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Couple of probs on YZ250F
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Posted by: R.P.M---------------------

I got YZ250F 04', the bike is great i start it on first kick even on cold weather.
the prob is that i feel it a bit lazy, and is get shutdown alot when i ride on tight enduro corss.
i may think that it's becuase that i putted 45T rear sporket and my tire is also 110.
theres anther prob that when im in fifth gear even on low RPM it act like i hit the rev limiter, altought i still reving.
what coould it be?
Thanks & Sorry for the bad english

Posted by: R.P.M---------------------

Mmmm nobody knows? or theres a problem with the way i describe that issue ?

Posted by: gaz1985---------------------

45t isnt that a bit low

Posted by: Ol'89r---------------------

Hard to tell from your description but it sounds like a jetting or dirty carb problem. Make sure your air filter is clean and drain the carb float bowl. I would remove the main jet and make sure it is the right one. Raising the idle speed will keep it from stalling in the slow corners.

Also, make sure your hot start valve is seated all of the way.

Posted by: R.P.M---------------------

Thanks alot, what you said about the hot start just make me think..
the hot start lever has reposition becuase i got new clutch lever. mybe theres something with it.
you are totaly deny those symptoms to the gear ratio?
today i rode in MX corss and i notice that it also choke a bit/delay when i try to accelerate. something like that the accelerte pump isn't timed well.
but when i just accelerate on open roads theres no bog or anything.

Posted by: Ol'89r---------------------

If the hot start plunger is not seating all of the way, it will cause a miss when accelerating. Make sure you have some slack in the cable and also remove the hot start plunger and inspect the rubber pad on the end. There should be a circle indented in the end of the rubber pad where it seats against the valve orifice. If it is damaged or not sealing all the way around the orifice, replace it. The hot start plunger can also become oxidized and stick in the bore.

On the accelerator pump (ac) be sure your throttle slide is opening a little bit before the ac pump rod begins to move. If the ac squirts fuel in the engine before the slide opens, it will cause a bog. Also clean out the ac pump diaphragm on the bottom of the float bowl. Water and dirt can collect in there and cause the ac pump not to work properly. You can adjust the ac rod by bending the tab on the throttle cable bellcrank.

I don't think your problem is the gearing. If everything is working correctly and the jetting is correct it should not bog regardless of the gearing.

Posted by: whenfoxforks-ruled---------------------

What part of the world does your flag stand for? What kind of temperature is it outside? When you compared riding mx and trail, was the temperature the same? Where exactly does the engine hesitate, off idle or further into the throttle? Thi is all assuming you have no mechanical issues. Are you positive about the hot start, and have you ever had any part of the carb apart? The mixture screw and accelerator pump have some very small o rings, there misplacement can cause a hesitation that is impossible to fix by jetting. How is the plug?

Posted by: R.P.M---------------------

well, it Israel ofcouse!
yeah the temp was pretty much the same, it hesitate at the beggining of the acceleration. it bog for around three times and then it fly. just going from very low RPM fast to High RPM.
i think that on first gear it's fine...but mybe it's just have enough power altuoght the timeing, fuel amount is wrong.
my carb just got jetted (some mechanic). here in israel we dont have dyno it's not common so i dont know if he did it on the spot.
he said that the plug is fine. the jetting was done becuase it was too rich.
if anyone got more to add please let me know.
i think i will just take the bike to him agian.
Thanks

Posted by: Bodge---------------------

does it bog when you open the throttle quickly?

Posted by: R.P.M---------------------

yes, but im not sure what happens when i open it slowly

Posted by: whenfoxforks-ruled---------------------

Israel! Well it says you do not know where you live, just a flag. Wire your ap adjuster, or a zip tie. Can you order a JD jetting kit? He would know exactly which leak jet to put in there, and maybe a pilot jet change. I am pretty sure its got something to do with the ap circuit. The leak jet may be clogged. There are some really small o rings, one is atop the mixture screw and the other is in the accelerator pump cover. Their mis alignment can cause a hesitation also. Leak jet, yamaha calls them something different, its the one in the bowl.

