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I'm a bit concerned here, your ring gap specs are twice what's they should be and if you can manage to get .008 into cyl that's twice the max limit. i would double check your bore and measure piston to figure clearance that way and see what you get.

looking at your two piston size measurements old vs new that's .006 difference right there.
that kits not going to work.
 

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Discussion Starter · #84 · (Edited)
I measured the bore of the cyl but I am getting a Telescoping Gauge for a more accurate measure of the lower cyl not the top. But it should be withing specs since it has no lip and stock by the book is 80.000 ~ 80.018 (3.1496 ~ 3.1503) Pretty much all are 3.150 or 3.151 hard to measure with that micrometer you have to press it against the wall, and I use the opposite head bolts as reference
The pistons are both 3.145 I was measuring at the top before but did some reading and in the book it says to measure right above the skirt
 

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I'm perplexed. The Piston sizes your giving don't come close to the correct size. For orange the size should be 3.1458 to 3.1459. you old one is 3.134 witch could be do to wear.
 

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Measure ring gap. make sure ring is square in bore. Use piston to push ring about an inch down from the bore top. Pushing it up from bottom so piston is fully in bore. The Piston top will make ring square in bore. You want to be above any ports
 

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Ok. Now we're cookin with gas. Those figures are much better. Just need ring gap.
The bore at 3.151 and your new piston size puts you at .0045 for clearance. Measure all 3 pistons put the biggest if there is one in the 3.151 bore.
 

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Discussion Starter · #90 · (Edited)
So I used both pistons one from below one from above and pressed the ring somewhere in the middle.
Then I took the .024 and it didn't go in or I forced it but could not slide it. I tried the .022 and pressed the tip in when I tried to slide it it caused the tip of the ring to slightly move as seen in picture number 4, but it does slide down with .022 but it won't pull up.
So I would say it's .022 and below so within specs
 

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Ok. The ring gap is high. Max is .018. and your on the outside on one bore by about a thousand. Your going to have a loose motor. And won't last as long as a tighter one. For sure the last time you'll rebuild it without new cyl's. Your only choice is to go with what you have or return piston kit and order top end kit or send cyl off to US CHROME for replating. SBT top end kit is $695 for everything. Us chrome about $600 to replate.
 

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Discussion Starter · #93 · (Edited)
So you're saying that the end gap from the manual listing of 0.45 ~ 0.60 (0.018 ~ 0.024), mine being at around .021 because as I said .022 is tight, doesn't fall between min of .018 and max of .024? .021 is between those two extremities.

Tested this now:

On an older ring at .025 the feeler slides pretty hard not extremely but somewhat tight.
On the new rings it's at .021 same tightness/hardness.

I just re-measured the bore with a Telescopic gauge and they're all at exactly 3.150
Then I re-measured the pistons with a longer nose micrometer and 3.147
Difference .003 something
Ring gap .021

When I did the compression it was after who knows how many years of not start condition and the valves were really bad.
What do you suggest try oversized pistons and by how much .025? It's way too much
 

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Ok. Im using my manual figures witch has ring gap at 12/18 thousand.
But going by your figures your fine.
Sorry, this is showing me there are differences between the two for what ever reason.
 

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Discussion Starter · #95 ·
Not doubting you by any means, but the add-on picture is from XL1200 manual. Just making sure. Still going to add the 242 Loctite even though mine doesn't show it. It makes more sense.
 

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no, your good to go. got thinking about why they may be different. and that is that the 800 generates several more hp per cyl than the 1200. I'd do as the video showed and just wipe out your cyl with wd40 till clean and put the topend back on. lube well with 2 stroke oil as you go. be sure to use locktite on the 2 screws in the power valve area. the one that holds the bushing in and the one for the linkage.
 

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Discussion Starter · #97 ·
Hi guys took a breather from the ski and took my boat out on the lake finally on Saturday so today I decided to go back and work a bit. I used blue Loctite(242) on the crank case bolts, and moved on to the valves that I got from Pro Marine. It was a shitty experience to say the least, they get stuck or are hard to turn, the are touching the body of the cyl. Really pissed me off. I already changed the power valve seals and this happens it's annoying. So I bitched out the seller and am waiting on them to be returned. Really bad experimentation on my part. I truly believe the guy is selling Unbranded Valves calling them Pro-Marine.
 

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good call on your part to send them back. they should float pretty much in the cyl. without the link attached, and bushing in place, you should be able to lift them in and out with very little to no drag. with all 3 cyl in place, and valves attached together, you should be able to easily turn the valves open/closed from the wheel with little to no effort.
 

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SBT power valves probably cost me more, but I know they came straight from the factory. Haven't fitted them in yet, but they come highly recommended. I will let you know if I have any similar problems. Still waiting for the gasket set to begin the rebuild.

Zardoz
 

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Discussion Starter · #100 · (Edited)
This is the SBT page an my model 2000 XL1200 not included
https://www.shopsbt.com/jetski/Yamaha-exhaust-valve-kit-gp800-xlt-gp1200r-98-05.html

This is the WSM page showing compatibility if you click on the valve and again it doesn't show the 2000 XL1200
https://www.wsmparts.com/results.aspx?id=Inventory/a_ID_3_-1_-1_-1_152_-2"
Actually look at the attachment below

The ones I just returned did slide in the slot easily, is the leverlink that when attached cause all the problem , probably because they are poorly made. The valve shaft did not easily slide through had to use round file to make it larger, then when installed they do not turn by hand the links are big, I filed them and still not good enough, really bad, but they were not WSM or SBT they were off the market Pro-Marine, which is probably BS.
But why is it none of the pages list mine as a compatible one. only XLT kit, GP1200R some 800's etc. are on the list. The Partzilla number is VALVE ASSY. 66E-1131S-10-00 WTF
 

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