2 much Pressure

[88CR250#13]

I bought CR250 from a kid a couple of weeks ago. He said it was an 88 but after looking at the vin, the year code is "M" which makes it a 91. Anyways, I got it cheap because the water pump was leaking. He said it needed a new water pump shaft. I replaced the water pump shaft, seal, gaskets, and the oil seal. Put everything back together and started it up. Still leaked. So when we took the screw loose to drain the coolant, it sprayed out with a lot of force/pressure. So I topped the coolant off and left the radiator cap off and started it back up. No leaking. Put the cap back on it would leak. I did notice that little bubbles were coming out from around the head gasket. Could a bad head gasket cause to much pressure? I don't know much about motors. Any help will be greatly appreciated!!

Also forgot to say that there are air bubbles in the coolant too. I can see them in the top of the radiator.

Thanks,
Tuc

 

[mideastrider]

Sounds like it needs a head gasket. But check the head bolts to make sure they are tight, Don't over tighten. I have saw them leak and the head bolts where not tight and just torque the bolts and it be all right. You may get lucky.

 

[88CR250#13]

Sounds like it needs a head gasket. But check the head bolts to make sure they are tight, Don't over tighten. I have saw them leak and the head bolts where not tight and just torque the bolts and it be all right. You may get lucky.

Thanks MER, I didn't think about that. I will check the manual for the specs and try that first.

Tuc

 

[rmc_olderthandirt]

If it pressurizes quickly then it is an indication of a head gasket leak. It is common for a small leak to allow the high pressure from the cylinder to leak into the water jacket.

I suspect that you still have a shaft seal problem, however. The radiator cap should limit the pressure to 13 PSI, which the seals should be able to withstand.

Did the new water pump/shaft/seals include the bearing? If the bearing is shot and allows the shaft to wobble the seals won't have a chance.

Rod

 

[88CR250#13]

If it pressurizes quickly then it is an indication of a head gasket leak. It is common for a small leak to allow the high pressure from the cylinder to leak into the water jacket.

I suspect that you still have a shaft seal problem, however. The radiator cap should limit the pressure to 13 PSI, which the seals should be able to withstand.

Did the new water pump/shaft/seals include the bearing? If the bearing is shot and allows the shaft to wobble the seals won't have a chance.

Rod

RMC,
I put in the new shaft, water pump seal, & oil seal but not the bearing. I did notice the shaft had some play in it. So I guess I need to get a bearing when I order the head gasket (the bolts where tight). The previous owner said he put a new head gasket on it but he may have not done it right because it leaks. Thanks for the info guys! I will let you know what happens.

Tuc

 

[BigRedAF]

When you buy a older used bike from a stranger it's hard to know what your getting.

When you get the head off put a piece of sand paper at least three times bigger than the head on a flat glass surface. Use fine grit somewhere in the 400 range, wet the paper and move the head around on it in a figure 8 pattern for a few circuits. Turn it over a check to see that all surfaces are smooth. I suspect a warped head or perhaps they cut it in the past and did a poor job.

If there are shinny spots and dull spots your head surface is warped. You'll need to keep the pattern going until it is completely smooth. Don't worry your only taking a few thousands of material off.

Be sure and use a good torque wrench and tighten in increments, use a criss cross criss pattern. Those heads use a low torque value so a torque wrench measured in inch pounds works best.

Good luck...

 

[88CR250#13]

When you buy a older used bike from a stranger it's hard to know what your getting.

When you get the head off put a piece of sand paper at least three times bigger than the head on a flat glass surface. Use fine grit somewhere in the 400 range, wet the paper and move the head around on it in a figure 8 pattern for a few circuits. Turn it over a check to see that all surfaces are smooth. I suspect a warped head or perhaps they cut it in the past and did a poor job.

If there are shinny spots and dull spots your head surface is warped. You'll need to keep the pattern going until it is completely smooth. Don't worry your only taking a few thousands of material off.

Be sure and use a good torque wrench and tighten in increments, use a criss cross criss pattern. Those heads use a low torque value so a torque wrench measured in inch pounds works best.

Good luck...

Thanks BigRed. I will do that when I go to the shop to work on it.