300/440/550 JS440 motor rebuild in need of help

K

koulton440

Location
vacaville, ca
Hello all im new here and just joined because i have some serious motor issues. I need some advice from people more experienced than me. My 440 bottom end upper case has a crack in it on the starter and i can't fully turn my motor over by. it gets to one point and gets stopped by something. I believe a bearing blew out on the crankshaft and cracked my case so im in the process of breaking it down right now.
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K

koulton440

Location
vacaville, ca
I assume that top end is really dirt with that rusty crust. Is that normal or really bad? The cylinder block is stuck and i cant get it off? What to do i already turn it upsidedown and jumped on it? Do i even need to take apart the top end to split the bottom end case? On the Flywheel is there another way to pull it of do you have to have that four bolt kawi puller?
 
RKO Motorsports

RKO Motorsports

Formerly 97gsxguy
Location
SE MI
Most of the crust is from corrosion from water entering the head. A top end rebuild would be a good idea. To get your cylinders off soak the studs and cylinder is PB Blaster, Aero-Kroil or another rust inhibator. Take a rubber mallet and carefully hit the cylinder to break it free from the cases. You don't need to take the top end off to split the cases but will need to if you want to remove the crank. You can rent a crank puller from autozone, advance auto, etc to pull your flywheel.
 
K

koulton440

Location
vacaville, ca
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Ya from the looks of this i think your pretty right on the top end rebuild. So now that metal is all over my motor and i have a cracked bottom case aand what ever else is wrong with that is it better to upgrade to a 550?
 
RKO Motorsports

RKO Motorsports

Formerly 97gsxguy
Location
SE MI
The 550 will bolt right in and the 440 electronics will work. You would need a 550 manifold and exhaust and possibly a 550 intake a carb.
 
TheBuzzard

TheBuzzard

Location
the jetski grave yard
koulton440 said:
Will the 550 motor built right in and how well will the 440 parts work with the 550 motor.
Click to expand...

looks like a piston skirt broke off and dropped into the cases. when the crank rotated, it tried to stuff the chunk thru the cases. realistically, your motor is wasted. it probably had a million hours on it and was dead tired anyway. you could use all you 440 parts on the 550 block, but the carb will be the tiny 38mm and the jets are drilled for the 440, so it wont run right. the 440 motor is a better motor anyway. i've had a few jetco stage 2 440s thru here that leave most 550s in the toolies.
 
K

koulton440

Location
vacaville, ca
my dad shot down my hopes of upgrading to the 550 so ill be sticking with the 440 motor since its my first rebuild. I want to actually try to rebuild this thing for fun so ive found a bottom end case for $60 now im looking in to new pistons and honing/boring/ resleving the block. What do i do hear and what the best kit i can buy?
 
RKO Motorsports

RKO Motorsports

Formerly 97gsxguy
Location
SE MI
They look pretty good. You'll need to measure them and see what milimeter they are at. 68.00mm is stock bore. As long as there isn't any big scratches or gouges that I can't see you will be able to use those cylinders. If your within tolerance of stock bore you should be able to hone those cylinders and get a new top end kit as well as a new crank and cases.
 
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