Hello all,

All worked out good with my 250. Rebuild tranny, new chain and sprockets as well as clutch kit. Runs Awesome. Next is pipe tach install and i think it might be close to keeping up with the bigger boys. I am looking at buying an 02 scrambler 400 2x4. The people claim it needs a water pump, but usually that means something else may be wrong. I am going to check the compression, and check the drive clutch / crank shaft for play. I am figuring that as long as the engine has good compression and no play i might be getting a good deal @ $450.00. I was wondering what and all parts i need to rebuild the water pump. I looked at the schematic, but i am used to just putting water pumps into cars so it is a little intimidating. I dont have the book yet but will purchase if i buy. Any advice?

 

The main thing that can get a little expensive is if the seals have been leaking coolant onto the counter balancer cavity long enough to eat the c/b bearings up,plus the shaft itself where the seals ride can get damaged. The inner bearing for the counter balancer takes an inside bearing puller (if bad) to remove it if the engine is still in the frame. The water pump seals do have to go a certain way and this is where the manual will help. There are two holes in the w/p pump housing that don't need to be covered up by the two seals or bearing. If the counter balancer outer bearing is bad,then the gear must be pressed off and the bearing replaced. Most people don't have the tools to do this,but here is one place that rebuilds your own for you. They build up the seal riding area on the shaft,plus replace the bearing if needed.Polaris ATV 400 350L Counter Balance Shaft Water Pump Repair Balancer | eBay
Plus to pull the counter balancer you need this tool,unless you're good at fabricating one. https://polaris.spx.com/Detail.aspx?id=56&cat=1&sub=24
The 350/400 isn't the easiest engine to work on as there are as many or more parts than a lot of 4 strokes have.
OPT

 

OPT,
Do you think that doing the work myself in the worst case scenario could be a good investment? I am not sure if I want to ride or sell, but I want to get my shop working again and save or make money at the same time. Any thoughts? I am sure if I buy you will be hearing from me again about fixing it. I always like second opinion and advice.

 

Is there anywhere i can get the drawing and specs for that and all of the pullers? I know a couple of machine shops and it looks fairly easy to make with the right tools. Is that gear the usually the only thing that needs replaced? Other than all the plastics and a few compents it can't be that bad. Easier with the engine in, or removed? I am figuring it needs a top end rebuild with a totally shot water pump.(so they say) could just be a rad cap or cavitation in cylinders at the least i think. I am concerned. I want it regardless, but I only like sure thing gambles.

 

Imo an 11 year old 400 needing water pump repairs(along with possibly other problems) is not really an investment to make money off of.If it's for your own use,then it might be worth it,but always expect the unexpected on these old 2 strokes. They can be a money pit as many have found out.I loved these engines when they first came out and still do,but there are so many parts to this engine.This is just an example of the 3 engine cases and bearings,water pump and counter balancer.Dirt Cheap Yamaha, Honda, Arctic Cat & Polaris OEM Parts & Accessories – Cycle Parts Warehouse Dirt Cheap Yamaha, Honda, Arctic Cat & Polaris OEM Parts & Accessories – Cycle Parts Warehouse

 

It looks liket the water pump alone if completely rebuilt would run about 200. If those seals are bad, i will have to split the crank and replace bearings. I might offer them 250 as startring point to try to get the number way down. If i have to split the crank i might as well do the top end as well while i am in there. I might be driving out in a little bit to go and get it. I'll let you know.