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Discussion Starter #1
Good day,

just acquired new to me 05 gp800r and 05 xlt1200 from a friend who wanted them gone. both with bad top ends. My first two PWC ever, and I'm pushing 50.

I'm pretty handy, but no mechanic. Disassembly went very well, straightforward. found problems with low compression.

maybe this topic is beat to death, but I'm planning on converting to premix. My general question is what to do at the carbs when they appear connected by some two cycle oil lines? Is that a pump of some kind on the forward carb? Do i need to do anything with them other than pump block off and little caps over barbs where lines were? Just leave the throttle cable for the injection disconnected? The oil injection only went to fuel and has nothing to do with crankcase?

Also, when I reassemble top end with new gaskets etc should i use copper spray a gasket on surfaces? or are the gaskets in the kit sufficient as they are?

Thank you all, this has been a handy forum.
 

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Fadagger, welcome to the forum.
Don't feel bad about age, bought my first after 50 and now own 4. 2 of them GP800r's

The 800 is a strong little motor once you resolve it's miner problems. Witch I'll fill in as I go. Bare with me.
For the head gasket yes you can, and I recommend the copper coat spray sealant on it. For a little more performance you can even remove the rivets that hold the layers together and use just one layer instead of both. this will bump up the compression a tad. Basically the same as taking .013 of the head.

What appears on top of the fist carb to be a pump is actually an accelerater pump for fuel, you want to keep that in tact.
The weak link in the oil system is the hoses.
The oil sys itself is pretty much bullet proof and I suggest leaving it intact as well. It's a variable ratio pump delivering 200/1 at idle up to 30/1 at wide open. This saves oil and fouled plugs. You here of people having problems, but it's because they aren't maintained. The hoses need to be replaced regularly and attached firmly. The hoses for the oil come directly up from the pump on the front of the motor to the top of the carb out by the air box. Tygon tubing from SBT works well for replacement hose. I secure them using wire ties and a tie gun (see pic). The tie gun can be purchased at Lowe's or an electrical supply house. You can also use otiker clamps. Pic for reference. Can order all in size needed. You want to leave plenty of slack in the tubing to allow for shrinkage as it ages. Replace at first sign of getting stiff/hard.
The power valves on these motors are there other weak link. You want to either install wave eater clips or new links to encapsulate the pivot pin to stop it from falling out.
If you don't have a manual for your skis I suggest getting them. They will be a big help. Look under the general pwc tab, Rodsatheart has a link to downloadable manuals. Hard copies can be found on eBay and around the net.

Hope this helps feel free to contact me or post more questions.
Dave,
Pic is my 02 GPr. Loaded for vac last summer.

P.S. forgot, factory parts are available at Babbittsonline or partzilla. after market parts at sbt, wsm performance parts
 

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Discussion Starter #3
Fadagger, welcome to the forum.
Don't feel bad about age, bought my first after 50 and now own 4. 2 of them GP800r's

The 800 is a strong little motor once you resolve it's miner problems. Witch I'll fill in as I go. Bare with me.
For the head gasket yes you can, and I recommend the copper coat spray sealant on it. For a little more performance you can even remove the rivets that hold the layers together and use just one layer instead of both. this will bump up the compression a tad. Basically the same as taking .013 of the head.

What appears on top of the fist carb to be a pump is actually an accelerater pump for fuel, you want to keep that in tact.
The weak link in the oil system is the hoses.
The oil sys itself is pretty much bullet proof and I suggest leaving it intact as well. It's a variable ratio pump delivering 200/1 at idle up to 30/1 at wide open. This saves oil and fouled plugs. You here of people having problems, but it's because they aren't maintained. The hoses need to be replaced regularly and attached firmly. The hoses for the oil come directly up from the pump on the front of the motor to the top of the carb out by the air box. Tygon tubing from SBT works well for replacement hose. I secure them using wire ties and a tie gun (see pic). The tie gun can be purchased at Lowe's or an electrical supply house. You can also use otiker clamps. Pic for reference. Can order all in size needed. You want to leave plenty of slack in the tubing to allow for shrinkage as it ages. Replace at first sign of getting stiff/hard.
The power valves on these motors are there other weak link. You want to either install wave eater clips or new links to encapsulate the pivot pin to stop it from falling out.
If you don't have a manual for your skis I suggest getting them. They will be a big help. Look under the general pwc tab, Rodsatheart has a link to downloadable manuals. Hard copies can be found on eBay and around the net.

