How to repair a cranckshaft rod

S

Seb62T

Hi,
This is my 8 hours new RIVA Welded cranckshaft...
rod.JPG


My jet drunk some water after a pretty fontain...
I am now the winner with this 760 engine.

I don't know what to do. Is there a way to change this rod (welded cranck)?
I thought : cut the two rods of this cranck and buit a two parts rod like on car engines and most 4 stroke engines ??

Why don't 2 stroke cranckshafts don't use this kind of rods ??
180px-Piston.jpg

I'm quite disgusted to spend 580 more $.

The lesson : keep these good 38's with this wonderfull OEM airbox if you don't want to swallow water !! I was using cutted 650 OEM aiboxes.

I will sacrifice some mid / top end by returning to the 38's... But at least, I won't waste bucks anymore (I hope ;)...)
 
superramjet

superramjet

Location
Hutchinson, Kansas
norcal ex said:
your joking right? once metal bends it looses its strength.... you can have the rod replaced for about 250...
Click to expand...

it wont bend again unless more water enters. I wouldn't do it on a high dollar stroker motor, aftermarket cylinder, etc. but if funds are limited and you want to get back on the water, i wouldn't hesitate. Say it does bend again , it doesnt really hurt anything internally, not a big risk and you can get back on the water for $50. I used to not believe it either but i know of a 3 cylinder thats been fixed that way and running for a couple of years now
 
Last edited:
S

Seb62T

superramjet said:
it wont bend again unless more water enters. I wouldn't do it on a high dollar stroker motor, aftermarket cylinder, etc. but if funds are limited and you want to get back on the water, i wouldn't hesitate. Say it does bend again , it doesnt really hurt anything internally, not a big risk and you can get back on the water for $50. I used to not believe it either but i know of a 3 cylinder thats been fixed that way and running for a couple of years now
Click to expand...

Ye but here it's highly bended... The risk is a connecting rod rupture. It could break my cases... I am using a ADA head 38cc domes with 760 cylinder.
If the connecting rod is not correctly aligned, i'll blow my cylinder and my pistons. I don't want to take the risk to break more parts.
I'll see how much is cost for a core exchenge in france.
I think it will be OK for 300€=390$
 
Speedfreak

Speedfreak

Location
So. IL
superramjet said:
hammer it straight, or you can have a machine shop press it straight, bolt it up in your cases /cylinders and check with a dial indicator
Click to expand...

I would beat it straight also. If you can. And save some money to have it replaced. It is hard to believe how bad a motor can be and still run fine. The hard part with straightening it is getting the piston to align with the cylinder. The piston held the wrist pin straight when it bent but there isn't a cylinder to keep it aligned when you straighten it.

I have had motors that needed to be replaced but the customer wanted to "just make it run". And years later it is still running. Rusted bearings that you had to break free with a pipe wrench and a quart of penetrating oil to bent rods. pistons with missing skirts and a JB welded hole all sorts of stuff.
 
dbrutherford

dbrutherford

Parts Whore
Location
Fairmont, WV
Buy a rod from Riva kit and have a local shop replace it. If you have ever had a set of cases ruined by a broken rod you wouldn't straighten it out yourself. I have one take out everything and I mean everything. That was an expensive repair!
 
SUPERTUNE

SUPERTUNE

Race Gas Rules
Location
Clearwater Fl.
Straighten rod? Are you kidding! Have you seen a motor that saws itself in half and ruins the cases, reeds, piston, cylinder sleeve, starter, exhaust manifold and even the bed plate mount! Not a cheap fit when they do this! Don't do it! Get a new rod and replace it CORRECTLY! Send crank to rebuilders like Crankworks, Pro-Tec, Jetworks, Riva, I'm sure I'd do it to prevent a failure with this kind of result!
 
eel

eel

Our home is girt by sea
yamasaki said:
dam, yeah. get it rebuilt. spend the money. lesson learned. life goes on.

or.. buy someone's used crank... thats what i usually do. ive never really had a crank i bought fail on me.. cranks ive had that have gone bad have either been bent rods (like yours), or cranks that got peppered with shrapnel from a top-end blowing up. that's probably the cheapest way out for you. used crank.
Click to expand...

Freshwater is so much nicer on stuff.

Where I'm from, you would consider buying a used condom before a used crank, unless you knew it's history.
 
tor*p*do

tor*p*do

Squarenose FTW
Site Supporter
Location
NW NC
throw a viagra into the top of the carb and crank her up!
that will straighten out your rod:fing02:



'til she blows :ugh2:
 
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