'79 KX250A5 with '79 KDX400 engine fitted ... KX400A5

[1022racing]

I also have a kx250a5 but I put a kdx450 motor in it with a thicker liner to accept a 74 kx450 piston which makes it a 477,I also had overheating problems,the fuel was actually boiling in the fuel tank,run clear fuel line and in line fuel filter to view,have not come up with a fix yet,also the 1980 kdx400 had a different pipe with a longer straight section much better performance,

[John Orchard]

ok next step in the project (yeh still got it), after riding one of the ex Gary Hacking's RM400T's, I was amazed at how much low rpm power it had, got me to thinking that I could get a bit more out of the KX, so I whipped the head off for a few measurements.

Squish clearance was 2.20mm, yes miles too much!  Combustion volume was 49.8cc, so I'll whip 1.00mm off the head sealing surface, that will take squish clearance to 1.2mm and reduce chamber volume by 5.2cc to 44.6cc.

Squishband width is 11.00mm, while I'd like it be 12 to 13mm for an 80mm bore, we'll give it a try and see what it's like.

Stock chamber



Measuring volume



Stay tuned (no pun intended  ;-) )

[Lozza]

I hope you don't have a domed piston?

[MaxPower]

Perhaps making a vented front numberplate can help with a tiny bit of air flow to the engine
It's strange Kawasaki never made one of these.

[Speed]

John, I hope that's FPV 49.8cc Not CCV.

[John Orchard]

Just fitted a Yam TT600 top triple-clamp (thanks for the heads-up Brendan) as I wanted rubber bar clamps, bonus the bar clamps aren't angled back like the original Kawa item :-)

I've got the '83 KX125 disc front-end back in, a 400 is too fast to have poor brakes  :-)  They now have Honda CR480 fork springs.

[John Orchard]

Have decided to turn the KX400 into a Vinduro bike, just put a new custom-made seat cover on, a KX250A5 cover with KDX screen printed on, got it from 'Pit-Replica'.

Got a 'period' KDX headlight shroud coming from BigK and ordered a TY tailight.  The bike still has the KDX400A1 lighting-coil, just gotta wire them in.

[bigk]

I have TY tail lamps in stock. They are great for vinduro bikes.
K

[80-85 husky]

the lights dont have to work unless your going for club reg....

[John Orchard]

Thanks K, add it to the pile  :-)

[John Orchard]

Next step in broadening the power was a change to the header pipe, the stock KDX400 pipe came out of the cylinder and went straight down, making for a very short header, I cut a section out of a spare pipe I had laying around and extended the header by 45mm, it now runs out to the left before running back under to the right side.

Much more low-down power that hasn't seemed to have dulled the top-end.  Next step is to increase the core size of the 250 muffler currently fitted.

[John Orchard]

Well I was a little sad having missed the VCM event this weekend, having put the disc brake front end in prevented me from being able to run the Evo class.  So with a couple of new axle spacers and a small brake anchor-plate, I made the A5 drum brake fit into the 43mm forks ........ just a day too late :-)

So now in a couple of minutes I can swap back & forwards from a disc or drum  :-D

[evo550]

....and queue evo fork eligibility argument ....

[80-85 husky]

should have strapped a headlight to it and ridden at Beaufort John, lovely bike for the ride....

[John Orchard]

....and queue evo fork eligibility argument ....

Yeh I don't agree with the new rules that allow components from non-Evo bikes, but this is only for club events.  It's an old SLS brake & the forks are stock early 43's so I think it's still 'in the spirit' of things.