Radiator and Carb issues. . .

[robwbright]

Hello all - long time since I’ve posted - haven’t gotten to ride much this year. . .

Some of you (XRPred, Rich R., etc. . .) aren’t going to believe this, but I’ve joined the 4 stroke revolution.

I recently purchased a 2002 YZ250f - I’d certainly not have purchased a 250f that old . . . except the price was right and the cylinder, head, valves, etc. . . were all recently replaced with new parts.

I got the bike for $1000.00 and sold the RM144 to my bro for $900 - the plastics on the YZF are beat up (got new plastics to install over winter for $80), needs chain and sprockets and new tires, but mechanically seems to be sound.

The bike has a full Yoshimura exhaust, GPR Steering Stabilizer, Tag Metals Triple Clamps, Tag Bars (replaced with my flex bars), suspension by Race Tech (springs also from Race Tech). I figured, what the heck - if the bike gives me a serious problem, I can probably make most of the money back parting it out on ebay.

Pics of before and after new plastics and graphics to come.

Now to the two problems. . .

Took the bike out for first real ride yesterday. 55 degrees outside. The bike will not idle with the choke off unless I turn the idle up really high with choke on - then it will idle semi normal with choke off. However, it seems to sometimes “stick” on a high idle with the choke off.

I assume the carb needs a good cleaning - that’s where I’m going to start. . .

Which leads into the second problem.

My brother and I were woods riding a couple miles from dad’s house. Really slow going, as the woods are pretty tight and the trails hadn’t been ridden much recently by anyone - thus, there were about 3-4 inches of leaves everywhere which made it REALLY slick (it's also been pretty wet here in SE Ohio). The idle was running high (high enough that the bike would continue moving forward significantly without giving it any throttle).

We had just completed a very slow, hilly section - lots of first gear lugging - when my front end began sliding down a slick off camber corner we were on. I kept the bike from falling, but got off and looked down - there was coolant streaming from the bottom of the bike for about 3-4 seconds. Lots of mud, so I couldn’t really see where it came from. I was very concerned that it might have been leaking for awhile and that I might be very low or out of coolant. Let the bike cool a bit, popped the rad cap and couldn’t see any coolant. (When we left the house, the coolant was at the top of the fins, but not all the way up to the cap).

As I was concerned about overheating my new bike, my brother rode back to dad’s and got some coolant. When he returned, I put (guess) less than 6 ounces in the rad and it was topped off. Kicked the bike over a couple times and it was still full. Started it, rode for 5-10 minutes and checked it again - still topped off. Got back to the house, popped the cap - still topped off.

Washed bike, started, rode up and down the street to get it warm, checked level - still topped off. Water pump appears to be working fine.

HOWEVER. . . steam was coming from the right side radiator - and kept coming for 5 minutes till I shut the bike off. Not a lot, but some. Seems to be more close to the cap, but it coming from the bottom as well. Coolant level appears to be staying the same.

I had washed the bike ½ hour before, so I don’t know if there could be “surface water” evaporating.

I’m suspecting the rad cap and/or a very small hole in the rad at the bottom and/or the coolant. The coolant looks VERY green as if it’s 100% antifreeze.

Ideas?

Thanks

 

[robwbright]

Forgot to mention that I put 93 octane in it.

I see that the manual calls for 95+.

Is that really necessary for a C/D rider?

Would 100LL avgas work?

 

[Matt90GT]

You can use pump gas 91. there is 2 rating scales on gas. Do some research there.

Clean the pilot jet out. It is causing your lack of idle without choke and running lean - IE running hot.

 

[robwbright]

Thanks.

Disassembled and cleaned the carb this evening.

Put it back together and started it up. Adjusted idle screw and got a nice, smooth idle in about one minute.

Gased it a couple times and it stuck on a higher idle - maybe 500-1000 rpm higher.

Within 15-20 seconds the front 6 inches of the header was so cherry red that you could almost see thru it.

Air leak, anyone?

Any other ideas?

BTW, what is the proper operating temp? Someone on one of the other posts said 280, but isn't that pretty hot?

