When to Rebuild Your Engine?

[brapperdoodle]

I’ve been thinking about this for a while and just wanted to start a thread and hear what folks opinions are. When do you decide to rebuild the top end on your ski? Is it a certain amount of hours? Seasons? Do you rebuild when you hit a certain low number on compression or uneven compression?

I think the crank is a bit more obvious, when you have the top end out you can check rod end thrust bearing clearance and also feel the smoothness of rotation on the entire crank… just wanting to hear some opinions on how you guys decide when it’s time to re-hone, re-ring, or re-build the top end or entire engine. When do you decide to put new o-rings in a girdled head?

 

[WFO Speedracer]

It depends on the engine of course , on a semi- stock 701 rebuild it when you see a drop in compression, if it's a stroker those have rebuild times that are usually set by the builder usually once a year on the top end and every two years they get a complete overhaul.

 

[Quinc]

I am doing a new set of pistons, rings, and bearings after 8ish years on my Reaper. After having a banshee brand new oem piston crack in half on me I figure its better to be safe.

 

[Sparkplug]

Depends. If it's a 701. When it goes boom

If it's a dasa or high end engine that If you put a rod through it, will be thousands of dollars in the trash can? Specified interval. Top end tear down for wrist pins every 50 or so hours. Crank check on v blocks every 100 or so hours. Don't rebuild anything that is within spec.

Taking the engine out and putting it back in nicely, takes more time than tearing down and rebuilding the engine.

 

[kevbo]

You want to schedule overhauls right before something breaks that destroys the whole engine. That can be difficult to figure. Completely stock engines usually last a long time. Corrosion, dirty carbs, or an oiling failure is the killer. Everything performance enthusiast do to their engines will shorten its life. Wide ports will require piston/ring replacement more often depending on how wide they are. A rev limit delete is hard on everything. High compression and timing advance is extremely hard on parts. In extreme cases it can burn a piston in less than a minute.

 

[Myself]

What I've seen through the years on stock (ish) 2 strokes.....IF, they've been winterized (stored) properly, AND, never deprived of oil...
top ends......typically 150-200 hours run time.
cranks....300-400 hours run time.
There are exceptions but of the couple hundred I've rebuilt for customers that actually have hour gauges, this seems to be the sweet spot.

 

[bored&stroked]

I rebuild when they stop working.

 

[fastgtfairlane]

im planning to do a "maintenance" teardown and inspection on my 735 after 3 years and probably 75+ hours. mainly to inspect the crank. still has same cranking compression psi it did after break in. just seen too many failed cranks after as hard as we ride. im also pushing 195 psi. i think teardown is obviously relative to the kind of riding and engine setup youre running. high compression with lots of timing is going to wear out much quicker in general.

 

[Vumad]

There's an inspection window on the side of the crank case that lets you know when a rod has gone bad.

In all seriousness, ask yourself if you would replace the pistons and crank on a 10 year old yamaha 2-stroke outboard with 500 hours on it. Stock - limited spec boats are probably fine until they have low compression or are making a crank noise. You can replace anything preventatively but I don't see the reason to spend the money on a stock - limited spec boat that's not being used for competition. Put a hardline Tach on it which will track your hours. The actual run time in hours on our motors is a lot less than we think it is. Also I am sure a lot of us think we ride a lot harder than we actually do. People run outboards at WOT for hours on fishing trips. We're tuckered out long before that. A lot of surf boats probably spend very little time off idle. blip, blip, blip, brraappp, blip blip... probably don't even reach wot.

 

[Myself]

Tech tip.......check color of spark plugs regularly. If you know what they're SUPPOSED to look like, it's a lot easier to spot potential problems BEFORE you window the case!

 

[fastgtfairlane]

Tech tip.......check color of spark plugs regularly. If you know what they're SUPPOSED to look like, it's a lot easier to spot potential problems BEFORE you window the case!

