MTX WATER PUMP (IMPELLER) REMOVAL

[stirlinggaz]

Hi all,
trying to split the crankcases on a mtx200 engine.
everything seems easy enough....
but it looks like i have to remove the water pump impeller.
its held on by 1 measly little nut.
but its left hand thread & the only socket that will fit is from a 1/4 inch socket set. (its a 12mm nut)
but i have no way of locking the impeller while i attempt to remove it.
the fan blades on the impellor are made of cheese & snap at the 1st opportunity.
i tried this years ago on the 125 & gave up as the fins kept snapping! (while trying all sorts of wedging/holding techniques, lol)
i dont mind destroying the little impellor as im sure i can get another from honda (at a ridiculous price)
but im stumped.
anyone offer any advice?
right now i have 2 engines, of reasonable condition.~
2 cranks,gearboxes etc.
2 atacs & at least 3 decent cylinders.
it seems such a waste to give up & junk it & put the leaking 125 lump back in!.
seeing as i have the 200cc expansion chamber (try finding a decent one of them), the 200 carb & everything else to make it a decent 200.
the 125 is just not powerful enough.
the couple of extra bhp & the atac valve combined, turn it into a decent green laner.
help!!!!
cheers,
GAZ

[gwernybwch]

Hi,

Something at the back of my mind tells me that it is possible to split the crankcases on an MTX without actually removing the waterpump housing. Have you tried this?

Once you have split the crankcases, it is possible to put the shaft in a vice and then unscrew.

Alternatively remove the cylinder and piston and locking the crank by putting an extension bar through the top end hole of the con rod.
I’m told that it is possible to unscrew the propeller when the engine is still in the frame by selecting top gear, with foot on the brake to undo it then.

Your right that the propeller is the most brittle metal known to man, and the thread of the propeller has spent years immersed in water therefore you might get some heat on it before trying to undo.

Just to let you know that the propeller is £20 odd quid and are different to those on a MTX125. The water pump shaft is only the same as the early MTX125’s and have been discontinued by Honda. So go careful!

[stirlinggaz]

hi,
ignore most of what i previously said.
the impellor isnt held on by a nut.
the whole thing screws of a threaded bar.
so if i hold the centre point of the threaded part, i should be able to unscrew the impellor.(rememberring its a left handed thread)
anyway, i think your right, im pretty sure i split crankcases before without removing the impellor.??????
anywhay the engine is out the frame, so the top end is off & im locking the conrod with a shaft (its coming out anyway if i damage it) but still wont budge.
the 125 & 200 water pumps look similar or at least could be bodged to fit, or it could be that i have an early series 125 (1985 drum brakes front & back) & the 200 engine is an early version also?
oh & i have a couple of spare gear boxes.
cheers,
GAZ

[Stovaxlover]

I managed to take my impellor off by holding the nut on the back of the alternator.

When u get it off could you let me know how the seals go together. Cant get mine to stop leaking.

[gwernybwch]

From memory I think that the actual water pump housing are the same on the 125 as the 200, but the propeller is thicker on a 200, therefore the pump housing cover is also different on a 200. The propeller on a 200 will have “KJ1” on it.

If you split the crankcases, there is a circlip on the water pump drive shaft. If you take the circlip off you should be able to tap the whole shaft out from the inside.
No need to take the propeller off at all

If you really need or want to take the seized propeller off, I would heat it up until red hot and then let it cool down naturally. That should be enough to unseize it.

The water pump drive shaft is the same on all MTX200’s – basically a straight heat treated shaft – and all early (front drum brake) MTX125’s. The later disc front brake 125’s also had the engine balancer built into the water pump shaft.

If you fit a 125 propeller to a 200 engine, I would be interested to know how the 200 engine copes. A lot of the reviews of the 200 when it first came out mentioned overheating problems and a lot of 200’s have had the thermostat in the cylinder head cover removed.

[stirlinggaz]

Hi,
i got the impellor off.
i just put the anti-backlash gear & shaft back in & held the backlash gears while unscrewing the impellor.
hey presto!
i was only removing it, as im attempting to split the crankcases. (but as i mentioned before, im pretty sure i didnt have to remove the water pump to split them, when i did this on another mtx engine some time ago)
so im now back to square one!
top end is off,
clutch is out.,
generator is off,
water pump is off.
& as far as i can see all bolts are out.
but i still cant get the crankcases seperated! & i need to, so i can fit the new/replacement crank in.
what am i missing?
cheers,
GAZ

[gwernybwch]