Float Valve question (GS850, BS32SS)

[Guest]

Hi

My bike has a fuel leak that emerges from under the air box, so it's off the road till fixed. I have a GS850G 1986 with stock BS32SS carbs.

I am due to clean the carbs anyway as it's not running right, and am currently waiting for the necessary parts to arrive in mid Dec (carb boots etc - i already received cycleorings's o-ring set).

The mechanic (I know you guys don't easily trust mechanics, but I can't do this work myself and he comes recommended) said the leak suggests that the petcock and carb valve(s) are faulty. The petcock was proved to be leaking and so I've ordered a replacement (new).

He said that the carb valves may just be dirty, in which case they will be dealt with during the carb clean, but he thinks the leak suggests that they are probably damaged and will need replacement with new parts. He'll only know when he opens the carbs to clean them in mid Dec.

So I am wondering whether I should already buy some replacement carb valves in advance of knowing whether they are in fact needed. My priority is getting the bike running again, and I'd like to avoid opening the bike in mid Dec only to discover I need to order more parts and then wait more for them to arrive. Depending on the cost, I would consider buying in advance, then perhaps reselling afterwards.


This is the component, right?

http://www.ebay.com/itm/GS1150-GS850-GS750-GS700-CARB-CARBURETOR-NEEDLE-VALVE-/300409191714?pt=Motorcycles_Parts_Accessories&vxp=mtr&hash=item45f1c87d22#ht_500wt_1204

Is the o-ring what cycleorings.com supplies as the Inlet Valve Seat o-ring?

The valve looks to be comprised of 3 parts. Are these the needle, seat and spring? Which part is the spring? Is it the part on the right side of the picture?


What is the experience of the forum members? Is a leak as described usually fixed by a good clean and o-ring replacement? Or does it indeed suggest that the valves themselves are damaged?


If the valves themselves are the issue, then is it likely just one of the components will need replaced or the whole assembly? The reason I ask is that needles seem to be fairly easy and cheap to acquire, whereas the seat is not, and I haven't yet found that third component in the picture. So I'm wondering if maybe it's possible to cover my bets by just buying some needles. What do you think?


Similarly, is it likely that all 4 are damaged or should I be able to cover my bets by buying maybe just one or two in advance?


Many thanks for any guidance on this
Assaf

[Tom R]

How was the petcock determined to be leaking? Does the leak from under the airbox happen while it's running or sitting? If while running, it could be needle seat, and if while sitting sounds like a petcock related issue.
I'd be surprised if you had to replace the needles and seats due to damage, they're pretty hardy; but the orings, which come in the kit, should definitely be replaced.
The spring is in the needle and that piece on the right just holds the seat in it's place, no need to replace that.

[hampshirehog]

The needles and seats do wear and it is a very common problem on a lot of bikes. If you are paying somebody to pull the carbs then I would replace them as a precaution.

[Steve]

If you don't need the filter screen and the hold-down, you can get replacement valves for a a bit less from =custom]Parts N More (<-- click link, scroll down to mid-page). They have a $35 minimum, but that is easy to reach. The float valve with needle is $8 (you need four, of course) you can also get the rubber plugs for the pilot jets and a BUNCH of other stuff, including brake rebuild kits.

The link I gave you above is for the 750. For some reason, they don't show the float valve with needle on the 850 page, but it's the same thing. Switch back to the 850 page to see what else is available from them. I have never had any problems with their products or their service.

Keep in mind, though, that they are in Canada, so might take a few extra days to cross any borders.

Which brings to mind: you don't have your location in your profile. Where are you that you happened to find an '86 850?

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[Assaf]

Firstly, Thanks very much for the quick responses and for reading the lengthy post.

I'm in Israel. As in Europe the 850 was sold here until 86/87.

The bike was off when I observed the leak.
My maiden ride on the bike had been the previous evening. In the morning I returned to the bike and saw the leak, a drop maybe every 5 seconds or so (i didn't time it, so can't be sure).

From the wet stain of gas on the ground I understood that it had been leaking all night.

The petcock was in the ON position, and when I disconnected the fuel line I saw that the petcock dripped at around the same rate. This proves it is damaged, right?

When I bought the bike (a week previously) the petcock had been stuck in the Reserve position. The mechanic freed it and put it in the ON position.

I don't know how the petcock operates, but I wonder if it had been put in the in the Reserve position by a previous owner because maybe in that position the leak was prevented? Is that possible?

I didn't think of that at the time, so I didn't put it in Reserve to test the theory. But I find it hard to believe the bike leaked petrol when I bought it, otherwise the owner would not have driven it 40 mins to my home dripping with petrol.

It think it must have occurred either because it was moved to the ON position and that makes a difference, or because it was damaged in the effort to free it and move it to the ON position. Any thoughts on this?

In any case, I stopped the leak by connecting a plugged hose to the petcock, and there is a new petcock in the post.

But even if the petcock leaks, then the floats should nevertheless prevent the carbs from overflowing, is that right? Hence the diagnosis of a problem somewhere there, likely in the float needle and assembly. What do you guys think?

thanks again

[Steve]

Thanks for the location update, that explains why you got one that is much newer than ours.
We (Americans) are aware that they were sold elsewhere much later than the '83 model that we had.
I am under the impression that some of the leftover '87s were sold as '88s.

