The factory race RC valves have the pivot mounted further away from the bore thus during their arc the sealing edge follows the bore more closely.
Yes, this is a definite problem with the standard valves. Especially if you level off the top edge of the exhaust port.
My next trick is to flatten and radius the RC valve and fit it to a cylinder with the top of the exhaust port set at 78 atdc and use the flat valve to present a straight horizontal timing edge to the cylinder at 80 atdc. That way I get the benefit of a flattened port roof, closely sealing RV valve and the improved flow coefficient of a radiused leading edge on the valve. Basically it should then behave like the Aprilia radiused exhaust port. All without doing any porting work on the cylinder itself. So reliable and cheap.
Any recommendations for a decent degree wheel/protractor?
I thought I'd bought the 'last a lifetime' type and shelled out too much money for one that has had half of the graduations flake off.
Laser etched numbers would appear to be the way to go but everything I see it way pricey given what it costs to produce that kind of stuff today.
Might be easier to commission or make a batch.
Here is what I use - simple to mount with a 6mm shaft.
Cheap as chips and accurate to 1/10*.
Easy angle measure from TDC or duration with a port stop.
Would never go back to a disc.
Rob did you use the Same EX Honda Rs125 pipe for both test as I doubt it would be the ultimate design for the short stoke engine either?
Yes, and you may be right but it has proved to be a very effective pipe. Very tolerant of my different engines.
My motors started at 16hp at 8,000 rpm and now 30 at 12,250 rpm.
Its not too surprising the RS pipe has worked well on all of them. Because its a good shape and a suitable length for lower rpm, power and exhaust temperatures. A length that is much the same as required for higher rpm, power and consequently higher exhaust temperatures. So basically the RS pipe has been the right length pipe for all my engines as they have developed increased power and rpm.
It works like this:-
A) Lower rpm = longer pipe.
B) Lower exhaust gas temp = shorter pipe.
C) Higher rpm = shorter pipe.
D) Higher exhaust gas temp = longer pipe.
A+B = C+D
I have tried to simulate better designs in EngMod but could not develop anything that was superior.
Yes, it has proved to be a very effective pipe. Very tolerant of my different engines.
My motors started at 16hp at 8,000 rpm and now 30 at 12,250 rpm.
Its not too surprising the RS pipe has worked well on all of them. Because its a good shape and a suitable length for lower rpm, power and exhaust temperature. A length that is much the same for higher rpm, power and consequently higher exhaust temperatures. So basically the RS pipe has been the right length pipe for all my engines as I have developed them for increased power and rpm.
I have tried to simulate better designs in EngMod but could not develop anything that was superior.
Did you try the Honda kit pipe as used by KTM as well? It could do with being a little shorter though given yours should be aiming a bit higher in the revs.
I will post pic as soon as I find it.
I believe this is the Last honda pipe as used by KTM as well.
This is the production 95 RS125 honda pipe
Originally Posted by Katman
I reminder distinctly .
Kinky is using a feather. Perverted is using the whole chicken
Interesting how far down the transfer ducts the staining stretches from combustion gases marking the transfer walls on this cylinder from a Honda NSR250. You can see why a cylinder overheats when there is insufficient blowdown time area for the reves being pulled.
I remember Speedpro talking about being able to look down the carburetor on one of his bikes being run up on the dyno and see fire dancing in the crankcase.
i once rebuilt a kx 500 engine...not only the transfer ports were black. the whole crankcase, the crankbearings, they looked terrible. and even the inlet was black!
for me this indicates the bike was either ridden the hell out of it and revved high the most time, the blowdown becomes insufficient at a certian engine speed as Jan, Wobbly and Frits explained .
Or it was ridden with respect and part throttle, wich makes the transferport entering exhaust gases issue worse.
i think this is more a blowdown than a transfer cooling issue. though cooling the transfer walls might help.
WATCHA GONNA DO WHEN THE ULTIMATE WARRIOR AND HULK HOGAN DESTROY YOU!!!!
I´m helping him with his twin Roost 100 (200cc)
Today we ported the block(not done yet) and made room for the Banshee V-force 4 reeds.
The reeds will be spaced out roughly 14-15mm
The Honda customer RS125 pipe has a Lt of around 824 ( including the front of the nozzle to point S )
This was matched to an EO of 82.5*.
That combination gave a good power spread and rpm capability near 13,000 in the overev.
Where as the so called "factory " specs " have an Lt closer to 800 ( same as an Aprilia ) and was developed to work with a EO at 80*.
That setup used PWM powerjets, and a completely different ignition curve suited to reving closer to 14,000 in the overev.
The A kit spec spec as used by KTM is nowhere near suited to the older customer Honda cylinder without all the other bits needed to all work together.
Here is a rear wheel dyno sheet showing a well tuned customer RS125, an A kitted engine and an A kit with powervalve.
Completely different tuning scenarios, so just bunging that pipe on an older engine simply wont work.
Using Engmod now it would be very easy to produce a pipe with way better power than either design, as long as the correct cylinder and ignition specs were followed.
Ive got a thing thats unique and new.To prove it I'll have the last laugh on you.Cause instead of one head I got two.And you know two heads are better than one.
Completely different tuning scenarios, so just bunging that pipe on an older engine simply wont work.
It is certainly what has worked the best for me so far.
Originally Posted by wobbly
Using Engmod now it would be very easy to produce a pipe with way better power than either design, as long as the correct cylinder and ignition specs were followed.
Hi Wob, I have given it a serious go but haven't been able to do it myself.
But if it would be easy enough for you, I would be happy to post my engine specs in EngMod format if you were willing to give developing a better pipe go.
We could post the design reasoning behind the engine and pipe and the dyno results here. It would be a very interesting and educational example of using the EngMod2T software.
The Honda customer RS125 pipe has a Lt of around 824 ( including the front of the nozzle to point S )
This was matched to an EO of 82.5*.
That combination gave a good power spread and rpm capability near 13,000 in the overev.
Where as the so called "factory " specs " have an Lt closer to 800 ( same as an Aprilia ) and was developed to work with a EO at 80*.
That setup used PWM powerjets, and a completely different ignition curve suited to reving closer to 14,000 in the overev.
The A kit spec spec as used by KTM is nowhere near suited to the older customer Honda cylinder without all the other bits needed to all work together.
Here is a rear wheel dyno sheet showing a well tuned customer RS125, an A kitted engine and an A kit with powervalve.
Completely different tuning scenarios, so just bunging that pipe on an older engine simply wont work.
Using Engmod now it would be very easy to produce a pipe with way better power than either design, as long as the correct cylinder and ignition specs were followed.
Wob think you have misunderstood the point I was trying to make, wasn't suggesting that blindly adding the works pipe was the answer, I was suggesting that I didn't believe the use of the Std pipe and rev perimeters with now de-stroked engine was the best combination. I simply suggested that Rob might be better served to follow the path of development that Honda had with the later models.
Originally Posted by Katman
I reminder distinctly .
Kinky is using a feather. Perverted is using the whole chicken
I was saying that putting the short A kit pipe on an older RS125 engine simply wont work - plenty have tried, and failed.
Sure TeeZee, you post the pack, and i will do a pipe,with some insights into the process.
Ive got a thing thats unique and new.To prove it I'll have the last laugh on you.Cause instead of one head I got two.And you know two heads are better than one.
Originally Posted by husaberg
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and part throttle, wich makes the transferport entering exhaust gases issue worse.
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