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bike wont start when warm. low idle. carb issues?

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Hey guys, bike starts great when cold, first kick.

 

but when riding, it feels like the choke it on, and it gets progressively worse to the point where it barely runs and wont start while hot. I think it was flooded, I took fuel line off and kicked and it eventually started. I seemed to have fuel coming out of the overflow hose though a little bit it seemed.

 

what do you guys figure it could be? my valves are fine, all that stuff is fine. the engine did seem to be a bit hot when I touched it, but the digital temp gauge I have tied into the rad line said it was 81C where it red lines at 110C

 

what is the stock setting for the throttle stop screw? (the big flathead one on the side)

 

I know the pilot screw is 2 turns out.  well 1  7/8   does an eighth of a turn really make a difference, really??????

 

thanks

Edited by cdf450

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There's a whole section just for jetting, repost this in there

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Could be a couple things.

 

1. The fuel screw is too far out (too rich) and is likely at almost 2 turns. And yes, an 8th of a turn matters. Set it at 1.5 and see how it runs.

 

2.The choke plunger is leaking and its pulling fuel all the time making it too rich.

 

3. There isnt a setting for the idle speed. Get the bike warm, set the idle to about 1800 rpm, set the fuel mixture screw until the idle speed is fastest, then RESET the idle speed back to about 1800. Done.

 

When ice cold, the bike shouldnt probably start on the first kick.

 

You dont need a pilot jet bigger than a 45, probably ever so if youve got a 48 or something in there, thats your first issue. Should be a 42 stock. Stick with that. Its not too lean even with a pipe.

 

A water temp of 81C is just about perfect (177-178F) Thats not hot at all.

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ok, I will set it at 1.5 and try again.  I re jetted it a few years ago with a JD jet kit and its ran fine ever since, I hant changed anything in years, its got a 170 in the bottom..... until my aftermarket fuel screw rattled out! the bike actually ran believe it or not but not very good.   I fiddled with the throttle stop screw in the process and ever since its been a royal mess with my carb.

 

I hope its not the choke plunger, that doesnt sound easy to fix. the choke feels fine though when I pull it.

 

ive got a stage 2 cam, my elevation and temp is different so there were a few changes with the JD jet kit, but its ran fine for 3 years until my fuel screw rattled out and I messed with the other screw :banghead:

Edited by cdf450

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Details you left out :facepalm:

 

You need to look up in the hole where the fuel screw goes and make sure you dont have two orings up there. If there is your fuel screw setting is way way out of wack.

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yeah sorry!  I have looked and I believe there is just 1 o ring in there, thats a good one though.

 

ive got it set to 1.5 turns out and it still kind of bogs and sputters on low end.  it idles around 1900-2000 RPM, it doest idle very smooth.  I am pretty lost here ive never had this many problems.

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well. I got it figured out, after much tinkering, taking apart the bottom of carb (slow jet was a tiny bit dirty)  as well as the rest of the carb was a little dirty, what do you guys think of that?   I ran the bike with no fuel screw for a little while not knowing, and could have possible sucked up some dust, although I wasnt in dusty conditions, more like wet and muddy for 10 mins till the bike wouldnt run.

 

anyways, the bike started first kick every single time, and it ran great at full throttle.   its idle is what was weird.... it was anywhere from 1800-2600 rpm just sitting there!

 

so we took the top of the carb apart and played with the needle.  I installed the JD jet kit RED needle on 5th position 4 years ago.  well about 300 engine hours later, that needle had severely worn out which totally makes sense while the bike ran great at WFO but idled very rough.

 

here is the black tarnish in the carb... how do I clean this or should I even worry about it?

 

2qdczro.jpg

 

and here is the worn out needle... ever see this before?

 

2nknrl.jpg

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Study that link koolaid posted above from dirt rider mag.

Install a ncvs needle and new vacuum seal on the plate or new plate and seal. If the carb is that dirty then Atleast tear it apart and let it soak all night in some pinesol then blow it out with compressed air and run fishing line through the tiny passages for the fuel screw and the other small hole that's located under the slide. If the pilot jet is that old then I'd replace that too. Get back to us if your still having issues after that!

