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Old August 9th, 2022, 05:37 PM   #1
notrocketscience
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Question Petcock off = good idle, petcock on = no idle? | Could use some help

Hi all, I hope you've had a better time than I have with your bikes. This post is a bit of a doozy so I added a TL;DR at the bottom.

For a bit of background, I have a 2006 EX250F that I bought used last September and have been attempting to fix up since. It's in pretty rough shape but has just over 6000 miles on it.

Things I've done:
- new battery
- new spark plugs
- cleaned and sealed gas tank
- cleaned petcock
- added inline fuel filter (for a lawnmower, I think John Deere specifically)
- cleaned carbs
- set carb float height to ~16mm (used depth gauge to get height from the lip of the bowl to the top of the floats)
- brand new gas (~costco regular~)
- set fuel mixture to 2 turns out instead of 2.5 (I think this helped get it running better when I was messing around with it today)

Today was the first time in a while that I've tried to start my bike since making the improvements. I turned my petcock to on and then cranked it for a while to prime my carbs, then when I tried to turn it over for real it fought me a bit and then gave me a pity start that lasted for a good 3 seconds. I tried starting it a few times after it quit to no avail, got pissed, then called it quits for a little while.

I remembered back in October I seemed to have success when I was either just filling my carbs after emptying them or when I set the petcock to off and starved my carbs of fuel. I have no idea why this was but it let me bike startup so I didn't ask questions.

So I did the same thing, I set my petcock to off and tried cranking it some more. After messing around with the throttle for a bit, I finally got the bike to start and it ran great! I shut it off and tried again to see if that was just a fluke, but it started right back up and let me reset my idle tuning to have the bike around 2k rpm (where it ran comfortably). After a bit of smooth idling, I noticed when I messed around with the throttle it lagged pretty bad. I figured this must be a fuel issue since I'm starving my carbs of fuel and I turned my petcock to on. After that, I ripped the throttle and it was quick and snappy. However, my moment of celebration ended pretty quickly because when I let off the throttle my bike slowly chugged to a stop yet again.

The bike seems to have a sweet spot when I'm starting it up where just the right amount of fuel is in the carburetor. I really don't understand it, but that's the best idea I can come up with right now. It may be a float issue, but I don't see how I can bend my tabs more to lower the fuel level further. Hopefully, there's something simple I'm just missing.


TL;DR - My bike doesn't idle and is incredibly hard to start when my petcock is on and my carbs are full. When I turn my petcock off and my carbs are full, my bike idles incredibly well (comparatively) but the throttle lags when I open it up. setting the petcock to on after it's already idling gives me good throttle control for a moment, but the bike slowly chugs to a stop.

I want to say it's a float issue, but that doesn't make much sense to me. I was hoping someone else may have had a similar problem or at least could offer me some guidance on what to mess around with.
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Old August 10th, 2022, 05:51 PM   #2
Ceeloo Yello
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You sure you are not putting it onto reserve instead of off?
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Old August 10th, 2022, 06:10 PM   #3
notrocketscience
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Quote:
Originally Posted by Ceeloo Yello View Post
You sure you are not putting it onto reserve instead of off?
Yep, triple checked that

On further inspection, it looks like the wire that connects the float valve to the float wasn't right. It bent out too far around the valve which didn't let the rubber seal on the opening. I just took some pliers and bent them back and now I'm getting proper sealing (I was checking with compressed air. Before it couldn't hold 5psi even while I was pushing the valves down, now it can hold 20psi easily on its own).

I'll throw my carbs back on my bike tomorrow and post an update if anything interesting happens.
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Old August 11th, 2022, 05:32 PM   #4
notrocketscience
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Originally Posted by notrocketscience View Post
I'll throw my carbs back on my bike tomorrow and post an update if anything interesting happens.
Update: Installed carbs and my bike ran great for a little while. It ran well enough that I was able to get it in first gear for the very first time. However, I'm still having an issue where the bike runs fine for a little while (longer now) and after a bit, it starts bogging down. The rpms eventually drop low enough that it dies off.

