Super Jet 701 motor mods

Vumad

Vumad

Super Hero, with a cape!
Location
St. Pete, FL
I don't think jetmaniac rebuilds cranks. His ads for his complete motors say he uses sbt cranks.

It's important to have realistic expectations about your crank. 3-4 seasons on a sbt crank is reasonable. A hot rods crank is $600 and oem is $800, while sbt is $200. If you plan to replace a sbt crank every 2 years or 200 hours, you have to get 6 years 600 hours out of hot rods or 8 years 800 hours on an oem crank.

My 2004 needed a new crank in 2013, 9 years, (unknown hours, first owner didn't ride a lot). I got the crank after I stuck a piston, and the mechanic said the cause of the seizure was due to a case leak (leak down before tear down).

I'm hoping to get 2 years or 200 hours out of my sbt crank. I'm at 8 months 50 hours on a full limited, and depending on how things go (water ingestion, how much is wot, etc). I'll probably push it to 4 years 200 hours. Only time will tell, but I don't see how a used oem crank that came from a 10 year old ski is all that great of an option.
 
lanmine657

lanmine657

Location
fortcollins
Is your boat the SN in your avatar? If so a mod I just did to mine that made a big difference is change out the stock thru pipe to a RN pipe, 1&7/8 vs 2&3/8, rad dudes sells them cheap if you can't find a used one
 
augustaf

augustaf

Location
central florida
cranks have a finite lifespan, might as well consider them a time change item. ( quite a few years for oem). You can't tell how many hours there are on a used crank by looking at it! When they fail eventually, they'll do it like in the op's picture. 760 cranks work just fine and are lower priced than 701 types. Been using them for years in BB Superjets. Here's a suggestion: http://www.yamahasportsplaza.com/oemparts/a/yam/5003a3f3f870021f60a12cd6/crankshaft-piston
 
Sparkplug

Sparkplug

Location
Red Bluff CA
I don't view a crankshaft as a replacement item. If its in spec, or hell even close to spec, then run it. Your wasting money getting a new one. I also have gotten prob 500 hrs+ out of a stock 92 sj, that I got used with a pipe, like 3 yeas ago. And I have no worries at all about the crank going out.

If I was buying a new crankshaft, id buy from the biggest name with the most money. They are going to have the newest best equipment. That's what matters most with machining. Ask me how I know.

I do recommend checking wrist pins and bearings occasionally. Those can wreck your day.
 
Kny21

Kny21

Location
Delaware
I don't know about it not being a replacement item.... but couldn't put a number of hours on it if argued against that either.

Wrist pin bearing definitely do though. So at some interval most our engines should be broken down and that's a perfect opportunity to check everything else.

An iffy crank isn't worth it to me, if it is to someone else that's fine just hope they'd stand by that statement when it comes time to sell.

Most $ isn't always the best, especially when running the smaller engines of this sport. YMMV.
 
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