Suzuki Quadrunner 250 — Wild series of fuel problems

[Jd101506]

Hi all! 
 

So I’ve got a early model (86? Maybe?) (slide carb)Suzuki Quadrunner I’m working on. I’ve having a series of really wild fuel problems and I’m hoping someone could point me in the right direction. 
 

So when I first got it the fuel pump and carb were both toast. Rusted, awful, unrebuildable messes. So I bought a pair of cheap Chinese ones of eBay and worked on the rest of it. 
 

Carb arrives first. I install it, hook a battery up, mainline some fuel into the carb and it runs. Sounds great actually. Ok, cool, runs good, I’m fine. Wait a few days and the fuel pump shows up. Install and the quad runs like absolute dog crap. It would hesitate, stumble, stall, the works. It does sit and idle and start up quickly though. So I assume it’s the fuel pump, so I end up saying screw it and I buy an OEM one. 85$. Meantime I can still get it to run well with drip feeding it fuel. 
 

New pump comes in and installed. Same thing. It stumbles, acts like it’s dying, may stall, etc. This new pump is an OEM Suzuki so my assumption is it’s fine? 
 

I ended up swapping the carb wondering if the float or something is actually my problem. This is a different carb, a WELL REVIEWED Kipa carb from Amazon. I install that and I have a whole different set of problems… this carb will run at mid to high RPM, idle adjustment screw be damned. All the way in or all the way out it runs at the same RPM. I ended up taking the main slide and needle out and I swapped it for a different one and the RPM dropped. Not a lot but a little. So I try and drop the carb needle as low as I can and it’s still funky. Something isn’t right. 
 

So after swapping that carb again I end up rebuilding the Mikuni carb from my Suzuki lt300, and swap the jets over from the Quadrunner rebuild kit I had ordered. Put that carb in and it does the same stupid high idle. I take the choke cable off the bike entirely and it makes no difference and the throttle cable has plenty of slack. As I’m standing there staring at it, it just suddenly drops the idle and sits there idling pretty happy… so I climb on, and it has the same annoying jerky, slow throttle response that the first eBay carb had. 
 

So to recap:

1x Kipa fuel pump kept pushing way too much fuel in. 
1x OEM Suzuki fuel pump made the carb from eBay smoke like crazy and idle adjustment did absolutely nothing. I could go a full 2 turns from the stock setting of 1-3/4 turns out in either direction and get the same awful running 

 

1x ebay carb worked well on a mainline of fuel right to the carb gravity fed. But runs like dogshit around the yard. Jerky and low idle and smoking on both the Kipa carbs and the OEM carb. 
1x Kipa carb runs at super high RPM and won’t settle down no matter what I do with the cables or anything else. 
1x rebuilt mikuni did the same as the Kipa but then randomly dropped rpm to idle and then started running like the ebay carb. 
 

So I’m appealing to the brains here. I find it hard to believe I’ve tried this many carbs and such and I haven’t found a working solution. As an aside, I’ve swapped the plug, done an oil change, and done a general inspection. Compression test I haven’t done, and I haven’t adjusted the valves but it starts easily. And runs easily mainlining fuel.

 

Sitting in the garage it sounds fine. I’m attaching a video of it running with the eBay carb and the OEM fuel pump. It’s just really weird. It feels like I’m flooding it because when it’s idling I can smell it and there is a little smoke from the tailpipe.
 

Ill add more video tomorrow of it running like crap around the yard.  

[Mech]

Carry on in the old thread so it's easy to check what's what and all the history.. My memory's not so good.

[Gwbarm]

I havent had good luck with Kippa carbs, they run , but not right, and cant adjust it out.

[Curtis Underwood]

To start with on the fuel pump, it should have three hose connections. One is the out to carburetor, one is from fuel tank, and one is a vacuum from the crankcase. The pump has diaphragm that the vacuum from the crank case pulls back and forth to pump the fuel if these lines are not on the correct places, it will not pump correctly but can give some fuel depending on the way it is connected.
After market fuel pumps may look the same but hook up different and also, they can be bad from the factory.
I had one I bought on eBay that would pump with line to carb off and not pump with line on. I replaced it with another one and solved the problem. The carb that runs good with just main lining to the card is probably a good carb and the others are probably even if one is an OEM carb. Most carbs are made in China even OEM ones.
My advice is to check to make sure the hook ups to the fuel pump is correct and if it is, replace the pump because that is where your problem most likely is with the carb you have mainlined, and it ran well.
I have heard aftermarket stuff is junk well I have used a lot of both OEM and after market and have had problems with both. I bought a new OEM carb for a Yamaha and had nothing but problems with it so I ordered an aftermarket. When it came in it was the exact same carb with exactly the same markings as the OEM and it worked, cost less and ran well.