1997 GTX off season rebuild start.

[AquaEye]

This thread is born out of the post "97 GTX. Normal engine noise?" posted June 24, 2025.
Have hoist, low profile shop cart, sling arrives next week. Pull engine & then to the 1st order of business, pull oil pump & bench test using factory procedure for validation @ 1,500 rpm. Marks will be aligned to simulated idle setting event so as to confirm .017-.087 ml @ 1,500 rpm for 30 seconds out of one port only or 1.74 ml for both ports using lab scales, 3ml lab syringe as tools. Question, what is the amount of oil dispensed @ w-o? Cant find that anywhere here, YT or factory manual.
Imo, idle oil amount to me is more important, right(?) I want to keep the oil pump. Been pre-mixing for decades & I'm tired of it & besides, I trust Mikuni.
Next, pulling cylinders/head. Using dial bore gauge, two bloodshot eyes, some lessons learned from rebuilding 2 stroke Kawi's & Yami's & with only 40+ hours on the engine & some clueless do-da luck, I might squeak by with just honing...or not. Piston>pin>bearing, very close inspection.
Time frame for this initial start/determination?
No hurry, still have plenty on my plate & a life to live for the rest of this season but I should have results on the oil pump bench test in a couple of weeks.
Will post with a few pics & maybe a video or two @ that time.
FYI: This is my 1st rotary ROTAX build & thou confidence is not high (out of my element, sort of ), you guys have been pointing me in the right direction. Many thanks now & more to come.

 

[mikidymac]

Just run the oil pump at close to 1500 rpm and make sure oil is coming out of it.
I honestly don't worry about them. In 35 years of working on these and tens of thousands of threads here I think I only ever heard of 1, that is one, ever failing.

 

[AquaEye]

Just run the oil pump at close to 1500 rpm and make sure oil is coming out of it.
I honestly don't worry about them. In 35 years of working on these and tens of thousands of threads here I think I only ever heard of 1, that is one, ever failing.

I have very good fortune with Mikuni products across the board but still can't ignore my nature to always dive deeper, to validate. It's who I am.

 

[AquaEye]

I have very good fortune with Mikuni products across the board but still can't ignore my nature to always dive deeper, to validate. It's who I am.

I would like to pick the brains of a few experienced operators of the 787. Focusing on the oil pump relationships here.
In a "perfect world" of engine integrity & comparing the PTO & MAG components so as to maybe reveal a trend(?).
*Which of the two spark plug always seem "sootier" or seem to be discernably different from the other?
*Same question of the rave valves?
*Which of the two cylinders always seem to have the higher compression?
*Has anybody disassembled an oil pump? Focusing on the separation distance of the two ports within the pump. (a pic would be nice).

 

[mikidymac]

They should be the same in compression and cleanliness.
It is a dual carb engine so you can tune them both to be the same. Oil pump provides the same oil to each cylinder.

 

[AquaEye]

They should be the same in compression and cleanliness.
It is a dual carb engine so you can tune them both to be the same. Oil pump provides the same oil to each cylinder.

A few other " experienced operators of the 787" from other forums are noting subtle differences in that "perfect world" that's pointing to a trend, a commonality. Apparently, I'm not the only one that drills deeper & that's refreshing.
Have yet to dissect an oil pump for the particulars but I'm patient.
Yep, learning as I go forward.

 

[etemplet]

Build it and run it. There is no carb tuning just proper set up and testing using the right parts (Read the Carb Thread and follow it). I've have personally had the oil lines I purchased fall to pieces in a matter of a couple of months, vendors very optimistic as to the quality of the crap they sell... it was suppose to be Tygon and it was an oil line that failed. ( I got lucky and it only destroyed the piston on the air compressor. I don't know what everyone is using today but now I cut a piece of the line I'm using, drop it in laquer thinner for 15 minutes. I also test it by lighting it on fire to see what happens. The junk usually falls apart after 5 minutes in laquer thinner.

I prime the oil pump using a drill motor in reverse. Check, check, check for leaks on the oil system, especially the oil tank at the seam. These skis are sneaky. Good Luck !!

 

[burtshaver2021]

Build it and run it. There is no carb tuning just proper set up and testing using the right parts (Read the Carb Thread and follow it). I've have personally had the oil lines I purchased fall to pieces in a matter of a couple of months, vendors very optimistic as to the quality of the crap they sell... it was suppose to be Tygon and it was an oil line that failed. ( I got lucky and it only destroyed the piston on the air compressor. I don't know what everyone is using today but now I cut a piece of the line I'm using, drop it in laquer thinner for 15 minutes. I also test it by lighting it on fire to see what happens. The junk usually falls apart after 5 minutes in laquer thinner.

I prime the oil pump using a drill motor in reverse. Check, check, check for leaks on the oil system, especially the oil tank at the seam. These skis are sneaky. Good Luck !!

Hi @etemplet , I use the the OEM line from BRP, it’s clear so you can watch them fill up, you know they are exactly the right size which is super tight by the way and the quality should be good enough to last 20 years. They come in 1500 mm lengths so enough to do 2 to 4 machines depending on which machines. If you need a part number let me know, I have all my receipts in a file so easy to find.

 

[Grim]

Burt send that part number.

 

[burtshaver2021]

Burt send that part number.

The part number I have on my last invoice is 219704404, that number had superseded roughly 6 part numbers. Next time I order, I think I’m going to order 4 packages of it, I’m going to start stock piling some parts just in case some of them start getting discontinued. After all, my 95XP is 30 years old now.

 

[etemplet]

The part number I have on my last invoice is 219704404, that number had superseded roughly 6 part numbers. Next time I order, I think I’m going to order 4 packages of it, I’m going to start stock piling some parts just in case some of them start getting discontinued. After all, my 95XP is 30 years old now.

I got an azzload of parts over here. LOL I used to order 5 of everything for spares. Yea I agree on the OEM hoses they lasted a long long time.

 

[burtshaver2021]

I got an azzload of parts over here. LOL I used to order 5 of everything for spares. Yea I agree on the OEM hoses they lasted a long long time.

For me, I will need something, but to get the free shipping have to order 99.00 or more so I always pick up a few extra parts, I worry that someday these parts may not be as readily available. Right now it seems that some of the young guys are into these 2 strokes but I wonder what it will be like in 10 years from now? Maybe by that time the sparks will be old enough and cheap enough that maybe some will go that way?

 

[mikidymac]

For me, I will need something, but to get the free shipping have to order 99.00 or more so I always pick up a few extra parts, I worry that someday these parts may not be as readily available. Right now it seems that some of the young guys are into these 2 strokes but I wonder what it will be like in 10 years from now? Maybe by that time the sparks will be old enough and cheap enough that maybe some will go that way?

Seadoo is discontinuing parts on these all the time, stock up while you can.

 

[Grim]

I'm more worried the govt will outlaw our 2 smokes....its already started in California!

 

[etemplet]

Sometimes it is cheaper to buy and old ski. LOL That's why I have so many in the yard. LOL

 

[mikidymac]

I'm more worried the govt will outlaw our 2 smokes....its already started in California!

Without getting too off topic.
It was a concern years ago, like 20. I'm not worried about it and live in California. The only banned them on a couple lakes and no new talk about it. I think we are safe until we run out of repair parts.