Crankcase mods for improved torque

vincbr900 · Post by **vincbr900** » Sat Aug 08, 2009 9:44 am

I heard a rumour there is several unused hp rattling around in the cases. I assume this is by devcon filling and griding, but where/when/what/why?

Does anyone have any before/after pictures or a how to?

Thanks!

mgtkr1 · Post by **mgtkr1** » Sat Aug 08, 2009 11:31 am

there are some pics somewhere mate, try case porting or flowed cases. the proper way requires some decent putty. you can gain a decent bit from doing cases alone!! not using putty still works but for ultimate gain i think its needed. i copied mj's and just from looking at where the gas now goes you can see how it will be more efficent.straighter path before you even have the bike assembled let alone tested on a dyno. i seem to remember mj saying a 3hp gain is possible!!look for the thread started by me, mj96 or rc46 irc. if not mj96 then mj43 (i get his user name mixed up!!)

ScottaKR · Post by **ScottaKR** » Sat Aug 08, 2009 12:15 pm

Have a look through this thread.
viewtopic.php?t=1418&highlight=case%2A
That'll give you a few pointers on what to do.

mgtkr1 · Post by **mgtkr1** » Sat Aug 08, 2009 11:30 pm

thats the one. mine are virtually the same as marks. next to a set of stan stevens cases its plain to see how much better the mj ones are. the cases are one of the kr's virtues. plenty of scope for improvent here.

TwoStroke Institute · Post by **TwoStroke Institute** » Sun Aug 09, 2009 8:50 am

Aprilia go for gas velocity over gas 'flow', seems to work very very well for them.

mgtkr1 · Post by **mgtkr1** » Sun Aug 09, 2009 12:11 pm

yep, i can see why. i think mj has the same theory of not just removing metal but what needs moving from where. ''whats needed'' almost all the material thats removed from cases is replaced on mj cases unlike the stevens ones ive seen . literally just aiming the charge to the transfers ducts rather than hacking material away and hoping it makes it better. the old bigger is better is not always the case

mj43 · Post by **mj43** » Sun Aug 09, 2009 8:32 pm

Velocity and flow

Gas has mass give it speed and a column of moving gas will have momentum. Momentum can be used to get charge into the cases. This same momentum can also be used get gas into the transfers. To me flow and velocity are related.

A man that I had a lot of time for said it is where you put it that counts. I have been following that philosophy now for a number of years with some success.

mj43 · Post by **mj43** » Sun Aug 09, 2009 8:35 pm

vincbr900 wrote:I heard a rumour there is several unused hp rattling around in the cases. I assume this is by devcon filling and griding, but where/when/what/why?

Does anyone have any before/after pictures or a how to?

Thanks!

I am about, a week or two, to publish the full specs of my 08 race engine. That will have pictures and a description of the crankcase mods.

The tune is reliable and I have repeated it several times - it is now time to move on and I have started work on the 010 engine which will incorporate a number of ideas I have been mulling over for a few years

mgtkr1 · Post by **mgtkr1** » Sun Aug 09, 2009 8:51 pm

woohoo

!! i know these ideas will be secret for now but i can only hope it involves a trick ignition with tps ect so you can crack 70hp dynapro WITH the huge gobs of midrange/drive you currently have. i know youve already cracked 71 on the said dyno but irc it came at great cost of grunt. anyhow, im kinda excited of the news your publishing the 08 spec, cant wait to see what this involves. i recall dean dicko commenting on the way your 07 bike pulled a few yrds out of his 83hp bdk fzr and saying how the sparrow kr was a tz pretending to be a kr1s!!!

KR-1R · Post by **KR-1R** » Mon Aug 10, 2009 2:27 am

here the post I was thinking of...

viewtopic.php?t=1186

mj43 wrote:Ok a piccy of how I flow the cases

Front oil pickup is filled then the oil hole is re-drilled - make sure it is clear and the correct size otherwise your mains will go west

Most of the work is on the reed side - smoothed and filled. Piccy not pretty but it works and is smoother than it looks

It can all be done with a Dremel - some JB weld make sure cases are free of grease and score the surface to give it something to bond to - and patience.

TwoStroke Institute · Post by **TwoStroke Institute** » Mon Aug 10, 2009 8:35 am

Anything that moves has momentum or kenetic energy.The greater the velocity the greater the kenetic energy.
These babies are the HP kings. At rumoured 56HP for a 125 look no further for inspiration.The transfer divider width gives away Aprilia think velocity is everything.

the-elf · Post by **the-elf** » Mon Aug 10, 2009 11:38 am

Been reading alot on the idea's behind high velocity ports. It seems to work well when applied to F1/bike and kart 4 stroke engines, and the same ideas should work well on a 2 stroke. It rubbishes the idea's behind highly polished and flowed inlets and instead concentrates on getting the mixture where you want it and keeping it there.

mj43 · Post by **mj43** » Mon Aug 10, 2009 12:12 pm

TwoStroke Institute wrote:Anything that moves has momentum or kenetic energy.The greater the velocity the greater the kenetic energy.
These babies are the HP kings. At rumoured 56HP for a 125 look no further for inspiration.The transfer divider width gives away Aprilia think velocity is everything.

56hp but at what rpm?

KR-1R · Post by **KR-1R** » Mon Aug 10, 2009 9:33 pm

.
.
these motors are disk induction rather than reed tho - potential advantages...

some factors affecting strength of induction charge...

SIZE of ports - port area
SHAPE of ports - trangular, round, rectangular
DURATION/SPEED - time which inlet port is open
PRESSURE differential (the difference between empty crankcase/cylinder and upstream of fuel supply.

basically DISK motors can be timed so that the crankcase develops ample VACUUM prior to disk/inlet port opening
a bigger pressure difference (like supercharging) accelerates the fuel charge - has a stronger induction pulse.
Also disk motors can have asymetric inlet/exhaust timing

Im only guessing with modern technology, disk induction can be electronically driven to the extent that 2 disks (back to back) could be used to vary the size/duration of inlet aperture (opening and closing) and lag and advance could also be programmed into the electronic motor driving the disk valve.
.
.

surely for the RGV challenge someone has to fit an electric water pump - might get 1 extra HP
.
.
.

TwoStroke Institute · Mon Aug 10, 2009 11:42 pm

The little Aprilia develops it's HP between 11-13,500 rpm, which even for an old vintage mx 125 isn't outrageous.
Disc induction has a few advantages but the KTM 125 and Ayoama's h***a 250 lack little in top end and arguably have better mid range drive. The reed being opened and closed by engine demand, at similar rpm will have roughly the same duration as the disc. With the disc the difference is it can be opened or closed exactly at the desired time. No need for electronics on the disc at least, the Aprilia LE spec has the best electronics there is. Cylinder pressure/detonation counter is linked to TPS, ignition advance, traction control(on the 250) and the power jet soleniod.
So cylinder pressure creeps up, dets register, advance is backed off, then the power jet is opened.No dets then power jet goes off and advance restored, all in the blink of an eye.

Most modern mx and GP 125's have a ramp over the crank

KR-1S.co.uk Forum

Crankcase mods for improved torque

Crankcase mods for improved torque

Re: Crankcase mods for improved torque

crankcase flowing flowed ported

disk induction and reed valves