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Old 11-26-2007, 11:00 AM   #1
leonphelps OP
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2004 WR250F questions

My 2004 WR250F is running rough. I bought it used and I think I am the third owner.

The bike is running poorly when i try to idle it without the choke. After a short time, well after its warmed up, I push in the choke and it will bog out when given throttle. It will not idle for a period of time, say 20 minutes, without the choke on. I have adjusted the idle but it seems too high so i turned it back. Another thing I do is tap on the carb with a wrench lightly and that seems to fix it so it will idle. Or if I dont tap it, after a short time of riding it seems to fix itself so it will idle.

It has a GYTR exhaust system. I have replaced the sparkplug, which looked fine. I just tore out the carb and am going to clean and inspect it. I have the yamaha maintance book so I will be following that. But of course I already stripped the phillips head screws on the bottom of the carb I am going to replace them with allen head bolts.

I have a friend who can help me out with that though......thank god for friends with special tools

I am going to check the parts inside the carb and see if they are origional or an aftermarket brand. Will they have any markings on them I should look out for? GYTR? Dynojet? etc...? I dont know if the guy just slapped the GYTR exhaust on the bike and didnt re-jet it or he did.

Any ideas with the carb? Its an FCR, I am thinking something is either dirty or wornout/sticking.
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Old 11-26-2007, 12:09 PM   #2
niccoIndy
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I think you are on the right track. Sounds like its time to rebuild/clean the carb. Given the response when you tap the carb that it runs better, my guess is the float is sticking. If it is sticking closed it will run very lean and or shut off. If it is sticking open then it will run very rich, possibly to the point of flooding. Did it have gas sit in the carb for any length of time? I have also seen carbs with a bit of water in them then when it gets cold out the water froze the float to the bottom of the float bowl.

I can't imagine that not rejetting would be giving you the severe symptoms you describe. I can imagine a loss of power if that were the case, but not to the point of it not taking any gas(I could be wrong).
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Old 11-26-2007, 10:03 PM   #3
leonphelps OP
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I'll get it apart sometime this week and see whats happening with it. Thanks...
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Old 11-26-2007, 10:25 PM   #4
Django Loco
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I've just got an '07 WR250 and I've been reading Thumper Talk the last 3 days straight to cram and get educated on this VERY COMPLEX machine.
Your problems are repeated about a 100 times over on TT.

There are A LOT of things to cover here. But knowing what has already been modified on the bike is JOB ONE.

The basic mods you will need to do are the following:

Make sure WR throttle stop is swapped out for the YZ one or CUT the WR one
to exact length. The Yam AIS kit comes with this and other stuff.

Cut or unplug Gray wire, located under left rear side panel. There are several
bundles there, take care to find Gray wire. Cutting it switches bike to the YZ ignition map.

Take baffle out of exhaust, replace with quiet insert (several available)
I ordered the Pro Moto Billet through Thumper Talk Store.

Pull snorkle out of air box. Although from what you describe you are now getting too much air? hence the bogging? Not sure, but bogging is a common issue with WR.

Air Screw. Pull plug out next to carb drain, use sharp wall board screw, just screw it in about 1/8" and the little tin plug can be pulled right out. carefully unscrew stock fuel screw (screw IN first to see where is was set!!!) now screw in new fuel screw that you can get to easily. I have the Zip Ty one, several others available. I bought the AIS removal kit (I bought the TT one, Yam GTYR makes one too) Makes working on carb easier and has other benefits as well. You also will need to deal with the Air Cut system, later on that and the Accelerator pump squirt duration. And lots more!!! Oh Joy!

Jetting:
rough beginning point after above mods:
Main jet: 175 (stock is 170) (for sea level to about 5000 ft.)
Pilot: stock seems to be OK. (42) or try a 45 but I doubt it. If you block off the Air Cut you need to go leaner on pilot.
Leak Jet: 40 (stock is 70)
Air screw should be between 1 turn to 2.5 turns out. If it does not run in that
range you've got other issues. My stock one was set to 1 3/4 turn out. Set for highest idle after all tuning is done. Set idle to spec....its very high...like
1500 to 1900 rpm.

Trust me, this in NOT an easy bike to tune or to work on. I've had 40 bikes,
and many many race motocrossers. This one is the toughest yet.

Read up at Thumper Talk, a ton on info. I doubt the carb is dirty or float bowl out of spec. Its just not set up is all.

What I've outlined is BASIC, there is LOTS more to do. From "squirt" duration ont the accelerator pump

On the plus side the thing handles like a dream, great suspension and the motor should last very well with minimal maintainance (relatively).

Good luck!

Django Loco screwed with this post 11-28-2007 at 11:38 AM
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Old 11-27-2007, 08:06 AM   #5
leonphelps OP
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I am pretty familiar with all the mods you are talking about. I am not going to do the gray wire mod. I understand it gives more top end. I live in connectiucut and the trails near me are tight, rocky and hilly so I need more bottom end. The yamaha gytr muffler has a removable baffle, so I left it in, its really loud with it out! I think I will get the external adjustable air/fuel screw for easy adjusting. Before I removed the stock one I counted 3.5 turns out, so I'll check out the rest of the intervals when I get it apart. The airbox has the mod also.

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Old 11-27-2007, 10:22 AM   #6
WoodButcher
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Quote:
Originally Posted by jbunceiii
I am pretty familiar with all the mods you are talking about. I am not going to do the gray wire mod. I understand it gives more top end. I live in connectiucut and the trails near me are tight, rocky and hilly so I need more bottom end. The yamaha gytr muffler has a removable baffle, so I left it in, its really loud with it out! I think I will get the external adjustable air/fuel screw for easy adjusting. Before I removed the stock one I counted 3.5 turns out, so I'll check out the rest of the intervals when I get it apart. The airbox has the mod also.

