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sorry I'm late guy's. working nights sucks.(6pm to 7am) was up 28 hrs by the time I got home this AM.
+1 to what Rods stated but I will add that both of these motors have power valves. and will require a bit of TLC for them as well. while its apart for the oil lines and carb build, you'll want to pull the covers and inspect the valves, and at the very least install wave eater clips. Myself I prefer the SBT linkage replacement, its a more permanent fix and a bit more work to install though.
keep the oil systems if there intact. if they are still there. they are very reliable if maintained. IE replacing hoses every few years. with the system in tact you can run several tanks of fuel before needing more oil if you premix you have to carry oil every time you go out encase you need to refill. not to mention very messy. not to mention the oil pump is variable at idle your running 200/1 and wot 50/1 so you actually save on oil in the long run.

the oil line (1/8") can also be purchased at SBT. or at any small engine (lawn mower) repair shop. as far as the line clamps go you'll have to look them up on line they come in package kits under Oetiker clamps. honestly though the wire ties work very well if you have the proper tools. go to your local electrical supply house or lowe's, home depot, and get a wire tie gun. its used to put on wire ties. it's the only way to use wire ties as a clamp. it pulls them down very tight and clips them off clean. mine will literally pull a wire tie in half. the higher end models have better tension control. Most importantly ALWAYS use the black wire ties, they hold up best to heat and sun.

the schrader valve Rods is referring to I believe is the one in the hose for your compression tester.

also for your carbs there are a few upgrades you may want to do as you rebuild them. you can find links to them under Zardoz's post on his engine build. I wouldn't do the jetting upgrade unless you plan to remove factory air box and install F/A's. but definitely do the fuel balance. the way I do mine is one carb at a time. and tag it for what cyl 1,2,3 they are different. and as Rods stated write down how many turns in to seat each mixture screw. when you put them back on the mount plate do not tighten them till all the linkage is connected and make sure all your butter flies close all the way. the linkage is preset so you have to let the carbs settle so that they all close. if you know what I mean...

a compression gauge is a compression gauge. no 2 stroke or 4 stoke. don't bother with harbor freight there useless. very poor gauge no where near accurate.
I wouldn't get overly concerned on compression just yet, you say they've set for a while and may have some light surface rust on the cyl wall that will effect your outcome. i'd add a teaspoon of oil to each cyl, crank them over put plugs back, get them running on the hose for a few minutes(10/15 min) let them cool and do this 3 to 4 times and then test.
when they set the bores get very dry and dont seal well
 

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I want to clear something up here real quick. What Rods is saying is for your first tank of fuel mix 5 gal at 32/1. Helps get motor well lubed after setting. The oil tank only gets oil in it. No need to measure it just fill it when needed.
 

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No anti corrosion spray. just a teaspoon or so of 2 stroke oil and roll it over a bit
For parts you can also use "Babbittsonline"
 

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Went to Home Depot and no Tygon, will probably order it. and the oil is a lot thinner than the fuel hoses Are zip ties tightened with a gun sufficiently strong or do I need the metal clamps?

As far as the filter I saw a water inlet filter see picture#1 item #15 and a bilge strainer, in the book got to locate it in the jet ski

OK took out the exhaust and there is a D-plate already

Pic #3 tank had water inside it smelled like has is that normal

Picture #4 the middle oil line came off pretty easy, the other 2 also came off but a bit harder
Picture 5 the carburetor filter box has only a metal mesh looking grill there are no filters
wire ties:
wire ties are fine. its all I use. just make sure to use the black ones and install them with a gun. and a lot less expensive than the clamps.
filter:
item 15 pic 1 is your cooling water inlet screen/filter. remove cover #17 and make sure the inside is clean and clear.
pic3:
is your water box and will have water in it that normal. some cooling water goes out through the exhaust to cool the system.
pic 4: the green fuel lines dont replace them unless you have to. they are a very high quality rubber and last a long time. only replace if it is hard and britle. just carefully cut wire ties and redo them. do replace oil lines and leave plenty of slack in them for shrinkage. this will help keep them from pulling off.
pic 5: the screen in the airbox is all there is. not really a filter more for flame arresting.
 

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1- The exhaust joint one from the picture has a lot of white build up, underneath the smaller joint 2 is better.

2- So the next step is to take out the carb assembly and rebuild it. Do I need to buy a new needle and needle seat? I got to find the best kit for this so help

3- I am also thinking that since I am here do I open the head and rebuild the upper end? For that I have to see how the pistons and cyl or sleeve cyl look, don't know if I need to have them honed or resurfaced. I think based on that I will order the rings. What do you guys think
the white is just corrosion it can be cleaned with dish soap and coarse steel-wool.