Posted by: R.P.M---------------------

i can order the JD kit from the internet but it cost pretty much...mybe i can just get a leak jet here (in israel).
what do you mean by wire my ap adjuster? isn't it something that inside the carb ? you think that it might got lose or something like that ?
anyway i think that i will take it to someone who knows better then me and i will also inform him on all the info you guys gave me

Posted by: whenfoxforks-ruled---------------------

06 and later fcr carb linkage. where you adjust the ap timing. JD sells o rings, you wrap around the adjuster to make it pump every time the throttle opens. As it sits now sometimes it does not pump. Backyard mechanics just safety wire it together, or a small zip tie. I have seen a complete replacement somewhere to fix this also.

Posted by: BSWIFT---------------------

Quote:

Originally Posted by whenfoxforks-ruled

Israel! Well it says you do not know where you live, just a flag. Wire your ap adjuster, or a zip tie. Can you order a JD jetting kit? He would know exactly which leak jet to put in there, and maybe a pilot jet change. I am pretty sure its got something to do with the ap circuit. The leak jet may be clogged. There are some really small o rings, one is atop the mixture screw and the other is in the accelerator pump cover. Their mis alignment can cause a hesitation also. Leak jet, yamaha calls them something different, its the one in the bowl.

I speak and understand English pretty well but even I don't follow you on this one. Got a diagram?
R.P.M., these guys have probably got the right things to try so hopefully the points will be refined to make them clearer, regardless of National Flags.

Posted by: whenfoxforks-ruled---------------------

I like pictures, do you see the o ring around the ap adjuster? This can be done with wire or a zip tie also.

Posted by: BSWIFT---------------------

There was a mod for the 03 450's that allowed you to adjust the AP duration. Took about 15 mins and it worked. This may actually do the same thing and if it works, it is much easier. Thanks for the pic.

For all of the US and Canadian youth on these boards, R.P.M. has done a great job of making his points with a minimal everyday use of the English language. International users that use English very little try very hard to communicate and they do it very well. Those of you who speak English daily should practice it when you post. DRN has always tried to get its users to use proper grammer and spelling, not being concerned with minor typos or mistakes but avoiding the chat room jibberish that is lacking in substance and effort. It is very easy to tell the difference and as long as someone is trying to communicate effectively, you'll receive help from knowledgeable people, like ol 89'r. Other's will jump in, as whenfoxforksruled, posted pics to clearify a point. When users make an effort, they usually will be rewarded with honest, accurate help. Their help may not resolve the issue but will help isolate a problem.
Sorry for the diatribe but this thread is a perfect example of someone trying to communicate across the language barrier AND the internet. Thanks.
Brian

Posted by: whenfoxforks-ruled---------------------

You have to first adjust the ap to just miss the slide when it goes up. On my sons 06 crf450 it meant backing the adjuster all the way out. Then you apply the ap mod (o ring) to keep the ap pumping everytime the throttle closes, then opens. Without it, sometimes it does not pump, it floats, this directly relates to a hesitation, unacceptable. After 06 they changed the design of the fcr carb. They put the fcr carb on every Japanese bike I have seen. Some have said that this mod makes the rod bottom out and you can feel it in the throttle. This is where the diaphragm comes in, you can either grind the nipple off, or buy one already modded. Personally, I could not tell that big of a difference. On the honda's the leak jet(the only one in the bowl) comes way fat, a leaner jet makes a world of difference. JD has fiddled with every bike he sells a kit for. Just beware of companies that advertise getting more fuel in on the ap circuit. It has a very important purpose, and beyond that you can say good bye throttle response. Misalignment of that very small o ring on top of the mixture screw can cause a hesitation also. If it gets cut and you can not find all the pieces, rest assured it is hidden in the passages from the bowl to the throat of the carb. You have to disassemble the parts of the car body. You need a special hollow torx driver to take apart the carb body.

Posted by: R.P.M---------------------

well, im sorry that i didnt have time to respond...anyway we checked the carb and it dosn't seems like it's the prob.
the guy thinks it's electrical problem (coil or CDI).
he told me to try and cut the neutral unit wire.
the one who connect near the shift gear lever.
so im going to get a cutter. if anyone thinks it's wrong move please let me know asap

will it cuase any damage?
Thanks

Posted by: Ol'89r---------------------

Did you reset the ap? Still sounds like carb problems to me. You may also want to check your valve adjustment.

I would not cut any wires until you have eliminated everything else.

What exactly is the bike doing? Missing? Bogging?

