125-200cc WB165 over heating

Hi all. Just wanted to get some ideas on why this is happening. I fill the radiators to the specified height and the bike keeps spitting coolant even when I ride a moderate pace. I installed a catch tank on it so that I at least dont loose all of the coolant and it can be sucked back in. The temps here have been in the low to high 30's. I am using engine ice. Can the addition of a flywheel weight cause this? I just installed a 10 oz. from Stealhy. I am wondering if my radiator cap is damaged? I have a PWK and my jetting is cucurrently a 180 main, 48 pilot, JD blue needle in middle position, air screw 1.5 turns out. I doubt that its the jetting thats causing this. I do have a IMS tank on the bike which some what does obstruct the air flow. I removed my radiator cap to confirm coolant flow. The bike seems to be running great otherwise. I do have the CR ignition and just used the screw marks to line it up and install it. Maybe the timing is off? Does anyone have a idea on how to properly set timing on the CR ignition? I will search in the mean time. Thanks in advance for your help!

I would look at the cap, air bubbles , is it burning any coolent ? . I have lots of single track miles on my big bores and have yet to see one even steam. Cr ignitions with FWW, wr ignitions etc - etc . You are jetted alot leaner on the main than I am.

I ran my YZ250 hard last year and never had a drop of coolant in the catch tank. Its not burning coolant that I can tell. The overflow bottle gets full to the point where it does overflow so you might be correct Dirtdame. This just started happening last week after the installation of the FWW so I suppose removing it would be the first logical step. I cant see that being the problem though. I have a race this weekend and if it is the radiator cap I might be screwed. TROFFER88 what are you running on the main? I am almost at sea level here. Thanks for the replies guys!

I was running the same jetting as you (JD blue with 180 MJ in 38mm PWK) with my WB 165, and although I did not have overheating issues, it was running much too lean on the mid to top end (I had some nasty pinging). In discussing this with Walt via PM, he said the JD needles are too lean beyond 1/2 throttle, and he recommended using the NOZI needle in the 4th slot down with a 185 MJ as a starting point for us Jersey sand fleas. This is what I have currently installed, but I have not yet ridden it. I will report back after this weekend.

I just pulled my radiator cap off and when I did it released some pressure. The bike hasnt been ridden in a couple days but I assume this is normal. Not to sound weird but I sniffed the underside of the cap and it smells like exhaust. I did the same on my YZ and it didnt smell like exhaust. What could this mean?

Thanks dfeckel. Are you running the Tri-County HS this Sunday? I plan on going even if I have to run the YZ. I guess I will try the 185 main and maybe richen the needle a bit. I am getting some exhaust spooge now where I wasnt before with the leaner jetting. I just dont want to start fouling plugs. Wonder what the richer JD needle is.....red or blue.

Motocrossmr,

I'm hoping to get the bike out Saturday for a shakedown run to see if Walt's jetting recommendation solves my pinging. Will you be down at the Tri County HS on Sunday? If so, I'll look for you. I'll be in a gray 4Runner with a landscape trailer and buddy with a butt-ugly 200 XC-W. If I see you in Millville, I'll let you know what jetting I settled on.

You might want to pop off your head and check the sealing o-rings. It sounds as if you might be getting exhaust pressure into your cooling system. That would certainly explain the coolant loss. If the o-rings seem correctly seated and in good shape, then I would retorque the head bolts and see if that helps. I kind of doubt that your FWW caused any of this. The jetting still might be suspect, however.

I would pop your head and take a quick look at the orings.. Although you would think it would burn water, there is a chance you are pressurizing the coolant system with combustion gasses, explaining the smell. Just a stab, also grab a temp gun or something and verify its hot, you might think your overheating but its actually just a duplicate symptom.

I'm pretty sure the blue JD needle is the richer one. The blue is for colder temperatures and the red is for hotter temperatures, if memory serves.

Yeah I will be there. I will look for you too. I have a dark grey Tundra with all my crap jammed into the bed. I will hopefully have everything squared away by then. I am going to go down and check the o-rings now. Good idea guys!

Maybe timing is advanced too much and causing to run hotter also

I seem to have found the problem. The inner O-ring had a section completely missing. This was a new OEM seal and I am just curious as to why this could have happened. Anyone ever have this happen? I dont think I pinched it but I suppose its possible. I would think I would have had a problem right away. If you look at the cylinder and head you can see where the exhaust gases were escaping. I have Town and Country sending me new gaskets and a CV4 high pressure radiator cap. I should have them by Saturday. At least my plug looks good!

Nice investigatory work!

i would think jetting and/or ignition so far off to boil it over would run and sound very bad

what pipe is that and did you have to weld the stinger back on?

Matt,

That is pretty bizarre. I have nicked an o-ring when putting the head on before, so I am always careful to make sure that it is well seated. I will send you the timing tool so you can get an accurate mark to go by for your CR ignition. Just send it back when you are done. My voyager tracks my engine coolant temps throughout every ride. I check it after each ride and it is rare that it makes it to 180 degrees much less boil. Typically takes a hot day and at least a half hour of under 5mph steep crap with multiple log jumps. My average running temp when looking at the graph is 130-140 degrees. I personally just have not had good luck with the JD needles for the small bores. But that is just me and my jetting is never the same as anyone elses. My buddies 165 likes the EEK needle and mine will sieze if I try it.

montgob1, the pipe is a FMF Gnarly from a KTM 200. Nasty early mid range hit that I toned down with Walts power valve spring kit and a FWW.

Walt, I really appreciate it. Let me know the shipping costs. Can you throw a extra piston ring in the box and I will get the check in the mail tomorrow? While going through all the spring combo tests I never had the bike over heat so for it to suddenly start was weird. The fact that the radiator cap smelled like exhaust gave it away. As far as the jetting is concerned the bike seems to be running really well. I just switched to the leaner jetting and am getting a little bit of spooge now. I might leave it as is for the time being until after this first race. I just dont want the bike to be running too lean.