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  1. #1

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    Question piston wash - way too rich? - and broken (not dropped) power valve!

    I rebuilt my motor earlier this year and I have about 15 hours on it now. I've been keeping an eye on the piston wash.

    According to what i've read here, it should be jetted about 115/135 (ported 1300, stock reeds, flame arrestors). I jetted it at 115/145 to stay on the way safe side. Returns are drilled out of the carbs and there is a 90 main jet in the return to tank.

    At the beginning, all 3 looked super rich. Then after a couple more rides, #2 started getting less wash. The wash that was there started getting filled in by brown. The piston always had a wet look about it, too (the other 2 were wet sometimes). I responded by turning the high speed jet on #2 out a little and in a little on #1 and #3. Now #2 is looking more brown and more wet, with just a little bit of wash, and #1 and #3 are clean, dry, with a huge amount of wash (seemingly more than before I leaned out the high speed a bit).

    So, my question is, can a piston set up way too rich show smaller areas of piston wash than you would normally expect from a rich setup? Could my #2 piston just be way too rich, or should I be looking for an air leak or something?

    It's been running okay up top, 65ish. It seems to load up a lot if I let it idle, though. Need to turn the low speeds in a bit. Could loading up too much at idle affect piston wash?
    Last edited by sleeper_dave; 09-17-2010 at 11:27 AM.


  2. #2
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    Quote Originally Posted by sleeper_dave View Post
    I rebuilt my motor earlier this year and I have about 15 hours on it now. I've been keeping an eye on the piston wash.

    According to what i've read here, it should be jetted about 115/135 (ported 1300, stock reeds, flame arrestors). I jetted it at 115/145 to stay on the way safe side. Returns are drilled out of the carbs and there is a 90 main jet in the return to tank.

    At the beginning, all 3 looked super rich. Then after a couple more rides, #2 started getting less wash. The wash that was there started getting filled in by brown. The piston always had a wet look about it, too (the other 2 were wet sometimes). I responded by turning the high speed jet on #2 out a little and in a little on #1 and #3. Now #2 is looking more brown and more wet, with just a little bit of wash, and #1 and #3 are clean, dry, with a huge amount of wash (seemingly more than before I leaned out the high speed a bit).

    So, my question is, can a piston set up way too rich show smaller areas of piston wash than you would normally expect from a rich setup? Could my #2 piston just be way too rich, or should I be looking for an air leak or something?

    It's been running okay up top, 65ish. It seems to load up a lot if I let it idle, though. Need to turn the low speeds in a bit. Could loading up too much at idle affect piston wash?
    pics help

    you are too large on the main jet

  3. #3

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    I'm intentionally too large on the main jet because I don't want to blow it up. Once I am sure everything is good i'll start to lean it out a bit, but for now, I want to keep it plenty rich. I will play with the needles to get everything even. I have a 135 and a 140 jet I can put in.

    I don't have any pics because i've just been looking through a scope. I'll pull the head and post some pics if needed.

  4. #4
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    Quote Originally Posted by sleeper_dave View Post
    I'm intentionally too large on the main jet because I don't want to blow it up. Once I am sure everything is good i'll start to lean it out a bit, but for now, I want to keep it plenty rich. I will play with the needles to get everything even. I have a 135 and a 140 jet I can put in.

    I don't have any pics because i've just been looking through a scope. I'll pull the head and post some pics if needed.
    pics really do help

    you will probably end up with a 125 main jet

  5. #5

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    I had 115/135 in it before the porting except it had a timing key and it still blew up #1. #2 and #3 looked good as far as wash goes with that setup.

    I doubt i'll get down to a 125 unless I bump up the primary. From all the reading i've done on this forum i'm thinking it should probably be 115/135, but i'd rather start rich and work my way down than start lean and blow it up. I do plan to leave it a bit rich anyway, as I do ride longish distances at 3/4 throttle and I don't want to have to worry about it. Before I dial them back a bit I want to see consistent wash on all 3 cylinders and get enough hours on it to make sure it's okay. The way I look at it is it should be fat enough now to tolerate an air leak or something without going too lean. Once I've got it broken in well and am seeing consistent rich wash across all 3 i'll dial it back to a 140 or 135 to pick up some speed.

