'01 KDX200 Boil-over incident

[peterryan01]

Hi guys,

I was out riding this weekend and I had a strange thing happen to me. First, I should say what my bike is running and equipped with: FMF Gnarly pipe, stock spark arrestor, Boyesen reeds, and an opened up airbox top. Those are all the exhaust mods I have. Then, I should say that I am running Prestone antifreeze (50/50) with anti-corrosion additive. I am running a 140 main jet with a BR7ES (one step hotter plug from stock BR8ES). I was riding at 10,500 feet in Colorado. The new plug is the only aspect that I can see that may have attributed to the boil. I usually run a 142 main at 8,000-9,000 feet and it runs great - after a long ride, I can still put my hand anywhere on the engine, and it is bearable. I have heard that a hotter plug may act as a glow plug and ignite the fuel too soon, but I'm not entirely sure how this would have caused my bike to BOIL at such altitude. Luckily, I stopped before the bike actually boiled over. I only lost ~200mL of antifreeze. I should also say that I was riding with my parents (including my mom) and she rides very slowly, so I was riding slow enough that I may not have been passing enough air through the radiator. If anybody has any suggestions about what I should do, let me know. I would like to keep the hotter plug, but I want to know if I should richen the jetting, or just drop the hotter plug and keep the jetting. I am so close on jetting for the altitude that I ride - I just need to know if anybody has any suggestions about the hotter plug, and what jetting adjustments need to be made.

Thanks,

Peter

 

[Robcolo]

You've got two choices - - either quit riding with your mom or read the thread on Evans coolant. My 220 always boiled over when ridden slowly. After installing the Evans NGP+ I've never had it boil even on the gnarliest, slowest of rides. Airflow is very important if you have a water based coolant in the bike. WHY would you install the B7 ? Unless the bike was repeatedly fouling the 8s, there's just no reason for a hotter plug. At 9000' & above, I'm running a 140 main, 40 pilot & needle clip in the very top slot - If you're going slow it's your pilot jet & needle position that is doing all of the work - not the main- so look there - try going richer 1 step on each [don't do both at once] & see if it runs cooler.