Is this an issue of running too rich? Is my engine being flooded after idling for a bit? I had the same fuel drain from my carbs as I did before I fixed my float valve issue, so maybe nothing changed at all.

I thought I might have a restrictive air filter so I took that out for a test and experienced the same issue. I even set my mixture screws to 1.75 turns out and had the same problem.

Does anyone know what might be my issue and how I can address it? From what I've researched all I can think is I am running way too rich still. In the meantime, I'm going to pull my carbs, re-examine, and see if there's any obvious issue staring me in the face.
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Old August 11th, 2022, 05:55 PM   #5
DannoXYZ
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Sounds like you have petrol flow problem. Could be petcock or it could be carbs. We'll need to do some testing and measuring to narrow down exact problem area. Numbers will tell us if a part is good or bad.

1. Test petcock flow. Unplug fuel-hose from carbs and aim into measuring cup. Set petcock to ON and attach vacuum-source to petcock and apply some vacuum. Some people attach hose and suck on it. Or use syringe. Let petcock flow for 10s, how much petrol did you collect?

2. Test petcock flow in RESERVE. Repeat test and let petcock flow for 10s in reserve position. How much petrol did you collect?

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Old August 11th, 2022, 06:52 PM   #6
notrocketscience
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Quote:
Originally Posted by DannoXYZ View Post
Sounds like you have petrol flow problem. Could be petcock or it could be carbs.

2. Test petcock flow in RESERVE. Repeat test and let petcock flow for 10s in reserve position. How much petrol did you collect?
I felt silly, but it is done. I have only run my bike on reserve for my testing (beats constantly moving around a full gas tank, plus I want to paint my tank soon so I've been keeping the fuel low in it to make draining easier).

RESERVE had a flow rate of 6.9 grams/s (1.104 gal/min or 0.773 gal/min depending on how the conversion works. The first is assuming water mass so 0.016gal/min per 1 gram/s, the second is applying that gasoline is about 70% of the mass of water)
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Old August 11th, 2022, 07:01 PM   #7
notrocketscience
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Looking at my needle valves again they're definitely better, but it seems like that wire is still rubbing the side ever so slightly. It looks like this is causing a tiny gap/leak if it is not pressed into place well enough. Does anyone have suggestions on how to fix this? I'm not sure I can bend the wire more, but I'll mess with it right now.
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Old August 11th, 2022, 08:41 PM   #8
notrocketscience
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Quote:
Originally Posted by notrocketscience View Post
Looking at my needle valves again they're definitely better, but it seems like that wire is still rubbing the side ever so slightly. It looks like this is causing a tiny gap/leak if it is not pressed into place well enough. Does anyone have suggestions on how to fix this? I'm not sure I can bend the wire more, but I'll mess with it right now.
welp...

I managed to mess around with the wire for long enough that I eventually snapped it. However, I think there's a silver lining. I looked up replacements and found that the current float needles I have appear to be WAY too small to get the job done properly. They're measuring in at 13mm length (including the spring) and have a body of about 3mm by 3mm.

now all I can do is wait and hope the replacements can get the job done. What would we do without amazon?
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Old August 17th, 2022, 10:47 AM   #9
notrocketscience
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Originally Posted by notrocketscience View Post
now all I can do is wait and hope the replacements can get the job done. What would we do without amazon?
Quick update. I got the new float needles which were HUGE compared to the old ones. From the look of things, they are working much better. I actually got to ride my bike for the first time ever (even got into 2nd gear, which is a massive accomplishment to me).

I'm still having the way-too-rich issue where my idle eventually dies, but now I think that might be from either improperly sized jets or improper mixture screw tuning.
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Old August 17th, 2022, 04:33 PM   #10
DannoXYZ
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Good job!!! Making progress!!
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