    Only thing is I think it might be so rich that it's showing me some odd results on #2. I just want to make sure that sounds reasonable before I try shifting it leaner.

    I'll pull the head one night this week, double check torque on the jugs, and get some photos of the pistons. I can reuse the head gasket if I use some copper spray, correct?

    Being that this is #2, I can't think of any reason for it to go lean. I would think an air leak would be more likely to affect #1 or #3, unless it's coming from the base gaskets, which is why i'm going to double check that torque now that it has some hours on it. It passed a pressure test before install, of course. I don't recall pop-off on the carbs but it was consistent across the 3. All this leads me to believe it might be so rich that it's showing wash more like it's leaner. But right now, if it is in fact leaner than the other 2, i'm still on the rich side of safe - which is why I jetted it so fat to begin with.

  6. #6
    Port wash does not lie... Something is up. A super rich condition will show up as a quarter size brown spot in the middle of the piston. Outer perimeter will be washed clean. Washed area will reduce to thumb nail size clean spots near intake ports when correct.

  7. #7
    Pipe water injector plugged on that cylinder?

  8. #8
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    I just saw your ported. Probably a 130 main then.

    usually when they go lean (from jetting) they wipe out 3 first, so if you took out 1 & 2 before you have something else going on in there

  9. #9

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    I'll pull the head and post pictures. #1 and #3 are washed clean near the intake ports with a clean spot across the center of the piston and brown around the edges on the exhaust side. Washed clean in smaller areas around the ports on the sides. #2 was like that, now it's down to a clean spot probably about the size of a nickel near the intake ports. Wash on #1 and #3 got more clearly defined and looked bigger when I went slightly leaner on the high speed needle, #2 got smaller when I went richer on the high speed.

    #1 went last time. I'm thinking it was fuel pressure (didn't drill the returns that time) and timing (stock 1200 ignition with a timing key). First time, machine was bone stock except d-plate and intake grate, and #3 went. Thinking it was lean in the midrange (it went after a 15+ mile ride almost all at about 3/4 throttle).

  10. #10

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    Well I got around to taking the head off and got some pictures. Getting a better look at #2 it looks a lot like the others but just wetter, and a bit darker. Looks like some of the wash might be shrinking but it's hard to tell.

    The big news, though, is that I lost the power valve in #1 without even knowing it. Last time I had it out it was only topping out at 62-63 rather than the 65-66 I got out of it previously, but it was a different lake and it was a little rough so I didn't think too much of it. I didn't have time to tear it down any further, but I didn't see any damage to anything except the two little marks you see pictured.

    Pictures should be in order, piston 1, 2, another of piston 2 (the shiny piston), and 3, then 2 more shots of 1 showing the piston damage from the power valve.

    I don't see any evidence of the power valve other than the slight damage on the top edge of #1. I'm not sure I even plan to take the piston out. The cylinder wall looks fine, the ring appears to be fine. I don't know how long it's been running as-is, but it doesn't appear to have screwed anything up, thank god - 15 hours on this motor so far, $3k into it. No real way the power valve could have made it from the exhaust side into the bottom end. it must be either in the exhaust or blown out the back of the machine. I'm going to have to pull the exhaust and look for it. I don't know why it dropped, I did have waveater clips installed on this motor. I'll have to pull off the power valve covers and check it out.

    Click image for larger version. 

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    So, what do y'all think of the wash? Other than rich, rich, rich. Do you think #2 is leaner than the other two because of the more black, or richer because of the more wet? I know they can all use a little less jetting but I want to get them even and responding as expected to adjustment before I lean it out too much.

    BTW that motor has been sitting for a few weeks so the wetness on #2 isn't like a sheen of fuel or anything. It's more of a shiny fresh carbon buildup, really. More sludgy, a little oily, not really gas-like.

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