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30 mph Top speed on WR250f?

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It's official. Something's wrong with my 2009 WR250f. It's top speed is 32 mph. I bought it last week because i heard that it can eaily do 70mph. Im hoping you you awesome people can point me in the right direction as im still unfamiliar with these bikes.

I've verified that the prior owner clipped the grey wire, added the YZ throttle stop screw, did the AIS and snorkel removal, and added an FMF TI Powercore exhaust (still has stock Jetting and ECU)

I'm 6'2" and 165 lbs, so it's unlikely that the bike just thinks I fat. I thought it was a gearing issue so I swapped out the standard 13t front sprocket for both a 12t and then a 14t with no significant difference.

It feels completely gutless in all gears and barely can climb a medium grade hill. What should I be looking for as I try to fix this?

Thanks guys!

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What is the rear sprocket size? I have an 08 with stock gearing of 13/50 and I assure you that 30 mph is not top speed.

Is the air filter extremely dirty? What about the valve clearances? Are they within spec?

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Great questions, rear sprocket is the stock 50 tooth. The Air filter is clean. I haven't checked the valves yet, I haven't picked up a manual yet, what should the clearance be on those valves?

Also, i'm fairly certain that the bike was riding fine when I test drove it, bought it and rode it very briefly afterwards. Since then, *I think* that it feels like its gradually losing power on each consecutive ride, to the point that today I stopped riding early for fear of causing further damage to the bike.

Thanks for your help!

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Is there something dragging? A brake locked up? Put the bike on a stand and verify that the wheels spin freely by hand.

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Has the headlight been unhooked or dors it work? The reason I ask is on the old wr when that circuit is broken the engine will cuttout.

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Have you checked the compression yet? I would also rejet, fmf reccommends this when you slap their pipes on. Also, you can find a pdf version of your manual online. Ill post a link for ya. It will Have multiple languages. So if you Have some freetime, upload It to a pdf unlocker and then you can delete all the pages that are not in your language.

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Nothing is dragging, although I did have to ask myself if I left the parking brake on :) the brakes are fine, wheels spin freely. The engine sounds fine, does not cutout or chug, its consistantly gutless throughout all the gears, and very slow off the line. it feels like the bike just naturally tops out at 30mph.

The headlight comes on just fine, and I really appreciate that insight, since those are the wacky things that only you yamaha owners know.

Could it be an unplugged vacuum hose? Could the stock ECU have gotten reset to a horrible setting after I swapped the battery? (Oh I did just put in a new battery, not sure if that's related?)

I'll check compression tonight, good call. And YES, please post a link to the PDF version on the repair manual if you have it handy, although I can Google it too ;)

Edited by Mromrell

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This is an odd one. Yes I think you still need to jet the bike but that should not have the symptom you are having.

 

Recently Crispy Fruit Loop (yes that is her user name right now) was having an issue with loss of power and we kept on going back to jetting or an electrical issue but could not figure it out. Finally she found out when she unplugged her neutral switch the problem went away. The difference here though is she had a sputter with her loss of power.

 

Seems like you are starving the bike for air. You sure there is not something crazy like the last guy or you left a rag in the intake while cleaning it and then accidently put the air filter over it?

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Ok, so I pulled out the carburetor for a basic inspection (deep clean will come tonight) it looks good. No obstructions, the throttle is making a full 1/4 turn just as it should.

I also pulled off the valve cover, and the valve clearances are all within spec.

Could it be a bad fuel/air mixture, or a setting on the carburetor is limiting the bike? Although I can Rev it plenty high, it's just that none of that power seems to make it to the wheel.

I'll check compression soon, but with power loss this bad, i assume think id hear some chugging or other related engine sound if it were a compression thing.

This makes me think it's got to be something with the electrical. A setting with the fuel mapping or an unplugged switch...

Those are the things that I'm most unfamiliar with on these Yamahas. I'll check the neutral switch, anything else?

