over heating and boil over????

[fast500#12]

i have put two new top ends in my bike in the past 6 months because of over heating and melting pistons? the bike runs great no water leaks 32:1 mix 10w40 in the gear box. i have changed the radiator cap twice because they fail pressure tests and the new one is good. but now i have melted piston number three. does any one have any sugustions. i am going to change my gear oil to maxima 85. i ride in sand and what ever else comes along. i am getting frustrated and constantly putting new piston kits in is getting spendy please help.

[Paul]

Is your water pump frozen solid? I race during the heat of summer (110+) in the Arizona desert @ speeds over 110 (15/42 gearing) and have NEVER melted a piston. I change radiator caps when I put a new topend in, and I run Maxima Coolanol. I race with 40:1, Super M and Sunoco Purple (111 Octane). Thats also the same mixture I use @ Glamis.

[kawdude]

My bike is a piece of crap (or was before the rebuild) and I screamed the engine the last couple time I rode it before tearing it down.  Would plugged radiator core cause this?  How about Timing, air leak, spark plug???

[fast500#12]

i don't think so because i had a loose hose once and it shot a good stream. but i'll check any way since i tore it down to bare frame for paint. and the top end is off. the bike is going to look very sweet when done, i may post some pics. thanks for the info paul.

[Paul]

Welcome, a good thing was brought up by kawdude - how are your radiator cores?

[kawdude]

Yes!!!  I made a good suggestion.  Woohoo

[fast500#12]

there in good shape no rust no leaks no cloggs

[Folke]

Check the bolt at impeller we have broken this many times so we change to an stronger, (stock bolt ar in aluminium).

[mikesmith]

Do you bleed the air from the system(air bleed bolt in the head),try running water wetter also.But theres something wrong if your melting pistons,I have ridden in 118degree weather and not melted a piston.Does your bike puke a lot of coolant,or can you hear it boiling?Where is the piston melting?Id look at my timeing,plug,jetting,fuel,and check the compression isnt to high from carbon or head work that was done,somethings wrong.

[Rick]

I suspect your coolant is going inside the engine.  Head gaskets are notoriously hard to seal, and if the motor has gotten very hot, the head can warp.  If you have not already done so, put on a new head gasket.  If you have put on a new head gasket and not surfaced the head, invest in another head gasket and surface the head as follows.

When changing the head gasket, tape a piece of 400 grit sand paper to a window and surface the head in a circular motion using firm even pressure until the head is clean and smooth.  Remove the studs from the cylinder and surface the cylinder as well.  This is tougher because of the size of the cylinder, but take your time and do it right.  This usually takes me about 40 minutes to do both the head and cylinder, so your arms are going to get tired, but this will assure you are not loosing coolant past the head gasket.

When reinstalling, use the stock gasket without any gasket sealer.

I assume you have checked your oil, but just in case...If the oil is milky, you have a bad water pump seal.

Good Luck.

Rick

[Sharc]

How's about your jetting...? How's your spark plug look...?

[fast500#12]

i checked the water pump this weekend and vuala there it is. the impeller bolt had backed out. the engine spins over and the impeller would dance up and down no spinny. so i installed a new bolt just incase along with a lock washer. my pistons were melting on the ehaust side. i sufaced the head my self of friday and made sure that it wasn't warped and its not. every one thanks for all the help. you all know that some times you think that you have thought of every thing and still have problems and some one points out the obvious and your like duhh. thanks every one.