Coolant leak

[1976RD400C]

How about flipping it over and pressing it out from the other side?

[Aloha808]

How about flipping it over and pressing it out from the other side?

That was my initial thought.  However, the bottom diameter of the boss is much greater and it is flush/even with the head.  I haven't been able to figure out a way yet. 

I have figured out that I can use a c-clamp to push it back in.

[teazer]

I have TZ heads with inserts and GT750 head with inserts (domes) and sealing them can be problematic. TZ is easy because it doesn't need a head gasket - just O rings.  the GT is a different story and it uses an oversized gasket that the insert fits through and seals with o rings.  best solution is BDK in the UK who do all O rings.

The second source of leaks is the same issue as here, sealing the insert against the shell of the head.  Stock heads rarely have sufficient material to seal effectively with an O ring round the dome, like that Banshee dome.  That's how Polaris and others used to seal their sled heads. And there's barely enough material to seal on teh top face of the insert against that flat surface, but that's all you have.

The reason they are a press fit in the head is probably to try to seal the head to the cylinder. They should not need to be a press fit in the head shell. Can you tell us what sort of head gasket you are using and what does the top of that insert look like?

[Aloha808]

I have TZ heads with inserts and GT750 head with inserts (domes) and sealing them can be problematic. TZ is easy because it doesn't need a head gasket - just O rings.  the GT is a different story and it uses an oversized gasket that the insert fits through and seals with o rings.  best solution is BDK in the UK who do all O rings.

The second source of leaks is the same issue as here, sealing the insert against the shell of the head.  Stock heads rarely have sufficient material to seal effectively with an O ring round the dome, like that Banshee dome.  That's how Polaris and others used to seal their sled heads. And there's barely enough material to seal on teh top face of the insert against that flat surface, but that's all you have.

The reason they are a press fit in the head is probably to try to seal the head to the cylinder. They should not need to be a press fit in the head shell. Can you tell us what sort of head gasket you are using and what does the top of that insert look like?

No head gasket.  I used Permatex Motoseal gasket maker.  I looked at the head surface after taking it off.  The seal or sealant looked got and no signs of leaking.  It was just the top of the boss where it inserts in the head. 

I did notice that the other boss insert that is not leaking has what looks like sealant around the top of the insert where the plug screws in.  The one that is leaking doesn't have any signs of sealant.  I guess I will find out when I get it out.

I don't have any pictures of the top of the boss insert.  The pictures I sent at he beginning of this thread might give you a better idea of what it looks like.

Thanks

[rodneya]

When I first got my banshee coolhead I trial fitted one dome without orings and it went in easy and was a pretty tight fit. I had to give it a bit of a whack with a deadblow to bet it out.
If yours has sealant in there it may hard to get out. Depending on the sealant used, some heat may help

[teazer]

When you press it out, check the shape of the O ring groove. It should be a square cross section to allow the round ring to deflect (squish) into the space and allow it to seal.  if the groove is round it won't seal.  Banshee inserts are usually machined correctly.

[Aloha808]

Finally had some time to work on the bike.

 I decided to sandwich the head between two pieces of wood and push the boss out with a jack.  It worked.

It appears that the sealant did not cover the entire perimeter of the top part of the boss, thus the leak.

I will be cleaning it up and using Motoseal to seal it. 

[Aloha808]

When you press it out, check the shape of the O ring groove. It should be a square cross section to allow the round ring to deflect (squish) into the space and allow it to seal.  if the groove is round it won't seal.  Banshee inserts are usually machined correctly.

Yep, it has a square cross section. 

Thanks

[m in sc]

yup. i think you def found it. man thats a shitty small detail to miss by the assembler.

[Aloha808]

Update:

I resealed and had no leakage.  Last time it leaked immediately. Installed the carbs with the Dynojet jet kit ( thanks Ken for your video on the jet kit).  The bike ran really well. Came home after it's first run and sure enough it was leaking from the same location. 

I guess I did not put enough Motoseal permetex gasket maker.  I was worried that I was going to put to much.  A timely mistake.

So, I am not planning on disassembly for a few weeks.  The leak is pretty minimal.  Maybe 10-15 ml (less then a half ounce) since I road it this past week. 

I am considering riding it a little prior to the disassembly again.  I am thinking it will not be a problem if there is enough coolant and the temperature is OK? 

Any thoughts?

[IR8D8R]

15 psi of pressure adds 45 degrees to the boiling point of coolant. Losing coolant is not the only consideration.
If it holds some pressure and loses it suddenly, the whole load of coolant can flash-boil.

Cooling systems are more complex than just circulating water. Somewhere in the engine the coolant is at the boiling point or the cooling system couldn't pressurize. It's specifically designed to do that. Taking out a thermostat is also a problem because it affects that process. Even more it can cause erosion in the engine due to cavitation where hot spots exist. If the system can't pressurize its efficiency is lower, and you still have places where the coolant boils. Without building pressure stopping the boil it can run away since boiling coolant loses heat transfer efficiency. A small leak defeats the whole scheme. Then you are dependent only on the sheer mass of the coolant taking away the heat at reduced efficiency. I don't recall there being a very large mass of coolant in an RZ. I don't own one so I don't know how hot they get. Might be OK if the system works well enough without a radiator cap. Losing pressure can be more catastrophic than never having any...

IR8D8R

[m in sc]

^ 100% agree

I wouldn't run it at this point. not worth the risk.

[Aloha808]

Got it.

Thank you gentlemen.


I will be fixing it again (third times the charm), before I run it.