# Brute Force 750 Rebuild Issues



## jpd298 (Sep 20, 2017)

Rebuilding a 06 BF. Rebuilt crank, new cylinders, new pistons, new rings, new gaskets, new chains. Build everything following manual. Turning engine over with plugs out to build oil pressure prior to starting, antifreeze is blowing out of the exhaust port front head. Tear everything down thinking it’s got to be a warped cylinder deck or head. Cylinder appeared to have a very slight warp of .001 inch in one spot as the head surface checked out perfectly flat. Replace cylinder with a new one, new OEM gaskets, switched to another known good head. Put everything back together and while cranking over again I have the same problem of antifreeze pushing out of a exhaust port. If I let the machine sit for 5 minutes, it will push out a significant amount of antifreeze. The antifreeze appears to be able to collect in the front cylinder while the engine is stopped, and then when cranked over all the collected antifreeze is pumped out the exhaust port. Ideas?


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## NMKawierider (Apr 11, 2009)

So you replaced the head and cylinder on that side. And I assume you used a new head gasket...cause the first one is compressed and no longer usable. Is there any stem or bolt seals that may have been left out?


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## jpd298 (Sep 20, 2017)

Yes replaced cylinder and head on same side and yes new OEM head gasket second time around. Stem or bolt seals? Did I miss something?


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## jpd298 (Sep 20, 2017)

Built the rear cylinder same as front and there is no problem with the rear.


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## drewski1126 (Jan 4, 2018)

Only thing I can think of is any leftover gasket material might be causing the leakage. 
Make sure you get it real clean and polished, and don’t leave any scratches


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## jpd298 (Sep 20, 2017)

Gasket surface was pristine clean on both build ups. Both surfaces were perfectly flat. I’ve built a lot of motors and this one has me stumped. The antifreeze is entering the cylinder without being pressurized. I’ve got the head bolts torqued to 38 ft-lbs. Maybe torque the bolts an extra 5 ft-lbs to see if that seals it up?


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## NMKawierider (Apr 11, 2009)

jpd298 said:


> Gasket surface was pristine clean on both build ups. Both surfaces were perfectly flat. I’ve built a lot of motors and this one has me stumped. The antifreeze is entering the cylinder without being pressurized. I’ve got the head bolts torqued to 38 ft-lbs. Maybe torque the bolts an extra 5 ft-lbs to see if that seals it up?


With it coming in with no resistance, it's probably not the gasket so I wouldn't risk stretching the bolts. Has to be a crack..I know it sounds unlikely having it happen on two different heads but..this sounds like a cracked valve seat or a crack or leaking valve guide-to-case. The cylinder probably isn't the issue.


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## drewski1126 (Jan 4, 2018)

Could do a leak down on test on the valves. That might get you somewhere. 


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## jpd298 (Sep 20, 2017)

I'm going to do a compression test and a leakdown test and see where that takes me. Im also going to try and put a camera in the spark plug hole and see if the antifreeze is entering through the valve seat area or the head gasket area. Thanks


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## jpd298 (Sep 20, 2017)

I put the brute in the corner as i worked on other projects, but wanted to give a follow up. I pulled the motor back apart and rechecked everything. The head and cylinders were fine and not warped or cracked. What i found was there was some fluid in one of the threaded holes where the head stud goes. When i went to torque the head bolts, the one head bolt was hydro-locking against the fluid in the hole giving a false torque reading.


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## drewski1126 (Jan 4, 2018)

Interesting. Glad you got somewhere with it. 


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