Hey y'all

Decided to start a new thread specific to the issue I am experiencing on my bike.

I finally got my bike up and running after I blew the head in November 2018. I had purchased a used engine with only 4000 miles on it and replaced its cylinder with the BB 351 kit. When I threw the engine in the bike, she fired up within in the first 10 minutes. I was so thrilled!

Since I applied too much tension on to the cam chain, I ended up seizing the head as well. Such a bummer I know! I took it to a mechanic and he polished the journals and got her running again but he warned me the bike is running a bit hot.

This has been my first week riding the bike since and all I can say is wow! The 351 changes the whole bike! I love it. But just as my mechanic said, the bike is running super hot. Keeping my right foot on the peg is almost unbearable. The fan is on the whole time. The spark plug, which you can see below, does not look good at all. It was new when I sent it to the mechanic. The bike now only runs while the petcock is on the "reserve" position. I have no coolant leaks nor white smoke spitting out of the exhaust.

Im super bummed about this as I would really like to ride my bike. Its been so long! and with this newly added power, Im fantasizing about her all day!

Maybe the head gasket is blown?
Maybe the cam timing is off? (which I doubt since the mechanic primarily works on KLX's and 4 strokes)
Failed water pump?
Poor coolant?

Really hoping some of y'all can chime in and make some suggestions as to what the issue may be?

 

Verify that the thermostat and water pump are functional. I'd pull the water pump cover and make sure the drive is working. If that's OK, I would remove the thermostat and run the bike to see if the condition is resolved. If it is, replace the t-stat. Because you're not losing coolant I don't think it's popped a gasket.

 

I did order a new propeller, gasket and O-ring for the water pump so was planning on inspecting it when the parts arrived. However, (excuse my ignorance) what exactly is the drive?

 

The shaft spinning the pump is the drive. I've not had a KLX apart, but make sure you have all the stuff in for the water pump drive. One time I rebuilt my TM125. It kept dragging down and starting to seize. I couldn't figure out why. then in checking the pump I found I had apparently dropped a little plastic drive plate. The oil pump drive was smaller than the ID of the pump drive shaft and this plastic piece keyed into the drive and the oil pump into it. Found it on the floor. Put it in and gee, the bike ran great, no seizures. Of course I had to pull the cylinder and have it honed and all. Lesson learned.

 

A few thoughts.

1. Remove radiator cap and check the fill level, if full with the cap off squeeze all coolant hoses to see if there's air in the system. Also, look for deposit build ups that may be blocking flow.

2. Check the orientation of the thermostat air bleeder hole. Put the thermostat and a thermometer in a pot of water and heat it. Make sure opening matches spec.

3. Did you rejet for the 351 install? I haven't researched the 351 much, but is there a possibility you're running super lean.