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#38226 - 04/30/08 2:31 am AMAL Carb Floods  
Joined: Feb 2007
Posts: 2,200
Semper Gumby Offline
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Semper Gumby  Offline
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Posts: 2,200
Atlanta, GA USA
This is a mystery I cannot figure out. I put two BRAND NEW AMAL 30mm carbs on the 1969 Firebird. The RH works fine but the left starts flooding after I shut down. Furthermore, if I start up again the engine bogs down (runs on one cylinder) on the initial roll on of the throttle until I get it 1/4 open then works fine. Idles fine - just that intial bog and the LH carb flooding after shut down. Fuel comes up the needle jet and out the front of the carb (center air hole that leads to the needle jet.

I have tried:

- Different float bowl.
- Different viton float needle.
- Different nylon float needle.
- Different needle jet holder and needle jet.
- Different floats.
- I have pulled the float bowl off the carb and hooked it up to the fueltank with a needle and float in and turned on the fuel. It shuts off at the right place. No amount of tapping will get it to overflow.
- I have tried different float gaskets.
- I have made sure there is no plastic flashing interfering with the movement of the float.

I am about to sacrifice a live chicken as I cannot believe I can't get this simple carb to work properly.

WTF over.


Gaggle of BSAs
a Honda
an old BMW
and a Montesa
Parking lot Elf in training
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#38227 - 04/30/08 1:34 pm Re: AMAL Carb Floods  
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Gunk Offline
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43.34 (4320') | -79.81 (-794...
When does it stop overflowing SG?


"he who laughs fast, laughs first"~Gunk
#38228 - 04/30/08 3:20 pm Re: AMAL Carb Floods  
Joined: Jul 2001
Posts: 12,081
Lannis Online content
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Lannis  Online Content

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Central Virginia
I've had this exact same frustrating thing happen to me, more than once.

Each time, it was solved by judicious handwork of the float gasket where it was invisibly interfering with the movement of the float, usually right around the pivot point. I've had to trim gaskets WAY back before they would work right.

Once sorted, I haven't had to fool with them again. Hope it's something simple like this.

Lannis


OK, I admit it, I'm addicted to brake fluid.

But I can stop any time I want.
#38229 - 04/30/08 3:50 pm Re: AMAL Carb Floods  
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Gunk Offline
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43.34 (4320') | -79.81 (-794...
That's so true Lannis.
I usually leave the bowl screws a little slack and then gently coax the gasket back as far as I can. Mind you the difference is barely perceptible, but it always seems to work.


"he who laughs fast, laughs first"~Gunk
#38230 - 04/30/08 6:20 pm Re: AMAL Carb Floods  
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Semper Gumby Offline
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Semper Gumby  Offline
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Atlanta, GA USA
Lannis...Thank you!

I will try it this afternoon!

Perhaps I can save the postage of returning the carb for another one.

Gunk - It stops overflowing when I turn off the fuel petcocks!!!!

Where is my razorblade - you may have just saved a chicken's life. wink


Gaggle of BSAs
a Honda
an old BMW
and a Montesa
Parking lot Elf in training
#38231 - 04/30/08 7:41 pm Re: AMAL Carb Floods  
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Semper Gumby Offline
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Semper Gumby  Offline
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Atlanta, GA USA
Alas Lannis noJoy.

I trimmed all but 1/16" of the gasket over the pivot pin and then went all the way around to the other pivot pin. (Air filter side of carb gasket) So I left a little gasket material over the end of the end of the pivot pin.

I did not trim the long way around towards the cylinder side of the carb.

Heat is a seems to be a factor. I shut down the bike it floods and before that it starts to run badly off the start. Could the plastic of float be expanding (Due to heat) into float bowl metal around the pin?


Gaggle of BSAs
a Honda
an old BMW
and a Montesa
Parking lot Elf in training
#38232 - 04/30/08 8:31 pm Re: AMAL Carb Floods  
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Gunk Offline
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43.34 (4320') | -79.81 (-794...
Very Bizarre.
Sorry SG, I misspoke.
Does the carb overflow when you first open the petcocks with a cold engine?


"he who laughs fast, laughs first"~Gunk
#38233 - 04/30/08 8:47 pm Re: AMAL Carb Floods  
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Randy in Seattle Offline
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Seattle, WA
Hmm, the float and needle work fine off the carb body but not when installed, right? So what is different about it being installed one may ask. You already tried the gasket. Does it have a float tickler that might keep it open? I sort of doubt the heat thing but you could estimate the looseness of the pin to float while you have it apart and open it up slightly with a number drill if that is a worry.

As far as start up goes I would guess that the offending cylinder has been flooded with gasoline and needs to clear out before it fires. Bad news for rings bty. Same for cranky running as excess gas is probably being sucked in and causing rich mixture due to float needle leakage.