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why would the pilot jet need to be replaced with age???

 

the bike ran great today, id rate the carb right now at 97%.... its a little boggy when im going fast down the gravel and just giving it 5% throttle, but othewise it ran great for 2.5 engine hours today, 30 miles of hard riding and long hill climbs in the coal dust.

 

that dirtrider article is awesome, a bit much for me but I defintiely learned a lot. thanks a lot for that koolaid  I would definitely look into replacing that wear plate around the 10th picture but thats about as deep as I would go into it.

 

am I able to buy a bucket of carb cleaner and just dip the whole carb into it to clean? 

Edited by cdf450

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The pilot because of your idling acting funny but if it's idling fine then leave it.. It's only five bucks and they clog up easy. DO NOT dip it in carb cleaner. The carb has gaskets from the factory in the middle of it and those cannot be replaced, you'll end up like me having to silicone the outside around it so air can't get through..

Ok so new ncvs needle

New plate and seal if the plate appears to be wore. If you've never replaced it then now would be a good time. If not then just the seal for the plate.

New jet needle, the part your needle rest inside gets wore as well.

The bogging part- I'd say either your ap needs to be cleaned or your getting air in from somewhere like a crack in the hot start but which would also explain your idle issue... Take your time and go through it.

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what year is the bike? there is quite a few post about the quick throttle bog. the oring mod or a qs3 will fix that if you have issues with that. i got a deal on a qs3 bought a carb off ebay and it had a new one one it, the adjustable leak jet is nice.

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what year is the bike? there is quite a few post about the quick throttle bog. the oring mod or a qs3 will fix that if you have issues with that. i got a deal on a qs3 bought a carb off ebay and it had a new one one it, the adjustable leak jet is nice.

 

the bike is an 05, ive done the thicker O ring mod on the Apump about 4 years ago.

 

it idles great now, it was idiling rough because my needle was completely worn out.

 

now, while riding very very fast, and keeping it 10% throttle just to maintain my speed, if you listen closely and feel closely it has the tiniest tiniest little bit of a bog, sputter. only at 10% throttle while going fast though. otherwise it starts fist kick and pulls those kill climbs very hard and effortlessly. 

 

I removed the 4 year old JD jet kit needle and installed the stock one. bike runs awesome.

 

I tried looking on ebay for that plate and seal and couldnt find anything... do you guys got a link?

 

dont think im getting air in from anywhere, although I should look at my hot start (I never even use it) and also the accelerator pump but its just so hard to get to and I am too lazy to take subframe off :(

 

thanks for the help guys, my bike hasnt ran this good in a long time!!! damn carb. 

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you can buy the plate and seal from honda, or just the seal from sudco i wouldn't  replace the plate unless it is bad. have you tried to lower or raise the needle this might help your problem. i had my carb bored and i think i changed to a nyqr needle sedrum recomended what needle to use and it seemed to be better than stock.also it is better to  buy a aluminum piece for the hot start cable end the plastic  ones tend to break and leak.

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Partzilla.com has everything out need. Do yourself a favor and order once to save money in shipping. The plate plus seal and ncvs needle can be found when looking up your model bike. If you want just the plate seal then look up lets say a 06 yz450f.

You want help and want to get your bike right but you won't go through the steps from the dirt rider mag or even go through the work to take your carb off... Either fix it or accept it.

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I dont think I need to rebuild every single little piece that deep into my carb to fix a minor problem, thats a little overkill.  I had a severely worn needle, and a fuel screw that rattled out, thats it.  its fixed now with the carb not even removed and and almost perfect now so im not going to take it apart and rebuild it to factory specs unless I really need to, thanks for the help though really appreciate it. that plate is something I would like to try though if its a major wear item, and who knows, maybe when the carb is off ill feel brave and really tear into it. 

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I think youve got a mental boogie man living in your carb. There really isnt much in there. Id bet your bog is just the accelerator pump being a tad plugged. But if you like the way it runs, just ride it. It may clear up on its own with enough fresh gas through it.

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