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YB 10 Fuel lines question
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Tirefriar



Joined: 18 Dec 2014
Posts: 659
Location: USA

PostPosted: Sun Feb 21, 2016 10:27 am    Post subject: YB 10 Fuel lines question Reply with quote

The fuel line from the fuel pump goes to the rail for the carbs. On that rail there are two fuel lines, one on each side of the main inlet, dropping down to ??

The reason I ask is that I was getting a fuel leak that at first I couldn't pin point. Today I started the bike and after about half a minute it started to leak fuel, again. I pulled off the left fairing and saw a loose line with fuel coming out. I pulled off all fairings and lifted the fuel cell. Saw that the hose came started at the left side of the rail, between the outer and inner left carbs. The only place I could find where it may go was a small black plastic connector. Unfortunately I didn't take any pics. Rolling Eyes
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Bud977



Joined: 03 Mar 2013
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Location: Sydney

PostPosted: Sun Feb 21, 2016 7:52 pm    Post subject: Reply with quote

It sounds like the float valves are sticking and the fuel is running out of the overflow. The float valves need a clean. This is pretty common for a bike that has been sitting around for a while.
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Tirefriar



Joined: 18 Dec 2014
Posts: 659
Location: USA

PostPosted: Sun Feb 21, 2016 10:33 pm    Post subject: Reply with quote

I received the bike from the seller with carbs cleaned. It is ridden with good consistency every weekend. Today I put about 150km on it. It does sit during the week. Would that short period of time cause floats to stick? I use only premium gas with an anti-ethanol additive from Lucas. I'd really hate to pull the cards on it now that the weather is just about perfect. Is there any type of cleaner or additive I can run through the fuel system?

BTW, I plugged both relief hoses into What appears to be a breather with dual inlets (just the right diameter for the lines) and rode it today with no issues. Did I fudge it?
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Jonny B Bad



Joined: 05 Dec 2009
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PostPosted: Mon Feb 22, 2016 10:36 am    Post subject: YB10 fuel lines Reply with quote

Tirefriar

If the float valves are letting fuel past and it gets into the cylinders, you'll have hydraulic lock and wreck the motor. I don't think there is an aftermarket provider of the float valves on those carbs - therefore they are relatively expensive to replace and not the kind of thing somebody would do if they were about to sell the bike. Either way, get it checked out, so it doesn't trash your motor.
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Tirefriar



Joined: 18 Dec 2014
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Location: USA

PostPosted: Mon Feb 22, 2016 3:46 pm    Post subject: Reply with quote

Sounds pretty serious. I conferred with the seller. He installed new needles while going through the carbs. His suggestion is to give the carbs a good tap to see if it will dislodge the dirt. When going through the fuel lines I didn't notice a fuel filter anywhere. I want to install one when I'll have access to the carbs. What is the best location or locations and filter to use?
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2bims



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PostPosted: Mon Feb 22, 2016 6:23 pm    Post subject: Reply with quote

Whenever I fit a new fuel filter (other than if its a specific In tank variety like on Ducatis..)...I tend to use this type.....glass and chrome....They can be opened up and cleaned out and re-used...I like them coz I can see (if its fitted in a good place) the fuel flowing...and whether it needs cleaning....

http://www.ebay.co.uk/itm/like/271969153108?adgroupid=13936810266&hlpht=true&hlpv=2&rlsatarget=aud-105106656306%3Apla-144478457826&adtype=pla&ff3=1&lpid=122&poi=&ul_noapp=true&limghlpsr=true&ff19=0&googleloc=1006620&device=c&chn=ps&campaignid=220881786&crdt=0&ff12=67&ff11=ICEP3.0.0-L&ff14=122&viphx=1&ops=true&ff13=80
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Tirefriar



Joined: 18 Dec 2014
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Location: USA

PostPosted: Mon Feb 22, 2016 10:15 pm    Post subject: Reply with quote

2bims wrote:
Whenever I fit a new fuel filter (other than if its a specific In tank variety like on Ducatis..)...I tend to use this type.....glass and chrome....They can be opened up and cleaned out and re-used...I like them coz I can see (if its fitted in a good place) the fuel flowing...and whether it needs cleaning....

http://www.ebay.co.uk/itm/like/271969153108?adgroupid=13936810266&hlpht=true&hlpv=2&rlsatarget=aud-105106656306%3Apla-144478457826&adtype=pla&ff3=1&lpid=122&poi=&ul_noapp=true&limghlpsr=true&ff19=0&googleloc=1006620&device=c&chn=ps&campaignid=220881786&crdt=0&ff12=67&ff11=ICEP3.0.0-L&ff14=122&viphx=1&ops=true&ff13=80


I can get these pretty easily. Will try to splice into between the tank and fuel pump.

