fuel float needle mod

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Fred
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fuel float needle mod

Post by Fred »

Well I dont know if its a mod or not , I did hesitate before I wrote the word 'mod' but there we go.

So every time I go out on the bike or just take it for a run round the carp lake I come back and it needs a little fiddle with idle mixtures. It been like this since we met. 9 years now!!.

I had my floats collapse last week, the carbs flooded and the floats had imploded from a spit back and now they dont float. I took then out and chucked it into a bucket of water and they sank, they are not supposed to do that,--they should float,.

So down the the lesbian motor bike shop with every spare part imaginable hanging above your head and guys wrestling with forks and clutches around your feet,--heaven or hell depends on your point of view. Brought out a huge plastic bag of floats, did not have right one but bought one any way as the floats were the same and I can de solder. 3 dollars= 100 baht

So 10 minute soldering job and the floats were off( note -- do one at a time to keep the dimensions same as before) and we were back in the carb.

But---- I looked at the needle and it has a silly spring on it, I did'nt like it, It was kind of weak so I soldered that too.

Hey--- thats how they used to be in the old days, solid needles -none of this needle damper crap.

Running again now sounds good. I would hate a reliable bike ---I would have nothing to do.

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hillsy
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Re: fuel float needle mod

Post by hillsy »

The spring is there to save the float and valve seat from damage due to vibration. The spring is supposed to be weak.

Not saying what you've done will definitely fail, but it's not a great idea.

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Fred
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Re: fuel float needle mod

Post by Fred »

hillsy wrote:The spring is there to save the float and valve seat from damage due to vibration. The spring is supposed to be weak.

Not saying what you've done will definitely fail, but it's not a great idea.
No-- it wont fail. Both sold needle valves and damped are available. With the new floats it could be possible that the damper spring could be compressed giving erratic fuel levels The float is attached to the carburetor my a basic hinge and pin, it only pushes slightly on the pin. Are you confused with the needle valve return spring?

Can you explain how a needle and the float that is floating in fuel can be damaged by vibration,-- and even the carb being on rubber mounts.

With a fuel pump feeding a higher fuel delivery pressure on the rear carb I think a more positive fuel level is a good thing.

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hillsy
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Re: fuel float needle mod

Post by hillsy »

If the spring is not deemed necessary, do you know why pretty much every carb uses them? You will be surprised how much vibration a carb sees even if it is rubber mounted. There's been a stack of times I have pulled a set of carbs and seen indentations on the float tab where the needle valve has contacted it when the spring has seized. Floats vibrate a lot even in a bowl full of fuel.

Fuel pump fed carbs are a different story to gravity feed as well - EG: the float needles are different between the gravity fed FJ1100 and the fuel pump FJ1200. Those carbs are identical otherwise.

Like I said, not saying what you've done is going to fail, but it's not an improvement by itself. Fixing the float was clever though - I'm wading through the same issue with a Z1300 - floats are bad but you can't buy them anymore. They are Nitrile (solid plastic), so I'm considering pulling the trigger on cutting the plastic off the tabs and replacing with new material.....but it's no turning back if I fuck it up.... :shock:

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Pvt_Nemesis
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Re: fuel float needle mod

Post by Pvt_Nemesis »

Ive seen needle float valves with a massive notch vibrated into the contact surface and another that had the tapering face concave, both having had the springs removed.

As the bikes came to me with this 'fix' already made I don't know how long they took to manifest but the XS850 only needed the valve replacing with a new one with spring to run perfectly and the 125 needed retuning of carb as well. Both bikes were high mileage!
Ya hya chouhada!

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Fred
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Re: fuel float needle mod

Post by Fred »

I too have seen wear marks on the tang but im not sure it is from vibration. Solid valves were all there was at one time and this includes all SU carbs on Jags and RR which dont suffer much from vibration.

Vibration on some engine can cause fuel to become frothed in extreme cases and cause a weak mixture. Im not sure how a spring on the needle will stop vibration in the carb.

The mark on the tang could be general wear , --lets face it that needle goes up and down a lot and its only brass. The spring is meant to close the valve shut as per the float level measurement , therefore we have to assume it is never compressed or the fuel level will exceed the set level and what would be the point of that.

The front carb float on the 1400 is a plastic job , mine has broken, I have tried every thing to repair it.

Im old enough to remember dropping floats into boiling water to expand the air inside to push back the float into shape and re solder. When it pops out to shape you then have to quickly unsolder the bleed hole and let air in so that when it cools it does not suck back the dent in the float. The boiling water trick will also show an air leak.

When soldering brass floats hold the float side ways or you will get solder inside the float and increase it weight and it will float differntly. You will notice that one of the floats has to be removed to get your soldering iron to the bleed hole. As long as you only remove one at a time dimensions can be retained.

The first most important part of the carburetor is to get the fuel level right, if not your wasting your time jetting. Just 1mm will richen your mix, the same as one notch on the needle.

Who the hell wants fuel injection when you can have fun like this.

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hillsy
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Re: fuel float needle mod

Post by hillsy »

Fred wrote:
I'm not sure how a spring on the needle will stop vibration in the carb.
It doesn't stop the vibration in the carb - but it insulates the float from hard contact on the float valve.