Thanks

 

[whenfoxforks-ruled]

ROB! Did you miss a bunch of threads or what? Did you see the new sister site????? The red header thing, thats fuel burning in your header, its too rich. Some believe it to be normal, I seen them white/yellow. Doing it with the choke on is normal. Adjust your mixture screw to attain the highest idle. See where its at? Did you check the ap squirt? Vintage Bob

 

[robwbright]

"Did you miss a bunch of threads or what?"

Haven't been on here in months - I've gotten to ride 3 times all year. . .

"Did you see the new sister site?????"

Have no idea what you're talking about. . .

"The red header thing, thats fuel burning in your header, its too rich."

I really don't know what I'm doing on motors - especially these 4 strokes as it's my first one. My father in law races modifieds and karts on the east coast series. He believes it's an air leak between the carb and the cylinder creating a lean condition. He's also not very familiar with "modern" 4 strokes, as they tend to explode in his karting series and he beats them regularly with his CR125.

"Adjust your mixture screw to attain the highest idle."

Please expound - what do you mean by "highest idle"? I can make it idle at (seemingly) 5000 rpm - but it doesn't make sense to leave it that way.

"Did you check the ap squirt?"

What?

 

[whenfoxforks-ruled]

http://flagofconviction.com/forum/ucp.php?mode=login , check that out, and kind of get to know your carb components. You have a 600 dollar state of the art carb, arguably the most complex also. Basic jetting rules still apply. If it runs better with the choke on, the pilot is small, or the mixture is lean. Its a bunch of fun to adjust, unless it has a aftermarket screw? Directed out the front/bottom? It would pay to check the plug, its a bunch of fun also, the gas tank needs to come off. But the plug, if its black may be a coolant leak, if its white, the guy is right and its an air leak. If its wet, I am right, your mixture is a tad rich. Not a bad place to be, but its a 4 stroke! Vintage Bob

 

[robwbright]

http://flagofconviction.com/forum/ucp.php?mode=login

Interesting site. I seem to recall being picked on over Ron Paul, etc. . . about 2-3 years ago.

Now lots of people are on board.

Glad to see the site. Sure I'll be over there occasionally.

But right now I'd just like to get the new bike running decent.

 

[Matt90GT]

your header will glow since it is Ti. It is air cooled, so get out and ride it.

For your idle, turn it down. You have it set to high from a plugged jet and causing problems with the TPS setting.

 

[robwbright]

your header will glow since it is Ti. It is air cooled, so get out and ride it.

For your idle, turn it down. You have it set to high from a plugged jet and causing problems with the TPS setting.

So you're saying Ti glows "more" than regular pipe metal (whatever that might be - aluminum, steel, etc. . .)?

No plugged jets now - cleaned them all and the idle problem was still there - although it did seem less pronounced.

On the throttle position sensor. . . when I cleaned the carb, I did remove the screw and started to pull it off - then thought better of it, as the manual said to leave it alone unless you're replacing it.

What can I do to resolve problems with the TPS?

 

[Chili]

Try running the bike with the tps unplugged.

 

[robwbright]

Try running the bike with the tps unplugged.

Are you recommending that as a cure for all of my issues or merely for the idle issue?

I gather that this is the purpose of the TPS. . .?:

http://www.thumpertalk.com/forum/archive/index.php/t-802585.html

The purpose of T.P.S. on bikes in general can be:

1. Alter the ignition curve based off of engine load. (ours are bogus).
2. Control servo or stepper motors for the purpose of exhaust valves in exhaust systems or other remote devices.
3. Traction control.
4. A reference voltage signal sent to the ECU to be used in concert with other input data for the ECU to make various decisions; ie fuel injection.
5. Can be used to arm or trigger solenoids or anything you want.
5. I use my own TPS strictly as a means of knowing where the throttle is accurately at all times while tuning so as not to guess, ie 1/4, 1/2 etc.

Thanks

 

[Chili]

I'm recommending it as a test to help diagnose your idle issue.