Sent from my iPhone
Gray wire won't affect the low end. So cut away and enjoy the high end when you do rev.

Sounds like the overall problem is the carb. remove all the jets and clean them with carb cleaner then blow them out with compressed air. Same of all passages in the carb. Then put it back together and see how it runs them. Check the float height too. And adjust the pumper according to the manual.

Recently went through the same exercise on my 03. couldn't get it running like I wanted with jet changes and finally pulled the carb and stipped it down. Ran great when I put it back in.

Just use a fuel stabilizer to prevent it from gunking up in the future.
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Old 11-27-2007, 11:36 AM   #7
Django Loco
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I agree about the Gray wire....from what I have read on TT low end power/torque are not effected with the YZ map. But mid range really is improved and top end of course too. The bike will now rev about 2500 rpm's
higher!!! No loss of low end. So in slimy woods just use the low to mid power,
should be OK. Hopefully it won't "Hit" when gets in the upper RPM's like a two stroke. That would be the only reason NOT to cut it. I've read dozens of reports on this....even from guys who were really relucant to cut the gray wire....all were amazed and happy with the change. YMMV.

If the bike has sat over long periods you could have a gunked up carb. Or if stuff got by the air filter or in the fuel. But most times I find CLEAN carbs inside. Float bowls don't get out of spec unless someone "fool's" with them usually. I would go ahead and measure it just to know. (make sure you do it right...many riders MIS measure the float level then "adjust it" and wonder why they have a "new" problem.) So tread lightly.

Good luck.
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Old 11-28-2007, 11:15 AM   #8
leonphelps OP
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Got he carb apart and cleaned everything. I soaked some of the parts in parts cleaner/degreaser for about an hour. Took off the gaskets and rubber parts first though......

Its got a 175 Main, the stock is a 170 per Django loco (Thanks for the info)

I couldnt find the numbers on the Leak Jet, So I am going to "ASSume" its a 40....

The needle was on the #4.

So I cleaned it with carb cleaner and blew it out with compressed air.

I put it all back together and will install it back on the bike sometime this weekend.

Will do the gray wire also...you all have convinced me!

Fingers crossed!!
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Old 11-28-2007, 11:45 AM   #9
Django Loco
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Quote:
Originally Posted by jbunceiii
Got he carb apart and cleaned everything. I soaked some of the parts in parts cleaner/degreaser for about an hour. Took off the gaskets and rubber parts first though......
How did it look inside? Grunge? Dirt? Sand? Anything at all?

Stock leak jet is #70, may be OK depending on your altitude, a #40 seems
to work well in many tuning scenarios.

Quote:
Fingers crossed!!
I'm in the same boat. Bike is all apart waiting for parts so I can do some test rides! I assume you tilted the carb over to gain access?

There are a bunch of things that can make this bike run poorly...I'm just hoping I've covered most of them and get it in the ballpark...tearing into that
carb is No Fun at all!
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Old 11-28-2007, 05:45 PM   #10
leonphelps OP
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Quote:
Originally Posted by Django Loco
How did it look inside? Grunge? Dirt? Sand? Anything at all?

Stock leak jet is #70, may be OK depending on your altitude, a #40 seems
to work well in many tuning scenarios.



I'm in the same boat. Bike is all apart waiting for parts so I can do some test rides! I assume you tilted the carb over to gain access?

There are a bunch of things that can make this bike run poorly...I'm just hoping I've covered most of them and get it in the ballpark...tearing into that
carb is No Fun at all!
The inside was a little dirty with black stuff that wiped off pretty easy but all in all it looked pretty clean. The bottom bowl was filled with brown stuff that looked like rust, but its aliminum so who knows what it was.

Not really dirty or sandy inside. So thats weird......

I removed the whole carb, no tilting involved.

And I saw that the gray wire was already done....
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Old 11-28-2007, 06:30 PM   #11
niccoIndy
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I am at a loss. Is fuel flowing freely from the petcock? Is the carb vent hose clear? Thats the only other things i can think of right off.
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Old 11-28-2007, 09:24 PM   #12
leonphelps OP
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So the brown stuff is Varnish. I soaked the jets, needles and bowl in a cleaner for about a hour, then sprayed with carb cleaner, then rinsed with water, then blew it all out. we'll see what happens.....
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Old 11-29-2007, 03:12 PM   #13
niccoIndy
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If varnish is the culprit what you did should take care of it.
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Old 12-20-2007, 09:51 AM   #14
leonphelps OP
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So I got the carb back together and installed. I added a external air/fule screw to help. I made the inital setting of 2 1/2 turns out and started up the bike. I let it idle with the choke on for about a minute, then let it idle for a bit with it pushed in. I tried to rev it slowly and then quickly....

So...its still doing what it did before!!!! Quick throttle opening the bike will stall out or bog terribly...........

It is perfect everywhere else in the throttle range

I got out the trusty Yamaha manual and did some looking in it. Under the symptom section..."poor response when throttle is opened quickly:"

1. Check over all settings......
2. Use Main Jet with lower calibration number
3. Raise jet needle clip position

Now this is the best part....

4. If these have no effect, use a main jet with a higher calibration number and lower the needle jet position......i.e. go the other way, cause we dont know either...

And check the accelerator pump is operating smoothly....

So I have not tried that yet or adjusted the main jet or needle. I put everything back the way it was...

Any ideas..??
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Old 12-20-2007, 12:58 PM   #15
jeff_in_rc
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Question

Did you take the accelerator pump apart? Is it full of junk to? Is it adjusted properly? How about the TPS? did you take it off when you cleaned the carb? If yes did you re-adjust it? Just throwing out a few things.
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