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Discussion Starter #1
First Post on this most excellent forum.

Just bought a 96 400 sportsman and doing a "quicky" rebuild to stop my oil and water from comingling. I've got the the Gasket and Seal kit coming tomorrow, and with a little luck I'll be pulling dead tree remains out of my backyard all weekend long. I've got the service manual, and everything seems to be pretty straight forward on this 2 cycle. But, I have a couple of questions.

The gears for the waterpump and crank look like they did battle with a bolt. They turn OK and there doesn't seem to be interference between the teeth. But I can't find any alignment mark on the pump gear. Can I put it in without the mark? (use the balancer orientation or count teeth from one of the holes)

The guy I bought it from replaced the piston with a 10 over wisco. The rings don't want to rotate around the piston. It's like they have little stops in the grooves. Is this just crap in the grooves or the way it is supposed to be?

Has anyone ever just removed the counterbalance shaft and hooked up an external pump for the cooling and used 40:1 mixed gas out of the tank?
 

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Welcome to the board!:med:
 

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The piston is suppose to have the ring stops on it ,should be toward the intake side of the cylinder . As far as the balance gears ,you can not run without ,the engine will self destruct ! You shouldnt have to remove them to do anything with the top end .
 

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Thanks for the Welcome, and thanks for the info guys. I figured that since most engines this size don't have counterbalance shafts it was in there to make the engine run smoother, tach highter and not to protect it. Any ideas on how to get the counterbalance back in alignment? The mark on the gear has been ground off.
 

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[/IMG]ok so I took some pics of a bottom end that I have laying around ,the gear on the crank has the Mark lined up with the key way . The balance shaft gear has the Mark 8 cogs (grooves) clockwise from the 6mm bolt hole . The only way I can think of how to find this point is to install the shaft and let the weights position it self then locate the bolt hole closets to the crankshaft ,then count from there . Hope this helps !
 

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Discussion Starter #6
counterbalancer......gone!

I didn't really have the option to wait for new gears (and I hate paying for stuff) so I put the engine back together without the counterbalancer. It works Great. Runs smooth enough for me. At really low idle the motor moves around a bit, but that's pretty easy to fix with a little more RPM.

The $35 Harbor Freight 12 volt pump moves the water around just fine, and I couldn't be happier with the pulling performance of this machine. I had to pull out 10 large tree trunks / limbs from my backyard (some weighed over 1000lbs) the 400 had no problem in Low all wheel drive. How did I ever live without one of these things!
 

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It'll probably be ok for slow speeds, but 1/2 throttle or more will kill the motor and other parts. It'll vibrate to death.
 

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Well, so far so good. I've run two tanks of gas through it. Had it running all yesterday wiith a plow pushing dirt around in my back yard. I couldn't be happier.

And actually, the only time there is any vibration is when it's at idle.

I understand that removing the counterbalancers from engines is a pretty standard proceedure for the guys that race dirtbikes. It frees up some weight, adds some horsepower, and allows the engine rev up a little faster.

I always assumed that I would put a new engine in this thing at some point (Hey, It was a $500 4 wheeler), but for the time being I'm just going to see how long it will last as is.

Plus, the old shaft with the broken gears makes a nice addition to the other interesting object I keep on the fireplace mantle.
 

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Yeah, we took balancers and anything else that added weight or slowed rotation from our racers. But we also rebuilt the engines on a very regular basis. Us poor guys two or three times a season, well healed guys a bit more. Had a small displacement flat track bike we removed the flywheel and all of the stators ect and used a total loss ignition system that ran a battery dead every other heat just so the engine would rap up faster. 'course that was back in the stone age. It was Bridgestone, lot of guys on the forum probably have never seen one. :)
 

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Could comebody please post a full picture of the gears installed? My father took off the gears without marking them. I have all the factory marks for shaft alignment, but no marks for gear mating. I understand the theory of how it works, but a full picture would tell me exactly where they meet to the tooth.

I've found a bunch of pictures, but none of them show both gears properly.
 

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I have a 1998 400 Sport which water got past the seals and all of the bearings were shot and I've had it apart for about a year. =
I've finally got around to putting it back together and I'm wanting to do it right.
I had the counter balance gear removed from the crank case by a machine shop. They did not mark the counter balance shaft or the gear.
I sent the counter balance gear off to Texas and had the shaft turned down.

I have read that the piston should be at TDC and the counterbalance should also be pointing upward at he same time

I have attached two photos which show what I think is right????

I'm hoping someone can confirm my thoughts as I want to do it right the first time.

When they are at TDS, all is good. Is this right????
 

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