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I still think it sounds like compression, never heard of the electronics being able to limit speed when malfunctioning 

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Really hard to say without hearing it, but you state it revs fine but won't get up and go? If it doesn't bog or backfire,etc I am doubtful it is fuel related. If it free revs but doesn't go under load it could be plugged up exhaust somewhere. Also what about slippage in the clutch or other components? Maybe put it together and make a video of what it does?

Edited by urrick15

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I think you can rule out anything inside the engine like compression, valve clearances etc.  It takes maybe 7 horsepower for a WR250F to go 30 mph, and if you have enough compression for the engine to start at all, you'll make much more power than what's required to go 30 mph. 

 

Sounds like someone has stuffed a rag in the carb or exhaust pipe.  Or you have mice or chipmunks loading your muffler with acorns or seeds?.  Don't laugh- back on the farm decades ago, a mouse thought my PE250's muffler was the ideal place to store soybeans.

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At this point, I was thinking maybe the exhaust is plugged too.  OP, can you temporarily remove the muffler and give it a quick ride?  (I don't know if those exhaust systems are 1 piece or not.)  It will be noisy as hell but you're be able to tell VERY quickly if that was it.

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Wonder if the spark arrestor screen is all carboned up?  You can remove that.

 

As to run it without the muffler- I wouldn't do that.  Not for the loudness but rather the hot air could melt something on your bike.

 

 

Another idea-  did you get the stock muffler when you bought the bike?   If so, just put it on for the test run.

Edited by BazookaJoe

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Hey Guys, I tried to check compression but my tool wont screw into the tiny Spark plug port... so that test will be forth coming. 

I did, however pull out the clutch. no wear or tear, the thicknesses were all within spec (~4mm for the fiction Plate, and ~1mm for the Clutch plate), there was no warping, although several of the plates looks burnt (See the picture here: https://goo.gl/photos/weonvpb9a1QuKWEC8 - What do you think?) 

 

I drained the oil, it was brand new. The seller said he just did an oil + air filter change and rode just once on the new oil), I can't be certain, but it didn't look like 21.9 oz of oil came draining out (I know some will still be in the Oil filter and throughout the bike) but that might have caused the burning on the clutch plates.

 

Wonder if the spark arrestor screen is all carboned up?  You can remove that.

Another idea-  did you get the stock muffler when you bought the bike?   If so, just put it on for the test run.

 

I'll check the arrestor screen, and yes, I also got the stock muffler, So I'll try swapping that out tonight as well, Lest tiny critters are calling that home. 

 

Thanks for your help on this! 

Edited by Mromrell

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Another possible (but probably not likely), is if there is a malfunction with the auto decompression mechanism on the exhaust cam.  If the auto decompression is stuck on, that would absolutely turn your bike into a complete pooch but would start just fine.  Verify if the weight moves to the outside of the gear and also rotate the engine so you can view the little "pimple" retracting properly.

 

Again, IMO, very doubtful that low compression is your problem.  If your engine has enough compression to start, geez, it would go at least somewhat respectable. But- if you do have bad compression, you would be having massive blow by.  Open the airbox cover and start up the engine.  If you have low compression, you will be getting air flow thru the crankcase breather hose which IIRC connects to the front top of the air box.

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The Spark Arrestor Screen is intact and clean as a whistle. so I don't think any critters got inside. 

 

 

Another possible (but probably not likely), is if there is a malfunction with the auto decompression mechanism on the exhaust cam.  If the auto decompression is stuck on, that would absolutely turn your bike into a complete pooch but would start just fine.  Verify if the weight moves to the outside of the gear and also rotate the engine so you can view the little "pimple" retracting properly.

 

How would I test for a malfunctioning Auto Decompress Mechanism? 

I did a compression test last night and only got 25psi  after several kickstarts, shouldn't that be closer to 160 psi?

 

g0fVMC3l.jpg

 

 

Also, I didn't get any comments on my clutch plates, so I'm reposting images. Are they too burnt?  is that the issue?

 

YDWDz6Vl.jpg  BHK08Chl.jpg

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I should add that even though I only had 25 psi on the compression test, I didn't lose an once of air even after letting the gauge sit all night. So, it may be low compression, but it's not leaking. 

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