ESE's works engine tuner

[Condyn]

I had issues with a 1-2mm wide iron bridge between aux and main before. This was an application where I had to make the aux tight to the main because of stud bore constraints. It overheated the bridge. I did not have oil holes drilled.

[peewee]

i always put oil holes in the piston for any type of exh bridge. also i grind a resorvoir into the liner below the bridge so it fills with oil at tdc then the piston walls carry the oil over the bridge on the next cycle. 1mm isnt much surface area and more than anything i figure they will wear down faster and perhaps maybe crack. only one way to find out

[jonny quest]

Holes in piston, channels.... for oil may help at idle.

Full song, full heat, they are doing anything

[wobbly]

Yes , in the Aprilia and the TM the piston skirt pushes on tongues each side below the boost port.
Holes got rid of wear marks in both engines.
And of course any RS125 Honda , RM/RGV125/250 with a T port would tear up the skirt without oil holes in no time.

[ceci]

I do well to show it or not, I know that I do not enjoy much sympathy and surely with things like this I will have less.

how a bout two fingers that slide into the reed cage and hold the petals open, obviously won't work on vforce reeds and more petals = more fingers.
could simply have the fingers attached by cable to the powervalve, no extra servo, 24/7 during the powerband.

That's the general idea, TerraRoot; the 24/7-valve and the exhaust powervalve can be synchronized.
But you do not need a fancy reed cage. As long as the engine is running below the powerband, it is not making power anyway, so the reed does not have to be sophisticated; a simple single reed petal will suffice. Remember, it is there only to start the engine. And instead of a finger to hold the reed open, you can mount the reed on a shaft; that makes swinging it out of the way much easier.
Here is that original picture once more for those of you who haven't seen it yet: over-engineered like I said. One shaft with one petal (and of course no gears) will suffice.

https://worldwide.espacenet.com/pate...%3DJPS6065228A

https://worldwide.espacenet.com/pate...4-946c2ad18c33

[OopsClunkThud]

The reason there might be no "real " flow till the Aux open is because the mains roof timing is way too low, ie they are virtually the same .
Thus a large amount of Hp bandwidth is lost , as stagger , where the main port is higher - gives rise to a much more intense amplitude wave front exiting into the duct, increasing both leftward and rightward wave action.

As it stands , due to the huge disparity in Blowdown path lengths the initial wave front will be reduced in amplitude and also severely smeared out in time.
In a conventional 3 port, if all are opened concurrently , big power losses occur on both sides of peak.
This shows the inherent limitations of using flowbench data to drive development strategy.
Edit - this is why the Aux are square , as the flowbench ( and the designer ) knows nothing about upward short circuiting from the A port.

Has opening the aux ports before the main been tried as a way of aligning the wave fronts given their different path lengths?

Opening the aux after the main would seem to "smear" the wave front even more, but maybe it puts it far enough behind the wave front that it doesn't disrupt things. With the extra path length and ~5° of stagger, back of the envelope looks like the aux could be as much as 1.5 bores behind.

[wobbly]

Yes Kawasaki built a 125MX with the Aux higher and their own power valve - was a dismal failure and was quickly replaced.
I did some consult work for a Belgian company building RS125 Honda cylinders , I got them to try reversing the timing angle on the T port.
That is the outer edges at 100% of bore were the highest.
In the end after lots of tests it proved to be no better , but lost quite a bit off the pipe.
The A kit setup was a dead straight timing edge @ 200* duration , that made easily the best power with the short A kit pipe/ignition/carbs etc.

PS - the staggered Aux dont have anything like the P Delta across the port into the duct , and work more as a bleed down of remnant Blowdown pressure rather than generating a high amplitude wave front, like the min does when opening by itself.

[JanBros]

Yes Kawasaki built a 125MX with the Aux higher and their own power valve - was a dismal failure and was quickly replaced.

not questionning your knowledge Wobbly, but the KR1S also has higher aux' and it's performance is at least on par with the other 250's. in fact it's still the fastest 250 production bike ever.
or is the BMEP of these 250's road bike not enough to make a difference ?

[Frits Overmars]

not questionning your knowledge Wobbly, but the KR1S also has higher aux' and it's performance is at least on par with the other 250's. in fact it's still the fastest 250 production bike ever. or is the BMEP of these 250's road bike not enough to make a difference ?

I encountered the higher-than-main auxiliary exhaust ports of the Kawa KR1S when a friend rode one in a Dutch Standard class of 400cc four-cylinder foul-strokes against 250cc two-cylinder two-strokes (life ain't fair).
The rulebook allowed no more than 1 mm deviation from all standard port dimensions and all I did on the cylinders was raise the main exhaust ports 1 mm and fit 1 mm base gaskets that were later substituted by fitting Yamaha TD2 pistons with 1 mm less compression height. I used cylinder head inserts that restored the combustion volumes and fitted homemade pipes. We were not allowed to do anything about the 28mm carbs; all I did on the intake side was shorten the inlet rubbers about 5 mm. With 73 rear wheel-HP it was the fastest bike in its class, making fools of those 400cc foul-strokes.
The point I am trying to make: the little Kawa was a fine bike alright, but I doubt its original higher-than-main auxiliary exhaust ports were of any benefit for power.
My guess: Kawasaki may have tried to avoid power valves in the main exhaust ports because of patent infringement reasons, so they put valves in the auxiliary ducts, and then it would make sense to make those auxiliaries higher than the main port.