 

[whenfoxforks-ruled]

I did hear guy talk to the effect it cures running issues. Unplug it and see? Its not like it will blow up or anything, foul a plug at worst? Vintage Bob

 

[holeshot]

I can't offer too much toward resolving your problem, but

1. Most people freak out when they see their 4 stroke header glow the first time. This is usually in low light conditions and it glows a lot more at high idle (like when the choke is on). If you go to a night race and are on the starting line, just tap the guy next to you on his shoulder and point to your glowing header. This will shake him up so much, he'll probably crash before he gets to the first turn. Nahhhh..most people have four strokes now, so they won't be fooled. This is more likely a red herring.

2. Premium gas from your local gas station is sufficient. The number in the manual is RON (it actually says RON in the manual). The number at the pump MON+RON/2 (RON being the higher number usually). This subject has been beaten to death here - I've already been schooled :whoa: Another red herring.

3. Four strokes don't like to be idled long - at least not as long as your trusty old two strokes. When people take delivery of their 4 stroke, they tend to start it in the garage and admire how cool it sounds for too long. Get it moving through the air.



The leak possibly could be coming from the weep hole at your water pump (leaky seal) - a common failure on hot running four stroke beasts, especially when left idling too long. Yes, the seal can leak intermittently and it's on the right side of your bike. Although you did say the steam seemed to come from the right rad.....

As far as the hanging idle - hmmmm - that's a tough one.. who put the cylinder head back together? Sometimes improper assembly can cause strange issues, but if it was put together wrong, it probably wouldn't last long anyway...so you'd probably know by now.

 

[robwbright]

This is going to make me look stupid, but oh well - I just want to get the bike right. . .

The guy I bought the bike from is a good friend of a good friend. He told me it was an 02 and I didn't really care what year because the price was right.

I finally got around to checking the VIN - it's an 03. Don't know if that makes any difference in this situation or not.

At any rate, here's an update on the situation.

Took bike to my father in law's garage last night.

Started it and within 15 seconds the header was bright red.

Began looking for air leaks between carb and cylinder. Reseated carb in boot and boot on cylinder.

Seemed to help a little, but not significant.

Restarted bike and ran it for about 2 minutes. Exhaust turned cherry red all the way back to the muffler.

Father in law concluded it was likely tight exhaust valves.

Pulled head cover and checked exhaust and intake valve clearances. (From what can be seen there, it does appear to be all new stuff in there). All clearances in the middle of the spec range.

Thus we were kind of at a loss.

Prayed for wisdom from God.

Pulled plug. Appeared to be very lean on idle and rich otherwise.

Tried fuel screw. After several adjustments, bike no longer gets overly hot immediately.

However, bike is hard to start (when hot - I don't suppose that's surprising, but it was not hard to start hot when I first got it), will barely idle with choke on and will not come close to idling with choke off.

Pulled carb again to clean again.

That's where we left it after 3.5 hours.

 

[whenfoxforks-ruled]

If it can barely idle with the choke on, and not at all with it off. The pilot may be too small. BUT, that depends on how many turns out the fuel screw is at? Adjust it too its highest idle, count where its at. Do not burn your self, that yellow/red header is really hot! Vintage Bob

 

[robwbright]

If it can barely idle with the choke on, and not at all with it off. The pilot may be too small. BUT, that depends on how many turns out the fuel screw is at? Adjust it too its highest idle, count where its at. Do not burn your self, that yellow/red header is really hot! Vintage Bob

You nailed it - the pilot was "too small", but not actually.

Upon my father in law cleaning the carb - again - he found a small piece of dirt in the pilot.

Reassembled, started. Bike runs great, idles perfectly.

This was after checking for air leaks, valve clearances, TPS, etc. . .

I would not have believed the pilot could cause a condition THAT hot when there was some air flowing thru it - when I checked it last week, I could blow thru it. At one point before resolution, we let the bike idle for 2 minutes and the exhaust was cherry red all the way back to the muffler.

Thanks for all the input, guys. Now, hopefully I can ride it a bit before the temps get to freezing.

 

[holeshot]

At one point before resolution, we let the bike idle for 2 minutes and the exhaust was cherry red all the way back to the muffler.

Yoiks :whoa: that is excessive - I would have expected glowing just a few inches beyond the bend (max).

With that much glowing .. you'd have enough light to read the manual and have the whole family toast marshmallows at the same time. :nod:

Nice you got it solved.... :cool: