01 WR426-need carb and cam set up advice


16 replies to this topic
  • jbowman502

Posted September 11, 2009 - 07:10 PM

#1

hello, just bought my first yamaha and my first big 4stroke, 01 WR426. very hard to start, has a racey idle, wants to stall, will only idle at approx 2000 rpm or higher, misses on midrange accel, and pops/backfires on decel. fuel overflows from the hose off bottom of float bowl anytime the gas is turned on. prev owner installed Big Gun exh with dual header pipe, removed grey wire. all stock other than those two mods. i installed a brand new NGK and removed and cleaned the pilot, leak, and main jets as well as needle and seat, checked jetting size against the yamaha service manual - jets are all stock. i checked cold valve clearance and the intakes were tight so i reshimmed all three with a hot cam shim kit and they are all now within spec but the cam chain seems to be loose - i can move it about a half inch when i press down between the two cams while the tensioner is fully extended. new cam chain and jet kit on order. i've read through all of the FAQs, jetting guide, and modification guide as well as read through a lot of old thread posts and here is my plan but i am hoping you guys might pitch in your two cents if you think i'm getting off on the wrong path or not. i'm hoping someone can tell me what the basic recipe is for a wr with a full exhaust:
-the local shop verified that the jet kit on order is for a yz, not a wr - should i cancel the order and get the JD kit i've seen so many times on TT?
-it's still very very very hard to start after cleaning carb, my right ankle is still sore :busted: adjusting tight intake valves, fresh gas in tank, and new plug and from what i've read, the JD kit doesn't come with a new pilot jet - don't i need to raise the pilot size to help startup? i'm in louisville KY, 'the Ohio River Valley' not sure of elevation.
-i'm planning on swapping in an 03 yz cam to accomplish two goals of switching to yz timing and eliminating the manual decomp
-i'm planning on switching out the throttle stop screw to a yz oem to compliment the grey wire disconnect as i've read in TT
-i've ordered a new needle and seat to cure the overflowing float bowl because adjusting float height does not stop the overflow from coming out of the hose off the bottom of the bowl, only shutting of the gas.
-planning on getting the zip tie fuel screw to help adjust idle once i've installed the jet kit, new needle/seat, cam and cam chain
do i really need to plug the pilot air jet and mess with the accelerator pump? thanks in advance, i've researched TT for about a week and have owned this bike for a bout a month so i'm excited to hear what you guys think is the best set up for me as an aggressive trail rider.

  • Pooley

Posted September 12, 2009 - 11:26 AM

#2

The very first thing to fix is the fuel leaking issue. It is either a improperly adjust float, or the o-ring for the needle valve seat has hardened up. I had the exact same problem this spring with my 01 WR426. Get a new valve seat and that should stop the overflow (assuming the float is adjusted properly). There will be absolutely no way to adjust anything else properly if excess fuel is in the carb.

As far as jetting and such, Michigan is an average elevation of about 700ft. My bike starts beautifully, and runs perfectly. I would try to compare your level of mods, and geographical areas to those in the Jetting FAQ as a starting point. I would definately look at the O-ring mod, as it is super simple and will cost you less than a dollar. It was far and away the most impressive mod I was able to do to my bike. All the stuff I did was documented here on TT, so search my posts and maybe something could help you. The only thing I ever plugged was the ACV, to mimic a YZ carb. To compensate I did install a larger jet.

Until you get your bike to run in a proper fashion, you may want to go step by step with your mods. In my opinion, if you do 6 mods at once, you may wind up chasing your tail. Granted, I am a super analytical, and step-wise type of personality, so jumping in with both feet like it sounds you want to do does not appeal to me at all.

Good luck and keep us posted on the progress.

  • Russ

Posted September 12, 2009 - 02:05 PM

#3

The only thing better than buying a new bike is having some cash left over to throw at some new stuff :busted:

Being that it is your first big bore 4 stroke are you up with the starting proceedure mate?? stay off the throttle, grab the brake lever or whatever else you can find to keep your hand off the throttle!

You will find, like I have that this place is full of people that know all there is to know about these bikes. Having had 3 426's I can say that once the jetting is sorted you will be getting many a smile raising minute from it. :thumbsup:

  • jbowman502

Posted September 12, 2009 - 03:40 PM

#4

The very first thing to fix is the fuel leaking issue. It is either a improperly adjust float, or the o-ring for the needle valve seat has hardened up. I had the exact same problem this spring with my 01 WR426. Get a new valve seat and that should stop the overflow (assuming the float is adjusted properly). There will be absolutely no way to adjust anything else properly if excess fuel is in the carb.

As far as jetting and such, Michigan is an average elevation of about 700ft. My bike starts beautifully, and runs perfectly. I would try to compare your level of mods, and geographical areas to those in the Jetting FAQ as a starting point. I would definately look at the O-ring mod, as it is super simple and will cost you less than a dollar. It was far and away the most impressive mod I was able to do to my bike. All the stuff I did was documented here on TT, so search my posts and maybe something could help you. The only thing I ever plugged was the ACV, to mimic a YZ carb. To compensate I did install a larger jet.

Until you get your bike to run in a proper fashion, you may want to go step by step with your mods. In my opinion, if you do 6 mods at once, you may wind up chasing your tail. Granted, I am a super analytical, and step-wise type of personality, so jumping in with both feet like it sounds you want to do does not appeal to me at all.

Good luck and keep us posted on the progress.


that is great advice. i agree with you. i will read through all of your posts, i'm very relieved to hear back from a knowledgeble and experienced owner of the exact same bike. i'll write again once i've done my research of your posts and update along the way. thans a million!

  • jbowman502

Posted September 12, 2009 - 03:50 PM

#5

The only thing better than buying a new bike is having some cash left over to throw at some new stuff :busted:

Being that it is your first big bore 4 stroke are you up with the starting proceedure mate?? stay off the throttle, grab the brake lever or whatever else you can find to keep your hand off the throttle!

You will find, like I have that this place is full of people that know all there is to know about these bikes. Having had 3 426's I can say that once the jetting is sorted you will be getting many a smile raising minute from it. :thumbsup:


yeah, no kidding! i love to blow cash on toys and tools. the way i start it is choke it, push easily on kicker until it comes to a stop, pull the decomp lever and push the kicker just past that point, allow kicker to ratchet back to top and then give it a good kick and in my case, repeat, repeat, repeat, repeat, dismount, catch breath, repeat, repeat, dismount, :banana: and yes, i learned the hard way not to give it any gas at all! flooded it big time the first day i got it home and worked up a heck of a sweat trying to start it! it starts a little easier since i learned that lesson and adjusted the valves but i can't wait to get the carb tuned so i can enjoy it. i've ridden a brand new yz back when they first came out, so i do know how it's supposed to behave and can't wait to get it propertly tuned. and yep you're right, these guys know their stuff. man am i glad to have this resource! thanks for writing

  • tcmII

Posted September 12, 2009 - 05:23 PM

#6

Follow Pooleys advice and check the float and seat. You can go wrong with a CCC member advice. (Pooley I will be at Color Tour riding my wr with number plates 827, maybe I'll see you there). I have a '98 wr400. I used to go through plugs and hard starts like crazy until I found the problem wtih the float. Fixed that and much better.

Also, the 03 exhaust cam is a great upgrade.

  • jbowman502

Posted September 12, 2009 - 05:44 PM

#7

just ordered the JD jet kit... i ordered the new float needle and seat last week so i expect them any day now. i'm going to pass on the BK mod too, not a big fan of drilling anything on my carb even if fuel doesn't go through the hole!

so first i'm going to fix the overflow with the new needle and seat/double checking float level, then i will get it jetted properly when the jet kit arrives. once the jetting is dialed i will do the o ring mod and adjust the squirt timing (not looking forward to that part) last i will put in the 03 yz exh cam and new cam chain and check valve clearance, shim if necessary.

