Kawasaki KLX 330cc Kustom Kraft Big Bore Install- a DIY guide.

Turn your timid little KLX250S into a Fire Breathing 330cc Monster!
That’s 80cc more displacement, 5-6 more horsepower and ~30% MORE TORQUE!
Kustom Kraft 330cc Big Bore Kit for Kawasaki KLX and D-Tracker- a DIY installation guide.
Note to the Pudgy Picture Thief: All text and images © Marc Nisam. All Rights Reserved.

Begin by removing the fuel tank and cylinder head cover bolts, then remove the cylinder head cover.

Drain the coolant remove the radiator hose and remove the thermostat-

Remove the throttle body assembly and the exhaust header. Remove the upper engine mounting bracket:

Remove the oil pipe banjo bolt:

Remove the camshafts and the front camshaft chain guide, then remove the cylinder head bolts, beginning with the smaller M6 bolts:

Once the two M6 bolts have been removed, remove the larger M10 bolts:

Remove the cylinder head:

Be careful not to lose either of the dowel pins!

Cylinder head-

Valves and spark plug-

Remove the lower radiator hose:

Remove the cylinder-

To remove the piston first remove the piston snap rings:

Then remove the piston pin:

Note- this step normally calls for a special tool: “Piston Pin Puller Assembly” but it’s not hard to make one using one of the cylinder head M6 bolts, some spacers and washers and the new piston pin to push out the old pin:

Push out the piston pin far enough that you can remove the piston:

No replacement for displacement! 330cc vs 250cc!

Lord of the Rings

Install the new rings:

First install the oil ring expander (the wavy ring) and make sure the ends touch but don’t overlap. The install the oil ring steel rails, one above the expander ring and one below. There is not “top” or “bottom” for these rings.

Next install top and second rings. Top ring is white/silver while second ring is blackish. Install these rings with the marks facing up.

Grease the inside of the con rod:

Install the new piston with the arrow pointing forward:

Install the new piston pin and new snap rings:

With the new piston installed make sure the ring openings are aligned as shown:

Apply liquid gasket to the upper surface of the crankcase, install the two dowel pins and install new cylinder base gasket and new cylinder:

I don’t have a piston ring compressor tool but find it’s not hard to compress these rings by hand. Oiling the piston rings and cylinder wall makes reassembly a lot easier.

New cylinder installed:

Install dowel pins, new cylinder head gasket and front camshaft chain guide:

Kustom Kraft 330cc Big Bore Kit for Kawasaki KLX and D-Tracker installation guide. Part Deux
Text and images © Marc Nisam. All Rights Reserved.

Reinstall the Cylinder Head:

Grease the cylinder head bolts and install the big M10 bolts first, torque in two steps, first to 11 ft-lbs, and finally to 34 ft-lbs.

Then tighten the smaller M6 bolts to 106 in-lbs.

Reinstall the thermostat-

Make sure the air bleeder hole is on top:

Thermostat installed:

Reinstall the oil pipe banjo bolt, using new crush washers, torque to 87 in-lbs:

With the piston at top dead center reinstall the camshafts as shown:

Install the dowel pins:

Install the camshaft cover, note that not all bolts are the same length. The bolts are numbered; tighten them in sequence to 106 in-lbs

Reset and re-install the cam chain tensioner, tighten tensioner bolts to 87 in-lbs:

Re-install the cam chain sub tensioner, torque to 11 ft-lbs:

Check valve clearances and adjust if necessary. On this bike the exhaust valves were within spec but the intake valves were a little tight so I re-shimmed them-

Reinstall the cylinder head cover. Note that the cylinder head cover bolt washers should be installed with metal side facing up. Torque the cylinder head cover bolts to 69 ft-lbs.

Reinstall the upper engine bracket; the large Upper Engine Mounting Bolt and nut are torqued to 37 ft-lbs and the smaller Upper Engine Bracket Bolts are torqued to 17 ft-lbs:

All that’s left to do is put in new oil and coolant, reinstall the throttle body and re-map the fueling. I’ve always been a fan of Dynojet PowerCommander Fuel Injection controllers-

Combine a PCV with an Autotune to take the guesswork out of your fuel mapping. The Autotune records your air-fuel ratios as you ride. Once the Autotune has recorded your AFR’s at different throttle positions and RPM’s it will suggest new trim values for your fuel map.

Dynojet PCV and Autotune come with excellent instructions so I won’t bother going into the installation and set up of those components here. Suffice to say, the stock fuel map is way lean for 330cc, but thanks to the Autotune I’ve been able to make a custom map for this bike and it’s running great and pulling hard. Hoping to get it on the Dirtshop Dyno before I send it back to its owner. Will post the dyno results here once I have them.

Let the Good Times ROLL!


Categories: DIY, maintenance, Motorcycle Product Reviews, Motorcycles, repairs | Tags: , , , , , , , , , , , , , , , , , | 3 Comments

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3 thoughts on “Kawasaki KLX 330cc Kustom Kraft Big Bore Install- a DIY guide.

  1. Wisnu

    Bro, do u think u can put the kit inside a Kawasaki Ninja RR Mono 250? They say it’s based on KLX 250 engine..

  2. Wisnu

    It’s 72 x 61,2 mm. Is it the same as KLX?

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