Installing a Kawasaki KLX 330cc Kustom Kraft Big Borel a DIY guide.

Discussion in 'Technical' started by TonyBKK, Apr 24, 2014.

  1. Turn your timid little KLX250S into a Fire Breathing 330cc Monster! :mrgreen:
    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:

    TBC :mrgreen:
  2. Cool, Looks easy but not for Me!!!
  3. Cheers Ian! Yeah, nothing too terribly complicated, just have to take it step by step and it goes together pretty easy. Stay tuned for the rest of the job :mrgreen:
  4. Kustom Kraft 330cc Big Bore Kit for Kawasaki KLX and D-Tracker installation guide. Part Deux :mrgreen:
    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! KawasakiSmiley2
  5. Nice write up but your cams don't look like they are properly aligned.
  6. Cheers :) The correct way to align the cams is to count the pins (32 pins from "in" to "ex") You're right that in this pic the exhaust cam is off by one tooth. I did correct that before putting in the cam chain tensioners :thumbup:
  7. This detailed write-up made me come out of the woodwork ( longtime forum visitor, firsttime poster - I'm 39yrs old, originally from Belgium. Rode Suzuki RM125 two-strokes back in Europe, now KLX250. You can understand my interest in more HP 8) )

    After reading the write-up & looking at the close-up photos, I am convinced that this install is BEYOND my tech abilities. And having some experience dealing with local Thai mechanics, I am equally convinced that doing this install correctly is WELL beyond their abilities. What's more, getting this sort of job right seems beyond the scope of the great majority of bike riders/amateur mechanics.

    Considering the large number of people I hear talk/think about getting a big bore kit for their KLX250, there could be a nice side earner in offering to do these installs, by the thread starter or someone with similar skills/experience. myself for one, would be an eager customer. If I give this job to the local Kawasaki dealer, it will just go horribly wrong.

    I thought going from 125cc two-stroke to 250cc four-stroke would be end up being approx the same, but it is really a significant step down. I am going to need those extra cubes 8) . Skilled tech guys who'd like to make an extra Baht, please speak up !
  8. ^ Cheers :)

    FWIW I know that there are some competent Kawasaki mechanics who install big bore kits on their time off. Most of the senior mechanics here have been sent to Japan for training and I trust their skills. Junior mechanics, maybe not so much, but I reckon many of them could get it done... I'm hoping Brian will do a write up of his experience with the installation of his OEM 300cc kit.

    Ultimately, if you can find a mechanic who is able to rebuild an engine, owns and knows how to use a torque wrench, they should have no trouble installing a big bore.

    I've thought about doing it as a side business but first off, "mechanic" is one of those professions that's off limits to foreigners in Thailand. Secondly a big bore it's a pretty big investment so if people are aware of the cost I'm not really sure how many would really lay out some ~40-50k baht to get one installed. (You're looking at about $1000 for most big bore kits, then another ~$300 for a PowerCommander or Carb...). Then there's labor, including the time it takes to set up and tune the bike... Discovered to my dismay that the sensor bung on the Kawasaki KLX250 is way smaller than the Dynojet wide band O2 sensor, so that necessitated welding a second bung onto the header:
    More time and expense... Personally I'd recommend a carb. Roughly the same cost as a PowerCommander but quicker to set up, can be serviced/repaired in the field, and gives you the option to add an oversized fuel tank.
  9. Thanks for the feedback. My KLX is carbed, thank God for that.
    Looks like I'll have to go with the Krabi Kawasaki dealer and hope for the best.
  10. Andamaniac what are you doing for jetting?
  11. I noticed the cam alignment issue as well and assumed that Tony was re-phasing the cams
  12. Even if he was doing the cam mod from the klx forums that pic would be incorrect. Btw the cam mod is not appropriate for a big bore. I previously did it on my stock dtracker and was quite happy..
  13. I have no idea about the "KLX cam mod" and am only familiar with re-phasing cams in general
  14. @ Mikerust, regarding carb jetting :

    I was just about to order the "Dynojet" re-jetting kit (USA, approx USD 50)
    But now I have been told to first stop by this local guy (farang) who says he wants to see my bike first, claims it may not be necessary to order a jet kit. ( I assume he plans to drill out the existing jet - not sure that will do it, though )

    currently my KLX250 has a free-flowing exhaust bolted on, and the airbox snorkel removed. I get HARD popping upon decelleration ( have been told this is indicative of a lean condition ). Engine seems to run hot ( also indicative of lean running ) - I wish they had a proper coolant temp gauge like they do on cars, not just an "emergency light" which you dont even know is functional. With a gauge you can see at all times if the temp is being registered.
  15. I've a jet kit, that I bought by mistake last year.
  16. Great pics, Tony. You did omit a few important things from the manual. If somebody tries this without reading the manual, there's not enough info. How about your add some extra pics from the manual, to make everything more clear?

    1) Apply liquid gasket to the upper surface of the crankcase - should only be applied in the front and back, where the crankcase halves meet, about 10mm wide. Service manual has a picture about that. By the way, by liquid gasket the manual means Kawabond silicone sealant, available from Kawasaki for over 1000 baht! A high-temperature RTV silicone, such as Permatex Hi Temp RTV, can also be used. There's a big write-up about sealants in here:

    2) Cylinder head bolts tightening - should be done in criss-cross fashion.

    3) Camshaft cover - two longer bolts go into specific positions, after that all the bolts should be tightened in a specific order, service manual has a picture about that.

    Tips - Tie a piece of wire around the cam chain and hang it from the frame or something else, holding it in tension. If the tension on cam chain is released, it might fall off from the crankshaft sprocket - if that happens, might need to take off the right crankcase cover to put it back on. When removing the cylinder snap rings, stuff rags under the cylinder (you did it by didn't mention). You don't want the snap rings to fall into the crankcase (BIG PROBLEM TO FISH THEM OUT!). Be careful not to nick the crankcase mating surface by the connecting rod falling on it.

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