Fuel level ?

[Mohawk]

Hi guys,

Finally got some time this week to look at my idling issue, its been a few months

So having cleaned the carbs for the 5th time & not finding anything amiss, I decided to check the fuel level before refitting the carbs to the bike.

I can only find a couple of references to the fuel level, so if anyone has a definitive answer to what the fuel level should be please let me know.

My float measurements are spot on at 17mm, but the fuel level is only halfway up the float bowl ! I have just fitted a rebuild kit with new float valves. So fairly certain its all good inside.

Thanks

[Mohawk]

OK so finally found my old manual for GPZ250 which is the grand daddy of the ex250 water cooled series. It says 0.5mm above top of float bowl +/- 1mm. So looks like mine is way to low, which might explain the easy start, but fails to idle after being revved.

If anyone can confirm that setting it would be appreciated.

[ducatiman]

i prefer using the float bowl seam, or just a tad under

[Mohawk]

Thanks Ducatiman,

[Motofool]

Originally Posted by Mohawk

......... My float measurements are spot on at 17mm, but the fuel level is only halfway up the float bowl ! I have just fitted a rebuild kit with new float valves. So fairly certain its all good inside.

Thanks

You are correct.
The 17 mm should be measured without the weight of the float putting pressure on the spring of the valve.

When using the method of communicating vessels (picture above), be careful to level the carb perfectly and to eliminate any little bubble.

[Mohawk]

Interestingly, after 3 attempts I now have the float set at 16mm & the fuel level right at the correct height, bang on the seam.

Strangely I had used the angled no pressure on spring measurement, but whilst I had the carbs up side down I decided to check the measurement & its identical ! With the old float valve, it would reduce from 17 to 14mm 1 with the new ones there is no change.

Checking the spring tension by feel both sets feel the same but obviously are not. Either way, fuel level is now bang on where its supposed to be. So will refit tonight & give them a whirl.

[sickopsycho]

Where is the adjustment of this level? As in, if it was too low like @Mohawk was, how do you raise it? Sorry- I'm more of a fuel injected guy and am trying to figure out the mysteries of these carbs...

[Mohawk]

You have to remove the carbs from the bike, then remove the float bowls from the bottom of the carbs, then look at the diagram above on how to set the float height.

Where (2) points to the spring pin on the float needle you will find it stay attached to the float via a thin wire, which passes around a metal tongue on the float. By carefully ending that tongue, you adjust the contact point with the valve spring.

To adjust first measure the fuel level as shown in ducatimans pic above with a clear tube, then with the carbs upside down, lift the float up, then using a fine tipped screw driver bend the tongue down a tiny amount as you look at it to increase the float height measurement & lower the level, or lever it up to reduce the float height & increase the level.

A half millimetre of bend at the end of the tongue will produce approximately 5mm of fuel level adjustment, so be CAREFUL & GENTLE with it.

[sickopsycho]

Originally Posted by Mohawk

You have to remove the carbs from the bike, then remove the float bowls from the bottom of the carbs, then look at the diagram above on how to set the float height.

Where (2) points to the spring pin on the float needle you will find it stay attached to the float via a thin wire, which passes around a metal tongue on the float. By carefully ending that tongue, you adjust the contact point with the valve spring.

To adjust first measure the fuel level as shown in ducatimans pic above with a clear tube, then with the carbs upside down, lift the float up, then using a fine tipped screw driver bend the tongue down a tiny amount as you look at it to increase the float height measurement & lower the level, or lever it up to reduce the float height & increase the level.

A half millimetre of bend at the end of the tongue will produce approximately 5mm of fuel level adjustment, so be CAREFUL & GENTLE with it.

Ok, that's kind of what I figured. I just 2 days ago had my carbs out and completely torn apart. I replaced the float needles as well as some other parts. So the tongue on the float that the float needle sits on is bent to adjust the fuel level... That makes sense. Thanks for the clarification.
One thing I guessed on and hope is right is the orientation of the float needles. The little wire you were referring to that hooks around the float has 2 seat flanges or something on one side. They look like they make contact with the body of the carb maybe when the needle is in the closed position? Anyway I wasn't sure which way they should face so I just guessed and made them both the same. I am not seeing any issues, does it even matter?

For clarification I'm talking about the 2 small semicircles in the thin wire near the top of the needle, not the hook on top that hooks over the float.

[Mohawk]

As far as I can tell it doesn't matter which way round they go. Ductiman will know if there is a correct way.

On another note,some good news, I refitted the carbs & I bored the pilot jets out to .6mm to see if they were the culprit. Bike starts & idles fine, not choke required & its cool here now. It has all the hall marks of running too rich, if I open the balance pipe to allow more air in it revs away to 4K, before it would just die as too lean. So new replacement pilot jets are on order, so once. Fitted should be mod done ��

[ducatiman]

the spring orientation doesn't matter...or shouldn't, provided the float valves are for the correct application.

Opening the pilots up to .6mm has netted you the equivalent of a #60 Keihin pilot. They are, in fact indexed in fractions of a mm. A common pilot for a US EX 250 is #35 (or .35mm, .0137") your #60 or .60mm would be .0236"

I can fully understand why the bike is running a bit rich!

[Mohawk]

Hi Ducatiman, I know they are measured in points of mm, mine looked clean, but trying various wire sizes showed they were tight. So I used the smallest drill I have to open them up just to prove a point, then I discovered the fuel level was wrong too to late to undo that, but as I've now got carb removal or fitting down to 20 minutes. I thought I see how it idles & what effects I could observe & yes it exhibits all the symptoms of to rich at idle. so new pilot jets will be here in a couple of days & hopefully I will get it fully assembled on the weekend.

Thanks for your input, been a while since I worked with carbs !

[ducatiman]

yqw

vfr, eh?

[Alex]

Everything up and running?