ATV/bike carburetor questions

[P49Y-CY]

My brother-in-law asked me to take a look at his Honda Recon ATV. I think it’s a 2004 or so. Cranks over but won’t start. I pulled the gas tank and carb and there was a lot of crud in the gas tank. The petcock will probably need to be replaced because the intake tube up inside the tank is pretty much shot, and gas only flows out when the tank is very full. (Also could not get the petcock bolts to loosen it, they just spin.) But, it still won‘t start even when the gas if flowing, so now I am thinking that the carb will have to be rebuilt or replaced.

My main question is, when the petcock is the “On” position, should gas be coming out of the drain from the bottom of the carburetor? (I am thinking no lol) But in other words, since there is no fuel pump, the gas is pouring out from the tank and constantly pressurizing the carburetor, is that right?

Is there anything else I should be looking at as far as this fuel system? I have not checked for spark yet but he seemed to think it was fuel related since he lets it sit a lot.

Thanks for any feedback - this is the first time I've monkeyed around with a carb since I had my 1969 Mopar - over 30 years ago!

 

[Tylerc]

Try running it off of carb spray and see if it fires, should eliminate everything but fuel problems

 

[Morgan]

The carb has an overflow circuit to dump fuel when the bowl overfills. The fuel flows in using gravity and is controlled by the float and float needle.
My first guess is that the float needle is stuck. Sometimes tapping the bowl gently will unstick the float needle, but you’ll need to disassemble the carb to clean and replace parts. Not a tough job.

 

[gimmie11s]

OP.. no fuel should not be flowing out of the carb overflow when the gas is on.

As fuel enters the carb bowl, the floats rise. When they rise high enough, the floats will engage the fuel stop circuit stopping the flow of fuel from entering the carb any longer.

When the engine uses enough fuel (as it is running) to empty the bowl, the floats drop allowing fuel to enter the carb again from the gas tank.

ATV carbs are actually very simple.. ive rebuilt many. Pull it off the quad and take it all apart, clean it all out real good with some wd40 and carb cleaner.

Reassemble once cleaned out and itll probably run fine.

 

[Morgan]

Also, tell your BIL to use ethanol-free fuel exclusively, or the problem will return.

 

[03cobra#694]

The carb has an overflow circuit to dump fuel when the bowl overfills. The fuel flows in using gravity and is controlled by the float and float needle.
My first guess is that the float needle is stuck. Sometimes tapping the bowl gently will unstick the float needle, but you’ll need to disassemble the carb to clean and replace parts. Not a tough job.

OP.. no fuel should not be flowing out of the carb overflow when the gas is on.

As fuel enters the carb bowl, the floats rise. When they rise high enough, the floats will engage the fuel stop circuit stopping the flow of fuel from entering the carb any longer.

When the engine uses enough fuel (as it is running) to empty the bowl, the floats drop allowing fuel to enter the carb again from the gas tank.

ATV carbs are actually very simple.. ive rebuilt many. Pull it off the quad and take it all apart, clean it all out real good with some wd40 and carb cleaner.

Reassemble once cleaned out and itll probably run fine.

These, make sure you pull the jets and clean them too. Should be a small thin one, and one in the center of the bowl/float. Pretty easy, I've done tons of generators, mowers and stuff that the neighbors just turn them off after using them.

 

[DSG2003Mach1]

we had to go through some ATV carbs last summer, we took them apart and cleaned up any gasket surfaces and got the one gallon can of carb cleaner, it has a basket to put your carb parts in/on and let the whole damn thing sit in the can fully submerged for however long it said. As mentioned pull the jets and make sure theyre clear

 

[apex svt]

These, make sure you pull the jets and clean them too. Should be a small thin one, and one in the center of the bowl/float. Pretty easy, I've done tons of generators, mowers and stuff that the neighbors just turn them off after using them.

X2

the low speed jet is tiny and can easily be clogged. I find it best to blow it out with brake clean, or sometimes run a single wire brush “needle” through the jet.
when you get it assembled stand the quad straight up until fuel starts running on the floor. Push it down on all 4 and try to start it. Old Indian trick.

 

[MFE]

Stuck float. Rap on the bowl with a wrench or screwdriver and it'll probably unstick and stop overlowing, but it'll need to be taken apart and cleaned, and possibly have the needle valve and seat replaced. All cheap and easy to do.

 

[nxhappy]

you need new jets, and the carb float is stuck. A new float needle will fix the float. sometimes you can clean the jets with a pc of 16 gauge wire and run it thru the holes

 

[rotor_powerd]

Pull the bowl and clean the float needle and make sure the float can go up and down freely. Spray the jets out with brake clean. There should be a fuel filter in between the tank and the carb, replace it too.

 

[DSG2003Mach1]

There should be a fuel filter in between the tank and the carb, replace it too.

I dont believe there is, thats maybe 2 model years newer than the ones we have but all ours have is a mesh screen where fuel enters the petcock (trx 300)

 

[rotor_powerd]

I dont believe there is, thats maybe 2 model years newer than the ones we have but all ours have is a mesh screen where fuel enters the petcock (trx 300)

Gotcha - I'm not overly familiar with Honda stuff. My old Raptor 660 was the same way, just screens before the petcock but my son's YFZ50 has an inline filter. My Raptor 700 doesn't have one at all, I assume just a screen of sorts on the fuel pump pickup. Interestingly enough, the YFZ50 is what gives me the most trouble - I've had to take the carb off and clean the float needle probably 3 times in the past year. It gets run the most too. My 700 is on E85 and it sits for weeks at a time but I've never had any fuel related trouble with it (knock on wood).

 

[DSG2003Mach1]

Gotcha - I'm not overly familiar with Honda stuff. My old Raptor 660 was the same way, just screens before the petcock but my son's YFZ50 has an inline filter. My Raptor 700 doesn't have one at all, I assume just a screen of sorts on the fuel pump pickup. Interestingly enough, the YFZ50 is what gives me the most trouble - I've had to take the carb off and clean the float needle probably 3 times in the past year. It gets run the most too. My 700 is on E85 and it sits for weeks at a time but I've never had any fuel related trouble with it (knock on wood).

We've always had more trouble with the small engine stuff, I think the carbs are so damned small the tiniest stuff clogs em up where it would pass through the carb of a bigger machine.

 

[P49Y-CY]

speaking of the petcock, is it common for it to be difficult to remove it from the gas tank? on this one i am working on, the bolts seem like they are stripped or something. they just keep on turning, but are hard to turn and do seem like they are getting at least some bite. i tried to pry up on the petcock a little while turning the bolts, but no luck. from what i can tell there are brass inserts in the plastic tank that they thread into. so maybe my next step is to cut the heads off.

i can tell that the screen portion of the petcock inside the tank is shot so i'm definitely going to need to replace it. some of the plastic screen pieces even came out when i first emptied the tank. but for whatever reason i can't remove the damn thing

thanks to everyone for all the good advice so far :cheers:

 

[08mojo]

Hopefully those brass inserts are not spinning with the bolts...