VK540 shutting off....help!!!

L

LQuig

New member
Joined
Jan 22, 2015
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7
Location
Newfoundland Canada
Hi folks,

I am new to this forum thingy - hope someone out there can help me. I am having a problem with my '08 VK540 that has me stymied. The problem started the year-before-last (the sled never left my trailer last year). In late winter of 2013 after a long run in the hills, the engine started shutting off and wouldn't keep running without choke. I put the sled away and forgot about it. Took it off the trailer the other day and started it up and it's doing the same thing.

After I greased up the suspension and checked the plugs, oil and stuff, I took off the drive belt, squirted some gas in the carb and it started right up - yesss!! It runs about a minute and shuts off! I thought - plugged filter, gas line or crapped out fuel pump. Disassembled the pump - all ok. Took the fuel line off the fuel pump and routed it to a fuel tank above the engine (also plugged the vacuum line from the engine to the pump so it wouldn't spray gas all over the place). Put clean gas in the elevated tank - started it up and it does the same thing - runs about a minute or less, then shuts off. The only way to keep it running is to choke it. It'll run all day with the choke on it.

So now I think - sticking float or needle valve at the fuel inlet to the carb. Paid $50 for a new needle and seat - same thing! Will not keep running without choke. If I let it shut off without choking it, it WILL NOT start without choke - remove the choke, it runs about a minute and shuts off.

Took the carb off AGAIN - checked the float height - OK; float is working good - not getting stuck that I can see; sprayed it all through with carb cleaner - it's squeaky clean inside!

What am I missing???
 
take the carb off and make sure all the jets and passages are clean 1st. then replace the fuel filter as it might be partly plugged.

if above does not work,


time to check for vaccum leaks with a can of brake cleaner or quick start. could be the carb boot or crank seals. with it running spray both down with brake cleaner. if it picks up rpm, that is the problem.
 
Pull all the jets out of the carb body to clean. Needing choke to idle is classic of a plugged pilot jet. The orifice is small and hard to clean well, worth it if in doubt to just buy a couple new ones, they're only a few bux.
 
I've checked the jets in the carb and they are clean - can see light through them no prob. Which one is the pilot jet? I see what I'm assuming is the main jet - in the tube that sticks right up into the venture. There is a needle screw on the top of the carb with a spring on it - I assume that's the idle adjust??? And then there are two other tiny brass orifices - one in a tube cast into the carb body down in the bowl that feeds a passage up toward the top of the carb and another in the bottom of the air inlet opening of the carburetor bottom. Any idea what each of these are for?
 
sounds alot like the pilots.They are in the tube in front of the main jets.If they are plugged,you will not have the motor running very long when started up.They are long looking with a taper to the bottom end,easier to get plugged up then mains.And also check the 3 little umbrella type screens.Where the needle valve drops into,that piece can be removed by first removing tiny Philips screw next to them(which hold it down).Pull this out and underside has the umbrella type screen.Clean them good also.
 
Ok so I blew out the carb AGAIN - took out the jets - Main in the bottom of the float bowl, the pilot jet also located in the float bowl in the tube just in front of the Main jet just like you said. Also took out the needle valve located on top of the carb pointing straight down (with a spring around it) right next to the rubber boot attaching the carb to the Y- adapter bolted to the engine cylinders. Blew everything out and poked dentist picks into the orifices - all clean! I also took off the boot where the carb mounts to the engine and inspected it carefully - slight hairline cracks but nothing through the boot at all. I removed the Y-adapter and discovered the bolts holding it onto the engine cylinders were not much more than finger tight! Replaced the Y-adapter and added some general purpose grease to the gasket between the Y and the cylinders and tightened it up firm.

Reinstalled the carb and ran it - seemed pretty good at idle. Just for kicks, I sprayed Quick Start on the rubber boot and the crank seals - NO change in engine RMP. The idle RPM seemed a bit high so I adjusted it down a bit using the plastic knob near the throttle cable connection to the carb.

The engine now continues to run without needing to be choked - making progress! The only thing now is when I open the throttle quickly, it sometimes does not want to go - just baffs out (makes a loud Braaaaa..... sound but does not stall) and the sled will not move. Again, when I pull the choke, the sled will accelerate and if I open the throttle slowly, it will accelerate - only if I "floor it" quickly, the sled won't move. So I adjusted the needle valve on top of the carb (initial setting was 1 1/4 turn out from seat. Backed it out in small increments and it improved the performance slightly.

Not sure if I'm heading in the right direction, though. Any thoughts? Should I continue to adjust the needle valve or is there something else I should be looking for/at?

I tried to attach a pic of my carb (sorry, it's rotated 90 degrees...my bad!) just for your info.

Any help will be greatly appreciated.

Leo
 

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this may sound off the wall. but had a polaris 44o that did the same..give it gas and it would bog out and wouldnt move. thought it was the carbs. cleaned them and it ran better but the sled wouldnt move.. like the motor had no power. seemed that the bushings in the primary clutch were bad. so had the clutch rebuilt. back on the trails i went. just a thought.
 
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