Back to the fuel leak ... If it were my bike, I would disassamble the petcock and clean it out. It is quite likely that the small plunger/o-ring assembly that is supposed to stop the gas flow is simply trying to do its job in a poor environment. It might be as simple as using a wire brush to clean the port that is supposed to be closed when the plunger/o-ring assembly rests against it.

Generally speaking, if a petcock leaks in the ON position, it will also leak in the REServe position. They operate the same way, but the REServe draws from the bottom of the tank, instead of several inches up. The PRIme position bypasses the need for vacuum to turn on the petcock, and will allow free-flow.

Although the petcock might have a small leak, the float valves in the carbs should have held it back. Your new o-ring kit from cycleorings should handle most of that, assuming that the float valves and seats are in decent shape.

Before trying to crank the engine over, remove all the spark plugs. Because there is no overflow relief mechanism on these carbs, there is no guarantee which way the extra gas went. Apparently at least some of it went to the airbox. More might have gone to the engine. If it went to a cylinder whose intake valve was open, the gas could flow into the cylinder and dribble past the gaps in the rings, down into the oil. (Check the odor of your oil. If it smells of gas, change it.) If the gas went toward a cylinder whose intake valve was closed, it could collect behind the valve, then drop into the cylinder when the valve opens. If there is more gas than there is room above the piston at the top of the compression stroke, BAD things can happen, so pull the spark plugs to give the gas somplace to go. Be sure to stand so you will not be hit by any spraying gas when you crank the engine.

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[Assaf]

Steve

Thanks for that link. Unfortunately, they don't show the part number, so I can't compare with my bike's fiche. But I see on www.cmsnl.com that indeed the same part is used on both models. That's a great price; I'll definitely get them. Thanks.

I suppose the 'hold down' is the part that Tom says 'holds the seat in it's place', it that right?

You say 'If you don't need the filter screen and the hold-down'.

Which part is the filter screen? Is it the part shown in the picture (in my original post) at the bottom of the valve seat? The bit that looks like some kind of metal mesh hemisphere, a bit like microphone head? It looks like it's attached to the bronze by some kind of dark plastic.

So is that a separate part not delivered as part of the seat?
Is it perishable and fragile and something I should get hold of ready to replace if necessary? I didn't see it on any sales sites. Where could I find it?

Thanks

[Steve]

I suppose the 'hold down' is the part that Tom says 'holds the seat in it's place', it that right?

You say 'If you don't need the filter screen and the hold-down'.

Which part is the filter screen? Is it the part shown in the picture (in my original post) at the bottom of the valve seat? The bit that looks like some kind of metal mesh hemisphere, a bit like microphone head? It looks like it's attached to the bronze by some kind of dark plastic.

So is that a separate part not delivered as part of the seat?
Is it perishable and fragile and something I should get hold of ready to replace if necessary? I didn't see it on any sales sites. Where could I find it?

Thanks

Let's use this picture for reference to the parts, and will answer your questions:


I suppose the 'hold down' is the part that Tom says 'holds the seat in it's place', it that right?
The hold-down is that hook-shaped piece that is farthest to the right. The semi-circle on the lower part of it straddles the shoulder of the float seat, the screw goes through the hole and holds it in place. The hook on the right side goes over the float, to keep it from falling too far out of place.

Which part is the filter screen? Is it the part shown in the picture (in my original post) at the bottom of the valve seat? The bit that looks like some kind of metal mesh hemisphere, a bit like microphone head? It looks like it's attached to the bronze by some kind of dark plastic.
Yes, the filter screen is the little hemisphere of metal mesh. It is firmly attached to a nylon band that clips over the brass float needle seat. In the picture, that nylon band is brown, but that is because it is stained with age. They actually start WHITE (natural nylon color). You remove the filter and nylon band as a unit by sliding a thin screwdriver or knife edge between the nylon band and the brass, and levering them apart. WARNING: it may fly, so aim it so it won't go very far.
NOTE: your petcock has a fine mesh filter to strain the gas before it leaves the tank. Each carb has one of these filters on its inlet, so you don't really need an additional in-line filter. Many new guys don't know about these filters, so install an in-line, which might be an incorrect model, and will cause more problems than it fixes.

So is that a separate part not delivered as part of the seat?
Is it perishable and fragile and something I should get hold of ready to replace if necessary? I didn't see it on any sales sites. Where could I find it?
You are correct, it is a separate part that is NOT delivered as part of the seat. I have not seen them available as a separate item, either. I think I have several of them at home that I could send you, but I won't be home for several weeks to find out if I have them.

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[Assaf]

Steve, that was very helpful, thanks.
and an very very generous offer regarding sending me filters.

I will have a think about what I need and be in touch.

I don't even know if I need the filters, my whole aim in writing this thread is to decide how best (and affordably) to be prepared for the possibility of needing to replace the valves, given that at this moment I don't even know if they are damaged.

I'm pretty happy buying 4 valves from the link you gave me, so I'll have a think about your filters too.

Many thanks

[Assaf]

Before trying to crank the engine over, remove all the spark plugs.

By 'crank the engine over' do you mean turn the key as if to start the bike up?

OK, I'll be careful about that.

[BigD_83]

By 'crank the engine over' do you mean turn the key as if to start the bike up?

OK, I'll be careful about that.

Steve means depressing the START button, thus turning the crankshaft...the pistons will move up and down, and the removed sparkplugs will allow any accumulated gas to escape without damaging the pistons, valves, etc