New pick up!

[Nate_YZ426F]

So I've been lurking here on TT while and finally decided to make an account after picking up a new toy! I pulled the trigger on an 02 YZ426F and couldn't be happier from the initial few rides. The power really really shocked me. I've ridden a fair share of 450s, and the only one I felt had a noticeable power difference was the brand new ktm 450sxf which is incredible (Keep in mind I'm not a great rider, and tend to ride around the farm more than the track). I have a few general questions though...

1.) I can't seem to find the stock gearing for the 02, can anyone fill me in?

2.) I'm coming off of a legendary 96 cr250 which was phenomenal in the woods, this bike should be a bit of a handful but I'm excited about the challenge. My only concern is the overheating - does this bike have a tendency to over heat on 1st/2nd gear trails?

3.) is it possible to swap the spark plug on these bikes without taking off the gas tank? I haven't tried yet but it looks verrry tight in there.

Also, the bike has a slight hesitation from low speeds when I crack it. I've read a lot about an off idle bog, but I wouldn't classify this as off idle. Is this normal for this bike? (It is colder here right now and the bike is a touch lean, so it could be that). I wouldn't assume it's normal, but it could just be because I'm coming off a great running responsive 2 stroke.

Thanks in advance!

[Will.A.R.]

1.) 14/ 49 from my sources

2.)sometimes, just keep moving and ur usually ok. Watch mud buildup.

3.)yes

4.) Clean carb, known pilot jet issues

[Nate_YZ426F]

1.) 14/ 49 from my sources

2.)sometimes, just keep moving and ur usually ok. Watch mud buildup.

3.)yes

4.) Clean carb, known pilot jet issues

Thank you! I appreciate the help!

[grayracer513]

3) Motion Pro makes a spark plug socket set that works very well.

 

4) The carb may need cleaning or not.  Check Common Threads for how to verify the correct pilot setting/size and read up on the "BK Mod" there as well.

[Nate_YZ426F]

3) Motion Pro makes a spark plug socket set that works very well.

4) The carb may need cleaning or not. Check Common Threads for how to verify the correct pilot setting/size and read up on the "BK Mod" there as well.

I've done some reading on the BK mod, I just don't feel comfortable doing it myself. I'm the opposite of mechanically inclined lol. Is there any other alternative for the mod? Sorry if I'm sounding redundant I've ran a few searches and can't find much specific to my case.

[sid_125_04]

When i did my 426 rebuild, find a 08 carb on ebay and be done with it....

[Nate_YZ426F]

When i did my 426 rebuild, find a 08 carb on ebay and be done with it....

Actually just bought an 05 carb on eBay. Was the swap easy??

[sid_125_04]

Yeh very simple just need a clutch perch with hot start on it. Also set of stg 1 hotcams is the way to go also

[Nate_YZ426F]

Yeh very simple just need a clutch perch with hot start on it. Also set of stg 1 hotcams is the way to go also

I ordered with the throttle cables perch and hot start all included. Really excited about throwing it on.. The bog was frustrating and I didn't like the idea of tapping into the carb. Also have a leaky petcock valve so I have a new one on the way. I'll post back here when I get everything on!

[Nate_YZ426F]

Okay so I ended up getting an 08 carb. Had a few issues while installing (bike was very finicky about idling/running, choke knob was stuck closed, hot start is really stiff) but once I tuned the fuel and idle screws a bit she runs pretty solid! I have a few questions though, the throttle cables that came with the carb were incredibly tight and causes the throttle to stick a little. Is there only one adjustment on these cables? Also my old petcock valve as leaky, so I ordered a new one, installed it and still leaks. After taking a closer look it looks like the leak is right where the valve meets the tank - I'm assuming the tank is the issue not the valve or its o ring. Are there any known issues/fixes for this with 426's? Thanks in advance

[SAKs YAMAHA]

Okay so I ended up getting an 08 carb. Had a few issues while installing (bike was very finicky about idling/running, choke knob was stuck closed, hot start is really stiff) but once I tuned the fuel and idle screws a bit she runs pretty solid! I have a few questions though, the throttle cables that came with the carb were incredibly tight and causes the throttle to stick a little. Is there only one adjustment on these cables? Also my old petcock valve as leaky, so I ordered a new one, installed it and still leaks. After taking a closer look it looks like the leak is right where the valve meets the tank - I'm assuming the tank is the issue not the valve or its o ring. Are there any known issues/fixes for this with 426's? Thanks in advance

 

do the throttle cables stick when detached from the carb? if so, look for a bind/kink in the cable, make sure the throttle tube is clean and clear, or just replace them. I never had any luck lubricating cables once they crapped out. if they run smooth when you take them off the carb make sure they have a almost no tension when installed/ adjusted and the butterfly valve isn't gummed up. it should open smoothly and snap shut, though you should not let it snap shut.

