Few problems after reassembling...

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Few problems after reassembling...

Postby Yuza » Sun Jan 14, 2018 7:40 pm

Hello all, I am putting together my SR42 after having stripped it off for some restoration and mods
Yesterday I fired it up and it seemed to run ok, but it stopped after 1 minute and didn't fire up again.
I noticed right carb was leaking from the seal so I didn't insist
Today I removed the right float chamber to check seals (carbs were cleaned with ultrasonic machine and had new seals, float needles etc, all from ebay so not oem) and it was ok, so I fitted it back and tighten a bit the screws and fired it up again.
Again it seemed ok but it stopped after 1 minute or so.
I was checking for leakages when I noticed fuel was leaking from the airbox hose. A lot of fuel...
I thought it could be coming from carbs directly for some reason, but from reading here I understand it should be the float needle not closing properly so fuel goes into engine, up to the head and to the airbox through the engine breathing hose, correct?
Will remove carbs again and recheck everything, but is this linked with engine stopping after a while? Does it get too rich or what?
I also noticed I have a hole in the bottom of the airbox, just above header, so I need a new one....
I was so excited when it fired up yesterday, seems there is still a long way to go...[WEARY FACE]
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Re: Few problems after reassembling...

Postby O.R. » Sun Jan 14, 2018 8:15 pm

Float needles are the problem. Did you replace the float needles only or float needles with the copper holder?
And did you set float with the Wettest or the >umperfect< method as described in the workshop manual?
The carb rebuild kits don't include the O-ring for the (grey) slide housing. So that could also be another point of investigation.

When fuel also flowed into your engine, then do an oil chance for sure. Fuel evaporates quickly and may damage your oil seals!
Air box replacement is a tough fight. Just some epoxy maybe...or an air filter upgrade :roll:
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Re: Few problems after reassembling...

Postby Yuza » Sun Jan 14, 2018 9:11 pm

I bought a carb service kit on ebay and brought it to my mechanic, I am not sure what was inside...he did the job, I just trusted his (big, tbh) experience
What is the Wettest method?
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Re: Few problems after reassembling...

Postby Yuza » Sun Jan 14, 2018 9:18 pm

https://rover.ebay.com/rover/0/0/0?mpre ... 1183172369

Same as this one, so needle and copper seat plus o-rings
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Re: Few problems after reassembling...

Postby O.R. » Mon Jan 15, 2018 4:56 pm

So your set contains 4 kind of O-rings. One for idle mixture screw, one for the copper seat for the float needle, one for float body and....I guess one for the slide housing :tup:
So all O-rings are included and float needles are fine. Looks good at first sight.

I've (re)built a lot of carbs, and experienced some problems with the O-ring for the seat for the float needle.
After some time, they sometimes do not seal anymore. So a quality issue. You can check this by trying to move/ rotate the seat very carefully.
Do NOT force. When the seat is loose, you've got a problem.

I use the rebuild kits for the float needle and float bowl gasket only. I immidiatelly replace O-rings for thicker O-rings made of Viton.

WetTest is a method for checking the REAL fuel level. Hereby making use of the physical law of communicating vessels.
Adjusting the floats as decribed in the workspace manual is a first step. But checking the fuel level is the only way you can be sure.
Hereby using transparant fuel hoses. Fuel level must be on the edge of float bowl and carb body. See pix @ The Dutch BIG forum
Besides, I use a handpump that acts like a fuel pump, so there is actual fuel pressure on the needle valves. So another "check" :angel:

Since you have fuel in your air box, the needle valves didn't cut off the fuel supply.....
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Re: Few problems after reassembling...

Postby Yuza » Mon Jan 15, 2018 6:01 pm

Thanks, very helpful.
Maybe stupid question: is the fuel in the airbox surely coming from engine’s breather or is there a chance it comes back from carbs through rubber manifolds?
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Re: Few problems after reassembling...

Postby O.R. » Mon Jan 15, 2018 6:20 pm

Engine breather comes from the valve cover and should only breah minor oil damp.

The carb breather is the upper hose between the diaphragm covers and should only breath fuel damp.
It compensated pressure in the float bowls due to the fuel flow.
Fuel will FIRST flow out of your emusion tubes and/or air jets.

The only wat fuel enters the carbs, is via the central T-piece between te carb bodies. In the carb bodies, the float needles should cut off the fuel flow when a certain fuel level is reached. In this case, I think one or two float needles didn't do their job.
You can also test this with your carbs mounted (like a WetTest).
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Re: Few problems after reassembling...

Postby Mr.Z » Wed Jan 17, 2018 10:22 pm

If your carbs leaked fuel in to the cylinder do check your oil level and smell, fuel could be leaking past your piston in to the engine..
SR43 float chambers have a over flow, they fit on the SR41 an 42 carbs
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Re: Few problems after reassembling...

Postby Yuza » Sat Jan 20, 2018 5:30 pm

Done few more tests today, with fuel off it runs fine, with fuel on or res it dies because of overflow, and starts again only with fuel off, full throttle and it smokes a lot.
There is also a difference in the idle speed if on side stand or kept vertical (it revs up), but I guess this is normal with twin carb
Next step is to remove carbs and have a visual check of float needles but I am wondering if the low price kit I have bought on ebay is maybe low quality also...
Original parts from Suzuki are damn expensive, maybe buying from Hessler would be better?
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Re: Few problems after reassembling...

Postby BigBob » Sat Jan 20, 2018 10:26 pm

I think Stefan gets his carb parts from Suzuki .....
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