Coolant on carb slide rubber intake boot & leaky carb

[robwbright]

Been working on the 2nd 03 YZ 250f I have. I've resolved a variety of problems (replaced fork seals, replaced a couple missing spokes, changed tires, etc. . .) and am getting back to the final issue - a leaky float . . . which I thought was causing gas to get in the oil. I thought this because the oil was very thin and smelled really strong of gas. Plus, about 1/3 of it evaporated in 3 or 4 days sitting out in a pan. I never saw any milky appearance to the oil.

Cleaned the carb, checked the float - it doesn't have any holes or leaks - floats in gas just fine and doesn't bubble when held under the gas.

I'm not sure how to measure the float (manual doesn't make sense to me) - but it looked to be hanging down further than the float off my good running (and not leaking) other 03 YZ250f - and this one was leaking badly.

I bent the little float do-dad and reassembled. Must have bent it too far because it wouldn't seem to let any gas in at all. Bent it back the other direction - about 1/2 way between original position and new position. It started leaking again.

I did get the bike started again (with float leaking) but it was smoking out the exhaust (white). Shut it down to deal with that later.

When I pulled the carb again to work on the float, I noticed liquid beading on the slide and the inside of the carb.

I looked inside the rubber intake boot the carb fits in and there appeared to be a little bit of green liquid in there.

Obviously, I have two problems. Any input would be appreciated.

1: How to fix/adjust the float?

2: How to explain/fix the coolant on the carb/intake?

To my understanding, the only things that can cause coolant in the cylinder are (a) leaky water pump seal; (b) blown head gasket; (c) warped head.

Am I correct?

I think I can check the water pump seal easy enough, but dunno how likely that is.

How do I check the head gasket and or head? I assume I have to pull it to check it? What am I looking for?

 

[robwbright]

The head and cylinder are off the bike. Prior owner put in a hot rods crank. Valves look very good (according to a guy that's totally rebuilt several 450 ATVs). However, prior owner of my bike reused the head gasket - thus, it would appear I have discovered the cause of the coolant leak into the cylinder.

The cylinder has a very small amount of scarring on the front and back - one mark can barely be felt by a fingernail and the rest is about as visible as honing marks. The piston has similar markings.

Rings look alright, but haven't checked them to spec yet. Assuming they're alright . . . and assuming the head is not warped and the cylinder is within measurement specs, I was thinking of new gaskets, honing the cylinder and putting it all back together.

Think it will be alright?

 

[Matt90GT]

you need to replace the piston and cylinder also if you have marks on them. Dont skimp. It will come back around

 

[robwbright]

you need to replace the piston and cylinder also if you have marks on them. Dont skimp. It will come back around

Normally, I'd agree with you. However, the scarring/scuffing is so light that it will likely come completely out with a honing.

Dad's been around dirt and street bikes for 4 decades. He says he'd use them.

The buddy who's helping me with the project has rebuilt several 450s. He says he'd use them.

My personal opinion from rather more limited experience is to use them.

Also, other than the light marks, the cylinder and head are within spec.

 

[2strokerfun]

On your carb issue, try replacing your float needle and seat. All the adjusting of the float in the world won't fix anything if your needle isn't stopping the flow when pressed against the seat.

 

[robwbright]

Needle and seat are fine. Blowing in the carb - it TOTALLY seals off.

Discovered the problem - prior owner had tightened the drain bolt too tight and cracked the bowl. I sealed it with epoxy.

 

[ellandoh]

Discovered the problem - prior owner had tightened the drain bolt too tight and cracked the bowl. I sealed it with epoxy.

what kind did you end up using??

 

[robwbright]

http://epoxyputty.com/putty.htm

 

[rmc_olderthandirt]

If your original assumption was correct and you had gas in the oil then you haven't found all your problems yet. If it was actually coolant in the oil then you might be at the point of knowing what needs to be done

If your cylinder has a mark that can be felt then you need to resolve that properly. Older bikes used to use straight cast iron cylinder sleeves which you could just bore out to the next larger size when they were damaged. Newer engines use a "plated" cylinder, so what would have to happen is that you bore out and then re-plate. Attempting to hone out a scratch from a plated cylinder would probably be a disaster.

Rod

 

[robwbright]

If your original assumption was correct and you had gas in the oil then you haven't found all your problems yet. If it was actually coolant in the oil then you might be at the point of knowing what needs to be done

If your cylinder has a mark that can be felt then you need to resolve that properly. Older bikes used to use straight cast iron cylinder sleeves which you could just bore out to the next larger size when they were damaged. Newer engines use a "plated" cylinder, so what would have to happen is that you bore out and then re-plate. Attempting to hone out a scratch from a plated cylinder would probably be a disaster.

Rod

Had the cylinder reviewed by 3 guys who all work on bikes (one of whom races 125cc and 250cc karts on the east coast series and does all of his own maintenance) - and all of them say the cylinder is alright . . . and it's within spec as far as measurements, as is the head.

I'm going with it as is.

As to the gas in the oil, I suspect the fact that the petcock is leaking when "off" has something to do with that. Thus, I have a petcock, rings, base and head gasket kit on the way.