So, what changes when the float and bowl is installed? Sounds like something is preventing the float from, er, floating. Or the float level has not been set correctly. When setting float level are you sure the float hinge pin is held in place as it would be when installed to the carb body? Hmm.

Randy


Randy
1972 750 Commando
1979 T140
1982 Sportster Ironhead
#38234 - 04/30/08 8:50 pm Re: AMAL Carb Floods  
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Randy in Seattle Offline
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Just thought of something to try. Try setting the float level intentionally a little low and see if the problem disappears. Hopefully that will give you some clues to the problem.


Randy
1972 750 Commando
1979 T140
1982 Sportster Ironhead
#38235 - 04/30/08 10:01 pm Re: AMAL Carb Floods  
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Semper Gumby Offline
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Semper Gumby  Offline
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Atlanta, GA USA
Hi Gunk,

When I first put the Float bowl back on I have moments of joy as after the petcocks are open it does not flood. But after start at first it runs fine then it starts to bog down on startup from stop signs/traffic lights. After shutdown it immeadiatly floods. Fuel comes out the air holes in the front bottom lip of the carb where the filter screws on and if I pick up the slide with the throttle I can see fuel pushing up through the needle jet.

Hi Randy,

At one point I tried four (4) gaskets, one on top of each other in an attempt to lower the fuel level to something reasonable and usable.
Alas it did not work.

The chicken is safe. The gentilman who sold me the carb has very kindly allowing me to send it back to him for an exchange.

I am still mystified.


Gaggle of BSAs
a Honda
an old BMW
and a Montesa
Parking lot Elf in training
#38236 - 05/01/08 11:37 am Re: AMAL Carb Floods  
Joined: Aug 2001
Posts: 155
Myles Raymond Offline
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Posts: 155
Glasgow, Scotland
Hi,

I found on one of the repro Monoblocs that the threaded part of the petrol pipe union that goes inside the float bowl actually obstructed the float if the union was tightened as far it could go.

I tried backing it off a few degrees and that was all it took to let the float move freely and work.

Comparing it with an original AMAL item I could see that the union it had been machined slightly longer than the original. Rather than leave it loose I put a fibre washer under it where the hex bolt part mates up to the outside of the float bowl. That worked fine.

Anyway, I only found out by taking the float cover off, using my finger to push the float bowl up then turning on the petrol - and out it pi**ed.

Although the float moves in an arc of about 1/4" only the last few microns of that actually seat the float needle. So the message is, don't check that the float moves - check that is seats the needle.

Here endeth the lesson.

Myles


Myles Raymond, Glasgow, Scotland.

1932 BSA L32, 1934 BSA R34, 1955 BSA A7ss, 1961 BSA Gold Star, 1954 BSA Daytona twin, 1959 NSU Quickly, 1975 Morini 3 1/2 Sport.

"A tidy workshop is a workshop where no work is ever done" - my Dad.
#38237 - 05/05/08 11:16 pm Re: AMAL Carb Floods  
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Semper Gumby Offline
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Semper Gumby  Offline
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Atlanta, GA USA
Well I tried it but no joy then there other carb started puking gas. That one was easy - the float had sunk. Brand new float full of gas.

AMAL has a quality control problem?

No matter - I return the carb tomorrow.

Thank you all for all the help.


Gaggle of BSAs
a Honda
an old BMW
and a Montesa
Parking lot Elf in training
#38238 - 05/06/08 4:29 pm Re: AMAL Carb Floods  
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Randy in Seattle Offline
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Seattle, WA
Just as an FYI, here is an interesting web site to bookmark. It was provided by another forum member and deals with tuning concentrics. Good info.

http://www.jba.bc.ca/Bushmans%20Carb%20Tuning.html


Randy
1972 750 Commando
1979 T140
1982 Sportster Ironhead
#38240 - 05/19/08 1:20 am Re: AMAL Carb Floods  
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Semper Gumby Offline
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Semper Gumby  Offline
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Atlanta, GA USA
Got new carb installed but am still waiting for Tri-Spark Ignition to arrive. When that is in I will run it again. Seems a waste of time till the ignition is up to snuff...

Thanks to Frank Deihl for taking back the voodoo carb.


Gaggle of BSAs
a Honda
an old BMW
and a Montesa
Parking lot Elf in training
#38241 - 05/19/08 3:05 am Re: AMAL Carb Floods  
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Rick Willmore Offline
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I'd off the chicken now anyway! In Franks honour.

Rick


'71 BSA Firebird/Lightning
'03 BMW R1150R Rockster
'76 Montesa 348 'Malcolm Rathmell' Cota
#38242 - 05/28/08 1:46 pm Re: AMAL Carb Floods  
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Semper Gumby Offline
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Semper Gumby  Offline
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Atlanta, GA USA
There is Joy in Atlanta.

Tri-Spark ignition is in and set. The new LH carb is in and the idle set and ...

...IT RUNS (whoohoo).