Answer 2: the needle and seat doesn't come with the carb kit so yes order them when you order your kit. some will tell you to use only mikuni kits and not the ones from sbt. but ive used both with no issue and the sbt kits are much cheaper. 1.2mm seats come in the carb. if your doing the upgrades on them use 1.5mm seats

answer 3: if your compression numbers where around 90 and your confident thats what they are, then yes it wouldn't be a bad idea. if they are sleeved then yes hone them. if there still original nikasil coating then just replace piston and rings and top bearings if bores are clean and not scored. ALSO check your power valves while your this deep in. pull the covers and make sure they have either wave eater clips on them or the sbt linkage. these motors are notorious for the pin falling out of the valve and blowing a motor as the valve and pin fall into piston.
if you need help id'ing sleeved vs nikasil jug post a pic of the top of the jug after the head is off and surface is cleaned. the nikasil is a very hard chrome coating they flash directly onto the aluminum wall of the cyl.
 

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Mr. Dave you have my eternal gratitude you sir are a gentleman and a scholar.

I just removed the exhaust manifold 8 bolts and it took an hour, the damn bolts were really tight so it was one turn rest one turn breath. But it's out.

So here's the corrosion on the ports. Looks pretty bad.

Tomorrow the head is coming out. I am really enjoying this even though the trailer has a metal railing cover with plywood and some carpet, keep banging my head, so I have to stay bent over and it's still easier than a car engine.

I will look at SBT for prices. The upper end kit $399. I found some kits on EBay for $300. I am going for the rebuild of the top end first then the carb. The oil line is really thin even compared to the fuel green lines. What size are those hoses 1/4 or 1/8?

The carb green hoses are ok a bit hard but maybe ok I can squeeze them but really hard rubber

Dave did you say to cut the old ties from the existing fuel lines and replace them(ties) even though I am not putting new lines?

And last I think you or someone else mentioned the crank seals and now I am really concerned they look like a pain to replace, what say you?


yes you need to be contortionist to get to some bolts. try doing the starter under the manifold......

the corrosion is not good. shows it wasn't flushed properly. you'll need to clean that out. try either white vinegar or CLR. get a tote and soak them. if that does'nt work i know what will but it comes in 5 gallon and runs about 100 bucks. you'll need to get it out of the exhaust, cyl's, head, everwhere you find it it will cause cooling issues. if I can find the link to one I had that was much worse then that I will post it. need to always flush with salt away/salt terminator after a salt water ride. even if it's brackish water salt is hard on the aluminum.

if the cyl are all good and just need piston kit I'd recommend finding a Wisco piston kit they are very high quality piston.
contact Zardoz as he's already done this.

for the fuel lines, feel for any loose ones and replace them don't have to do all. if they twist around easy then replace that one.

Rods mentioned the seals. the thing is your dealing with an 18 year old ski and time isn't on it's side any more. yes they are a bit of a pain mainly in getting the coupler off rear and getting flywheel off the front. you can lock up the motor with some rope in a cyl to help with the coupler removal. bring piston all the way up then about 1/3 way down then fill with rope and compress rope to the head. just don't let rope get into a port.I be leave couple is left hand threaded. once thats done spliting the case and replacing seal isn't bad. just need a tube of yamabond adhesive to put back together.
 

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1- So to get to the seals I have to remove the starter and generator and then the flywheel bolt ( that is where the rope trick comes in?) and then I pull out small generator cover or housing in the picture? Then do the bolts for the crank housing? Is there a timing involved with all this that I have to worry about.

Wouldn't it be easier to remove the block and work on it outside at this point. How hard can that be? I'll go check

2- The trick with the rope I assume is done before the head comes off. Here's the diagram of the crank case, point me in the right direction.

CLR calcium lime rust remover from Target? How about hydrochloric acid or muriatic acid used in pool treatment. Since I am dipping at 20:1
Yes to do the seals the motor must come out of ski. Starter doesn't need to come off.
The whole front of motor must be removed generator/lighting coil. and coupler from rear must come off. Yes timing is involved. You Can mark to put it back the same and be close enough if you use a very fine mark.

CLR, yes, don't know about hydrochloric or muriatic. You don't want to eat away aluminum just corrosion.

