Super Jet Is this what they call pitting?What next

[munki63]

Don't bother with checking it, your lower rod bearings are toasted and SBT cranks are 200 bucks.

I just got off the phone with x-metal, Im upgrading to a 771 and I was going to send my crank for them to look at but if SBT @ 200 It would be smarter to just buy one of there cranks, but I thought those cranks were crap...or was I misinformed...

 

[#ZERO]

I just got off the phone with x-metal, Im upgrading to a 771 and I was going to send my crank for them to look at but if SBT @ 200 It would be smarter to just buy one of there cranks, but I thought those cranks were crap...or was I misinformed...

I've yet to have any problems with them but did have one with a Hot Rods crank that was more than twice the price.

 

[Matt_E]

I just got off the phone with x-metal, Im upgrading to a 771 and I was going to send my crank for them to look at but if SBT @ 200 It would be smarter to just buy one of there cranks, but I thought those cranks were crap...or was I misinformed...

You can get your current crank rebuilt to OEM specs, trued, welded, for about $500.
I would not stick an SBT crank in a spendy big bore engine.

 

[munki63]

Brian sells them for 650 new....is there any chance that my crank is ok, or is it pretty much F***ed

 

[Matt_E]

Brian sells them for 650 new....is there any chance that my crank is ok, or is it pretty much F***ed

To be frank, you'd be a foolish fool for even thinking about using that crank in your new big bore.
It isn't just about the potential damage that broken sleeve caused.
The crank has a lot of hours on it, and a crank doesn't last indefinitely.
And when it does fail, it can take out your fancy new ported cases and cylinder, possibly the starter, reeds, and even the intake manifold.

 

[munki63]

Good point Matt, next question why did this happen? I really don't want it to happen again!!!

 

[Matt_E]

How many hours did you have on that bore?
If it was relatively new, then improperly chamfered ports could have done that (more likely to stock or break a ring, though)
Really, it's just one of those things that happen, given enough time.

 

[munki63]

The top end was redone a year and a half ago (5 months of riding)... So IMO not very much time at all
Just new pistons(82mm), they were stock sleeves

 

[WAB]

I would not even want to pay shipping to have that crank 'inspected'. Its got metal in it for sure, and possibly pressed into the bearings.

 

[munki63]

I would not even want to pay shipping to have that crank 'inspected'. Its got metal in it for sure, and possibly pressed into the bearings.

Ya, your right Im not going to bother getting the crank inspected, here is a picture of the cases after I got them apart

Looks worse then it actually is

 

[nick chastain]

throw it on cragslist for cheep... wait better not if i see it ill buy it

 

[munki63]

Ill sell you the pistons and domes if you want

 

[chriselmore_1]

"get pitted... So pitted...

 

[munki63]

Wapac!

 

[MileHighJSC]

When the intake port looks like yours, 99% of the time a small fragment from your crank (most likely a tiny piece of lower rod bearing cage) got "chopped" by your piston as it entered the combustion chamber, breaking a chunk out of your sleeve.

 

[waxhead]

What bore size were you on
I have seen this when people go to 85mm on the stock 61x sleeves

 

[munki63]

I don't remember, 81.5 or 82... I had a little more play in the rod on that side so I'm guessing a ring might have caught? If anybody wants the other piston it's pretty much new, only had 1 1/2 short Canadian seasons on it lol

 

[djkorn1]

ports not chamfered? Did you snag a ring on the port?

 

[munki63]

I must have, the crank seems fine so nothing blew apart off the crank, reeds looked almost new

 

[MileHighJSC]

Ran it for a 1 and 1/2 seasons with unchamfered port than snaged a ring, unlikley. Cranks can seem ok, that aren't. are all the reed peddle screws in place? Are all the butterfly screws in place? What kind of intake screen are you running? Could a small debris bouncing around your engine compartment get down the carb? Was the spark plug fully intact ? When your motor goes down make sure to clean the whole exhaust tract out, header, pipe, water box, exit pipe. It is possible for water to carry debris back to the combustion chamber.