro]

and you told me off for going on about my crank seal. (which you still owe me for...)

Are you blaming crank seals for Taupo blowups??

[Gigglebutton]

i think the derbi 50 s are around 14hp much more than 15hp from a 50 would be hard work at the kart track,ask Dave how much his RG50 makes,fast bike,but Mark on his semi stock Aprilia with maybe 12hp beat all the top 50s and 100s 2 years ago.your looks to be the best for the kart track but the RG50 frame will need work to get the most from it.

The motor is designed for both F4 & F5. The 2 curves on the graph are the motor in its 2 different states of tune. F5 is not 11hp yet, Speedpro tells me 14hp is achievable . Time will tell. F4 is a very different state of tune. The motor will not last long like this but hopefully with a bit of help from the boys and not to many seizes we can get it to hang together. I have made a load of bits to get it to handle,Big brake,17'' rims, Rear height adjuster, Braced swing arm, Fork brace, Fork emulators, Not sure what to do with the rear shock yet. Trying to get it sorted before i give it to my daughter. I have bought an Rs roller for F4 in Aus but have to get it here some how.

[TZ350]

Add a 1/2 throttle plate and the flow wont be as disrupted , as it would be with a plane "gate" when inserted.

Attachment 238004

Could these SU carb parts be used along the lines that Wobbly suggested for my project to extend the lower rpm range of the GP by varing the inlet area and closing point ..........

[F5 Dave]

The motor is designed for both F4 & F5. The 2 curves on the graph are the motor in its 2 different states of tune. F5 is not 11hp yet, . . ..

??? What do you mean by that???

So the blue line is not a 50 if it is for F4?

I struggled to see how you achieved a rear wheel BMEP of 165 from an RG