Type of Water Pump Kit?

Hello, I currently traded for a 1998 Yamaha YZ400 and I want to replace the water pump because the "weep hole" is starting to leak a little. I was wondering if there is any aftermarket water pump kit that is worth it? I have come across Hot Rod water pump kit at http://www.motosport.com/dirtbike/Hot-Rods-Water-Pump-Repair-Kit and I was wondering if anyone knows anything about these. Or do I just need to replace the oil seal that's part of the kit or the O-Ring seal?

My experience with this is to use OEM parts .. IMO

I agree with Backyard Hack, my buddies 99 KX 125 needed a wp rebuild and I asked around. A local mechanic and a few others all insisted that he use oem parts. It cost a little more but hopefully he'll get another 14 years out of it.

Thanks for the advice. Is there a specific part that I should get just like the seals? Or should I get the entire set up

The Hot Rod kits are just low cost, rebranded replacement parts. Use OEM. Get them cheap from the TT Store.

You will need both shaft seals. You may need the shaft bearing, a cover seal, and possibly the shaft itself. Inspect the shaft for a groove worn in by the old coolant seal (not the one cut into it deliberately). If there is one that you can catch a fingernail in, scrap the shaft.

Also, be sure the drive tab is not excessively rounded over. It is normal that they can be rotated up to about 30 degrees in the socket they plug into.

You may find this helpful: http://www.thumpertalk.com/forum/showthread.php?t=940018

Thanks a lot grey, it helped simplify some things. I am going to pull the water pump assembly out today and will let you know how it goes and if I got any other questions. This type of job shouldn't take long correct?

Not more than 1.5 hours, probably. Draining oil and coolant is the most annoying part.

Yea and it sucks because I just changed the oil in it a day ago and haven't ran it so I gotta drain abd maintain the oil lol.

I agree, go with OEM. I always replace both seals at the minimum, quite often I replace the bearing as well since it's cheap and I'm in there. I have seen a few shafts that needed replacing as well. It's not a hard job, about 1.5 hours if you've never done it before, about 45 minutes if you are used to doing it. I lay my bike on the left side so I don't need to drain the oil, unless it is due for an oil change anyways.

The whole is where it leaks from. Should I change the impellar fit the leak out only the 2 oil seals and the O-Ring. I'm just trying to minimize the cost. What about the gasket. If you look at a model I'm taking about numbers 4, 5, 8 and 10


That hole is where it's designed to leak from if the seal(s) fail. Open it up and replace what shows to be necessary.

pulled off the water pump casing to see the outside of the impeller, once i drain the oil the rest of the casing will be off. I can't wait to pull everything off and get the seals fixed.

Grey: When i pull the system out will it all fall apart of will it keep its order, so i will know the correct order to put it back in.

It shouldn't all fall apart. You will have to pull the kick starter off to get the inner clutch cover off. I leave the outer clutch cover right in place and remove everything as one. When you pull the inner clutch cover the water pump will come with it. Then you just put a wrench on the water pump shaft on the inside of the inner clutch cover (where there are two flats on the shaft) and put a wrench on the hex head of the impeller and spin the impeller off of the shaft. Once the shaft is out you can pop the seals out and put in the new ones, then put it back together. I like to put a little grease on the new seals when I put it all together, but that's just me.

Thanks KJ, I failed to mention that there was still quit a bit of coolant left in the case when i drained it. Also I want to go ahead and replace my radiator cap, because I think that could be causing some the problem. Any suggestions on a new radiator cap and what level like a 1.6 or what (sorry i don't know much tech talk about radiator caps) Also I will be putting oil on the seals also lol

You could use a 1.6 bar cap, but if you can get by with the 1.1, that's overall a better choice for most people.

Use coolant to lube the coolant seal, not oil or grease.

Thanks gray. I just got hp coolant 50/50. I know the coolant doesn't really matter but the amount? I read your post for a 450 I think. You said it takes 1.05 quarts of coolant. Is this the same for the yz400? And will the .05 make a big difference if I just put the quart in it?

Fill it. All the way up. As it heats the coolant will expand, some will be pushed out, and the level will "self-adjust".

Pushed out of where? Because that's what I did the first time it started to leak and when I removed the case a lot of coolant was still left in there, that's why I'm thinking the seals might not be bad and just need a new cap but I should have my back tire on it shortly so I can drain everything and pull it apart. Because where the bike is I have no room because of my pit bike lol.

Pushed out of the radiator overflow tube.

Thought I would put some pics of the progress. New rear tube and tire are on. Working on pulling off the entire casing. On my old bike that I took the clutch apart there was a screw in the middle to release the basket. I don't see one here. Do I have to remove all the disc plates? And yes all the bolts are removed only thing holding it on is the clutch basket. Also any hints on removing the kick starter I removed the bolt and put WD-40 and tried to pry it off with a flat head screw driver but no go.


Edited by Kicker98

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