DR350 Thread

Discussion in 'Thumpers' started by leonphelps, May 16, 2007.

  1. RuggedExposure

    RuggedExposure Now with more rugged

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    The bowl:
    [​IMG]
    [​IMG]
    [​IMG]

    The tip still looks new:
    [​IMG]

    Inside the float valve is clean and has a new o-ring (thanks to the badass Mr. Bender)
    [​IMG]

    [​IMG]

    I didn't take apart the slide assembly just to show pics of the needle, but the needle is in the 2nd position from the top and everything is assembled correctly. Also, there is little to no play in the slide (moving it from airbox to engine direction) and no side to side play:
  2. RuggedExposure

    RuggedExposure Now with more rugged

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    Here is the choke/enrichener with the o-ring in place:
    [​IMG]

    and the port it goes into is clean:
    [​IMG]

    [​IMG]

    This carb is seriously clean enough to drink out of. Every nook, cranny, jet, emulsion tube, and piece that is removable has been acid washed, scrubbed and cleaned. Nothing has been changed from when it was running great.




    I got the jug off:
    [​IMG]

    Like most of you know, I'm no expert. But the inside looks really smooth and almost no scoring from the rings except for these little marks:
    [​IMG]
    They are criss crossed... obviously the rings didn't do this???

    and the piston:
    [​IMG]
    [​IMG]
  3. 2old2Bbold

    2old2Bbold was 2bold2getold

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    The cross hatch on the cylinder wall is caused by the finish hone rotating and moving up and down slowly in the final step of honing the cyl to the correct size. It's supposed to produce a finish to hold the correct amount of oil and help seat (wear in) the rings. I've seen worse looking bores and the rings don't look stuck or worn down to nothing. Still wouldn't use em back. The best bang for the buck is to replace every thing you can with new parts, up to a point. Other wise you've got your same old motor back, and all that time, work and money for nothing. The piston should have an arrow on the top that points forward (exhaust side). On most pistons the wrist pin is off set to on side, either front or back depending crank shaft direction of rotation. to help with piston slap noise.
  4. PHILinFRANCE

    PHILinFRANCE Long timer

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    Cheers mate
    The o-ring looks ok but will give it another looking at and i'll check the floats , but all 3 to have a hole seems unlikely

    Phil
  5. tntmo

    tntmo Been here awhile

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    That is called cross-hatching. It's good if it's still there, means there is very little wear in the cylinder. That looks great. A couple of scratches in the lower left of the picture...can you feel those with your fingernail?

  6. tntmo

    tntmo Been here awhile

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    Oh yeah, I also wanted to let you know that I never use a ring compressor on the DR piston. Just squeeze the rings together by hand as the piston goes into the cylinder. It's slightly tapered on the bottom and goes together easy.
  7. 2old2Bbold

    2old2Bbold was 2bold2getold

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    That fuel's got only one way in there. It's got to be going around the seat (o-ring) or past the needle (needle/seat interface or not enough float pressure) or too much fuel pressure from stopped up tank vent???
  8. Vankaye

    Vankaye n00b on the move

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    Hang in there Man! We've all had bikes that tried to out wit us. But you're doing great!

    Sorry, i have nothing technical to offer you at this point. You're in over my head :1drink

    Oh, how do the ring retention pins look inside the ring grooves? If the rings are able to jump
    the pins that could cause enough blow-by to kill the compression.
  9. Wadester

    Wadester Rides a dirty bike

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    Yeah, that's from the last hone job - on the other hand, those marks look way fresh! Like PO did a ring job and it didn't take. I have done cheapie ring jobs on cars - just ridge ream/hone/new rings and keep on. Usually works fairly well. But also, with hard rings (cr-mo) sometimes they don't seat properly - tho this usually means excess blow-by (crankcase gets combustion gas). I have had old rings unseat and lose all compression - perhaps this was a way-cheapie job, with old rings but a new hone job? You'd need to measure the bore to tell - maybe take it with you and let a shop measure it. If it is past a certain size, you'd need to bore it (check manual).
  10. mouthfulloflake

    mouthfulloflake Not afraid

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    I would put the piston and cylinder back together, verify your timing chain/cam relationship to the crank.

    and look elsewhere for your issue.
  11. Greg Bender

    Greg Bender Long timer

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    I had a Moto Guzzi V700 that gave me fits after getting warmed up and having no power. I checked everything over and over again (read = *many* hours). Come to find out two of the push rods were expanding (with heat) at an odd rate. No one had ever heard of that one before (particularly because the ends were tight and the tubes were not full of oil). Once I swapped the push rods, all was right with the world. But I chased my tail a long time getting to that point.

