Suzuki ATV Forum banner

1 - 20 of 38 Posts

·
Registered
Joined
·
25 Posts
Discussion Starter #1
So my issue lies I believe within the fuel system. I received the 4 wheeler and it wouldn't start and run. After getting it going by adjusting the float and unsticking the valve underneath it ran for a few months strong up until recently when it became harder and harder to start and then would bog when going under throttle until it reached higher rpms where it would clear up.

Eventually it wouldn't start any more but when I cranked and would apply throttle the crank would speed up.

I rebuilt the carb now and it starts but doesnt want to idle when the intake boot from the airbox to carb is on and/or choke being on.

I'm kinda confused at where to go from here. I took apart the fuel pump and it ran with the fuel pump front and rear diaphrams off and the fuel petcock off which makes no sense so I ordered a petcock but could that be the general issue? Any advice is appreciated. I'm a mechanic but not a atv guy.
 

·
Super Moderator
Joined
·
7,695 Posts
The fuel petcock could be the problem. Then fuel petcock has fine screened pick up tubes within the fuel tank to filter out any sediment and other crap before it leaves the tank. It is possible that these pick up tubes are partially clogged up. Though a long shot, it is plausible. The other issue with the fuel petcocks that is common is that the diaphragm within it goes bad and causes all sorts of problems. But this problem is only limited to the vacuum operated style fuel petcocks, (On/Pri/Res). The non vacuum style fuel petcocks (On/Off/Res), don’t have this issue. And seeing your quad is a ‘92, you should have the non vacuum operated style fuel petcock on yours.


Sent from my iPhone using Tapatalk
 

·
Registered
Joined
·
25 Posts
Discussion Starter #3
I dont have a vacuum operated petcock. Mine is on, off, res. The issue seems so odd. I ordered a petcock so I'll see hopefully by this weekend if that fixes it. Otherwise I guess I'll be taking off the carb and fiddling with things.

What is the height of the float supposed to be?

Also are you supposed to adjust it when the carb is upside down or right side up? I've seen both.

I adjusted the idle screw countless times to no avail with any change. I really need to get it to idle a bit before I can really adjust it. Plus I need to fab up a tool to adjust it when it is running since it is impossible to use a standard screwdriver and adjust it. I may make a screw with a finger adjustment on it somehow.

Anything else to look at?
 

·
Super Moderator
Joined
·
7,695 Posts
I don’t know the float specs or the method to adjust it. But I can probably do a bit of digging around and find out. Unless someone else beats me to the punch. As for making a special screwdriver. I believe someone on the Forum has actually tried this already. Believe he said it didn’t work very well. So he gave up and takes the carb off each time to fiddle with it. Maybe you’ll be able to improve upon it. Anyway, I’ll look for the specs and method of adjustment sometime tomorrow and get back to you. Just remind me if I forget.


Sent from my iPhone using Tapatalk
 

·
Super Moderator
Joined
·
7,695 Posts
Nope I didn’t, sorry I forgot. I’ll try and find them later for on tonight.


Sent from my iPhone using Tapatalk
 

·
Registered
Joined
·
7 Posts
I have a 96 that I bought new. Still runs like new but about once every 2 years it begins to idle poorly and I have to remove carb and clean it carefully and thoroughly. After cleaning it runs great.

6 months ago I did this, but this time it did not help so I purchased a carb kit. I dont remember where I bought from but after putting it in it ran good for about 2 months, but then started to backfire. The spark plug was very black so the machine was running very rich.

I opened the carb back up and looked at each piece carefully and found that the main jet needle that came with the kit was not same. I purchased a new jet needle and new needle jet that was a genuine suzuki matching part number and installed them. I put the pilot screw at 2-5/8 out and put it back in.

It ran 98% perfect after this. Was still a little rich (black plug). I moved the ring on the main jet needle to the fourth position from bottom. It now runs so awesome it is super fun to ride.

Sent from my SM-G965U using Tapatalk
 

·
Registered
Joined
·
25 Posts
Discussion Starter #12
Float height is .51" +/-.02". See attached specs. You measure with carb tilted until it just barely sets the needle. If you try to measure completely flat it will push in on the spring on needle and give false reading.
Barely sets the needle? Could you elaborate a bit more? Do you mean from when it barely starts to move up?

