XJR1400 Big bore kit
The XJR 1300 would have to be one the best all round road
bikes, very functional and practical, maybe a little heavy, not that you
notice too much when you're riding it, nice comfy seat for Princess to
rest her toosh on so you don’t get an earfull at the end of a ride, good
size fuel tank, no fairings to damage when you drop it and a great looking
big chunky engine, last but not least the price tag. No need to say any
more.
But how do we make it go like a 1300cc bike should? Easy...
bore it to 1400cc, add in some flat slide carbs and a good exhaust system,
now you’ve got yourself about 160 hp of grunt.
Hang on tight cause here’s how to do it.
Wossner, a German piston manufacturer whose customers
include F1 teams make a piston kit which has pistons and sleeves
4 mm oversize, bringing the capacity up to 1400cc.
The crankcases are large enough that no other machining
apart from the barrel is required and it all drops in with room to spare.
The stock barrels are bored to take the new cast iron sleeves which are
then bored to suit the forged pistons.
We had already ported and flow tested the cylinder head
on a previous occasion so no further work was required other than a general
inspect and decarbon, and reseating the valves.
By the way, this bike has now clocked up over 50,000 km
and was already putting out 145 hp (stock is 110 hp). The owner was complaining
of clutch slip which he puts down to some silly business in front of his
mates while under the influence of some kind of liquid available in a green
bottle. So yes they are strong engines which if looked after can take on
the extra load for many hard kilometres without a problem. Even so we decided
to play it safe and not put in too much compression, bearing in mind that
the owner doesn’t always have premium fuel available to him.
 The
machining work turned out taking longer than planned because not only did
the barrels need to be bored to a fine tolerance, but the cast iron sleeves
which were then inserted required another 4mm of machining to accommodate
the larger pistons.
Apart from that it was all plain sailing, though we did
modify the spiggots on the Keihin flat slides, moving the carbs about 15mm
closer to the cylinder head.
The cams and the cam timing all remain stock standard
and in fact we didn’t even need to do any major rejetting work. The dyno
runs speak for themselves, you be the judge.
What it Costs
It's not cheap but the result is well worth it.
Wossner Piston kit $1500.00
Keihin flat slide carbs $2200.00
or Mikuni flat slides $1650.00
Port and flow Head $1200.00
Machine and fit sleeves for new pistons $850.00
Over 4 into1 exhaust $1495. 00
Labour to strip and assemble $800.00
Dyno and tune $350.00
Gaskets $200.00 |
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