Carb Overflowing

[patta]

Hi,
Debz was riding her 640 adventure, excelerating away from roundabout and bike went 'bang' and lost all power. It would appear that the bang was excess fuel in the exhaust. Bike turning over ok but fuel coming from carb bowl overflow. I've had carb out and cleaned it, float, etc seems to be ok. Put it all back together and no different, still won't start, petrol still coming out of overflow. Has anyone else ever experienced this? And does anyone know of a quick way to get the carb out?

Thanks

Iain

[Island Hopper]

Sounds like your float needle or needle seat may have given up the ghost. I had it happen on my 03 Adventure, one minute the bike was running fine and the next it was crapping out and leaking fuel. I replaced the needle/seat + the float and after a little tinkering to adjust the new floats height the bike ran the best ever. I couldn't see anything wrong with the old float but I replaced it anyway just to play it safe. My method to take out the carb isn't quick but it works for me and that is to dissassemble the carb in place starting from the diaphram/ slide, vents,hoses and then cable connections and then rotate the carb {after loosening the clamps} and remove the float bowl + float cage and maybe the idle adjuster, after all this the carb is small enough to roll up through the gap in the frame rails.

[skip]

Hi
The Mikuni carb fitted to the 640 KTM Adventura is the same as on the 97-2005 Suzuki DR650se this make for cheaper carb parts. Hope this helps Skip

[patta]

Originally Posted by Island Hopper

Sounds like your float needle or needle seat may have given up the ghost. .

Hi
Have ordered the parts that you suggested.
I’ll fit them on Saturday and see if they do the trick.
I would like to try and get the float setting right first time,
what setting did you use?

thanks for your help

Iain

[Island Hopper]

I believe my float setting is somewhere around 14 or 15 mm but can't say for sure because I had the carb apart several times to adjust the fuel level lower before I was satisfied and did not note the final measurement. Once things were setup my fuel economy improved {20-23 KM/PL} and the engine runs hitch free on a rough terrain test. One other carb related problem I experienced while we're on the subject was the vacuum hose from the fuel pump deteriorated on the end where it bends to attach to the intake manifold spigot, this allowed air to leak in causing the bike to run lean {opposite of your problem} but it happened around the same time as my needle/seat failure so it's worth checking while the carbs out and you have room to look at things. Hope you get it sorted out, good luck................David.......

[Bill Shockley]

Patta,
Be a believer, the carb will come straight up between the frame rails. Remove the front faring and gastank and seat. Loosen clamp at rubber inlet manifold, carb to engine, front of carb. Unhook fuel line to carb before starting.


Remove hose on top of diaphragm cover if there is one. Remove clamps, rear of carb, connection to airbox on the rubber connector.
Pull airbox rubber off back of carb and from airbox and push it downward while lifting the carb up so they pass each other. It is a messy, nasty job and a tight fit. Use finesse. Be gentle. Turn rear up, pull up. You will get it.
It will come up and out with all cables and tubes attached. Be gentle on all wiring so you do not hook it. when carb is out put a rag over the hole in the frame and you can work there. Be careful not to loose parts. If bowel screws are tight put a locking pliers on screws to turn. there is a gas drain if you want to use it.
This is how I set the float height.
With bowl off attach a piece of gas line. Blow on gasline with carb upright raise the float. Note where air stops going in. This is the actual height. set it level for the float arms a indicated in manual.
On my 640 Adventure the rubber needle failed at 11K miles, 17K KM. It has to be replaced with every 16K KM service so just do it and carry a spare. Everything else should be good but check the diaphragm. It is possible a piece of shit is stuck at the needle so disassemble the float and look-clean. Do not loose parts. Put together opposite of removal. Clamps on connector to airbox are hard to start. Get a and an attractive assistant. Have fun.
Good luck,

Bill in Tomahawk, WI

[Island Hopper]

Never tried to hard to take the carb out in one piece, I just figured I was going to take it apart anyways to clean it so why not reduce its size while on the bike. For float height tuning I leave the carb in place and pop the float cage out to do small adjustments {.5mm at a time} reassemble and testrun. It would be nice to get it right first try but it didn't work for me. My initial setting with the carb completely out was to set the floats parallel to the carb body which was too rich and hence the further adjustment. Bills method of blowing air through the needle/ seat sounds a little more precise than just eyeballing it and may be the choice method to get it right on the first try. .......good luck..........David.