Hope this helps feel free to contact me or post more questions.
Dave,
Pic is my 02 GPr. Loaded for vac last summer.

P.S. forgot, factory parts are available at Babbittsonline or partzilla. after market parts at sbt, wsm performance parts

Thank you for your prompt resp
 

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Learning your forum, thanks again for the response

After disassembling power valves from heads, power valve wedge part was completely missing in real cyl, stem was still in head with pin. wedge was still in frony cyl but broken off of stem and gunked in place. Getting new cylinders anyhow, but any cause? and where did the broken piece of PV go? don't see it in the crankcase.

The PDF file of service manual is gonna help a lot.

One last thing (until next time), the accelerator pump for fuel mounted to the forward carb, does that get rebuilt with the carb? or need to be?

Thanks,

Tom
 

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Hi, Tom,
How many hours on ski? Witch ski?

The blade of the power valve broke up and went out the exhaust. It's either stuck in the stinger part above the carbs or in the water box. in the compartment under the battery box. It's the large aluminum can on the left rear corner. The replacement valves from SBT have held up well for me and they come with the retaining link. The valves have a tendency to crack if they get over heated. The factory valves weren't that great at holding up.
Are your current cyl's sleeved or nikasil coated? Post a few pics if possible.

The diaphragm for the accelerater pump is replaced separately. It doesn't come in the kits. It can be purchased at SBT. Look in fuel tab for your yr, make, model. I'd replace when you do carbs. Be sure to use the genuine Mykuni kits when you do the carbs. After market kits can cause problems. The needle and seat are purchased separate also. If they've not been changed they should be 1.2mm. I would suggest reusing the original spring for the needle. Or you'll have to test your pop off pressures.
 

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Discussion Starter #6
18446
18447


These are pics of the carbs and of the oil injection pump on the GP800R

After reading several opinions, I'm going to keep the injection. Is there a hose kit to be ordered? The stainless bands on the tee and the white things on the injection lines (Check valve? Filter?) have me thinking they should come preassembled as a yamaha part, or do they need remade by me? Not sure how to redo these lines without improvising a barbed tee and oetiker clamps or other clamps.

Fuel lines seem supple, but should be replaced?

I'm not sure how to check hours without trying to start the craft. I would speculate over 200, but thats a guess.

Any way to test oil pump with it off? Looked in pdf manual, didn't see direct instructions for a lot of this.

Current heads do not appear sleeved, they are scored moderately. Not severely, but enough if I had to guess. Shipping them to SBT with cylinder exchange for a return of sleeved heads in a total top end kit.

Thanks again for your help. I'm in Central Ohio BTW. These will run in upstate MI fresh water only. Many possible riders adding fuel/oil etc. Another reason not to do premix.
 

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Tom,
Sorry so long to reply, been writing this on and off all day.
Yamaha used very high quality fuel line. I'd leave it be. Unless you find a problem, such as a cut or to short.

The T line off your oil pump is fine, short of getting rid of the stainless wrap clamps and either using wire ties and gun or otiker clamps. Thats just an oil return line to the tank for any excess oil. The hoses will pull off the T then remove the clamp replace the hose and reattach the line with wire ties. That stainless band is just a small spring clamp.

The little white pieces are check valves. They have an arrow on them just be sure to get them the right way around. No hose kits, have make your own. For oil line I use tygon tubing from SBT (1/8"). Leave some slack to allow for shrinkage as it ages. Becarfull with the check valves there expensive at $30ea.
I use wire ties to hold my lines and they work fine. You just have to use the tie gun so there real tight. For a tighter better seal you can use the ties from "watcon" they actually have a rounded end to help seal around small line. (See pic1)
If you carefully cut the ties on your fuel or oil line with wire cutters you can redo them to tighten up the seal on them without shortening the length.
If your cyl's are not sleeved you can have them replated in nikasil. U.S.Chrome will replate them. Filling in the scratches. It's a bit more expensive than SBT kit though. The cyl's are originally hard chrome plated aluminum. This allows them run cooler and last a bit longer than a sleeve. Just sharing info.

