Most HP a KR has shown on a dyno?

TwoStroke Institute · Post by **TwoStroke Institute** » Mon Sep 21, 2009 3:57 pm

As topic title suggests.
I would be of the opinion that a disc valve non-pv engine would be able to see 55-60RWHP. Has anyone tried to develop the engine/ignition? Has anyone ever stuck RGV carbs on a KR?
Just wondering

the KR kid · Post by **the KR kid** » Mon Sep 21, 2009 11:58 pm

Do you mean tandem twin or parallel twin? Tandems were rated at 45 for the Jap market, the parallels hit 55-60.

Just wondered coz of where you posted your thread...

TwoStroke Institute · Post by **TwoStroke Institute** » Tue Sep 22, 2009 4:34 am

Hmmm maybe DISC VALVE might give a small clue?

ScottaKR · Post by **ScottaKR** » Tue Sep 22, 2009 7:43 am

The RGV carb conversion is a bit tricky (got a pair sitting in the shed), as the manifolds curve about 90deg meaning a custom adaptor setup would need to be made which is out of my budget atm

.
The main problem for us Tandem owners is the lack of replacement pistons available. I recently purchased a pair of KMX125 pistons @ 2mm o/s (dimentions match nicely), only to find they are massively heavier than the KR item, so I'm loath to use them as I'll have to rebuild/balance the cranks so it dosn't shake itself to death (would rather use RG150 slugs and bore it to 300cc, but need longer rods).

I remember someone saying that increaseing the disc valve opening duration has shown good results on a standard motor, but don't think anyone has bothered to dyno test this.

TwoStroke Institute · Post by **TwoStroke Institute** » Tue Sep 22, 2009 1:58 pm

You want to make an omlette you have to break some eggs.
A KMX isn't a performance engine stands to reason it wouldn't have a performance piston.
Problem seems to be the 25mm comp height of the piston, making it a prime candidate for a rod/and piston swap to something that can handle some HP(YZ,KX,TZ or Cagiva Mito SP). Does anyone know the standard rod length? Is it the same rod as the KR-1? 106mm centre to centre???
If the standard disc lokks like it has less than 180 deg of duration it needs all the help it can get. For some boogie around the 200-210 deg is needed.
So I suppose the answer is nobody has had a serious attempt at tuning one?
Hopfuly have a set of cylinders her to look at shortly

TwoStroke Institute · Sun Oct 04, 2009 11:30 am

I have a set of cylinders and after a wee bit of massaging.It looks as though 30-odd HP per cylinder will be a doddle with the correct disc timing and pipe

ScottaKR · Post by **ScottaKR** » Mon Oct 05, 2009 6:22 am

Cool.

Have you worked out a replacement piston/rod combo for it?

TwoStroke Institute · Post by **TwoStroke Institute** » Mon Oct 05, 2009 6:59 am

Yes. *ASSUMING* the stock rod is 106mm centre to centre.There is 2 readily available and cheap options
RD 350 110mm rod with a TZ 4DP piston.
110 + 8(half of the gudgeon)+20.5(compression height)=138.5mm installed height
or
RD 400 115mm rod with cagiva Mito SP piston
115+8+17=140mm

v's
Stock
106* +8+ 25=139mm

If it were me the 115mm+SP piston is the ideal as this is very similar to what an Aprilia GP bike runs.

crazy · Post by **crazy** » Thu Apr 08, 2010 2:00 pm

RD400, yam bits find there way into a lot of bikes.
Yam250 rod conversion for OSSA engines works a treat.
Mito pistons are readily available.

Crazy

StrokerBoy · Post by **StrokerBoy** » Thu Apr 08, 2010 3:36 pm

TwoStroke Institute wrote:So I suppose the answer is nobody has had a serious attempt at tuning one?

There have been a few raced but no-one's ever been forthcoming with what they've done to them or what the results where. And I have asked.

Kawasaki issued their own KR tuning manual (in Japanese) but I've never been able to get a hold of a copy.

Looking forward to seeing how you get on. =D>

TwoStroke Institute · Post by **TwoStroke Institute** » Fri Aug 20, 2010 3:30 pm

I suppose you would know Stroker boy has anyone put a KR engine into a more 'ahhem' modern frame?
I have been playing with a ROTAX 256 engine recently and seeing some very good results (lets say a number above 74HP and below 80HP) and think there is MASSIVE potential in this engine.
Running it as a 'twingle' seem to be the go, and even with 28 or 34-6mm carbs should see mid 60's HP, probably to much for the frame to cope with.

TwoStroke Institute · Post by **TwoStroke Institute** » Wed Mar 16, 2011 1:18 pm

I have secured a complete bottom end and just annoying the seller to get it shipped. Let the fun begin. Looking at frame donors, any suggestions, the horrid VTR250 shitbox looks like a good candidate.

StrokerBoy · Post by **StrokerBoy** » Wed Mar 16, 2011 2:44 pm

TwoStroke Institute wrote:Stroker boy has anyone put a KR engine into a more 'ahhem' modern frame?

Like this one below ?

Not really heard of any. Bloke I bought my rolling-chassis off kept the engine with a view to putting it in a Spondon chassis (one designed for a Rotax tandem-twin) but as far as I know he never got round to it.

TwoStroke Institute · Thu Mar 17, 2011 12:30 pm

Yes he should be shot at dawn for that, no IRS even bodgy VW style front suspension AND ruining a perfectly good bike

TwoStroke Institute · Post by **TwoStroke Institute** » Thu Apr 07, 2011 2:41 pm

After cracking open a few covers I found some odd ball things, a second dummy flywheel, a dampened primary, ah yes the crank dampers and reed valves.

Positives are think a dry clutch would be do-able, well made engine and globs of potential.

Wishlist would be a cylinder with stud spacing similar and a powervalve.

Is that back lash in the primary normal?