got a water pump query help

[tommrth]

it apears my 89/94 sr model kdx uses a different waterpump seal and inpeller than similar age bikes its ally instead of steel from looking at the parts fiche
im thinking it might be the same as the 95-present bikes .
so does this look like a h series pump and seal??

 

[Tom68]

Looks similar to my 1991 KDX250F sr, mine seems to be sucking air, will hold pressure forever with tester, but somehow loses water when riding.

 

[tommrth]

interesting the files i looked at showed the same impeller and seals for the 200r and 250r
got a parts fiche with the frame number and have ordered the seals bit hard to tell if they are the right ones or not

Tom68 how much water is yours leaking?

 

[Tom68]

Losing maybe .25 litre for 60k ride seems the more stops i have the worse the problem. There is no external leak but the sytem pressurises when you rev the motor,5psi per crack of the throttle, I only tested 4 cracks of the throttle as this was 20 psi.I know that sounds like a head gasket but it doesn't leak back into the cylinder so I think its pulling air past the water pump seal.I recently replaced the water pump seal and found two problems, first the supplied oil seal was the wrong O.D and the two bearings that support the water pump shaft have worn the housing, this has me wondering if theshaft cocks over at high speed and allows air to get past the seal. Might try bypassing the water pump and see what happens.Sorry about the long winded answer but incl' info in case anyone is having similar problems.Testing can wait, riding tomorrow.

 

[Tom68]

A follow up to my last reply incase anyone is interested, put the pressure tester on with the water pump by passed still get pressure with revs, at least i know its the head gasket now.