 

did the petcock come with a new seal? if it did, check for cracks around the screw holes or warping. I had a warped 450 tank. I just filed/ sanded down the plastic unlit it was flat again and stopped leaking. not a lot, just a little was needed. I don't know of any common defects with them.

[Nate_YZ426F]

do the throttle cables stick when detached from the carb? if so, look for a bind/kink in the cable, make sure the throttle tube is clean and clear, or just replace them. I never had any luck lubricating cables once they crapped out. if they run smooth when you take them off the carb make sure they have a almost no tension when installed/ adjusted and the butterfly valve isn't gummed up. it should open smoothly and snap shut, though you should not let it snap shut.

did the petcock come with a new seal? if it did, check for cracks around the screw holes or warping. I had a warped 450 tank. I just filed/ sanded down the plastic unlit it was flat again and stopped leaking. not a lot, just a little was needed. I don't know of any common defects with them.

Thanks for the post! I actually finally found some adjustment tips for a crf450 that worked the same as my bike. I'll definitely try the sanding on my tank as the petcock did come with a new seal. Good idea, thanks for the help! This forum is amazing lol

[SAKs YAMAHA]

Thanks for the post! I actually finally found some adjustment tips for a crf450 that worked the same as my bike. I'll definitely try the sanding on my tank as the petcock did come with a new seal. Good idea, thanks for the help! This forum is amazing lol

You have to find the bad spot first before sanding it down. I use a machinists straight edge. But u can use anything known to be straight and use a flashlight on the opposite side. If you see excessive light passing through, then you found the problem.

[Nate_YZ426F]

You have to find the bad spot first before sanding it down. I use a machinists straight edge. But u can use anything known to be straight and use a flashlight on the opposite side. If you see excessive light passing through, then you found the problem.

Got cha, I'll take a peak tonight when I get off work and post back

[Nate_YZ426F]

Okay got the tank leak fixed (or atleast I hope, has held up a day and a half). I just found out something though.... The bike doesn't go into 5th gear. It's as if it doesn't exist!! What do I even do about that?? I never ride in 5th much anyway but it still bothers me. Also when I 4th it's like the clutch randomly grabs?? Very confused any help would be great

Edited January 9, 2016 by Nate_YZ426F

[grayracer513]

Time to rebuild the transmission.  The lugs on the gear sides that lock each pair onto the shaft when they are engaged are worn to the point they will not hold in gear.

[Nate_YZ426F]

Time to rebuild the transmission. The lugs on the gear sides that lock each pair onto the shaft when they are engaged are worn to the point they whill not hold in gear.

Oh gosh... Roughly what would this cost for a shop to do? Like are we talking 500 or 1000+

[Nate_YZ426F]

If it means anything 1st 2nd and 3rd click fine and have no issues. It goes into 4th fine, just jerks at high rpm and 5th is literally non existent.. Like its not even there as if it were a 4 speed tranny

[grayracer513]

I understood that in the first place, and I know why it happens.  As for prices, probably 250-300 in parts, all inclusive, plus labor, which would be for the complete removal and disassembly/reassembly of the engine unit.  The head won't have to come apart, nor the crank be completely removed, unless something else is found.  Somewhere between $700-$1200 altogether, probably. 

[Nate_YZ426F]

I understood that in the first place, and I know why it happens. As for prices, probably 250-300 in parts, all inclusive, plus labor, which would be for the complete removal and disassembly/reassembly of the engine unit. The head won't have to come apart, nor the crank be completely removed, unless something else is found. Somewhere between $700-$1200 altogether, probably.

Thanks. Sorry for giving too much info I just wanted to make sure I covered the whole situation. This blows