Coolant overflowing from reservoir

[BettinANDlosing]

Hi Kymco Forum, this is my first post. Very good info here, this is just the first time I've been stumped on any Kymco (I work at a Kymco shop too  ) I have a B&W 250 that I got for $100, rebuilt everything, new crank MRP 300cc top end, Naraku cam and a lot more. The issue is this: the coolant slowly gets ejected out of the radiator into the reserve bottle. It's not extremely fast but it will overflow the reserve after an extended period of driving, if I went 100 miles without draining the bottle and refilling the radiator it would spill out the reservoir. I've replaced all the coolant hoses, checked the clamps, tried two different new radiator caps, drained and re-filled coolant multiple times always making sure to bleed from the bubble hose and at the radiator. When I got the scooter I rebuild the pump seals and gasket, no leaks what-so-ever. I am baffled at this, and have resorted to using a syringe to refill the radiator once or twice a week at this point. A lot of people on different forums I read say headgasket for this type of problem but this top end has maybe 2000 miles on it, all properly torqued to spec. If anyone has ran into this, or know any special bleeding procedure for the 250 L/c motors chime in, thanks.

[zombie]

The only thing that will force an overflow is expansion of the coolant. You have to find the highest point in the plumbing to bleed the air.

If it were a bad head gasket to coolant would be draining. Someone else here went thru this same issue sooooooooo many times he sold the bike, and later found out it was as easy as getting the trapped air out of the system. I think it was Jpreston. Try searching his radiator/overheating posts.
 I think you will find the Tstat housing has a hose w/ a 90* bend that traps air near the top of the cylinder. The other thing was the bleeder you refereed to is actually a fill port. The bike has to be warm so the Tstat is open, and with the radiator cap off, and the bike running you fill the coolant thru that "bleeder". That is supposed to expel air as it fills.

[BettinANDlosing]

Thanks, I'll look around for his posts. I'm a determined individual so no selling the bike until I figure out what is going on here!!!!

[zombie]

I remember the posts... I have had the same issue with a particular Marine engine that I had to fill by adding a 3 way valve at the Tstat.

Here is the search page result... It's in here somewhere.  http://www.kymcoforum.com/index.php?action=search2

Crap it didn't link... Jprestonian / overheat all the posts are there

[BettinANDlosing]

So by "Bleeder" i meant the vacuum line size hose running from t-stat to the radiator, is this the line you put the 3 way valve in? Please explain, thanks.

[zombie]

I'm talking about a completely different engine but it had a similar problem. Spewing coolant due to an air lock in the system that piss poor design did not compensate for.

You have to look at it logically... Where can air get trapped, and how do I get it out. With the Tstat open is where you have to begin. Sometimes you can force the air out by running with the radiator cap off, and filling up as the air surges out. No guarantees there.

Sometimes you can loosen a hose, and the air will expel. You have to find where air is stuck.

Just for double checking... Pull out your spark plug, and post up a pict taken so we can see into the insulator.

[mrbios]

... the coolant slowly gets ejected out of the radiator into the reserve bottle. It's not extremely fast but it will overflow the reserve after an extended period of driving,

1. Use a pressure tester on the radiator.

2. Perform a simple "leak down test"  - don't need the gauge.  Remove the thermostat, bring piston to TDC and apply compressed air.  If the head gasket is leaking you will get air bubbles in the coolant.  Listen for air leaks in crankcase  (exhaust valve leak) & carbs (intake valve leak).

[BettinANDlosing]

I have came to the conclusion that the headgasket is bad. I can burp the coolant, all the air bubbles come out but the level just keeps rising rising rising in my burping funnel. When I ride, then let the bike cool down, then check the level in the radiator its all air even after just a day of riding. I have a message into Joel at MRP to order a headgasket and basegasket and see if that fixes it. Hey, gives me an excuse to bust out the Dremell and port the head while I'm in there!!!

[mrbios]

... I have a message into Joel at MRP to order a headgasket and basegasket and see if that fixes it....

I hope the new gaskets fix the leak; keep us updated on your progress.

[BettinANDlosing]

Wow MRP does not stock gasket kits for their 300cc kit. Possibly just going to buy a stock 250cc top end. Keep you guys posted.

[mrbios]

Wow MRP does not stock gasket kits for their 300cc kit. Possibly just going to buy a stock 250cc top end. Keep you guys posted.

Wow, what a let down.  I'm still waiting for the screw in the bottom of the carb float bowl that I ordered 5 weeks ago.  I decided to seal the hole with epoxy until the part arrives.  What happened to the gasket supplied with the kit?  Did it get damaged during install?

[zombie]

It's the same w/ Malossi. and Polini. They never have the gasket kits... Ir=regardless of the supplier.

That's the shi_ that gets frustrating... You learn to order in advance for all the "peripheral" stuff.

[mrbios]

It's the same w/ Malossi. and Polini. They never have the gasket kits...

Is it even possible to order a gasket kit for these brands?

[zombie]

Yes but it is usually 2-3 weeks before you see it. I order 4-5 sets at a time, and re-order when I get to two.

[mrbios]

Yes but it is usually 2-3 weeks before you see it. I order 4-5 sets at a time, and re-order when I get to two.

Ok, good to know.  How often do you change your gaskets and why?