Yamaha TRX850 Enthusiasts Forum

Hey guys,

Bike has started making some pretty aweful noises and it's coming from the waterpump region, i havne't yet pulled it apart but i figured i should look for new pumps incase i find it to be terminal and i can't put it back together... I've had a look on Kedo, but couldn't find anything useful, any ideas where i might find replacement water pump housing and impeller shaft?

any suggestions as to what else may be in that region that could give me grief? i'm thinking one of the balance shafts possibly, but don't know for sure...

Cheers

well...................I have a water pump lying around but I don't think you can buy the parts anywhere but Yamaha.
There is of course a bearing in the back of the pump which is the most likely thing to fail noisily.
There is a mechanical seal on the pump shaft which can fail and allow water into the oil - doubt this would make a noise unless the water has got at the bearing. This seal is not available as a TRX850 part but I believe that the YZF750 uses a similar pump and I think you can get the seal as a spare part for that model. Is your oil level going up?

If a balancer shaft bearing has gone then it could be really nasty.

If you pull the pump off be very careful - there is a shim on the shaft which tends to stick to the nylon drive gear then fall into the crankcase. It is very unlikely that the shim will come out with the pump, although you may be lucky. If it falls in, then you will either have to be very lucky with a magnet or split the cases to find it. Oil pan off will be the minimum, and with the engine in the frame this will be a bastard of a job.

A new pump is only about £150.

So basically... it's bad news no matter how it unfolds... last time i had to change a waterpump it cost me $35... but that way my Toyota Crown...

i'll be keeping an eye on the oil/water to see if anything is going strange there, i was only trying to figure out how they would drive the pump internally without having a seal between the water pump and the oil... i figured they'd be smart enough to not make it something that could fail catastrophically...

if it's balancer shaft, i'm assuming that's an engine out, and total strip down kinda job? hopefully the engine will hold together until end of semester, then i'll strip it down for peace of mind i think... been on edge for a while now...

balancer shaft is a total strip down. there is a needle roller bearing on one end of the shaft. if that fails it can seize and/or spew needles all over the shop. worst case would be it takes out the rest of the moving parts of the engine. I doubt there is a much better case scenario.

I think there may be 2 seals in the pump. a regular oil seal behind the bearing and a mechanical seal behind the impellor. it is essentially a sealed unit though.

Heard what youngy said I wouldn't keep waiting.

Nah, i won't be waiting, Long weekend this weekend, so will be visiting my mechanic (Dad) to put the stethiscope on it, and try and isolate the noise...

if it's water pump i'll get it fixed pronto, if it's not waterpump... i'll stab myself with the stethiscope...

youngy - may be in contact RE your waterpump...

Okay, Update on this...

Confirmed the noise is coming from the waterpump, so i pulled the cover off, and it's as clean as a whistle inside, couldn't feel ANY movement in the shaft (except rotation obviously)... but i couldn't ge the back cover off the engine, i wasn't game to pry at it too hard incase i broke something... how do you get it off? is it just a matter of prying till it comes loose or is there some clip/keyway or something i need to undo? How do i go about replacing the bearing in the rear housing? are they servicable or is it just a matter of buying the rear housing with a bearing? are they available genuine (do i want to go there)? any suggestions?

Cheers

There is an o-ring around the back half of the pump body, sealing the pump in the crankcases, which makes it a swine to pull out.

If you are going to remove the pump without splitting the cases, you will have to lever the pump out of the crankcase. If the shim doesn't come out on the shaft use a magnet on a stick to pick the shim off the drive gear inside the cases. If it drops into the cases you will have to split the motor to get it out, unless you're very lucky with the magnet.

The bearing is retained in the back half of the pump by a circlip. The bearing is not available from Yamaha but you may well be able to get a suitable one from a bearing factor. The seal is not available either. Yamaha only supply the pump as a complete unit.

Getting the pump back in is a complete bastard with the cases closed up. I won't say it can't be done, but it's not easy to get the o-ring started into the hole in the cases, particularly without losing the shim inside the motor and getting the drive shaft into the gear, but if you can get it started you can use the 3 mounting bolts to jack the pump in.

You can get the seal, but not if You ask for one to the TRX. (Yamaha...) Someone else has to fill in, because my memory fails me again, could it have been the YZF750 or the FZR1000 that had exactly the same seal?

I was maybe lucky, but I didn't find so hard to get the pump back in? And as the happy-go-lucky mechanic I am, I discovered the shim first after removing the pump, luckily still sitting on the drive gear...