The drz400s rebuild, stronger...faster...somthinger!

Discussion in 'Thumpers' started by focallength, Oct 5, 2012.

  1. focallength

    focallength You're Welcome

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    Ok, so my drz has 12500 miles on it, I do regular msintenance and keep her in good condition. I have her all set up like I want, and just put a new fcr-mx carb on a week ago.
    So engine mods have always been an after thought.
    2 days ago while coming home from a ride in the moutains, she up and died on me, wouldnt start, wouldnt crank...so as I sit :cry on the freeway it suddenly dawned on me...i can make her better, what a great opportunity!

    So I set about pulling her engine, seperating the head and cylinder.

    Visions race through my head, big bore kit, headers, exhaust, hot cams, ti valves!

    So heres the plan, I got the head and cylinder off, ill pull the piston doon and check for crank play. I have to check the oil and water pump and inspect bearings. I may split the case and do s bottom end rebuild along with gears. Im going to have to get a new head but I can have a bomb proof head built. Maybe 440 big bore kit. But first things first, I have to see how far the damage goes and what condition the internals are in after 12500 miles.

    Now I have medic school in 3 months and when that starts the bike wont be touched if shes in pieces so, the goal is christmas.

    Btw its an 08, I would like to keep the reliability and get a little more oomph, im willing to trade a little reliability for power. Ill most likely do a 434 bn with e cams or stg 1 hot cams. My mechanic says he can build a top of the line bomb proof head. New blank head will run me $600. Built will prob be $8-900


    Pics to follow as well ad updates stay tuned!



    Muched exhaust cam side race, for some reason I lost oil, head just seized, good thing is damage looks limited to the head
    [​IMG][/IMG]
    #1
  2. focallength

    focallength You're Welcome

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    :puke 12500 miles, despite 91 octane gas, regular oil changes, regular plug changes/inspections, look at those deposits...
    [​IMG][/IMG]
    #2
  3. Spacelord

    Spacelord Mutha Mutha

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    Big bore
    FCR
    MRD exhaust
    either hot cams stage 1 or cams from a E model

    Nice horsepower and torquey.
    #3
  4. focallength

    focallength You're Welcome

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    So the piston sezied, I had to hit it down with a rubber mallet so I could pull the cylinder.
    once the cylinder was off the piston/engine turned over easily by hand. Some scoring on the cylinder walls, piston edges has some chipping and...sand in the cylinder...how the hell did I get sand in there?!
    Anyway heres the top of the piston in the cylinder
    [​IMG][/IMG]

    Cylinder, not gouged those are piston deposits, from when the piston seized and deposited metal onto the cylinder walls.
    [​IMG][/IMG]
    #4
  5. GAS GUY

    GAS GUY MILE EATER

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    Wow, I would like to know what the root cause is.This seems like a premature failure.
    #5
  6. Off the grid

    Off the grid Seeker of the Unf

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    Why not just get a different bike? There are many better bikes out there than a DRZs.

    And a grenaded engine at 12k miles? :huh
    #6
  7. focallength

    focallength You're Welcome

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    Havent pulled the side coverd so I dont know if the pump failed.
    i do know the bike was running hot and burning oil. I had done an oil change a few days prior. No smoke, when I went to drain the oil there was very little in there. The drain bolts were tight so no leaks. There was also little coolant despite recently changing it. No oil in the coolant. Hopefully some questions will be answered when I dig into the engine.

    Why would I get a new bike? I can build an engine for less than a grand, I can build a 50 hp engine for 15/16/1700, a new bike will cost 3-4x that minimum plus all the hassle/cost of new farkles. Cheaper to rebuild it in any form.
    #7
  8. WayneJ

    WayneJ City Slicker

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    Owner/operator error.

    If you don't put oil and water in an engine after you drain it out, it will go :kboom
    #8
  9. focallength

    focallength You're Welcome

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    Really?! You mean the engine dosent just magically create its own oil and coolant? Im shocked...shocked I tell you.


    A new head is the expensive part, top and bottom rebuild kits run roughly $500 total.