I have this filter (the clear cone) on my BMW R100GS:

http://wiki.gstwins.com/index.php?n=Upgrades.FuelFilter

It has dual Bing carbs and these seem to work great. I am thinking of going with these, may be have one between the tank and fuel pump and then another one from the fuel pump to the carbs, unless this will impede the fuel pressure at the final destination?
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vort28



Joined: 22 Mar 2010
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Location: Northwest , UK

PostPosted: Tue Feb 23, 2016 8:08 am    Post subject: Reply with quote

I had a similar issue on my YB11 when I got it.
Sometimes it would run OK , other times it would just start leaking fuel. I went all through the fuel circuit. Found lots of small issues and every time it got better but would still leak fuel every now and then. Cleaned the carbs about 10 times and every time found something that I thought might be the issue, checked the float valves every time and reset fuel height. But ultimately bought some new float valves from Holland and that cured it.
Even if they don't look damaged the seal may not quite be good enough. Buy new one's , will save you lots of grief in the long run and you can fit in less than an hour , start to finish.
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Tirefriar



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PostPosted: Thu Feb 25, 2016 7:37 am    Post subject: Reply with quote

Vort, how difficult is it to install new floats? What tools are necessary? Can I do it in-situ or do I have to pull the carbs? Again, the seller went through the carbs and installed new needles.
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vort28



Joined: 22 Mar 2010
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PostPosted: Thu Feb 25, 2016 8:07 am    Post subject: Reply with quote

It is probably possible to do in situ but would be very difficult.
I would take the carbs off.
Simple enough job. Can't be specific about YB10 as don't have one.
Carbs off
Drain float bowls
Remove 3 bolts hold float bowls on
Remove float spindle and then float.
Float valve will fall out
Check float for cracks, fuel ingress.
Put new float valve in
Set float hieght
Replace float bowl

Simples
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Jonny B Bad



Joined: 05 Dec 2009
Posts: 555
Location: NE London

PostPosted: Thu Feb 25, 2016 9:22 am    Post subject: Float valves Reply with quote

You definitely need to remove the carbs, because the cross member of the frame sits immediately behind the float bowls. Once you have loosened the screws on the lower clamps on the rubbers between the carbs and the head, with a long shaft flexi-screwdriver, you need to release the idle screw, which is bolted to the cross member. The rubber boots hold the carbs pretty tightly in place, so I use a piece of wood to gently prize them off. A smear of silicone grease inside the boots eases re-assembly. Make sure the cables are adjusted for a nice throttle action before re-assembling the whole thing and don't forget to reconnect the choke cable. From memory, the float valve seat is incorporated in the float assembly and therefore you replace only the float valve, rather than valve and seat on later carbs. You don't want to replace the entire float assembly, as that is prohibitively expensive and not necessary. I would caution against messing with the float height - it is difficult to measure and too much bending of the tang which adjusts it can render the expensive float assembly junk. Unless somebody has been fiddling with the float height in the past, there should be no need to adjust it.

These are downdraught carbs on which the needles and needle jets are prone to accelerated wear. If the previous owner only replaced the needles, you should replace the needle jets as well while you are in there, because wear on the needles will have lead to wear on the needle jets. Factory Pro in the US do a set of coated needle jets (greater longevity) and titanium needles (ditto) which I would recommend, to give you trouble-free fuelling for years to come.

People complain about these carbs but they work well, if properly maintained. Hope that helps.
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vort28



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PostPosted: Thu Feb 25, 2016 9:35 am    Post subject: Reply with quote

As I said , can not be specific about YB10 as don't have one.

However not checking and setting the float height when you have just changed the float valve is a mistake. Not only will the valve be slightly different than the one being removed, tolerance in machining etc but the float height might actually be the issue for the carb flooding in the first place.
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Jonny B Bad



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PostPosted: Thu Feb 25, 2016 9:38 am    Post subject: YB10 carbs Reply with quote

George

With regard to your earlier point on the breather pipes. These will be the float bowl breather pipes. When these bikes were made, we had yet to embrace ram-air. With forward facing holes in the frame, through which the carbs take their air supply, arguably we have an early form of ram-air. The carb breathers for the under side of the slide are plugged into the frame to access the chamber fed by the afore-mentioned forward facing holes. On the original YB8s and YB10s the float bowl breathers just vented to the atmosphere behind the motor. Ram-air convention says that all of the breathers for the carbs should be exposed to the same pressure as the main air supply, which would suggest that the float bowl breathers should be plugged into the air box. That is what I have done by drilling a hole in the back of the air box, tee piece on the breather pipes, tube on the third piece of the tee and feed that through the hole in the air box, having found a suitable rubber grommet to ensure a snug fit. Works well for me.
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Jonny B Bad



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PostPosted: Thu Feb 25, 2016 10:15 am    Post subject: Float height Reply with quote

Vort

Wear on the float valve tip that might have lead to floats sitting too high, should be addressed with new valves. In my experience, the only thing that mucks up float heights is inexperienced human intervention. They are set at the factory to achieve 14.7mm, or what ever the setting is. Unless one is an experienced tang bender, with a measuring device that will take you to tenths of a mill, I would suggest that there is room for mucking it up.

These are unusual carbs that can run lean, suggesting that float height is set too low, i.e. fuel level is too low, but in fact mixture screws have a far wider range of useful adjustment than later carbs - as much as 5 turns out, compared to the more usual 3.

You're absolutely right that the experienced carb man would check float height, but the enthusiastic amateur, (no disrespect George!), is probably well advised to leave well alone, unless aware that they have been fiddled with in the past.
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vort28



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PostPosted: Thu Feb 25, 2016 10:24 am    Post subject: Reply with quote

Agreed, they are not the easiest thing to set but need checking as this is not a factory fresh bike and they could be set to anything.

I know on the first strip of my YB11 carbs each float was set differently and from memory they were 6mm to about 11.5mm . Resetting them cured the problems I had slightly.
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