The pump can be tested but it's a pain. Have to turn it at a particular RPM and measure output. Not really nessesary. I have 2 vxr pro Yamaha's that are 25+ yrs old still on there original pumps probably a couple 1000 hrs on them. (Note be sure to set cable timing on the pump) marks on pump cam/body most align. This sets ratio to throttle (pic2). Very important to prime the system after hose replacement. Open the bleed screw on pump till oil appears solid. Then using a drill and 1/4" drive six point socket turn the pump counter clockwise till oil reaches both carbs.
 

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Not sure if this helps, but my ski manual suggests after rebuild to run oil injection and also premix 1st tankful at 50:1 for breakin. I have a 93 tiger daytona, never needed to rebuild yet so i may be way off course.
 

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Grease monkey,
Yes, your correct. You want to mix 5 or 6 gallons at 50/1 plus oil injection. Also want to go easy on it for that tank. The second reg full tank a bit harder but keep full throttle runs to bare minimum to none. Varying rpm, no constant speed.
 

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Discussion Starter #10
All very helpful information. I'm rather meticulous in nature, and want all to be just so.

Grease monkey, thanks for the additional advice, I'll make sure the break in procedure happens as laid out.

When reassembly is complete I'll keep you posted. Thanks again Dave

BTW the XLT1200 looks more of a PITA to work on, gonna give that some thought about having it done professionally.

Have a great day.

Tom
 

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Discussion Starter #11
Finally finished assembly today of GP800R

rebuilt carbs & accelerator pump with Mikuni kits,

New gaskets all around

New cylinder heads and pistons (125 psi each compression after install)

New oil injection lines throughout

Premixed first tank of fuel

Started right up, ran smoothly. Don't know when I'll have a chance to get it on the water.

Thank you for all your help with this project.

Final diagnosis,

Ski has 184 hours on it, both pistons badly scored. When I drained the premix tank it was not thick like oil, and reeked of gasoline. Many people ride this ski and someone filled oil reservoir with gasoline not knowing gas tank was in front. Guess I'll have to label fills more clearly.

I would guess i have 15 to 20 hours in entire project and @$800 in parts and supplies. Found the process very enjoyable and educational.

Considering trying XLT1200 . But then again, might not.

Thanks again Dave,

Stay safe and healthy.

Tom
 

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Tom,
Glad to here all turned out well and running good. Hope you get to enjoy soon on the water. When you tear one down and put your heart and soul into building it back up. you gain a whole new respect for them.
Hope all is well with you, and yours, stay safe.
Dave,
 

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Discussion Starter #13
This is an old thread I know, buuuuut. Reading the other threads about yamaha 800's, and your description about cleaning out the crankcase...

This is one of the pistons from the gp800r I removed.

The other one is similar.

I know I have this waverunner already assembled and running, but looking back, do you think there are bits of metal possibly in the crank case that will cause me needle bearing problems? There was maybe half inch of two stroke oil in the crankcase, enough I couldn't see the bottom. It never occurred to me to check for bits cuz everything looked so clean, i did not remove the oil. You can kinda see a bit of the crank in an above picture.

my question is, did the scrapings from the piston and cylinder bore go out the exhaust, or do I need to pull this engine back apart to clean out the crankcase? I'd rather not, but what's a few hours if it saves a crankshaft?

Tom





pis1.jpg
 

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Tom,
Man I am sorry. Somehow I missed getting that part to you.
I don't know how. I went back through the whole thread and never mentioned it. There will be lots of very fine aluminum shavings in the base
In your case now. I'd pull the exhaust, head, and both cyl's, & Pistons. I would do all this in the ski don't pull the motor.
Then fill the base up. holding the rods turn the crank then suck it out with a turkey baster. Do it over till you don't see flakes in the fuel. Then oil it up good. Pour oil into the crank holes on either side of the rod in the base. The bottom rod end. Then assemble again. Be sure to put Pistons back in the same cyl's.
P.M. sent to you
 
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