Posted by: R.P.M---------------------

well, i didnt rest the ap. i brought it to mechanic and he thinks its not carb prob.
it a little bit hard for me to explain what the bike doing. i guess becuase im not sure about the defenition of missing for example.
mybe missing is the word....but i will choose cutting. on/off on/off. so i guess it can be fuel off/fuel on or spark on/spark off.
i already changed the Spark Plug. after that he told me it might be the Coil or the Cdi.
and then he talked with a friend of him who told him to try to disconnect/cut the neutral unit wire.
he also check the Hot Start thing and thinks the valve are fine (but listening - the motor sound timed well).
i hope that soon we will get anther bike and we will replace the CDI/COIL and check them.
anyway he want first to eliminated that neutral unit wire. i guess that i wont be lazy and i will remove the fuel tank and disconnect it.
the weather is prob now :\

Posted by: Ol'89r---------------------

Quote:

Originally Posted by R.P.M

im not sure about the defenition of missing for example.
mybe missing is the word....but i will choose cutting. on/off on/off. and thinks the valve are fine (but listening - the motor sound timed well).
i hope that soon we will get anther bike and we will replace the CDI/COIL and check them.
anyway he want first to eliminated that neutral unit wire. i guess that i wont be lazy and i will remove the fuel tank and disconnect it.

R.P.M.

Cutting on and off would be the same as 'missing'. That would also be different than bogging.

I would remove the gas tank and disconnect the wire instead of cutting it. While you have the tank off, check all of the wire connectors and wires for loose connections or broken wires. Remove the kill button and try it again. Make sure your breather hose that is attached to the top of the engine is not plugged with mud or kinked /obstructed in any way.

Check your valve adjustment. Tight valves can cause many problems and the only way to tell if they are ok is to physically check them.

If you still can't find the problem then trade the cdi and coil with another YZF.

If the bike is 'bogging' or not taking the throttle from low rpm's, that would be your ap adjustment or jetting.

Posted by: R.P.M---------------------

Quote:

Originally Posted by Ol'89r

OK, i will check the wires first thing tommrow. he said its common to cut/unplugged that wire becuase it's not necessary (is it true?).
i already checked the breather and it's fine.
it wont be easier to trade first the cdi and the coil then check the valuves?
about the problem i got with the fifth gear, he suspect that the gear is starting to slip. it still not jump back to 4th but sliping.
By the way, theres any difference in the cdi/coil from 04 to 05?

Posted by: R.P.M---------------------

i just checked unplugged the neutral unit wire and it still missing.
i will get CDI and i will check it.
he claim that's eletrical problem.
im not sure, its missing on the same spot everytime...
by the way...what will be the best jet for my bike?
it's 04' with FMF F/S and twinair filter. im around 100-300m above sea level.
i had 180 and i replaced to 168..wich is small. i guess ineed 170?

Posted by: mox69---------------------

Do you know the total hours or miles on the bike?

Search this website (or the internet) for valve check or valve adjustment. If you have never checked this it would be a good idea to do so. It could be the cause of your problems. It will require something like a "feeler gauge"

Posted by: R.P.M---------------------

Quote:

Originally Posted by mox69

Do you know the total hours or miles on the bike?

Search this website (or the internet) for valve check or valve adjustment. If you have never checked this it would be a good idea to do so. It could be the cause of your problems. It will require something like a "feeler gauge"

i will let someone with better knowlage then me to do it.
anyway it dosn't sound like theres problem with the valves but i guess i will check it after i wil check the cdi+coil.

Posted by: whenfoxforks-ruled---------------------

I would not EVER recommend cutting wires. What is the temperature in Israel? From the main jet change I am guessing its 120 degrees Fahrenheit. If you are in winter like I am, you should be putting a bigger main jet. A 180 and dropping to a 168 is incredible. Stock jetting should be good for a starting point. Check the ap, take the subframe with the air box off. You can see the back of the carb. Twist the throttle and see if you can see the ap squirt from a closed throttle position. It should squirt as soon as the slide goes by. If your carb has issues it will cause a bog all the time. If you are way lean you will get a bog all the time. I would get a second opinion if you have another mechanic in the area. If your bikes clutch is slipping it will feel like you hit neutral, and 5th gear is where it shows first.

