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  1. #1
    Buaidh No Bas howestek's Avatar
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    Mudbug Problem - Opinions Welcome

    I went to the Mudbug after performing the following mods on my '03 1300r with a 13/19 prop:

    R&D 45cc heads
    R&D rideplate
    87mm nozzle
    R&D Race Filter
    VF-3 reeds
    1200 intake grate
    Riva EFI
    Jetworks kit (duckbills and syphon tube)
    Intake tunnel reinforce.

    The rpm's had been steadily building as I put it together. The last mods I did (Jetworks and removing the syphon spout) actually raised my rpm's from a peak of 7340 to 7390 and a speed at mudbug of 69 mph at half a tank. I had great hopes of changing my prop there to bring down the rpm's and improve the speed. Rob from Georgia offered to help me bend the new prop. It wouldn't happen as I lost 200 rpm's, 2 mph, and 60 psi on cylinder # 3. Before the trip I was at cyl1- 148, cyl2- 148, cyl3 -150.
    After the rpm drop, cyl3 was at 90 psi. Adding oil only raised it up a few psi. Plug 1 was caramel, Plug 2 was a little darker caramel, Plug 3 was dark (blackish) with grit on it. All were dry. I pulled the head on cyl-3 and noted that the head looked good, the piston TOP looked good, and I could feel grooves on the cylinder wall. There were no outright gouges, but I could definetely feel a low spot (see picture). Just for grins, I cleaned up the head gasket, sprayed it with copper seal, and tried again. No joy.

    I guess my question is (finally), what looks to be the culprit and what is the best way to go from here?? I will pull the cylinder and check the piston as soon as I get a chance. Assuming the ring is damaged, and I see nothing outright as of now, should I renik and replace the piston? ( I have an email into Millenium) Should I send the cylinders off for porting and renick, etc, etc.? Which way do y'all recommend I go?

    My EFI settings are 7,7,2,9

    Thanks
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  2. #2
    Crash Test Dummy Smitty's Avatar
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    If it's a severe enough groove to lose PSI, you need another cylinder and rings. Post a request on the "Looking For" area, someone will have one. Make sure you check your piston when you pull the jug, and make sure any cylinder you install matches the piston.

  3. #3
    Happily Self-Employed WFO's Avatar
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    Steve, call me when you get a chance. I have a deal for you

  4. #4
    The cylinder may just need to be cleaned with acid and replace the rings. But you need to find out what caused the problem first. How do the other cyl look? Call Lowell Horning he will be able to help you out.

  5. #5
    Crash Test Dummy Smitty's Avatar
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    Re: Mudbug Problem - Opinions Welcome

    Quote Originally Posted by howestek
    I went to the Mudbug after performing the following mods on my '03 1300r with a 13/19 prop......actually raised my rpm's from a peak of 7340 to 7390 and a speed at mudbug of 69 mph at half a tank.
    It's been awhile since I had my GPR.... but if I recall, those RPMs are too high for that prop and 69 MPH. I used to race a friend who was turning those RPMs, we were both running 13/19 and I was going faster (68.5) turning 7150 RPMs. She had some sort of high speed cavitation going (and it pissed her off to no end, lol).

  6. #6
    Buaidh No Bas howestek's Avatar
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    Re: Mudbug Problem - Opinions Welcome

    Quote Originally Posted by Smitty
    It's been awhile since I had my GPR.... but if I recall, those RPMs are too high for that prop and 69 MPH. I used to race a friend who was turning those RPMs, we were both running 13/19 and I was going faster (68.5) turning 7150 RPMs. She had some sort of high speed cavitation going (and it pissed her off to no end, lol).
    I'm not sure whats going on. I watched the rpm's build as each mod was done, and each mods resultant rpm increase seemed believable. After the last mod, I intended on going to a solas 14/20 or 14/21 to bring the 7390 rpms back down to @7100-7150. I believe that the mph would have risen substantially. Hopefully, when I get it apart, I'll find the root cause.

  7. #7
    Buaidh No Bas howestek's Avatar
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    Quote Originally Posted by John
    The cylinder may just need to be cleaned with acid and replace the rings. But you need to find out what caused the problem first. How do the other cyl look? Call Lowell Horning he will be able to help you out.
    Hopefully, I'll find out tomorrow. I ended up in the hospital this morning and couldn't tear anything down . With any luck, just cyl-3 has a prob.

  8. #8
    mtrager's Avatar
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    Howestek,

    I meet you at the dock after you took your head off.

    Get a magnifying glass and look deep down in that plug and look for detonation.

    You have lots of fuel on the bottom and lots in the mid range and very little on top.

    Please let us know what you find. Also how many hours did it last ?

  9. #9
    Buaidh No Bas howestek's Avatar
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    Quote Originally Posted by mtrager
    Howestek,

    I meet you at the dock after you took your head off.

    Get a magnifying glass and look deep down in that plug and look for detonation.

    You have lots of fuel on the bottom and lots in the mid range and very little on top.

    Please let us know what you find. Also how many hours did it last ?
    Haven't been able to break it down completely yet (painkillers, been sleeping alot) Will try today. A local Performance shop owner looked at the piston top and swears that he sees deto on the perimeter of the piston top. To me it looks like debris from the cylinder scoring deposited on the edge of the piston. I'll look with a magnifying glass today.

    As far as fuel, I played with the red settings and saw no rpm difference between 1 and 4 so I backed it to 2 to be safe (maybe not safe enough!) It seemed to jive with what other board members with unported skis were reporting.

    I would say that it lasted, in this configuration, about 7-9 hrs. 3 hours with the jetworks.Total engine time about 77 hours. As a side note, until the bug, I had been running 93 octane exclusively. At Doirons landing, all they had was 92. I assumed that would be sufficient. Surely that wouldn't cause deto? If it did, I probably wouldn't be the only one having probs.

    Thanks, and I'll let ya know what and if I find something.

  10. #10
    r33pwrd's Avatar
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    My setup is pretty close to yours and I run 92 octane but my rpm's are only about 7200 After reading this post I got myself a compressions checker and will she what she has tonight.

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