ESE's works engine tuner

[peewee]

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.

with thick gaskets do the nuts pull down the corners and the middle is bowed up ? i remember seeing a cyl with a extra bolt half way between the corners ,probly for that reason im sure. brc500 i believe it was

[JanBros]

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.

tnx again. I have saved a quote from you explaining what you did with the cylinders on that specific bike from your friend, but there was nothing in it about the cylinder head.
the cracked ears are "common" on tuned KR's, happenned to mine to and I never use base multiple gaskett's (or thick ones, or lose base plates) to raise the barrel

[pete376403]

tnx again. I have saved a quote from you explaining what you did with the cylinders on that specific bike from your friend, but there was nothing in it about the cylinder head.
the cracked ears are "common" on tuned KR's, happenned to mine to and I never use base multiple gaskett's (or thick ones, or lose base plates) to raise the barrel

Did you ever machine the top of the cases where the barrel sits to ensure it was flat and square? I recall reading that earlier Kawasaki (early 70s F9) cases were not machined as pairs and could be mismatched at the barrel join

[husaberg]

Did you ever machine the top of the cases where the barrel sits to ensure it was flat and square? I recall reading that earlier Kawasaki (early 70s F9) cases were not machined as pairs and could be mismatched at the barrel join

I have mentioned this before but i believe the old 1970's Kawsaki multis were not line bored which i why people say not to run lab seals in them unmodified
but Legend is Yamaha and Suzuki miultis were.
no idea if it true or not but i have seen tales of lab seals being added to Kawasaki threes and them only lasting a couple of hundred Km's.
Honda i think went through a stage in the early 80's were then never line bored cams and caps etc.

[JanBros]

Did you ever machine the top of the cases where the barrel sits to ensure it was flat and square? I recall reading that earlier Kawasaki (early 70s F9) cases were not machined as pairs and could be mismatched at the barrel join

no and there are no problem's whatsoever with the KR1-cases.
what you do have to check is the height of the barrels, there can be a fifference between them. and always first tighten the headbolts before tightening the barrels.

and KR1's do not have a single seal between cylinders, each crankcase has their propriat seals, so no need (or probably space) for lab seals. in between both crankcases is the gear for the balance shaft.

[Frits Overmars]

I have saved a quote from you explaining what you did with the cylinders on that specific bike from your friend, but there was nothing in it about the cylinder head.

With the 1 mm base gaskets, and later with the 1 mm shorter pistons, I had to restore the combustion volume somehow and I did not want to shave the cylinder top decks.
Raising an exhaust port in order to adapt a standard cylinder is something you can do in a paddock if need be; shaving the cylinder top decks is not. So I modified the 2-in-1 cylinder head and made inserts.

Here is another modification that I did not mention before. If you remove the reed valve bodies an look into the cases, you will see that the cylinder sleeves are rather obstructive. But you can grind a lot of sleeve material away without affecting the piston support area.

A bike that leaves its rivals standing draws attention and rumors about illegal works cylinders arose. The KR1S cylinders have resonator boxes coupled to the auxiliary exhaust ducts but I suspected they would bring unwanted heat into the cylinders, so I blocked them. This enabled me to omit the boxes, and without those I could fit the right hand cylinder to the left and vice versa: My engine without the lateral boxes that are so prominent on the standard engine below, had a proper works look .

[JanBros]

mostly people mount extra spacers to the KIPS boxes, never tried it, but will try blanking them off.

yep, a lot off material can be removed in front of the reads to improve flow

original :


what I made of it :


I also cleared an original head and installed inserts, but later I developped a complete new head and had it CNC'd



sold about 18 of those heads

[JanBros]

and made extra sealing for the KIPS valves, placed in the barrels


also use 4 kit-valves (one side open), needed to reverse rotation of KIPS-motor and make new links so they all turn correctly

[yatasaki]

Made double KIPS boxes ...nothing happened, my guess is that KIPS duct is too small.

[Frits Overmars]

yep, a lot off material can be removed in front of the reads to improve flow

Yes it can, Jan. But what I was trying to point out, is that the part of the cylinder sleeve that enters the crankcase, obstructs the inlet flow, and it can easily be ground away, like along the yellow lines in the picture below. And no, that is not a KR1S cylinder; you wish! I just chose this picture because it was suitable to show what I mean.

[JanBros]

the next revision of one of my engines is going to be much more work than expected

[F5 Dave]

Let's talk about running it on fermented coconut oil. The grinding stage will absorb most of your time.
In the interests of science of course.

[husaberg]

Yes it can, Jan. But what I was trying to point out, is that the part of the cylinder sleeve that enters the crankcase, obstructs the inlet flow, and it can easily be ground away, like along the yellow lines in the picture below. And no, that is not a KR1S cylinder; you wish! I just chose this picture because it was suitable to show what I mean.

That leads to a question when Jan did the work with the reed valve did he mod that part of the original cylinder i understand he made a few changes but i dont recall him or you ever saying what changes wre made.

A technical explanation? Nah, too much to do today. But since you were kind enough to post that picture of your sex six sisters, I will show some curves of my own.
When Jan Thiel went to Derbi to design the bike we now know as the Aprilia RSA125, he encountered the 125 cc reed valve Derbi ridden by Lorenzo the previous season. Jan played around with the reed valver as well, because he wanted to find out the differences between reed valve and disk valve power. He managed to extract 2 HP more from the reed valver than anyone else had ever done before (never mind the fairy tales of reed valve 125s producing over 50 HP; those Horses must have been Shetland ponies, probably measured at the piston ring).
My graph shows the power curve for the Aprilia RSA, the Aprilia RSW and that best-ever reed valve Derbi. It's not quite in the same league as the rotaries, hmm?

EDIT: Shame on me; I discovered that I posted a wrong graph (and I do not have the correct one at hand here in Holland). Power curve DERBILOR shows the reed valve Derbi as Lorenzo rode it. After Jan finished playing with it, it had 49 HP. Still, the best-ever disk valver produced 10 % more power than the best-ever reed valver.

[Frits Overmars]

That leads to a question when Jan did the work with the reed valve did he mod that part of the original cylinder i understand he made a few changes but i dont recall him or you ever saying what changes were made.

I must have a stack of Derbi drawings somewhere back in Holland but don't recall every detail and maybe some mods were never captured; Jan had a knack of modifying and testing first, and having the mods drawn afterwards. But it's safe to assume that Jan tested every mod you can think of, and then some.
Besides, you can ask Jan directly; he is looking in from time to time.

[husaberg]

I must have a stack of Derbi drawings somewhere back in Holland but don't recall every detail and maybe some mods were never captured; Jan had a knack of modifying and testing first, and having the mods drawn afterwards. But it's safe to assume that Jan tested every mod you can think of, and then some.
Besides, you can ask Jan directly; he is looking in from time to time.

Jan Thiel the name ring a bell....

To meet the RSA power was used 5 days per week by 6 people and with it the aid of the drawing room, and electronic engineers. And that over about 12 years is not that simple ! We started in 1995 with 46.5 hp, and ended in 2007 with 54hp, so 0.6 to 0.7 HP per year on average. Actually seems very little , but it was a lot of work ! We made about 300-400 cylinders per year. So to get that far, there are at least 3600 cylinders made. But maybe 4800 !, I did not count them .... Of course, a lot of cylinders were equal to each other ! But we surely tested 30 different types of flushing channels, and also exhaust conduit 20 different types. Estimated that another 100 different cylinder heads and of course lots of exhaust pipes!