    One thing I did notice, the front lower engine mount bolt gets pretty coroded. Being as these bolts have no seals, liberal waterproof grease is in order when I reinstall them.
    #9
  10. markk53

    markk53 jack of all trades...

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    But with the cost of those "better bikes" the OP could do his engine with a big bore, pipe, and maybe a carb, even pay someone for the work, and pocket the difference.

    If he does the work he ends up with a great engine for probably grand, could have the suspension tricked out and maybe still be around maybe $1500 and have a great ride.

    So what is going to be better for a grand, even two grand?
    #10
  11. HighwayChile

    HighwayChile greetings from Wa state

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    ceramic coating internals might be worth checking into as well if you are keeping it long term
    I"ve heard of aftermarket gear sets, plenty of $ Im sure is it the entire set or just an OD 5th?
    #11
  12. focallength

    focallength You're Welcome

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    Clutch side cover off, everything looks good, cant detect any visibe gear wear even on the plastic gears. Everything turns smooth and easy. Clutch basket has some visible wear.

    [​IMG][/IMG]

    I dont see any bluing of metal, so everything looks ok, ill still split the case to replace the main bearings and countershaft bearings at the minimum.

    Im torn between stock and BB...i like the reliability of stock, maybe just some e cams and e base gasket, combined with the fcr-mx carb should yield nice results. I hear the 434 BB only yields 4 hp. so...

    Does anyone make metal gears to replace the plastic ones?
    #12
  13. Spacelord

    Spacelord Mutha Mutha

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    I have 4K on my big bore, no issues.
    I expect it will easily do 12K.
    #13
  14. DR650SEDDY

    DR650SEDDY ride2discover

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    After ur done rebuilding ur engine you'll have a blast. I know many who've done the big bore kit and they're happy with the results, i was gonna do this SUZUKI JE DRZ400 DRZ 400 BIG BORE 434CC CYLINDER KIT just for the heck of it. Keep up the good work focallength.
    #14
  15. focallength

    focallength You're Welcome

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    Im just concerned about the reliability of a BB, I dont want to tear the engine down every 6k miles.
    #15
  16. One Less Harley

    One Less Harley OH.THAT'S GONNA HURT

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    might as well do the 434 BB, as it doesn't cost anymore.
    #16
  17. focallength

    focallength You're Welcome

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    I havent heard any negative on a BB kit, however the very nature reduces longevity. Im slightly concerned with the head bolts. I had a xr600 with a 660 BB kit (10% over bore same as a 400 to 440) and it pulled the head off.

    The big suck with my bike is I need a new head, thats $600 for a blank head. Im not reusing any parts from the seized head.

    By rebuild I mean the kits they sell on line, theyre mostly bearings and gaskets, top end comes with a new piston...I dont think I need to go hog wild on a head, nothing fancy just stock parts aside from cams.
    #17
  18. Kawidad

    Kawidad Long timer

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    I would also suggest pulling apart the oil pump and look for wear/scoring. Then replace if necessary. :deal

    I rebuilt a blown up Yammie once and the oil pump had sucked some material and was surprised at the noticeable wear on the internal parts. :freaky
    #18
  19. Luke

    Luke GPoET&P

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    I was helping a friend with a DRZ that had a chronic overheating problem. Repeated blown headgaskets, warped head, etc. It turned out that the waterpump impeller had unglued itself from the shaft and would turn on the shaft with only a little resistance. Or, not turn when the bike was running. It looked good, though.

    Doesn't sound like your problem, but it's easy to check when you're in there.
    #19
  20. focallength

    focallength You're Welcome

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    So im slowly going over the frame as well, looking for damage. I have noticed 3-4 spots where the paint has chipped away revealing some surface rust. Need to take care of that, just need to find a similar color spray paint...

    Im srarting to think a yearly engine pull is in order, theres alot of nooks and crannies that harbor dirt/mud. Plus engine mounts need greasing. Pulled the frame drain plug to check the filter, looked clean aside from a lone long hair?!

    Plan on splitting the case tomorrow and seeing what parts I need to start ordering.

    Stay tuned...
    #20