With at least a 10x magnifying glass. Youll really be able to see any issues with the plugs that the naked eye can't detect. That's how I found a bad crank in an old 550 Reed engine I had. There were small pieces of metal on the plugs inside where the porcelain is. Would've never seen it without the magnifying glass

 

[bird]

I kept track of how many hours by the amount of oil I was using. Being conservative I got 1000+ hours out of my SXR 800 engine. Being realistic I got more like 1200 before it let go. There were signs, it had piston slap from the sleeve skirts bending. Guess that's a common problem with these Kawasakis engines...but at 1000 hours anything can happen. It had a high compression head, timer jump, and a speedy sprocket flywheel for mods. Added the wet pipe in 2019 after I rebuilt it completely. Now I don't ride as much as I used to, still get out weekly, just not every every day.

My first three years I had my SXR, I put 14-15 gallons of Amsoil in it. Then I dropped down to about 10-12 gallons a year until it let go on Halloween 2018.


Run a good oil, check compression each season, and ride that sucka! Stock engines will go a long time.

 

[WFO Speedracer]

If you don't pull it down every few years and do at least a visual inspection and measurements you are literally rolling the dice, these standups take on a lot of water and a lot of it goes through the engines, the same engine in a sitdown ski will last much longer with a lot less maintaince.

 

[Myself]

I kept track of how many hours by the amount of oil I was using. Being conservative I got 1000+ hours out of my SXR 800 engine. Being realistic I got more like 1200 before it let go. There were signs, it had piston slap from the sleeve skirts bending. Guess that's a common problem with these Kawasakis engines...but at 1000 hours anything can happen. It had a high compression head, timer jump, and a speedy sprocket flywheel for mods. Added the wet pipe in 2019 after I rebuilt it completely. Now I don't ride as much as I used to, still get out weekly, just not every every day.

My first three years I had my SXR, I put 14-15 gallons of Amsoil in it. Then I dropped down to about 10-12 gallons a year until it let go on Halloween 2018.


Run a good oil, check compression each season, and ride that sucka! Stock engines will go a long time.

With that amount of hours the piston slap will be common on ANY 2 stroke. It's not just a Kawi thing. The quality oil you ran had a big part in that. I have 2 different customers with 951di Seadoos that have 500ish hours and never been apart. That engine is well known to start rattling at around 150 hours. Both those customers maintain properly and run high quality synthetic oil. I also put a cdi in A Waveventure 1100 2 years ago that had over 900 hours on it then.......customer has always run synthetic Yamalube. I winterized for them this year and the gauge is inop but it's still running and has around 115psi on all 3. So, there's always exceptions.

 

[WFO Speedracer]

The Yamaha and Kawi sitdowns overoil the engine , this has a lot to do with the longevity compared to premixed engines used in standups , not great for spark plug life but as long as you have good oil lines they go forever.

 

[fastgtfairlane]

The Yamaha and Kawi sitdowns overoil the engine , this has a lot to do with the longevity compared to premixed engines used in standups , not great for spark plug life but as long as you have good oil lines they go forever.

I run my skis at about 34-36 to one oil ratio using pennzoil semi synthetic oil for extra protection against moisture. Cheap insurance in my opinion

 

[WFO Speedracer]

I run my skis at about 34-36 to one oil ratio using pennzoil semi synthetic oil for extra protection against moisture. Cheap insurance in my opinion

Yep I always run everything at 40:1 more oil make more power to a certain extent.

 

[JC-SuperJet]

 

[WFO Speedracer]

View attachment 444101

All that but you didn't post it, fail fail fail fail !

 

[bird]

I run my skis at about 34-36 to one oil ratio using pennzoil semi synthetic oil for extra protection against moisture. Cheap insurance in my opinion

With that amount of hours the piston slap will be common on ANY 2 stroke. It's not just a Kawi thing. The quality oil you ran had a big part in that. I have 2 different customers with 951di Seadoos that have 500ish hours and never been apart. That engine is well known to start rattling at around 150 hours. Both those customers maintain properly and run high quality synthetic oil. I also put a cdi in A Waveventure 1100 2 years ago that had over 900 hours on it then.......customer has always run synthetic Yamalube. I winterized for them this year and the gauge is inop but it's still running and has around 115psi on all 3. So, there's always exceptions.

Synthetic Oil is not 100% Synthetic oil. Dominator is 100% Synthetic. My crank bearings were all still smooth and neither piston had scuffs on them.