Question - should i reconnect the grey wire while i'm doing all of the above, and then disconnect the grey wire, install YZ throttle stop screw and plug ACV as the last steps before installing the YZ cam in order to completely mimic the YZ set up? it appears that right now by having the grey wire d/c, i have a WR carb on WR timed top end with a YZ ignition so i'm thinking i should plug that grey wire back in for now. thanks again for your help. your posts were very helpful.

  • jbowman502

Posted September 12, 2009 - 05:47 PM

#8

Follow Pooleys advice and check the float and seat. You can go wrong with a CCC member advice. (Pooley I will be at Color Tour riding my wr with number plates 827, maybe I'll see you there). I have a '98 wr400. I used to go through plugs and hard starts like crazy until I found the problem wtih the float. Fixed that and much better.

Also, the 03 exhaust cam is a great upgrade.


will do! i'm (im)patiently waiting on the big brown truck with my new needle and seat and i will make sure the float level is correct in the meantime. i apologize but i don't know what you mean when you say 'you can go wrong with a CCC member advice.'

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  • Sider_steve

Posted September 12, 2009 - 06:14 PM

#9

fuel overflows from the hose off bottom of float bowl anytime the gas is turned on.


Would that be the hose attached near the drain plug?
Could the previous owner have drained the float bowl and left the drain screw open?

Also here is a link to the most asked questions about the 400/426/450.

http://www.thumperta...ad.php?t=440631

  • tcmII

Posted September 13, 2009 - 04:12 PM

#10

Sorry about that, I meant you "can't" go wrong. It was a shout out to Pooley being a member of the Cycle Conservation Club (CCC).

It is a statewide club people travel from all over the county to ride with the CCC, like the Six Days of Michigan. Being the club is so big I may have met Pooley and not known it.

Anyway the last club ride of the season is the Color Tour held 1st weekend in Oct. I'll be there, maybe I'll meet him then.

  • Pooley

Posted September 14, 2009 - 12:42 PM

#11

...(Pooley I will be at Color Tour riding my wr with number plates 827, maybe I'll see you there). I have a '98 wr400...


I'll be there on Saturday only, driving up, riding and driving home all in one day. Between motorcycling, deer hunting, a friends annual 3-generational family lamb roast, that is the only time I have. I probably stand out pretty well at a CCC event. Look for a short (5'9") guy wearing primarily black who can't touch the ground on a WR426, with FMF Q, TT stickers on a beat up mostly whitened front fender, beat up rad guards, and a huge grin on my face :busted: .

...once the jetting is dialed i will do the o ring mod and adjust the squirt timing (not looking forward to that part)...



Timing the squirt is really easy, if you have the carb off, just do it to start as it will help everything else too. Time the squirt so that it barely misses the slide as it is lifted. You will not be able to adjust the duration of the squirt, but you won't need to.

...Question - should i reconnect the grey wire while i'm doing all of the above, and then disconnect the grey wire, install YZ throttle stop screw and plug ACV as the last steps before installing the YZ cam in order to completely mimic the YZ set up? it appears that right now by having the grey wire d/c, i have a WR carb on WR timed top end with a YZ ignition so i'm thinking i should plug that grey wire back in for now. thanks again for your help. your posts were very helpful.


Disconnect the grey wire, install the YZ throttle stop, take the top off of the airbox all to start since those are the standard free mods that everyone does. Personally, I think tuning the carb is EASIER with the ACV disabled. You can actually hear a difference on decel if your fuel screw is to rich or lean. ACV (if i remeber right) was an enrichening circuit on decel to keep the bike from popping on decel, eliminating a potential way of tuning the bike. I think I went up a size on my pilot jet when plugging the ACV, because I could actually tune it properly.

I run with my WR with no grey wire, with WR timing. I don't do any motocross, just trails, so the WR timing is a better fit with more low end grunt, and less top end.