Yes the rope trick you put in through plug hole before head removal.
If you do a pressure test on motor before disassembly you may not need seals just yet. Remove carbs and block off holes with rubber plugs. Then put the manifold back on and cap the end. Then you can pump it up through one of the pulse fittings for carb. Should hold about 6/8 psi for 10/15 min.

found thread on corrosion I had with GPr from salt water and not flushing. the stuff i used had sulfuric acid but I don't know what it would do to the bore of cyl. I only did exhaust and head as I replaced cyl's.
http://www.pwcforum.com/yamaha-jetski/53202-white-corrosion-water-jacket-help.html

pressure testing how to:
http://www.greenhulk.net/forums/showthread.php?t=9408
 

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Just realized I told you wrong there is no timing involved. as the stator comes off with the cover and won't need to removed from cover. And flywheel is keyed and it's what you'll be removing. Best I can tell from your picks those are nikasil cyl's still but to be sure I need very clear pics of the top of the cyl's.(head gasket sealing area) use some fine sand paper to lightly clean surface first.
Do you have a ball hone?

Once the front cover is off you'll need to remover the flywheel. Then the coupling from rear of motor. Then remove the bolts from the base and split the case halves. If you have the Yamaha manual it's pretty detailed. Be sure to get true Yamaha seals no after market.
If you get stuck holler.

For power valves pull the cover and take the valve out and clean thourghly. Inspect the valves for any fine cracks at the base of the shaft and that it moves freely in the jug. Would suggest you get the SBT links for the valves. Be sure to use blue loc tite on all screws for power valves.
 

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Don't have a ball hone yet but will get one from Amazon any idea what size is for this one

I will sand the cylinders soon and post pictures
Thank god there's no timing.

You're talking about the crank seals to be Yamaha's right, are the SBT any good, could not locate the Yamaha ones yet

Between the 2 crank case halves is there a gasket or use gasket maker black?

I will buy the power valves gaskets and there are some seals inside too. I will look for the SBT links those go inside or outside the power valves?

Also I took apart the generator how often does it go bad and does it need rebuilding. Same with the starter
Don't bother with hone. If there nikasil you would need a diamond hone.$$$$$$.

Go to Babbittsonline for crank seals they'll be genuine Yamaha. No seal on halves. I've always used yamabond for the case halves. It's made for just that. But blk RTV would work. Just be very lite with it, don't want it squishing out all over inside into bearings.

The links for the power valve replaces the original links and keeps the pin from falling out of the top of the valve. There under the cover attached to the shaft and valve.

Genny and lightning coil rarely fail . Just clean out the cover good.
 

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I can do a diamond hone, used it before. I would feel better to have honed rather than not
So I want to hone the cyl I usually use WD40 for that always have on cars at least. But in the cyl I noticed that below the piston line there is hollow space so I just gone the area that make contact with the piston rings.


There are 3 seals one on the generator side and 2 on the flange coupling side. I found them Crowley Marine https://cart.crowleymarine.com/ for $50 shipped. The other guys charged $10 more.
93101-34001-00 / 93103-35011-00 / 93101-34002-00

I was thinking of buying the gaskets separately they're not that many that way I can buy Yamaha oem and then pistons separately

Dumb question I have, do I really need to buy new pistons, can't I just clean the old ones? Probably yes, I am just voicing my concerns out loud.

You told me where to buy the piston set set earlier trying to locate it,

Here are the pictures of the cylinder as you requested, sanded 400 then 600 first

ok. I would say that your cyl's are still original nikasil. if they were sleeved you'd see a ring about an 1/8" back from the lip of the cyl. I don't see that. how many hrs on ski? you should be using a diamond ball hone and I have yet to locate one. it would need to be 3.25 diameter. use ball hones on 2 stokes due to porting. 20 weight motor oil works better than wd40 and go easy. only want to break glaze. could also send to US CHROME to hone if need be.
I use the gaskets from SBT with no issues. may be cheaper to buy top end set and then single of others you need.
yes to new pistons the cyl's don't wear much but the piston does. that's why they use the hard chrome over aluminum. also for cooling as a steel sleeve holds heat.
get pistons, wrist pins, wrist pin bearings, and rings,
get up with Zardoz he's got somewhere he's found Wisco piston sets.

if your looking at he power valve cover on the cyl, to the right on the top edge of cyl there should be a stamped 2 digit number. what is it? it indicates your bore size. will send that as an edit to post.
 

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No the 98 is a non power valve 1200. Different Motor. Not sure pistons would interchange.

