97 SX Blown Motor

D

driftbuster

New member
Joined
Nov 22, 2004
Messages
13
Location
Harvard, Il
Blew the motor on the 97 600 twin. Clutch side piston melted near exhaust and piece gone. Mag side looks good but shows a little minor scoring. Crank looks good. Cylinder head OK. Very little pitting.

Not sure what caused it yet.

Any ideas? (Carb, Water Pump, Oil Pump?)

I plan to clean the carb completely. (not sure if this is the problem because it was completely cleaned during the summer. (removed all jets, screws, used good carb clean, compressed air, checked jets by spraying cleaner thru them and could see spray coming out. 1 1/4 turns on airscrew. Plug looks pretty good. Not white, not black, just tan


Main reason for post:
Looking for a good Cylinder
or
Motor,

or a good place to have them reconditioned.

Does anyone know if a 96 or older motor will work in this sled. (A-Arms, vs. PoGo Sticks)?

Located in South East Michigan.

Thanks
 
Dude, I fully understand your situation. Scored a piston at the end of last season and had to do an upper rebuild this fall. If the cylinders are not pitted you can save them and just replace the pistons, rings bearings and stuff. If you see a different color on the cylinder wall and it is raised, most likely that is melted aluminum from your piston. Moranic Acid will clean this off. I then took a Hone Tool and ran it in the cylender. A honing tool will not hurt the nikacell coating of the Cylinder.
Go to your local Yamaha dealer order up a stock or aftermarket upper rebuild kit and bearing set, install and you are good to go.

I went aftermarket and replaced both pistons right away as both cylinders had to come off for the lower gasket to be replaced. It cost $300 for the full kit. That included Pistons, wrist pin, C clips, rings and Gaskets and then bought the bearings as well. I went aftermarket as the pistons are lighter and supposidly stronger than stock.

skibkr
 
Yamahas use Fuel screws not air screws. Stock setting for that motor is 1-1/2 turns out. I remember that several people used to suggest running them at 2 turns out to help eliminate an off idle bog. If you were running at 1-1/4 you may have been running too lean on that setting.

Also, if you're running your jetting on the edge, and you get ahold of some oxygenated fuel, it will be lean. If you regularly run oxy-fuels you should go up at least 1 maybe 2 sizes.

Whatever caused it, melted piston by exhaust port is a too lean condition.
 
Last edited:
If the piston is scored at the exhaust side then you had a lean condition which can be caused by air leak, plugged carb. If it is just one piston I would rebuild that motor and not look for a used one. Stick with OEM piston. I would never mix match pistons in any machine.
You may find parts on this site in the classifieds that will save you money.
Piston, clip, needle bearing, rings and if you look here you may find a cylinder.
 
I agree yamyrider on not mixing OEM with aftermarket that is one reason I replaced both sides right away. The main reason was it only took 15 min to do the other side as everything was already torn apart that far.
My case I scored the right piston on exhaust side because my oil cable streatched and I was running 3/4 oil at WOT (according to the marks).
Now I know one more items to watch.
Not sure on the 97 but my 95 had an idle mark and a WOT mark on the oil pump.
 
skibkr said:
I went aftermarket as the pistons are lighter and supposidly stronger than stock.skibkr
Click to expand...

Wrong,wrong,wrong......... stick with oem pistons and rings, there 100%
better than aftermarket, ask anyone!!!!!
 
Blown Motor

Thanks everyone for the info.

I am still looking at reconditioning the cylinder, new pistons (it sounds like EO is the way to go), rings, clips, bearings for both sides,

I am still interested in finding someone with a good cylinder that does not need to be reconditioned and try to save a few buck if I can.

Still looking. If anyone has one, please contact me.
 
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