Cylinder porting again for 70hp

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manosnad
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Cylinder porting again for 70hp

Post by manosnad » Wed Jun 12, 2019 7:06 pm

Any opinion for porting map ? I have read and I have a photo from old site teamsparrow 70hp ,is this possible ?

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martin
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Re: Cylinder porting again for 70hp

Post by martin » Thu Jun 13, 2019 8:34 am

70bhp at the rear wheel.

Think you must of been in a deep sleep and dreamed this
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Re: Cylinder porting again for 70hp

Post by scooble » Thu Jun 13, 2019 4:10 pm

MJ did once say he got 70hp on a Dynojet, but reckoned that equated to about 64hp on a Dyna Pro.
Might be work asking Ben Ludford, as he built a KR with different rods, bespoke pipes TPS, Powejets and Zeeltronic

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Luders
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Re: Cylinder porting again for 70hp

Post by Luders » Thu Jun 13, 2019 4:43 pm

70bhp was from a high reading dyno and it was lean at the time of the run, it couldn't have been used in that state.

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KR-1R
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Re: Cylinder porting again for 70hp

Post by KR-1R » Thu Jun 13, 2019 11:38 pm

.
.
up 2PS from 1988 (70PS @11750rpm)
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viewtopic.php?f=22&t=10279
to copy one thing is plagiarism - to copy two things is called research

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JanBros
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Re: Cylinder porting again for 70hp

Post by JanBros » Thu Jun 13, 2019 11:50 pm

manosnad wrote:
Wed Jun 12, 2019 7:06 pm
Any opinion for porting map ? I have read and I have a photo from old site teamsparrow 70hp ,is this possible ?
if it is, your cylinders will certainly crack at the rear where they are bolted to the crankcase. not enough metal.
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Re: Cylinder porting again for 70hp

Post by Gerrit » Fri Jun 14, 2019 12:39 pm

I have a 4DP TZ250 cylinder and the base flanges are not only 19 mm thick but also have generous fillets; the KR cylinder base flanges are only 13 mm thick and have sharp corners where they join the cylinder. KHI could easily have changed this during the KR's production run, but didn't. Probably they didn't get enough guarantee claims to make them update the castings, which they could easily have done.
If I ever win a huge prize in a lottery I'll have a batch of cylinders cast with proper base flanges. Oh well, at least one can dream......
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Re: Cylinder porting again for 70hp

Post by Luders » Fri Jun 14, 2019 1:44 pm

Image

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Re: Cylinder porting again for 70hp

Post by Luders » Fri Jun 14, 2019 1:49 pm

Image[/url]

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Re: Cylinder porting again for 70hp

Post by KR-1R » Sat Jun 15, 2019 12:06 am

Image

1991 YZ125 3XJ
main 25.5mm
subs <27mm
transfers <40mm

Image

Image

how much does port chamfer effect port height when comparing motors or data
Image

Image
to copy one thing is plagiarism - to copy two things is called research

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KR-1R
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Re: Cylinder porting again for 70hp

Post by KR-1R » Sat Jun 15, 2019 2:01 am

Image
KR-1R wrote:KR250 EXdur (BBDC ABDC) ** SCAVdur (BBDC ABDC)
B. ........186° (93 93) ** 126 (63 63)
C. ........186° (93 93) ** 126 (63 63)
D. ........188° (94° 94°) ** 126° (63° 63°)

KX125 ........EXdur ** SCAVdur
90 (50.6) ......187° (93.5 ..) ** 131 (65.5 ..)
91(50.6) ....... low speed 187° high speed 191° (L93.5 H95.5) ** 131 (65.5 ..)
the 1990 KX125 was 'rated' @ 38.5PS and used similar F3 KIPS with bridged exhaust

191° is 84.5 ATDC and 25.9mm main exhaust with 26.8mm subs

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^^^ too high

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A 50.6 stroke against 54.5mm i have tried to compare like for like using crank angles
A page with the port map dimensions from RS/TZ over multiple years Some Table Data
From the table note the Sequential opening of A then B then C transfer ports

Image

a conclusion you could make without doing a simulation model is...
the standard KR-1 exhaust opens too late ~91.5deg ATDC (the fuel is burnt, work done, the piston slowing on stroke) - should be nearer to 82-84° (192 duration) = 25.7mm ATDC
the standard transfers flow too early (not enuf blowdown - © 2Tinstitute) opening just 25° after the exhaust port .
By raising main exhaust roof alone this increases the delay (blow down) to 31° after exhaust which is much closer the 32° A-transfer timing found on eg the H0NDA RS125/250.

Start with a conservative main and see how it responds by artificially raising it with thicker base gaskets.

because the KIPS system has no yamaha spool PV or guillotine power valve arrangement you WILL sacrifice low down power if you port to a high exhaust. You will be making a motor with less powervalve benefits. There has been some vigourous debate here on height of subs in relation to main.

these timings are only a fraction of the story.
Like on a four stroke, knowing the cam timing is only part of determing how it might perform.
It doesnt tell you the lift or overlap or the size of valves or shape of ports, compression ratio and everything else that adds up to making most power.
to copy one thing is plagiarism - to copy two things is called research

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martin
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Re: Cylinder porting again for 70hp

Post by martin » Sat Jun 15, 2019 6:34 am

Ben. Who welded those plates to those cylinders. ?
Looking at that photo. I think of Gary and Bernie with the 300cc engines
They are running with nearly 70bhp at the rear wheel.
Gary has spoken to me and is concerned about his cylinders cracking
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Luders
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Re: Cylinder porting again for 70hp

Post by Luders » Sat Jun 15, 2019 8:50 am

I also had the area where the base nuts attach welded up and use rotax nuts which are 11mm spanner head. I am no longer in touch with the person that did this I'm afraid Martin.

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Re: Cylinder porting again for 70hp

Post by JanBros » Sat Jun 15, 2019 11:19 am

martin wrote:
Sat Jun 15, 2019 6:34 am
Ben. Who welded those plates to those cylinders. ?
Looking at that photo. I think of Gary and Bernie with the 300cc engines
They are running with nearly 70bhp at the rear wheel.
Gary has spoken to me and is concerned about his cylinders cracking

you are not out of the woods by welding the back, because than the front is the weakest part and they start to crack ...
and remember : welding must be done before plating !
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