Coolant Flow Question - Interesting...

[razorboy]

Hey Fellas,

Gonna test out the gurus here a little.
I am in the final stages of mounting a KX85 motor into a Honda RS125 chassis. For those of you who don't know, the RS125 is a roadracing chassis, GP bike. My son starts racing it in 2 weeks.
Anyway, the swap has given me a few issues to deal with and I hope the gurus here can help me resolve at least one.

The basic question is which way is the coolant flowing through this motor? I am assuming it gets pumped into the cylinder sidewall from the waterpump and exits out the top of the head into the rad and then around again....is this correct?

Now to why I am asking this question?
The reason is that I want to rotate the head by one stud position to the left. The reason is that we are using the RS125 radiator and if the head is pointing forward, the hose that goes from the head to the top of the rad is going to be a difficult problem. The bend will be too drastic and I doubt I can find a suitable hose to do the job. If I rotate the head counter-clockwise by one stud, it puts the head in a position where the hose can basically drop right on.

Just worried about the nature of the design and if I am presenting a cooling problem to the motor by doing this? Has any other 2-stroke motor been built that has its head coolant port to one side or the other?

Any ideas are welcomed!

Cheers
Bernie

 

[thejake456]

The basic question is which way is the coolant flowing through this motor? I am assuming it gets pumped into the cylinder sidewall from the waterpump and exits out the top of the head into the rad and then around again....is this correct?

"yes it does flow this way."

 

[IndyMX]

I'd think that it wouldn't matter much, so long as when you turn the head, it still matches up the water jackets so that you still have flow.

Maybe you could put the head on like you are wanting to, and connect a hose to the water pump inlet and apply some water pressure see, if you get water coming out of the fitting on the head.

 

[griffbones]

You are correct on the dirrection of flow.
But if you rotate the head you will need to modify the head gasket. Where the water exits the head the head gasket has a restrictor in it (stamped into the gasket and says up). This isn't just to tell you which side is up on the gasket, but is also there to slow the flow down enough so that the water can pick up the heat from the cylinder. The gasket is also indexed to the locating pin, so you can't simply turn the gasket. If you cut off the indexing tab you might run into problems with head gaskets getting cut from movement between the head and cylinder. I knew a guy a year ago that couldn't keep head gaskets in his son's KX85, when I looked at it for him I noticed that he was missing the indexing pin. We installed a pin and a new head gasket and it never leaked again.
So you may have to get creative with the head gasket, but I 'll bet you can come up with a good work around.

 

[razorboy]

You are correct on the dirrection of flow.
But if you rotate the head you will need to modify the head gasket. Where the water exits the head the head gasket has a restrictor in it (stamped into the gasket and says up). This isn't just to tell you which side is up on the gasket, but is also there to slow the flow down enough so that the water can pick up the heat from the cylinder. The gasket is also indexed to the locating pin, so you can't simply turn the gasket. If you cut off the indexing tab you might run into problems with head gaskets getting cut from movement between the head and cylinder. I knew a guy a year ago that couldn't keep head gaskets in his son's KX85, when I looked at it for him I noticed that he was missing the indexing pin. We installed a pin and a new head gasket and it never leaked again.
So you may have to get creative with the head gasket, but I 'll bet you can come up with a good work around.

Ahhh,

Thats a very good point!
I didn't think of that because the test head I was using for mockup didn't have the indexing pin in it.
Going to go have a look again today.
If I can find the hoses to do it, I would most assuredly like to leave it in its normal orientation. This is a backup idea in case I run into issues finding a proper hose.
If you think thats an issue, wait till I get to the lower rad outlet which sits about 1/2" from the exhaust pipe and points right at it.................yeesh!

Cheers
Bernie