It's a bit like putting struts on your bike instead of rear shocks. Sure, they both do the same job of holding the arse of the bike off the ground but the shocks absorb the impact on the suspension components.

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Fred
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Re: fuel float needle mod

Post by Fred »

hillsy wrote:
Fred wrote:
I'm not sure how a spring on the needle will stop vibration in the carb.
It doesn't stop the vibration in the carb - but it insulates the float from hard contact on the float valve.

It's a bit like putting struts on your bike instead of rear shocks. Sure, they both do the same job of holding the arse of the bike off the ground but the shocks absorb the impact on the suspension components.
Wow --thats not really the same thing but the spring on your suspension allows it go up and down without the jolt. The level of your arse is not critical. The fuel level in the carb is carefully set to a predetermined height and is critical for correct carburation. I don't want it to go up and down. If you are then saying that it allows the float to go up and down then I don't want that iether

If the spring is compressed at all then you have a too high fuel level.

When Mikuni make a carb they have no idea what you are going to do with it or or what bike it may be used on or for what purpose. They try to make it do for all uses.

If the spring moves at all it will be very small momentary movement probably for off road use. Im not doing trials with my 1400 or the wall of death so a steady fuel level is fine.

Steve Mc queen jumped over the barbed wire fence in Germany escaping from prison with a Triumph. He probably had a sold needle. Seemed to work ok

These little mods personalize your machine to you own particular use. A hemi in a drag car would have hardly any resemblance to the engine built it in Detroit.

Most of the public are not able to make personal modifications or alterations,--- the carb manufacturer has to cope with that. ;IDunno:

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hillsy
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Re: fuel float needle mod

Post by hillsy »

Fred - the whole point is the spring absorbs the vibration and limits damage to the float / needle valve / seat.

The spring is strong enough to hold the float in the correct position without compressing - that's why you set the float height with the carbs angled so the float is just resting on the float valve, not with the spring compressed.

But anyway, kudos to you for fixing the problem with your floats using what you had available [emoji106]

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Fred
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Re: fuel float needle mod

Post by Fred »

[quote="hillsy"]
The spring is strong enough to hold the float in the correct position without compressing -/quote]

I think you mean that the spring is strong enough to hold the needle valve closed without compressing.

Not much point in it being there then is it.

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hillsy
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Re: fuel float needle mod

Post by hillsy »

Fred wrote:Not much point in it being there then is it.
The spring is there to dampen the impact on the float tab, needle valve and seat. Every motorcycle carb I've seen this side of the late 70's has sprung needle valves. I've seen carbs where the spring has seized and you can see accelerated wear on the needle, valve seats and float tabs.

It's there because it's an improvement over previously not having it there.

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Fred
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Re: fuel float needle mod

Post by Fred »

I tell you what Hillsy some people have totally re jetted their carburetors, changed exhausts, cut out the air boxes, Changed plugs to iridium, used stronger springs on the clutch, changed tyres to tubeless, and even changed light bulbs to Led's and even --yes even put car tyres on the back.


what Bastards. Im going to change the fuel flow pipe next so the lower carb is not fed at a higher pressure!!! :naughty:

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hillsy
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Re: fuel float needle mod

Post by hillsy »

Fred wrote:I tell you what Hillsy some people have totally re jetted their carburetors, changed exhausts, cut out the air boxes, Changed plugs to iridium, used stronger springs on the clutch, changed tyres to tubeless, and even changed light bulbs to Led's and even --yes even put car tyres on the back.


what Bastards. Im going to change the fuel flow pipe next so the lower carb is not fed at a higher pressure!!! :naughty:
Car tyres? Dont start a DS debate..... :lmao:

Change is good when it improves stuff, but people also do this sort of shit:

Image

Seriously - look at those retarded tyres and the almost complete lack of suspension.

They think they are making something "cool" but they are just fucking up a once functioning motorcycle.

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Re: fuel float needle mod

Post by FallenAngel »

Fred wrote:But---- I looked at the needle and it has a silly spring on it, I did'nt like it, It was kind of weak so I soldered that too.
and you will find out after your tang brakes from the vibration opening the needle valve dumps fuel on your hot exhaust ignites and burns your bike to the ground
Fred wrote:Hey--- thats how they used to be in the old days, solid needles -none of this needle damper crap.
And that is why the introduction of that weak spring to the needle valves in current carbs
But then again
Fred wrote:but when you are me and have my money I can get what I want.
Or do no mater how ignorant

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Fred
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Re: fuel float needle mod

Post by Fred »

Oh no my bike exploded today. Actually it did'nt and wont.
I cant tell a lie --its just not me.

I soldered the front up today as well . I was amazed at how far out the float measurement was. and it runs great a good solid idle like a Cadilac.

I also found that the distance between the slide bottom on the front is 1/2 inch and the rear was only 3/8ths. I made up a collar that fitted on the slide and now I dont have that slight hesitation from idle to 1200 rpm,( Im a slow rider, I drive in town).

I have removed the carb so many times I can take out the idle jet in the time of half a song on the radio---1.5 minutes.

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Re: fuel float needle mod

Post by hillsy »

Nice diagnostic tinkering Fred [emoji106]

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