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  1. #1
    matt160580's Avatar
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    Pro 785 PTO holed!

    Alright chaps!

    Returned from my sunny holidays in Scotland, Tralee bay an amazing place the bay was like glass perfect ski conditions. Action pic of me and my son ripping up the bay attached!

    Before I start just want to say a BIG, BIG thankyou to Lugs for sending me the part for the water routing mod, also sent me the tap and drill bit more than I was expecting! Thankyou! Trust worthy guy and pleasure to meet!

    On the second day of what can only be described as power boat madness The ski lost pwer and died shortly after starting about 10 mins. I tried to restart a couple of times but on the third or fourth attempt the engne locked up. I had to get towed back int shore, I clamped off the intake pipe before hand and it was a slow jurney back! 10 mins ski += 45 mins towing! You can cover some serious distanceon this thing without realising!

    When I got back keen to see what the problem was I took off the head and found pto holed! The next day I looked in the ski to find alot of two stroke oil in the bilge, so there is definately a leak somewhere. So I can only assume this is the the cause, I need to investigate further. There is water in the bilge because I drained the stringer and manifold some has just escaped on tow.

    A couple of observations though when I got back the pto exhaust valve was very loose on the cable so much so I doubt it open properly. I missed this on my pre ride check.

    There was no water in the bilge or seperator and oil and fuel where full. I've just started putting yamalube in from valvoline mineral based so don't think that has anything to with it?

    So some what do you guys think?

    1/Obviously find where the oil is comming from, can it be the crank/block subsequent damage?
    2/With the size of the hole in the piston do I need to strip don to crank if any debris have fallen?
    3/Can I refurn the head and polish I suspect there will be soe minor indentations after?
    4/Will need to get a rebore/sleeve as there are two deep cut in the cylinder don't think honing will sort.
    5/Are ther any alternative pistons I can use I recall reading somewhere but can't find where there is an alternative.
    6/Thinking about rebuilding the carbs whilst I've got my sleeves rolled up can anyone recommend where I can get a carb kit I've been quoted £45 each! Springs, o rings and diaphrams etc.
    7/ Can I take the PTO jug off whilst leaving the engine in? The rachet set I've got wont fit the nuts on the carb side becasuse of clearance?

    So what you guys think?

    Cheers

    Matt
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  2. #2
    thester71's Avatar
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    Thats definatly a lean burndown, did you do a leakdown test on this motor? Actually all the pistons look lean they need more fuel, what setting are you running on the mixture screws? I have a spare head you can have, just pay the shipping. I wsould try to find a factory polaris piston, but if you can't, you can use a piston from a 750, but you need to have the cylinder clearance set for the 750.

  3. #3
    matt160580's Avatar
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    Hi Thester

    I've just been running as it was set when I bought it about 5 weeks ago. I did a compression test all was OK. Thats very kind of you, I'd really appreciate the head if you can send let me know how much you want and I can send you the money via paypal if thats OK with you. I can get a genuine piston for the pro 785 they come as kits for £75 piston, pin and clips thinking I may as well replace the small bearing as well hopefully the rod is still in tact once I lift the jug. Can you point me in the right direction for more info on leakdown test? I havent done this, as you an probably tell. I'm going to rebuild the carbs and fuel lines anyway, taking the ski 400 miles to break down on the second day something I want to avoid next time. I was gutted!

    Matt

  4. #4
    matt160580's Avatar
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    Rebuild project

    Alright I decided yesterday to strip the ski right down to the crank and get it rebuilt. So far so good taken out the tripples. Looks like the bottom part of the rod got tewed up, who knows what damage its done to the crank! Click image for larger version. 

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  5. #5
    She likes the bike. But the ski gets her wet!!!! xlint89's Avatar
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    The connecting rod broke?

    Did it do any damage to the engine case or cylinder?

    There's a chance that rod was bad when you got it. Possibly hydrolocked and knocked the crank out of phase. That MAY have lead to the holed piston too.

    That sucks........

  6. #6
    100 MILES OF HEAVEN AND I AM SMACK IN THE MIDDLE KEYZBUM's Avatar
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    Quote Originally Posted by matt160580 View Post
    Alright I decided yesterday to strip the ski right down to the crank and get it rebuilt. So far so good taken out the tripples. Looks like the bottom part of the rod got tewed up, who knows what damage its done to the crank! Click image for larger version. 

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    wow ,, sorry to see that bro,,that crank is toasted if the rod broke like that

  7. #7
    Derwood98's Avatar
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    Send it to Jay at Sharp's Marine. He will get you taken care of, at a great price, plus they have rods for our application if you get your crank done with them.

  8. #8
    matt160580's Avatar
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    Quote Originally Posted by xlint89 View Post
    The connecting rod broke?

    Did it do any damage to the engine case or cylinder?

    There's a chance that rod was bad when you got it. Possibly hydrolocked and knocked the crank out of phase. That MAY have lead to the holed piston too.

    That sucks........

    Yeh the rod broke tore up the big end

    Scored cylinder so will likely need a replate. Not sure yet about crank case took the engine out yesterday it's sat on my garage floor as I type. Going to start stripping it down this week. Yeh sounds like you could be right just hope its not damaged the case it does look as though it's going be damaged or at least scored. That could explain the the two stroke in the bottom of the ski. If the case is damaged can they be repaired, cracks holes? I've just emailed Randy at Sharp's see if he will rebuild the crank and replate cylinder for me. Hopefully he will.

    Yeh that would make sence, thought it may be the carbs at first.

  9. #9
    matt160580's Avatar
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    Cheers Derwood - Just PM'd you been reading your posts and would like some info off you if poss.

  10. #10
    thester71's Avatar
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    Quote Originally Posted by matt160580 View Post
    Yeh the rod broke tore up the big end

    Scored cylinder so will likely need a replate. Not sure yet about crank case took the engine out yesterday it's sat on my garage floor as I type. Going to start stripping it down this week. Yeh sounds like you could be right just hope its not damaged the case it does look as though it's going be damaged or at least scored. That could explain the the two stroke in the bottom of the ski. If the case is damaged can they be repaired, cracks holes? I've just emailed Randy at Sharp's see if he will rebuild the crank and replate cylinder for me. Hopefully he will.

    Yeh that would make sence, thought it may be the carbs at first.
    Jay from sharp's is on vacation till the begining of september basically, I see him logged on here though, I would send him a PM and leave a message on the machine at the shop.
    Contact lugs for the cases, he might part with a set.
    Also, your head will ship out tomorrow.

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