    Regards,

    Gregory Bender
  12. RuggedExposure

    RuggedExposure Now with more rugged

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    No, those are very fine and cannot be felt with the fingernail.

    I did not know there are any pins in the ring grooves, I'll have to look closer at the piston tomorrow. its almost my bed time.

    I doubt the PO did any sort of piston work to this bike. According to him it probably didn't even have 2k miles on it and I believe him. The bike never left his pecan farm and everything else on it is pretty much new. Is it possible that my auto-decomp in the cam is what took a shit?

    Remember that this bike ran like a raped ape for 2-3k miles. Then on one 2hr trip it started having problems and has been getting worse and worse. It barely had compression when I took it apart (whereas a few weeks ago when it first started showing signs of problems it would still start and idle fine).

    Maybe the auto-decomp is the culprit for everything???
  13. 2old2Bbold

    2old2Bbold was 2bold2getold

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  14. 2old2Bbold

    2old2Bbold was 2bold2getold

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    Here's you some gearing info also from DisTech's thread. http://www.advrider.com/forums/showpost.php?p=12104148&postcount=120
  15. slartidbartfast

    slartidbartfast Love those blue pipes

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    On one of my XS650s dirt dauber wasps sealed off the air gap between the cylinders. Subsequent local overheating (maybe) led to overheating of the rings and the oil control ring lost its "spring". In my case the bike just started making huge clouds of smoke but if the compression ring lost its temper, you would lose compression.

    If you've got it apart, touch up the honing (if you don't know the technique to get good cross-hatch, get someone who's done it before to help you) and replace the rings. It won't cost much and you will have eliminated one potential source of the problem.

    Did you check the valve timing before you pulled the head off?
  16. markk900

    markk900 Been here awhile

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    R/E: that cylinder looks fine, and the rings are not stuck so this is not the problem at all. I realize its good to replace stuff when its apart but if it were me I'd not buy anything, or hone anything on that cylinder. The fine scratches and even the small ridge at the top of the stroke are not causing the issue. Put it back together and forget that as the problem, unless you are really OCD then you could decoke the piston and get rid of the munge.

    Did you do the leak test on the head/valves? Once its back together check the operation of the decomp....

    Edit: I wanted to say like TNTMO I don't use a ring compressor either - just fingers and the chamfer at the bottom of the cylinder. However, you are naturally "stressed" right now and getting the piston into the cylinder while compressing the rings with your fingers can sometimes be frustrating, so it may be $10 well spent.

    BTW: just did another motor last week (small honda) with compression issues - it was a bent valve and it was pretty straightforward to replace.
  17. RuggedExposure

    RuggedExposure Now with more rugged

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    [​IMG]

    I used the rubbing alcohol as suggested, and the valves held every drop for half an hour. Nothing made it through.

    So if my piston rings looked squared away, and my valves are holding. What in the blue f*** happened to my compression?

    We know its not the:
    -coil
    -plug
    -spark plug boot
    -plug wire
    -cdi
    -regulator
    -carb
    -valves
    -piston rings
    -kill switch
    -wiring harnesses
    -bad gas
    -exhaust being obstructed/clogged
    -air filter

    ...
    is there anything left other than the auto decomp???
  18. RuggedExposure

    RuggedExposure Now with more rugged

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    How would one go about checking the valve timing?
    Could this be a problem that would slowly creep up out of no where?
  19. bullittman281

    bullittman281 Been here awhile

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    The small locating pins for rings are typicly a two stroke thing. Cant let a ring move and get the end caught in a open port. Its very doubtful that the dr has them.

    Normally its good form to stuff new rings in and replace things when they are this far apart but for the moment I wouldn't put a dime into it until I located the problem. Some where there is a deeply embedded gremlin that needs to be flushed out. Until it surfaces though I wouldn't buy any thing.

    Its got to be an electrical or carb gremlin. As may times as that carb has been cleaned it has to be electrical. I'd reassemble it making sure the cam timing and de-compressor are good and then I'd re visit the electrical system with a clear head.

    bullittman
  20. bullittman281

    bullittman281 Been here awhile

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    The cam chain can stretch and it will drift, but that wont be enough for it run *that* bad. The other way it can move is a sprocket has to jump links on the chain or a key gives it up and a sprocket is allowed to move on the crank or cam. Just set it all back up like the book and makes sure that its good, and you will then know that its good. I doubt you have any problems with the cam chain, other than reassembling it.

    bullittman