yfz450 with yz125engine need help

[TSI2FLY1991]

I have a yfz450 chassis with a yz125 engine installed for my son and can't figure out why
It won't stop boiling out coolant it does it when you get temps are around 168deg jetting seems
Good plug is dark so I know its not lean I'm using the yfz450 radiator timing is set and stock
Any help please

[hawaiiysr]

Are you sure you routed the radiator hoses correctly? Are you getting flow? Start the quad and remove the radiator cap is the fluid flowing? Is your water pump working correctly? Check to see if the bearing is not frozen.

[TSI2FLY1991]

Yeah checked waterpump its working fins are perfect and can see it moving in radiator also the lower hose feeds the pump and upper comes out of the head two strokes don't have compression at the bottom end below cylinder do they ? Or do they have crank case pressure

[Logan #34's Dad]

Get a new radiator cap.

[TSI2FLY1991]

Replaced cap before posting this I should of put that on here also did a leak down test on head no bubbling in radiator but when you run the engine with cap off you can see little bubbles there is no bleeder screw in the head so maybe a issue or I was thinking base gasket but don't know if there is any sort of presure in the crank case on a two stroke I've been building this quad for months now and all done except it overflows but when it comes out the overflow the coolant temps are only at about 160-178 was where I seen it starting to drip any help would be great

[Logan #34's Dad]

Maybe its is normal to "leak" or "drip". Does the dirt bike have an overflow bottle on it? If so, think of that bottle as an expansion bottle not an overflow. In other words, when the water gets hot it expands and has to have somewhere to go. As the engine cools it will pull the needed fluid back into the radiator.

[TSI2FLY1991]

I have a bottle on it works tell you ride it for awile then it pushes it out of there also it has me beating my head againest the wall what temp should it get before it pushes coolant out cap I have a 1.1 cap on it and it has the yfz 450 radiater I just don't understand it won't push anything out tell I rev it drained transfluid no coolant in there new oem base gasket and head o rings another leak down on head still no bubble in radiator I just can't figure it out I'm thinking maybe crack in cylinder ? What does everbody think

[TSI2FLY1991]

Ok just got back in from the shop I got the coolant temps up to 174deg reving it up after letting it run for 10min or so is this normal the reason I'm asking is I put a washer in the return now it it don't push out the overflow tube just wondering what temps or as long as is it don't boil over do you think its fine