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post #1 of (permalink) Old 08-28-2001, 08:29 PM
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YZ250 Runs Poorly

Just purchased a 1999 YZ250 and it runs poorly. It seems like it is cutting out and bogs down at lower RPM's. If I wind it up into high RPM's it runs better but still not well, it hesitates. I think it is either the carb or timing. Any advise would be appreciated. It has a FMF Fatty pipe, I assume the carb was not re-jetted. Is this necessary? The reeds have been replaced by previous owner but I have not taken them off to look at them yet. It starts fine and idles well. I would prefer to do work on the bike myself but need some direction. Any help would be appreciated. Also, it seems to burn alot of gas, more than normal. The plug has been replaced, no change. Filter looks fine. New gas mixed properly with Yamaha oil. Help please. E-mail me if more info is needed. Andy ([email protected])

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post #2 of (permalink) Old 08-28-2001, 09:50 PM
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Re: YZ250 Runs Poorly

Yeah, it had to be rejeted after that pipe, and...you don't need to time a two stroke.

<font color=blue> I'd rather be STROKED than BORED...
post #3 of (permalink) Old 08-28-2001, 10:23 PM
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Re: YZ250 Runs Poorly

fgsacts,
Do you know if the bike has alot of time on it. Was it raced or just play ridden?
Anyway it could be as simple as removing the carb and cleaning it out. If you have some mechanical ability this is no problem. Make sure the jets are clean and the seat for the needles are ok. Check to see if the clip is on the jet needle. Start simple and go from there. While the carb is off you can look at the reed valve assembly.Why were the reeds replaced previously?
Sometimes new jetting is needed with aftermarket pipes. Sometimes it's not. Go to the FMF site they will have the info or where to get it.
Oh yeah...get a manual too. Should be the first tool you get for a new bike.
One more thing... the rotor and stator housed in the left side cover. Remove the cover and make sure the stator is secured tight.
Good Luck!!

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post #4 of (permalink) Old 08-28-2001, 10:40 PM
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Re: YZ250 Runs Poorly

There's a link to thier jetting chart on the FMF homepage.

post #5 of (permalink) Old 08-28-2001, 11:20 PM
portgrinder
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Re: YZ250 Runs Poorly

uh, ya you can change the timing on a two stroke josh

check and clean the carb. sounds maybe too rich.

You wear your silver chain but the cross won't stop the lies,you believe in nothing
Kenton Thomas,Portal
post #6 of (permalink) Old 08-29-2001, 06:27 AM
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Re: YZ250 Runs Poorly

portgrinder has a good point. Check the air screw for proper adjustment.

post #7 of (permalink) Old 08-29-2001, 10:42 AM
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Re: YZ250 Runs Poorly

first off you dont have to jet if you change pipe, jetting is only necessary if the bike needs to be jetted. you can change timing fuknut. if they are after market reeds this will automatically richen your bike. pilot air screw should be 1-1/2 turn out. pull off exhaust pipe. look up port and see if there is alot off blow by on piston. (there will be black carbon streaks past the two rings on piston. slight blow by is ok as normal wear occurs, but if the piston is totally black its time for a top end. i have a pc pipe and shorty si. delta valve and one up on main and my bike is fine. stock carb besides that. make sure reeds are in correctly and not frayed(sp?)(stop plates are even on both sides of reed petals.) make sure float bowl is not sticking. the intake side of piston doesn't wear as much due too cooling effect of intake charge so if there is blow by here that is sign of wear and possibly over heating. i dont like yamalube. run at least 93 oct and try swicthin to better oil(no spectro ****t either) and at 32:1 or 40:1 w/full synth this is what i run. w/ 50% 108 leaded fuel. repack and clean all holes in silencer core(burn core w/propane torch till red and carbon will crack off and repack) also make sure header is tight against port so you do knot loose back pressure. make sure filter is super clean, fresh plug. there also should be marks where your stator is supposed to be aligned for timing. i have a 99 also. but mine runs-haha. let us know !

When in doubt, GAS IT
post #8 of (permalink) Old 08-29-2001, 10:58 AM
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Re: YZ250 Runs Poorly

curious what you paid. and should read float not sticking not float bowl. make sure your airbox and reed clips are tight on carb and head. also take off stator cover(left chain side) and spray wd-40 on seal behind stator. if the rpms of the bike go up your main seal is leaking in air leaning your bike out and causing it to run poorly. this must be replaced asap if this is the case. is your gear oil gray, your leaking radiator fluid into trans, or trans fluid into crankcase thru bad seal causing it to bog due to extra oil and it gets burned at high r's.

didn't you ride it before you bought it.

When in doubt, GAS IT
post #9 of (permalink) Old 08-29-2001, 04:34 PM
portgrinder
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Re: YZ250 Runs Poorly

ya yz has pretty much all the good points covered. although just plain ol water makes your oil grey too. and iff you mountain ride often water is bound to get in from time to time from breather hoses

glad to see somebody else uses the wd40 trick

You wear your silver chain but the cross won't stop the lies,you believe in nothing
Kenton Thomas,Portal
post #10 of (permalink) Old 08-29-2001, 10:18 PM
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Re: YZ250 Runs Poorly

Thanks for your response and advise. I paid $3200.00 for the bike. I rode it but not hard, was in the guys neighborhood (pavement) and it was raining. Bike is in great condition, not just new plastic. I am not overly concerned at this point. I have tinkered with bikes my whole life, mostly Harleys, just not to familiar with two strokes. Almost always had to re-jet on a Harley, also no reeds to be worried about. Need to buy a manual for specs ans stuff. Plan on doing top end this winter unless it needs it sooner. Thanks again, it sounds like you know what you are talking about. I will e-mail if I get in a bind if you do not mind. Let me know if you think of anything else I need to know. Later.

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