Both plugs(N3c) previously sooty are coming out tan now. The new carb doesn't flood!! (The chicken is safe)

For the first time in 6 months it looks like I can actually go out and ride!! I'm going to put in some new plugs and do a plug chop to see if I've got the needles and the main jets set right but I suspect they are just fine. beerchug

The only snafu I had in the whole set up was when I forgot that the BSA A65 timing runs counter clockwise. The instructions didn't say and I chose the default CW point for the static timing set up. This caused about 30 seconds of panic followed by about ten minutes of trouble shooting before I figured out what was going on. As advertised the idle is smooth and there is no detonation "plinking".

One other thing I have found is that the full advance timing mark on the Lucas rotor has nothing to do with the full advance point that appears when I use the timing plunger in the front of the case. I had to make my own mark on the rotor! Has anybody else run into this? Perhaps I've got a rotor from a different make machine from the PO?

Thanks to TriSpark for making a simple set up with no remote box. It's waisted spark with two six volt coils in series but it works great.

One more dumb question: Both 6 volt coils I got from my supplyer were dented. I checked the resistance between the two terminals and came up with the same number - 1.8 ohms. So I installed them and they work. Is this temporary? Should I yank 'em and send them back? Or just live with the dents and be happy?


Gaggle of BSAs
a Honda
an old BMW
and a Montesa
Parking lot Elf in training
#38243 - 05/29/08 7:21 pm Re: AMAL Carb Floods  
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kelvin Offline
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Wollaston Northants
THe reason the timing with the insert is different to the marks on the rotor is different is because the insert in the crank holds the engine btdc. The marks on the alternator are to be used and alighned using a strobe at 5000 RPM
Kelvin UK

#38244 - 05/30/08 1:22 pm Re: AMAL Carb Floods  
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Semper Gumby Offline
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Semper Gumby  Offline
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Atlanta, GA USA
Ah ha! So here is the rub - I thought they were supposed to agree - That they were both supposed to be the full advance postion. If I had to guess which one was most accurate at 34 degrees Before Top Dead Center I would guess it would be the timing insert on the crank itself. The rotor could have come off of any number of machines...right?

This is confirmed by what I went through while setting up the Tri-Spark ignition. When I first set it up I aligned the timing pin (in the forward hole) with the line on the rotor (with strobe) and the bike plinked under load above 4000 rpms (too advanced). Since this is not supposed to happen I went back put in the timing plunger inserted in the crank and punched my own mark under the pin pointing to the Lucas rotor. When I set the full advance timing to my point, suddenly the bike works like a charm with no plinking. I don't have a degree wheel but my guess is the Lucas rotor line corresponds with about 40 degrees BTDC. I don't think that is where I should set the advance just based on how the bike performs.

Are you saying different Kelvin?


Gaggle of BSAs
a Honda
an old BMW
and a Montesa
Parking lot Elf in training
#38245 - 05/30/08 2:03 pm Re: AMAL Carb Floods  
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kelvin Offline
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Wollaston Northants
I set my timing using the insert and the paint dot. As the bike starts easy and runs well I did not see any reason for any more messing about.
The pinking I get is if I am in a high gear pulling hard. I think with the unleaded 95 octaine petrol the old timing settings are redundent and you just have to do the best you can. The saying is if its not broke don't fix it.
Kelvin UK.

#38246 - 05/30/08 5:32 pm Re: AMAL Carb Floods  
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Semper Gumby Offline
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Ah ha! Sounds like what I am doing. Case closed.

TTFN,


Gaggle of BSAs
a Honda
an old BMW
and a Montesa
Parking lot Elf in training
#38247 - 05/31/08 1:34 am Re: AMAL Carb Floods  
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BSA_WM20 Online content
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BSA_WM20  Online Content
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Sydney Australia
It is worthwhile to find TDC very accurately then stamp a refference mark on your rotor with a center punch or fine chisel.
Having done this you can use that mark to verify the timing mark on your rotor.


Bike Beesa
Trevor
#38248 - 05/31/08 3:12 am Re: AMAL Carb Floods  
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Smurdley Offline
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I found this out also when I just installed a Pazon ignition. The plug in the front of the case holds the crank at full advance position (34 deg btdc - A65). Open up the drive side cover and you should see the needle pointing at the timing line on the rotor.

Mine didn't line up with the original marks on the rotor - it lined up with some home-made marking that I enhanced. But, the more work I do on the bike, the more I learn!


OVBSAOC #4062
1968 BSA A65L Lightning
2005 Triumph Bonneville
#38249 - 05/31/08 4:59 pm Re: AMAL Carb Floods  
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Semper Gumby Offline
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Semper Gumby  Offline
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Atlanta, GA USA
Yesh. Always learning but forgettting how to spell.


Gaggle of BSAs
a Honda
an old BMW
and a Montesa
Parking lot Elf in training

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