I looked up Lexington KY: Elevation: 978 FT (298 M). Pretty close to Michigan. So, I'd probably start with copying my setup, or someone close to you mod-wise who is extremely happy and use that as a baseline. Pay close attention to which situations, terrain and weather cause the bike to stumble, surge, rip your arms out of the sockets and cause you to giggle like a little girl with a new toy that has more power than 99.9% of mere mortals can use. Then come back here, tell us all about your ride with those specific situations thrown in, and that you need to adjust your jetting to correct them.
For your curiosity http://www.cycleconservationclub.org/ I don't have a clue what KY has to offer.

So before you start tuning, I would personally start by doing the following: YZ throttle stop, airbox, ACV, O-ring, AP squirt timed, grey wire. Then install your jets and JD kit to something that you think will work based on what others have done here. That is basic setup that will work well. Then go ride, and report back. No one setup works for every bike, but I bet TT'ers could get you 90% finished from the get-go just through research and planning.

  • jbowman502

Posted September 14, 2009 - 05:30 PM

#12

Would that be the hose attached near the drain plug?
Could the previous owner have drained the float bowl and left the drain screw open?

Also here is a link to the most asked questions about the 400/426/450.

http://www.thumperta...ad.php?t=440631


thanks for writing. when i pulled the bowl off last week, it appeard that the brass overflow tube in the bowl is the source for the hose so i automatically assumed that the bowl was overfilling due to faulty float needle and/or seat but i am on my way out to the garage to make sure i didn't over look this simple fix. i'll write back in a few and let you know. thanks for sending the faq link it was one of the first things i studied after reading the survival guide for newbies but i will read it all again, lots of great info.:busted:

  • jbowman502

Posted September 14, 2009 - 05:36 PM

#13

Sorry about that, I meant you "can't" go wrong. It was a shout out to Pooley being a member of the Cycle Conservation Club (CCC).

It is a statewide club people travel from all over the county to ride with the CCC, like the Six Days of Michigan. Being the club is so big I may have met Pooley and not known it.

Anyway the last club ride of the season is the Color Tour held 1st weekend in Oct. I'll be there, maybe I'll meet him then.


Right on! I kind of thought that the 'can' was a typo just wanted to make sure. maybe i will make it up that way for to ride with you guys when i've got this thing running smoothly

  • jbowman502

Posted September 14, 2009 - 05:47 PM

#14

ok i can save a little face because the drain plug was securely tightened so i'm pretty sure it's the needle/seat combo causing the overflow/leak. i'll post a reply and let you guys know how the jet kit and needle/seat works out. thanks guys

  • tcmII

Posted September 16, 2009 - 06:08 PM

#15

We look forward to you coming up. I regularly see license plates from Ohio, Indiana and Illinois at events and I know that last year they acknowledged a rider that (I think) came in from Iowa.

I also know that people come from all over to ride the Six Days of Michigan.

  • jbowman502

Posted September 16, 2009 - 08:24 PM

#16

I'll be there on Saturday only, driving up, riding and driving home all in one day. Between motorcycling, deer hunting, a friends annual 3-generational family lamb roast, that is the only time I have. I probably stand out pretty well at a CCC event. Look for a short (5'9") guy wearing primarily black who can't touch the ground on a WR426, with FMF Q, TT stickers on a beat up mostly whitened front fender, beat up rad guards, and a huge grin on my face :busted: .



Timing the squirt is really easy, if you have the carb off, just do it to start as it will help everything else too. Time the squirt so that it barely misses the slide as it is lifted. You will not be able to adjust the duration of the squirt, but you won't need to.



Disconnect the grey wire, install the YZ throttle stop, take the top off of the airbox all to start since those are the standard free mods that everyone does. Personally, I think tuning the carb is EASIER with the ACV disabled. You can actually hear a difference on decel if your fuel screw is to rich or lean. ACV (if i remeber right) was an enrichening circuit on decel to keep the bike from popping on decel, eliminating a potential way of tuning the bike. I think I went up a size on my pilot jet when plugging the ACV, because I could actually tune it properly.