Also is it from the bottom of the plastic black floats to the surface for the cover?
 

·
Registered
Joined
·
25 Posts
Discussion Starter #13
What could backfiring out of the intake mean? Itll happen right before it shuts off.

This is all prior to me changing thepetcock. That'll happen most likely tomorrow.
 

·
Registered
Joined
·
25 Posts
Discussion Starter #14
Got the petcock on. Checked the fuel bowl float height and it is under .51" if I'm doing it right. I hold it at 45° and right when it touches the valve I measure. O adjusted the fuel/air scree out to 2 5/8 turns. Now it seems like it's not getting fuel. It will just crank and not come close to starting, however if I remove the fuel line and spray brake clean into it to fill the bowl it starts and idles fine until it runs out of brake clean.

On a side note, what a mess changing a petcock is. I also was lazy and didnt drain the tank completely either.
 

·
Super Moderator
Joined
·
7,695 Posts
Yeah, you need to drain the tank pretty much. I’ve read about someone running their quad till about half a tank or a bit less was left. They then tilted their quad on its’ side to remove the fuel petcock. As for the specs, sorry about that. I had company this evening and I totally forgot. At least woodduder was able to get you those specs.


Sent from my iPhone using Tapatalk
 

·
Registered
Joined
·
7 Posts
Barely sets the needle? Could you elaborate a bit more? Do you mean from when it barely starts to move up?

Also is it from the bottom of the plastic black floats to the surface for the cover?
I meant to say barely seats the needle. Your needle should have a spring in it which you do not want to compress while taking the measurement and you do not want gravity compressing it either. With the carb in your hand, as you rotate (start with float bowl at the "6 o'clock" position and rotate towards the 2 o'clock position) the float will swing until a point where you see the float stop swinging freely. Stop the rotation as soon as notice the float has stopped moving and this is when the needle has seated. This will occur when you have the bowl facing at about "2 o'clock".

Once the needle seats (you will know because the float stops swinging freely), you take the measurement.

You will notice that you can still push on the float and the spring in the needle will compress, but you DO NOT measure with spring compressed. If the carb were sitting so float was straight up, there is a possibility that your measurement would be off due to slight compression of the spring.

Measurement is from carb body to the upper side (upper while the bowl is facing upwards) of the metal plate that the plastic float is molded to.

All this information I am giving is assuming you have the stock Mikuni BST31SS carb on the machine.

Sent from my SM-G965U using Tapatalk
 

·
Registered
Joined
·
7 Posts
Now it seems like it's not getting fuel. It will just crank and not come close to starting, however if I remove the fuel line and spray brake clean into it to fill the bowl it starts and idles fine until it runs out of brake clean.
.
You have blockage in the fuel or air passages of the carb if this is happening. The carb is a very finicky piece of equipment and one little micro spec of trash will prevent air and fuel from flowing properly. Clean it thoroughly but be gentle not to damage any micro passages while doing so.

The needle at 2-5/8 is definitely not your problem.

Sent from my SM-G965U using Tapatalk
 

·
Registered
Joined
·
25 Posts
Discussion Starter #19
I'll have to take it back apart and blow everything out with air and clean it back up with brake clean. Theres no fuel coming from the fuel line to the carb at all when cranking it. I can remove the fuel line and its dry
 

·
Registered
Joined
·
25 Posts
Discussion Starter #20
So I started to take it back apart and decided to just replace the fuel lines and delete the little factory in line filter. I also blew through every existing line that I didnt replace with just my own mouth to free up or see if anything was clogged and found nothing. I found that even when I had the petcock open and just the fuel line running under the tank I was getting no fuel so I messed with the petcock until I was getting drips out of it. Put it all back together and it fires right up and idles fine now.

I'm not sure if there was air trapped in the line or what the issue was but I have it running now.

Now I have to fix how it has low power and hardly wants to rev up to start. Itll almost bog fir a couple seconds prior to revving up
 
1 - 20 of 38 Posts
Top