Sorry did a bit of research and wiseco doesn't make a piston for the power valve 1200 motor. ProX would be next choice. You will need to accurately know bore size. This is where the stamped number on cyl comes in that I talked about last night. will need to know.
 

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These are all the numbers I could see on the cyl
So it says 66V00 then in another picture there is an 8
________90720
________Y-3
https://www.ebay.com/itm/YAMAHA-XL-...ash=item3f807578c7:g:2XUAAOSwbopZQBnP&vxp=mtr

It's $103 per cyl for the 79.90mm bore I want something at a better price if at all possible.

So SBT and WSM are junk right?
the "8" is the stamped number I'm referring to. so that color codes your pistons Orange. that give you your piston size. Are all 3 marked 8?
I wouldn't say that sbt's top ends are junk. I've used them there ok. never used wsm before so can't say other than I know a few who have and say there ok. the two sbt top ends that I've used where complete tops cyl, pistons the works. that was a few years ago and there still running ok. I wouldn't even think about using there motors though. there junk!
 

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If it we're me I'd go with wsm kit. I would go to SBT and replace your power valves for security. Again. These motors are notorious for valve failures. They come with everything including the link to secure them. One of my 800's only has 32 hrs on it and one of the factory valves had hairline cracks that only showed up when I dye checked it.
 

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So forget the ProX, on the WSM kit on the pistons how can I tell which size to get since I have the orange pistons originally, and the bore id 79.90 give or take. Do they expand under heat, don't want them to freeze up. Read about how some pistons are cast iron and wiseko get loose because they are forged or something. The WSM are pretty straight install for standard?

OK I just called EWS Motorsports directly and bought this for $300 PayPal there was a $30 discount for buying straight and through EBay.

https://www.ebay.com/itm/272334753106?ssPageName=STRK:MESINDXX:IT&_trksid=p3984.m1436.l2649

Now I have to do the valve deal.
On the power valve I have to get all new valve kits that include the valves, should I look to see if they had a valve job already, didn't open them up yet? Shit you dyed checked it is that a required procedure to check valves?
Wow the valve kits are $99X3 just for valves?
if you called them directly and gave them your piston size and info you should be good. just be sure to check your piston to cyl clearance its shown in the page image in the above post.

let me explain. I went back and read your first post to recall info and your not being familiar with 2 strokes. Basically, with 2 stokes the location,size,and shape of the ports in the cyl control your power band. witch is the point at witch the motor develops peak power. with the power valve motors the exhaust valve is basically a gate. not really a valve as you would think of in a 4 stroke. through a servo motor the power valve is moved as the rpm increases to change the location of the power band. as the valve opens its changing the location and shape of the exhaust port. there by changing power band.

that explained, check your valves carefully. they don't have to be die checked it's just I have a large shop at my discretion, and am a machinist/mechanic by trade. there are 2 typical points of failure. either the link pin at the top falls out and down into cyl. or the blade breaks off at the stem and falls into the piston side. now,that being said. sometimes they have been known to fall through and out the exhaust without incident but that's rare.

When you open them up more then likely there will be a lot of sludge under the cover. that's typical, it's from the 2 stroke oil. look at the schematic. https://www.babbittsonline.com/oemparts/a/yam/5003a4c7f870021f60a13103/cylinder-crankcase-2 #'s 12/13. if there is a wave eater clip on the linkage you'll know. it's an after market tin clip that goes over the link to keep the pin from falling out the side of the link. if it has the SBT style linkage (#12) then maybe the valves have been replaced (sbt style have a closed end on link). you can reuse your valves if there cleaned and check out ok. but at almost 200 hrs I'd replace the valves they've been through a lot of heat cycles. SBT has the best value on valves. there a good after market valve and come with a permanent fix to the pin failure with there linkage. I realize that it's 300 bucks but it's cheap insurance and way cheaper than a new motor. this is just my .02, giving you the info to make an informed decision.
hope this helps.
 

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The parts clean up looks good.

Yes you can use copper spay. If the sealing surface is extremely pitted I recommend repairing surface with JB weld. Build it up and carefully file back down without removing surrounding aluminum.

Can repaint with regular engine paints. Doesn't have to be high temp exhaust paint.

One thing I noticed in your pics is the anode in the cyl's is pretty eaten up. You may want to replace them. That's the little piece held buy the screw in the top.
 

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As for the gaskets most you will find are already coated with an adhesive to make them bond. If there straight paper I rub in a little grease on both side to help seal and makes for easy removal later.
 
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