Modded 701 reliability

I’ve been thinking about getting a modded superjet (engine mods include factory b pipe, girdled head, and ported cylinders) and was wondering how reliable it would be. I ride jet skis hard and 6/7 days a week in the summer so I really need something that I can ride like how I do lol. Will a motor like this be fine or should I stay stock? Thanks!
 
Mine just cracked the skirt off the front piston, it had the same stuff done to it, I bought it with good compression this spring and probably only put 10 hours on it, I just swapped it to another hull and looked at the pistons through the exhaust port when I did that, they looked fine, that was like 2 running hours ago, front piston cracked right in half, rear piston was halfway cracked. So my advice would be even if it shows good compression, it may be prudent to pull the cylinders and mic the pistons and bore to make sure they’re not out of spec and you end up doing a complete rebuild instead of just a top end. Although, atleast in the dirtbike world, a lot of people will put a top end in any two stroke they buy first thing so they know how many hours are on it. My stock superjets give me just as much trouble as this one however none of them have blown up yet, also with unknown hours.
 
In general I would say that a modded 701 62t is almost every bit as reliable as a stock engine. Obviously a modded engine is expected to wear out much sooner than say 20 years of service but 6-10 years should be achievable. It also depends on how the ports were done - top end porting? freeride porting? polished only stock porting? and of course what your definition of riding hard is. My opinion of riding hard is not letting off the throttle for more than a minute at a time and then back on to wide open again. But that is what racing is all about. Freeride guys are on off multiple times a minute and being driven hard for us is the big air bad landings or flat bottoming on a landing. Also the porting if it was done by templates, it would be important to know which templates. Yamanube templates offer a very reliable design whereas the RaceLogic templates were known for snagging rings. I know because I tore a piston crown off due to a snagged ring 2 years ago. After reporting using Yamanube templates and a complete top end, my ski has been running strong. Also it depends on how it was ridden prior to your getting it. If it has seen a lot of water ingestion that will shorten the engine life considerably. If you were to take a stock engine and modify it well either yourself or have a reputable builder do it for you, then you shouldn't have any worries about having a 1 season engine life span only, it should last you for a good few years at least.
 

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My first standup was a 91 SN with a ported 701 and Coffman pipe. I lived on a lake, rode daily and got 7 years out of it. I finally broke a reed petal and lost it in the engine, prompting a rebuild.

Yamaha has very simple but durable engines. The same crank was used in the 650 through 760 platforms, (some minor differences), and is now being used in SS900 cc setups that still last a few years with good maintenance.

Use good oil and keep the water out and I don't see why a ported and piped 701 wouldn't last just as long as a bone stock motor. Maintenance will be key regardless of the motor.
 
i'd be willing to bet those were WSM or some other junk new pistons that failed.
I just tore apart a motor that had very low hours on the top end, had WSM pistons and also had cracked skirts.
good thing I tore it apart.
when buying used, its always a crap shoot on what you get or how long it lasts
 
I will when I put the new motor together, luckily I have a spare ported 61x motor that came with the ski. I doubt the squish was too tight though it only read 165psi on a good gauge when it was running good, never noticed any detonation.

I just checked, (ski only blew up on saturday and I was still racing sunday) and they were wsm pistons! lol. I dont think I would write them off just from this, I have no idea how many hours were on the motor or how loose it could have been set up to begin with. Although in the future I may go wiseco with the hope that a forged piston will loose compression before cracking the skirt. The motor I'm about to swap in looks like it has no time on the top end, and they are oem ART pistons so I'll run that for a while.

Does anyone here follow a rebuild schedule for top ends? I looked for a bit for a TBO on a 701 and found people going 400+ hours on a top end no one I saw said they just do a top end every X hours like most dirtbike people will. At least with a 701 you don't risk having to get your cylinder replated I guess.
 
I run ProX in my dirtbike, I think its better for the plated cylinder, In an iron sleeve I think the stronger forged piston may be beneficial despite its higher CTE. I think were getting a bit off topic now though. For the original question I think all I meant to say is you never really know what your getting used even if it looks good. I assume most people agree that a piped, ported, high compression 701 is still very reliable if its in good shape or freshly rebuilt to begin with.
 
i'd be willing to bet those were WSM or some other junk new pistons that failed.
I just tore apart a motor that had very low hours on the top end, had WSM pistons and also had cracked skirts.
good thing I tore it apart.
when buying used, its always a crap shoot on what you get or how long it lasts

Just to not totally blame the wsm pistons, I did measure that blown up motor, the non cracked piston was 3.187" like its supposed to be. The cylinder clearance was .010" at the tightest, .017" at the loosest. The out of round was most likely from the piston slapping around, but there's no way it wore .005"-.006" in the other direction, there is still some faint crosshatch in that direction for confirmation. So this thing was way too loose to begin with. Not sure if wsm pistons are junk or not, but it wasn't their fault this time.
 

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An of course different mods can add a bit more risk of bad things happening. Advanced timing for example. Bang for the buck/risk versus reward, I'll keep my timing stock, thank you very much.
 

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How in the world your riding a stock setup and enjoying it is beyond me. Mod that bad boy and start to really enjoy riding. If your really worried skip the porting, otherwise a head and pipe combo setup properly should last years.
 
Well I found this superjet too but it seems like its been raced. Is racing your ski really that bad for the motor. As you can see in the pics it has a ride plate, long steering nozzle, reversed trim kit, and will go 60 mph. Is this a pass or is it fine?
 

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That’s not a race ski, but looks like a well built freeride ski. Lots of good mods on that one, decent price imo. Has everything you’d likely want and motor setup by jetmaniac, wouldn’t hesitate to pick that up.
 
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