Author Topic: Another bs350 leaking carbs thread...  (Read 6334 times)

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Offline hardy

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Another bs350 leaking carbs thread...
« on: June 12, 2015, 08:10:26 AM »
Hi guys,

Finally got the bs off the stand from its tidy up (read get running not restore for the moment) and put in some fresh fuel and oil.  Started up 2nd kick:)

But as before I pulled it down, the left hand carb leaked. The gasket was buggered so I thought this to be the cause. After further inspection it looks like the carb bowl has been over tensioned in the past warping the body of the carb. A show stopper!

I've attached a pic of how far it is warped...

I'm guessing the carb is now terminal? Does anyone have any leads for another working carb or someone who can machine the gasket face true?

Ryan
« Last Edit: June 12, 2015, 08:16:17 AM by hardy »

Offline hardy

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Re: Another bs350 leaking carbs thread...
« Reply #1 on: June 12, 2015, 09:50:03 AM »
After some googling. I think this is now a wanted add!

I had a look on eBay but it would be luck if the draw what you get. . .

Would anyone be able to help me with a good quality spare carb?

Offline bsforever

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Re: Another bs350 leaking carbs thread...
« Reply #2 on: June 12, 2015, 10:20:06 AM »
Ryan, just wanted to set your mind at ease..... the carb is fine, mine are the same way. I am sure you will get a response as to the 'why' it is as more read this thread. I would check the needle valve and the float level on the carb. bsforever

Offline hardy

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Re: Another bs350 leaking carbs thread...
« Reply #3 on: June 12, 2015, 10:50:17 AM »
I set the float height at 24mm and checked the needle and seat shut off the fuel. All ok...the needle and seat are new.

The carb seems to leak out the front. I lapped the fuel bowl flat with no luck...

You can see in the pics the before and after!
« Last Edit: June 12, 2015, 10:53:15 AM by hardy »

Offline slawsonb

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Re: Another bs350 leaking carbs thread...
« Reply #4 on: June 12, 2015, 11:35:51 AM »
My carbs look like your first pic as well.
Probably a dumb question, but is the float bowl gasket new? They tend to flatten after very few tightenings.
...bert
« Last Edit: June 12, 2015, 09:16:36 PM by slawsonb »

Offline ziggy stardust

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Re: Another bs350 leaking carbs thread...
« Reply #5 on: June 12, 2015, 02:15:23 PM »
I also lapped the fuel bowls when I had leaking carbs recently and fitted new gaskets, cleaned the needle seat and checked everything. I ended up having to set the float heights at 28 mm to stop the leaking.

Z
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Offline OldSwartout

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Re: Another bs350 leaking carbs thread...
« Reply #6 on: June 12, 2015, 08:46:52 PM »
I also lapped the fuel bowls when I had leaking carbs recently and fitted new gaskets, cleaned the needle seat and checked everything. I ended up having to set the float heights at 28 mm to stop the leaking.

Z

That seems to be the answer. I had to lower mine also.  It was fine at the normal setting if it was on the center stand, but would leak when on the sidestand, leaving an embarrassing puddle.

Karl Swartout
Mooresville, IN
BS175 Roadracer. BS200RS, BS175HS
BS350 GTR

Offline slawsonb

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Re: Another bs350 leaking carbs thread...
« Reply #7 on: June 12, 2015, 09:15:52 PM »
Good tip Z and Karl. We should start to rewrite the specs with our "vintage" bikes in consideration. Things tend to change as they wear in and as long as the 28 setting does not adversely affect performance (running too lean/starving,etc.), sounds like the safest bet.
...bert

Offline hardy

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Re: Another bs350 leaking carbs thread...
« Reply #8 on: June 12, 2015, 10:56:40 PM »
I will try to reset to 28mm today and c what happens. I noticed that it doesn't leak of carb is held off the bike and upright...

I have put anew gasket in with no luck. I also have 2.5 needle and seats not 2.0 (what I had in stock at the time) so might help the fuel refill quicker to the lower float height?
« Last Edit: June 13, 2015, 12:49:30 AM by hardy »

Offline hardy

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Re: Another bs350 leaking carbs thread...
« Reply #9 on: June 14, 2015, 07:12:56 AM »
28mm float height solves the issue, but it's not a fix as such...

I fitted the float bowl today without the gasket and then measured the gap with a set of feeler gauges. I found there to be a 0.3mm gap. I'm guessing that the gasket doesn't crush enough at this point causing the leak...

Guess the only real fix is to find a good second hand set? Would anyone have a set they are willing to part with?

Offline BRT-GTR

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Re: Another bs350 leaking carbs thread...
« Reply #10 on: June 14, 2015, 08:30:48 AM »
       I've had similar problem with carb leakage, it seems the base of the carb body also gets distorted so although lapping the fuel bowl helps it does not cure the problem.
 The carb base gaskets are made from quite a hard material and are not able to take up the distortion. Provided the needle valves are shutting off properly, you could try a softer gasket material or just use a petrol proof sealant with the standard gaskets..
 Brian.
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Offline hardy

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Re: Another bs350 leaking carbs thread...
« Reply #11 on: June 14, 2015, 08:42:15 AM »
Both would work I guess.  I was thinking of stripping the carb and setting it up in a mill. Idea here is to try and make the gasket face flat again.

Anyone tried this? I guess it would be pretty tricky to clamp?

Offline ziggy stardust

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Re: Another bs350 leaking carbs thread...
« Reply #12 on: June 14, 2015, 03:07:12 PM »
You can make a good seal with RTV sealant, I tried it and it worked but that was before I set the float level at 28 mm. The petrol then flowed from the over flow but didn't leak from the bowl seal even though it was distorted before I lapped it.

Z
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Offline BRT-GTR

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Re: Another bs350 leaking carbs thread...
« Reply #13 on: June 14, 2015, 04:06:23 PM »
  Does the left hand carb only leak when the bike is on the sidestand as Karl noted above. Although you will have to solve the bowl gasket leakage issue a secondary problem could be that your sidestand has been strained at some time allowing the bike to lean more than it should. This would explain why raising (or lowering ) the float level to 28mm cures the problem. Check the 'U' shaped lugs at the top of the sidestand, they can become bent causing the bike to lean too far. The carbs did not leak out of the overflow tubes when they were new. Try putting a spacer under the stand to see if it stops the leakage.
   Brian.
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I'm so glad I grew up in the 60s & 70s. I did so much stupid stuff and there's no record of it.............Anywhere !!

Offline slawsonb

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Re: Another bs350 leaking carbs thread...
« Reply #14 on: June 15, 2015, 11:20:59 AM »
And if it does stop the leak, carry the spacer in your back pocket. ;D
...bert

Offline moonpup

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Re: Another bs350 leaking carbs thread...
« Reply #15 on: February 01, 2020, 01:00:19 PM »
I thought I'd resurrect this old thread to bring light to another possible issue that may be the cause of some members fuel leak problems....... the brass overflow tube in the float/fuel bowl.

Fuel dripping from the overflow tube is often thought to be the result of leaky float needles. However, just like the petcock tubes that crack and split, the overflow tubes are also prone to do the exact same thing. I recently checked 4 float bowls and 3 of the 4 leaked! Luckily none of mine had cracks, but they leaked at the base where the tube is inserted into the bowl. My fix was to pull the tubes, clean them up and then re-insert them with a little epoxy.
Re-tested and they now show no leaks.  banana

Here's a video that I found on you-tube to help show testing & repair......

« Last Edit: February 01, 2020, 01:11:37 PM by moonpup »
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