I run with my WR with no grey wire, with WR timing. I don't do any motocross, just trails, so the WR timing is a better fit with more low end grunt, and less top end.

I looked up Lexington KY: Elevation: 978 FT (298 M). Pretty close to Michigan. So, I'd probably start with copying my setup, or someone close to you mod-wise who is extremely happy and use that as a baseline. Pay close attention to which situations, terrain and weather cause the bike to stumble, surge, rip your arms out of the sockets and cause you to giggle like a little girl with a new toy that has more power than 99.9% of mere mortals can use. Then come back here, tell us all about your ride with those specific situations thrown in, and that you need to adjust your jetting to correct them.
For your curiosity http://www.cycleconservationclub.org/ I don't have a clue what KY has to offer.

So before you start tuning, I would personally start by doing the following: YZ throttle stop, airbox, ACV, O-ring, AP squirt timed, grey wire. Then install your jets and JD kit to something that you think will work based on what others have done here. That is basic setup that will work well. Then go ride, and report back. No one setup works for every bike, but I bet TT'ers could get you 90% finished from the get-go just through research and planning.


My JD jet kit arrived today but no needle and seat yet. I am ordering the needle/seat as well as an RD fuel screw, a few pilot jets, and the yz throttle stop from sudco tomorrow with two day shipping so I should have everything i need on saturday. hopefully the beast will be starting easily and running smooth by sunday afternoon. You guys have a great time and be safe this weekend. That lamb roast sounds freakin awesome by the way. My next post will be with some tuning feedback on sunday night. hopefully i will be giggling like a girl with sore arms and blistered palms. thanks again for all of the great info! i really appreciate it.:thumbsup:

  • jbowman502

Posted October 27, 2009 - 08:08 AM

#17

okay, thanks again for everyone's advice. i installed the JD jet kit along with a one size larger pilot jet to help starting. the jetting instructions don't call for a pilot increase but i went ahead and increased it because the bike has been so hard to start. i also went ahead and installed the thinner of the two o rings that come with the JD kit for the o ring mod. And, of course, I put in the new float needle and seat kit from sudco along with a manually adjustable RD fuel screw from sudco.

The first test was to see whether or not the fuel overflow problem was fixed by the new needle and seat - so i put it all back together and opened the petcock-no overflow! so far so good - next test was kick starting - choked it and it started on the first kick!

After letting it warm up and playing with the fuel screw a little bit i took it for a spin around the block and it is running really strong. i haven't had a chance to take it out on the trails but as soon as i get a chance i'm going to do a tuning day to include testing diffent needle clip setting, trying no o ring and the thicker of the two o rings for the o ring mod. i didn't get around to playing with the squirt or the ACV and will probably leave those alone until i can see how it behaves off road.

one thing that came up when i was removing the throttle cables is that the previous owner somehow managed to chew up the round holes that accept the cable ends on the throttle cable wheel on the carb that actuates the slide. the cables were already damaged from previous removals so i've ordered a new set of cables but i can't find the throttle wheel! if you go to the online parts store, yamahaoftroy.com, and even the dealer, this part does not have a part number and isn't available! anyone know where i can find it or maybe a used one? i need it because it's very difficult to install the cables onto the throttle cable wheel and the cables are so damaged that the throttle does not snap closed as it should now so i've got to manually open and close the throttle.

also i wanted to let you guys know that BIG GUN is offering a refurbish kit for any of their exhaust for 60 bucks that includes repacking and replacing any missing hardware and upgrade to the new EVO can. the billet tips are extra.

hey guys i am really pleased with how easy it is to start and how smooth it's running so far so i really want to thank you guys for your help especially pooley. i will write back again soon once i've done some more tuning and testing. :bonk:




 
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