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  1. #1

    Keihin Pop-off Spring Question

    I bought a 1999 Polaris SLH 700. It runs strong, but as soon as you release the throttle it stalls. Another thing I noticed is that one time it was on the hose it revved high with the throttle closed. I'm thinking it's the rear crankshaft seal because I went through the carbs and checked the pop-off pressure. Also when I got it the PTO cylinder had burned the piston. It was taken apart when I got it so I didn't get to see the piston, it came with a new piston and a bored cylinder. The pop-off pressure was a little off but not bad enough to cause the stall. I'm pulling the engine to replace the seals, but I'm going to replace the springs in the carbs to be safe. My question is, when I went to order the replacement springs I found there are 2 parts numbers. One of them is a 40 gram spring and the other is a 70 gram spring, how do I tell which one I need to order?


  2. #2
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    There is probably no need to replace the springs. What is very critical, I have found in these carbs is the height of the regulator arm. .060 below the casting. I had all kinds of running problems on my 99 SLTH until I got the regulator arms set correctly. When you replace that seal, use the double seal setup like used on the later model Polaris motors.

    http://www.greenhulk.net/forums/show...=1#post1667413

  3. #3
    Cool, I'll check that. I ordered the double rear seal for it.

  4. #4
    Click avatar for tech links/info, donation request K447's Avatar
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    Quote Originally Posted by LaserLTV View Post
    ... I ordered the double rear seal for it.
    Polaris OEM seals, not aftermarket.

    Polaris OEM seals have been strongly recommended by multiple experienced engine builders. Apparently they are better quality than most (all?) aftermarket seals.

    Related tip. You can use the Polaris Teflon lipped snowmobile seal for the inner seal of the pair. At least, I think it was the inner seal that was Teflon

  5. #5
    I read through the information on polarispwcknowledge and ordered the part number (2qty)#5412091 for the rear and #3610044 for the front, that's a great resource. I found it through the link in your sig on another post.

  6. #6
    She likes the bike. But the ski gets her wet!!!! xlint89's Avatar
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    Make sure to do a leak down test after you reassemble the engine. That should show you if any air leaks are present.

  7. #7
    One of the engine builders I know said to make sure I pack grease between the two seal to prevent moisture from getting in the void between the two seals.

  8. #8
    Well, I took the engine apart today and found two problems. The first was the PTO crankshaft seal (single aftermarket seal) was completely worn out. It was worn through to the spring and the spring had popped off the seal. The other problem is that the person that rebuilt the engine did a crappy repair on the case. The rod bearing had gone bad and the rod beat a small hole in the bottom of the case. He repaired it with epoxy and the oil had soaked through it. He didn't even remove the paint on the outside of the case where he epoxied it, it popped right off as soon as i touched it. Most of the used cases on eBay have scars from rod damage, so I'm going to try and weld it. I've welded a bunch of aluminum over the years including cylinder heads on my race car, so I don't think welding it will be a problem. If it doesn't work I'll buy a used case on eBay.

  9. #9
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    Good plan. When you re do the seals go with the double seal setup like the 1200s.

  10. #10
    Rasta Mon Condoms We Be Jammin!!!!! TxVirageTx's Avatar
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    if there are any cracks in the cases i'd terminate them by drilling a hole at the ends and then wedling everything.

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