DisTech's DR350 rebuild

Discussion in 'Thumpers' started by DisTech, Nov 27, 2009.

  1. BSR-1

    BSR-1 Adventurer

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    I'm with you for the most part but am I reading you right that you are running with zero squish clearance?

    & I'm assuming that you used some type of sealant on the base in place of a gasket?
    #61
  2. slowsuki1

    slowsuki1 Been here awhile

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    yes zero squaish clearance, piston at top dead center is level with the top of the cylinder.

    yes i use the permex copper spray made for head gaskets on the base, also use it on the head gasket as well. it is a little messy but cleans with carb cleaner sprayed on a towl after it dries. need to cure 24 hours before starting engine, do not try to fuge or you will be disasembling and resealing it.ask me how i know.
    #62
  3. BSR-1

    BSR-1 Adventurer

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    how many hours (miles) do you have on this motor?

    did you actually measure the squish or did you just eyeball the top of the deck?
    #63
  4. procycle

    procycle Long timer

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    In that case the squish clearance is equal to the thickness of the head gasket. Probably around .040" to .050".

    Any motor set up with a true zero squish clearance would destroy itself in short order. You have to have some clearance to allow for the piston rocking in the bore, rod & crank stretch at high rpm, parts expanding when hot, etc.
    #64
    overborked likes this.
  5. slowsuki1

    slowsuki1 Been here awhile

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    well yes it has a headgasket .032 copper. i only have around 200 miles on it but it runs great with no pinging, i do run lucas octane booster , it is the only over the counter stuff sold around here that works. do not need it, but runs better with it, plus it has top end lubracateing qualities.

    i used feeler gauge with piston at tdc to get zero.
    #65
  6. procycle

    procycle Long timer

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    So it actually has .032" squish clearance. That's just about perfect. :thumb
    #66
  7. mito-nx

    mito-nx Dutch Humor

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    Hello,

    I am surching for a Mikuni TM33, the flatslide allso used on the DR350.
    Has someone off you any idea who has a nice one to spare?
    #67
  8. slowsuki1

    slowsuki1 Been here awhile

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    one other trick i used, was to cut 2 1/2 inches off the fork springs and add OD pvc spacers of the same length , made a big diffrence in front end diving when braking and better all around handling, also used 10wt fork oil. i am a big boy at 280+ so if you do this mod and are lighter might not want to take off that much.
    #68
  9. DisTech

    DisTech Been here awhile Supporter

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    Thanks and wow, your bike sounds awesome. You say, fcr37 and ported head? What are the details on the head work? Did you have the intake enlarged? better yet do you have a build thread somewhere?
    #69
  10. DisTech

    DisTech Been here awhile Supporter

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    Thanks for the info jcalis. I just got the motor out of the 94 tonight. Tomorrow I'll pull the head and see if it interchanges with the 99 head.
    #70
  11. DisTech

    DisTech Been here awhile Supporter

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    Everything except some of the motor mounts have been removed.
    [​IMG]

    All mounts removed. On my DR650 rebuild people asked why I didn't just lay be bike on it's side and take the motor out. So, I thought I'd give it a shot. It didn't work.
    [​IMG]

    Laying on it's side does not work because you have to spin the motor and then tip it out. There is a trick to it with it upright as well.
    [​IMG]

    If you're not lifting the motor from below it will want to fall backward and jam up in the mounts. Once I stuck that little piece of 2x4 under the motor it swivled and popped right out.
    [​IMG]
    #71
    cgunzelman likes this.
  12. SloSolo2

    SloSolo2 Long timer

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    Thanks this post probably saved me 30 minutes and a backache this week. I'm off Wed/Thurs/Fri and plan to strip my 98SE down to the frame for paint.

    Jamie
    #72
  13. DisTech

    DisTech Been here awhile Supporter

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    Cool, hope you post about it.
    #73
  14. DisTech

    DisTech Been here awhile Supporter

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    Forgot to get a picture of this yesterday. Those tabs look like they are there to protect the leading bolt from impact and I guess they do but they also get smashed around the bolt head. The left one I couldn't get a socket or wrench on and had to use a cold chisel to beat enough space so I could turn the bolt. I got the mounts off, but those bolts still wont come out of the holes. I wonder if a newer skid plate will protect the bolts enough so I can grind those tabs off?
    [​IMG]
    #74
  15. DisTech

    DisTech Been here awhile Supporter

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    Frame weights determined by "accurate" bathroom scale!
    • 94 DR350 - 26lbs
    • 93 DR350S - 26.5lbs
    [​IMG]
    1. Steering column lock on S model.
    2. Gas tank mounts on the bulge on the S and the indentation on the dirt model.
    3. Dogleg for side stand switch on the S model.
    4. Passenger peg mounts on the S model.
    5. Left side rear (plastic?) mount has two bolt holes on the S and one on the dirt model.

    The 94 dirt frame need some additional work. The cross member has a cracked weld on the left and there is a crack in the main tube at the other end of the cross member.
    [​IMG]
    #75
  16. DisTech

    DisTech Been here awhile Supporter

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    It looks like jcalis is correct. The 94 dirt head appears to be identical to the 99 street head. So there are just two types of DR350 heads. 90 - 93 with manual compression release and 94 - 99 that can accommodate manual and auto decompression.
    [​IMG]
    #76
  17. DisTech

    DisTech Been here awhile Supporter

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    The left is the 94 dirt with manual and auto decomp and the right is the 93 street with manual decomp only.
    [​IMG]

    The automatic decompression assembly is interesting. The centrifugal weight operates a little cam on the cam! As I understand it, when you are trying to start the bike (kick or electric) the cam slightly opens both exhaust valves (corrected by ProCycle). Once the bike starts the centrifugal weight flips the auto decomp cam to the flat side and the valves are allowed to operate normally.
    [​IMG]
    #77
  18. DRjoe

    DRjoe Long timer

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    the auto decomp is the same on the dr650 in fact the 350 head looks very similar to the 650. i wonder what the difference is in valve sizes and cam size.
    #78
  19. procycle

    procycle Long timer

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    The compression release slightly opens both exhaust valves. The intakes aren't affected.
    #79
  20. DisTech

    DisTech Been here awhile Supporter

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    I was looking at what lobe lined up with what valves and not paying attention to what the rockers were doing, doh. Thanks Jeff.
    #80