Posted by: oldguy---------------------

Actually Eric Gorr cut the wire on all of our YZFs the first time he worked on each. I replaced the unit in the engine that the wire ran to with a site window so I could verify oil level with a quick glance so I guess cutting the wire is a safe move.
RPM to set the jetting it is also important to work with air temperature as well as elevation. Do you have the Yamaha manual for a referance on jetting? From what I remember there is a chart in it that gives recomendations at temperatures and elevations. If you do not have a manual I can hunt mine down from the 2004 I have and scan and post it. Unfortunately the earliest I will be home to do it is sometime Sunday (early Monday for you)

Posted by: R.P.M---------------------

Quote:

Originally Posted by oldguy

Actually Eric Gorr cut the wire on all of our YZFs the first time he worked on each. I replaced the unit in the engine that the wire ran to with a site window so I could verify oil level with a quick glance so I guess cutting the wire is a safe move.
RPM to set the jetting it is also important to work with air temperature as well as elevation. Do you have the Yamaha manual for a referance on jetting? From what I remember there is a chart in it that gives recomendations at temperatures and elevations. If you do not have a manual I can hunt mine down from the 2004 I have and scan and post it. Unfortunately the earliest I will be home to do it is sometime Sunday (early Monday for you)

Thanks, but i already did the safe way and just disconencted it. it didn't solve the problem.
i replaced the cdi with other bike and the guy who take care of it said it over. im not sure about it.
but he claims that what i feel now is happning becuase i need to change transsmision gears. 5th and 3th.
and ofcourse do a little bit of jetting cuz 168 is small.
so i guess i need to open the engine. so i will also do some valuve checking and timeing chain with the gears.
any other things i should check ?
and what should be the price for fixing 3th and 5th gears and timeing chain + cdi ?
Thanks

Posted by: Ol'89r---------------------

Quote:

Originally Posted by R.P.M

but he claims that what i feel now is happning becuase i need to change transsmision gears. 5th and 3th.

and what should be the price for fixing 3th and 5th gears and timeing chain + cdi ?
Thanks

Ok, now we are starting to get somewhere.

What you describe as missing may be your gearbox jumping in and out of gear. If this is the case, the bike should run smooth in all of the other gears. If the bike accelerates smoothly in the other gears, that would eliminate a miss in the engine. (Ignition, carburation, etc.)

If it only does it in 3rd and 5th gears you most likely have worn shift dogs or bent shift forks or both. Most likely both. When the shift dogs (the little engaging dogs on the sides of your gears) wear on the edges, it rounds them off and produces a taper on the dogs and the mating gears. Under power, the taper forces the gears apart and eventually bends the shift forks. If you continue to ride the bike it will only get worse and could damage the rest of your engine. The engine oil and gearbox oil is the same oil. So, any bits and pieces in the gearbox can get into the engine and cause more damage.

I have no idea what it would cost to have this done in Israel. Not sure what they charge for labor there. You can check on the parts prices online at one of the Yamaha dealer sites.

While the engine is apart, you will also want to check and possibly replace the piston and check the valves. New rings and gaskets are a must. Your mechanic should be able to measure the wear on these items and determine if they need replacement or not.

Posted by: R.P.M---------------------

ok, thanks. just hope it will end with thies and not other things.
i guess only the parts will cost me around 500$-600$
thanks! i wont touch the bike until i fix it.

Posted by: R.P.M---------------------

well the guy opend the engine and i need to change some of the gear parts.
so i already got CDI and got some parts for the gear. i guess that in a week i will get my bike back home agian then i will know if it's need some jetting too.
anyway thanks for all the info and advises.
im not sure if it's allowd but i just wanna mention that i bought the OEM parts from Shop called Generationmx and the price and service was really good (just my own advise for you).
I also gonna get rid of my gearing setup (13-45 and 110 Wheel).
for a stock one.
Thanks!

Posted by: whenfoxforks-ruled---------------------

Good luck and let us know how it turns out!

Posted by: R.P.M---------------------

well, the problem with the slipping gear mainly on 5th gear has passed away but it still
CcccuttttTTTiiIInnG!
i guess i should check better the AP/Carb.

Posted by: R.P.M---------------------

Well after a little (very little) working on the carb, the prob solved!
the needle were to high and ichanged the pilot jet.

thanks agian for all the advises!

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Couple of probs on YZ250F

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