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  1. #1
    Yamaha artisan Cutlass's Avatar
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    Hard to start when warmed up

    Working on a 2002 GTI LE with the 717 engine, single carb. It runs really good and the compression is 135ish on both cylinders (a little low?).
    When you shut it off after riding, its hard to restart. After some research, I found 2 common concerns for this: Rotary valve clearance and leaky needle/seat.
    So I measured the rotary valve clearance at .025" or more. I stopped sticking feeler gauges in at that point because it was way out of spec (.010" to .014" is spec). Took the cover off and it was worn quite a bit and had a sharp lip/edge around the outside diameter where the valve worn into it. So I ordered a SBT reman'd cover and installed it. Measured the clearance at around .019"...still out of spec but way tighter.
    Disassembled, cleaned, and checked pop-off for the carb. All good there, N/S holds pressure and pops-off normally.

    Back together for a water test and this thing still runs great(maybe better, got 2 mph faster) but is still hard to start when warmed up. Before it was nearly impossible, now it starts okish when holding the throttle wide open. I can live with that maybe but I'd like to fix it.

    So do I need to tighten up the rotary valve clearance more or does it need a top end to bump up the compression or does it need something else?


  2. #2
    woodsrider40's Avatar
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    Sounds like you need to get the rotary valve and cover from SBT to fix it. I've done many of those.

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  4. #3
    Yamaha artisan Cutlass's Avatar
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    I have the SBT cover. You think I should have replaced the rotary valve at the same time? Do they wear down thinner as they grind away the cover? I guess that would explain my excess clearance.

  5. #4
    woodsrider40's Avatar
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    If the clearness in spec with old valve it should be good but if it has any nicks or groves it needs to be replace.

  6. #5
    Yamaha artisan Cutlass's Avatar
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    It was slightly groovey and my measurement is .019", which is outside of the .012" to .014" spec. I slide the rotary valve away from the block a bit and it doesn't look like there is anywhere on the block.
    So I'm guessing a new rotary valve will tighten up my clearance and fix my hard start. Dang, I wish I would have done that to begin with. LOL.
    Any thoughts on SBT vs OEM rotary valves? Are they the same or is there a quality difference? I tend to lean towards OEM for most things.
    Thanks guys!

  7. #6
    woodsrider40's Avatar
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    SBT rotary valve is the same as OEM just be sure to get the right one for your ski. I have used the carbon fiber ones from part unlimited which did good and if something get caught in there it will break the carbon and not damage the block in a lot of ways. BUT it is tricky to get the timing right because of the different degree, so I would just get the SBT. Have a timing degree wheel on hand to get her in time which you can get from SBT also if you don't have one already. Off to the lake !

  8. #7
    Yamaha artisan Cutlass's Avatar
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    Can I cheat and just mark where the old one came off and put the new one on in the same place?

  9. #8
    Did you check for seat leakage and pop off with the cover on or off? Sometimes putting cover on will cause a leaker.

  10. #9
    Yamaha artisan Cutlass's Avatar
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    I checked with the cover and diaphram off. The lever arm was a little high so I adjusted that a little bit as well. I could definitely check it with the cover on next time I have the carb off.

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