[husaberg]

I encountered the higher-than-main auxiliary exhaust ports of the Kawa KR1S when a friend rode one in a Dutch Standard class of 400cc four-cylinder foul-strokes against 250cc two-cylinder two-strokes (life ain't fair).
The rulebook allowed no more than 1 mm deviation from all standard port dimensions and all I did on the cylinders was raise the main exhaust ports 1 mm and fit 1 mm base gaskets that were later substituted by fitting Yamaha TD2 pistons with 1 mm less compression height. I used cylinder head inserts that restored the combustion volumes and fitted homemade pipes. We were not allowed to do anything about the 28mm carbs; all I did on the intake side was shorten the inlet rubbers about 5 mm. With 73 rear wheel-HP it was the fastest bike in its class, making fools of those 400cc foul-strokes.
The point I am trying to make: the little Kawa was a fine bike alright, but I doubt its original higher-than-main auxiliary exhaust ports were of any benefit for power.
My guess: Kawasaki may have tried to avoid power valves in the main exhaust ports because of patent infringement reasons, so they put valves in the auxiliary ducts, and then it would make sense so make those auxiliaries higher than the main port.

https://www.kiwibiker.co.nz/forums/s...post1130300124
https://www.kiwibiker.co.nz/forums/s...post1130300150

Golly frits that was 10 years ago when we had almost the same conversation.

[Frits Overmars]

Golly frits that was 10 years ago when we had almost the same conversation.

Time flies, doesn't it? But when re-reading that old post of mine, I noticed an error.

Fitting Yamaha TZ250G pistons (lighter, stronger, cheaper(!) and with 1 instead of 2 rings and 1 mm shorter from pin centre to top edge), raising the centre exhaust to the same height as the auxiliaries and milling the cylinder head made it faster than all the foulstrokes.

Ø54mm Yamaha TZ250G pistons in those Ø56mm Kawa KR1S cylinders wouldn't have worked very well. I used the older Ø56mm Yamaha TD2 pistons in the Kawa.

[JanBros]

I used cylinder head inserts that restored the combustion volumes and fitted homemade pipes. We were not allowed to do anything about the 28mm carbs; all I did on the intake side was shorten the inlet rubbers about 5 mm. With 73 rear wheel-HP it was the fastest bike in its class, making fools of those 400cc foul-strokes.

anymore info on the cc's and squish area of the head ? and stretching your memory/kindness : dimensions of the pipe ?
and with that power, what about the cracking cylinders arround the stud holes ? first the rear crack, and when you strengthen the back of the cylinders, the front crack one off the reasons most KR owners don't seek outright power but wider powerband and torque.

don't know if you've ever heard of the RGV-challenge ? http://www.rgv250.co.uk/forums/topic.../?_fromLogin=1

for those without a login :

I must admit to having a chuckle about all the tuning threads on this forum.

With so many people trying to tune the RGV isn't it time you lot came up with a half decent tune that was proven and available to all. There must be enough collective experience on this site to come up with a decent motor.
I have seen lots of bling bits for the RGV - heads, valves, pipes, ignition etc but I have yet to see a decent 250cc motor. Note the emphasis on 250cc.
VJ22 barrel is half decent, transfer port area is good, only weak point is the exhaust port which I think is too high (and people insist on making it higher) and doesn't have enough time area. Crankcases and flow through them needs work but this seems to be an area that is never touched (got the best part of 6hp on the KR from case work).
So I am going to set the forum a challenge
Build a VJ22 motor that out grunts on Krazy Katt's dyno my KR (got to think through how this will be decided)
Then because dyno runs are one thing and the track is another put the engine in either an Aprilia or an RGV chassis and beat my KR's single lap time and average race time (at least 8 laps) around Cadwell. You can choose your chassis and your rider. This test is the ultimate you need a good engine for a fast lap time and to keep it up for 8 laps it must be reliable.
Details of the engine spec (tune) must be made available on this forum so others can build a decent RGV engine.
I will put up as a prize ?500 as an incentive for you lot to do it - prize to the first entry to succeed
I will have a chat with James (Krazy Katt) and Jim (Arch) about the rules (they don't know this yet) and will post the final set up here.
If you manage to do it I reckon you should pay me - but first lets see if you can do it





challenge came from Marc Jordan, the guy that se the Bonneville record on the KR. no one succeeded , and if memory serves me right, not even one came close or had a go on the specified dyno.

[Frits Overmars]

anymore info on the cc's and squish area of the head ? and stretching your memory/kindness : dimensions of the pipe ? and with that power, what about the cracking cylinders arround the stud holes ? first the rear crack, and when you strengthen the back of the cylinders, the front crack one off the reasons most KR owners don't seek outright power but wider powerband and torque.

It wouldn't surprise me if Husaberg is going to point out that I answered these questions ten years ago as well, but for now I will stretch my memory.
My Kawa KR1S combustion chamber shape was the same as that of the Aprilia RSA from 15 years later, with 50% squish area and 1% squish clearance, but with a lower compression ratio: 12:1 if I remember correctly. I can't help you with the exhaust pipe dimensions; my memory is not that stretchable.

I never cracked a cylinder stud ear, but I've seen it happen with Honda, Kawasaki and KTM cylinders. But I've never heard of KR owners seeking wider powerband and torque instead of outright power in order to avoid the cracking and I cannot imagine that it would make any difference at all. From what I've seen, using huge stacks of paper base gaskets seems to be the #1 cause for the cracking.

[F5 Dave]

I remember reading that they could be quite variable in barrel height. Measure everything.

[wobbly]

Shit yes, I should have remembered the KR1S as back in the day I had a production line going modifying them - I would have done at least 20.
This used an alloy base plate cut out by a CNC wood routing machine , as there were no laser or water jets here back then - as you are right Frits a bunch of paper would crack the ears off.
It was the fastest bike in proddy racing , but our tech rules were very lax back then and Honda generally was the way to to as the F2 kit parts went straight on and no one knew how to
discern ( or didnt care ) the changes.