[Bill Shockley]

Trust, the carb will come out in one piece. I didn't believe it at first but it does. Also you can unbolt the subframe and pivot it back but you need to grease it and hit both tabs with a hammer to make it go back together. This sounds worse than it really is. You also haveto loosen the exhaust where ot attaches to the subrame. Another way to set the float is to tilt the carb at a 45 degree angle. If you go over to Adventure rider there are plenty of experts.
Bill.

[patta]

Well did not get float right first, second or third time!

In fact not got it right yet, fuel still coming out of the overflow,
I need more hours in the day or need to spend less time at work.

While I had the carb out the first time I replaced the cross head screws with allen head screws now I can take the carb bowl, float and needle valve out of the carb without the need to remove the carb.


Bills method of blowing air through the needle/ seat works a treat with carb in place and should save me loads of time.


need to get it sorted out soon or Debz is going to get to put even more miles on my 640

[Island Hopper]

Patta, did you have a good look at your float to make sure it still sealed? Once in a while a float will develop a leak and partially fill up with fuel and will not have enough lift to activate the float needle properly in its seat. I check this by setting the float in the floatbowl or shallow tray of fluid and marking the waterline on the side of the float and let it sit a while. Check it again after 20 minutes and see if it's still floating at the same level ,then hold it submerged for a bit and see if it bobs back to the level. You can do a running check on your fuel level by hooking a clear hose to the float bowl overflow drain and bend it up beside the carb, with the engine running crack the bowl drain screw a little and observe the fuel level in the tube. If it climbs and holds steady just below the bowl gasket line {1 or 2 mm} the fuel level is OK if it climbs above that the level is to high. I did this when I was troubleshooting my carb and found when observing fuel level, it would hold at the right level for a little bit and then climb up and the engine would sputter and die. Because my level held for a while and then climbed I suspected the float was sinking but as in my earlier post it checked ok and ended up being the needle/seat causing the problem. One other thing to check is run a gravity feed fuel line and bypass the fuel pump to see if you still have the overflow problem, I haven't heard of a diaphram pump going into hyper mode, it's usually the opposite. I set up an I.V. type remote tank for running the bike in stripped down mode while I was tinkering on things. Hope you get it sorted out, good luck........David...

[Bill Shockley]

Patta,
With the carb in place you can hook up the gasline from the tank and check for sealing at the rubber tipped float needle with the bowl off.
Have you replaced it??
They are only good for 15-20KM. The vibration in the engine wrecks them in my opinion.
Well anyway make sure you have a good seal.
Be careful of FIRE<FIRE<FIRE if you are in the gas.
Bill.

[Stealth]

This happened overnight to my 06 Adventure, even with fuel tap off. Probably just some crap in the tank caused a stuck float, but all was ok after a short ride.

Update: Seems surreal, but there is some fuel coming from the carb overflow hose, but the screw seems tight???

[patta]

Hi Stealth
[Update: Seems surreal, but there is some fuel coming from the carb overflow hose, but the screw seems tight???[/quote]

I think the fuel you are seeing will be coming out of the bowl overflow which shares the same drain pipe as the bowl drain screw

By the way still not got the thing to work yet

Iain

[Stealth]

Thanks Patta, I had a sneaking suspicion that might be the case, but the parts list doesn't show it at well.

But this gets worse...now it couldn't get enough fuel and was dying every km or two. A forty minute ride took me two and a half hours! Its back with the dealer.... Good job I didn't go with the 100km dirt road loop I contemplated at first.

Gee I'm missing it already!

[patta]

Originally Posted by Stealth

...now it couldn't get enough fuel and was dying every km or two. A forty minute ride took me two and a half hours! Its back with the dealer....

Hi Ian
please let me know what the dealer has to say.

And which Pirth do you come from? (up north or down south)

cheers
Iain (spelt the proper way)