October 14, 2013 at 6:26 pm #12825
I recently purchased a shifter with a stock Honda and Keihin pump around carburetor. On track the motor runs without issue. The problem is when restarting the kart after it has been stalled. Usually when it’s shut down after a run it will start without a problem. When stalled it appears flooded and will not start with a strap or pushing the kart in gear for as much as 75’. The only way I have been able to start the kart is by blowing in the carburetor vent lines and forcing the gas back into the tank. My current jetting is 50/182. I have tried both richer and leaner jetting with no affect. I rebuilt both fuel pumps and replaced all fuel lines when the kart was purchased.
The clutch has heavy springs and my daughter hasn’t consistently gotten the knack of smoothly engaging the clutch. This is the reason the kart has been stalling. Being used for autocross, she has to stop and start a few times while she makes her way to the line. Is this symptom typical of a pump around carburetor? If so would I be better off switching to a typical carburetor with a float?October 14, 2013 at 7:48 pm #12834
If you have a pumparound carb they have a tendency to flood the crankcase if the fuel level in the tank is high enough.
Solutions include keep the fuel level low(er) in the tank, or put a valve in the line to toggle it on and off.October 14, 2013 at 11:19 pm #12846
Another thing that can flood the cases is when the kart rocks back and forth when in gear and sitting in the back of the truck. BTDT…took a long time to clear out the motor.October 15, 2013 at 5:40 am #12851
So far I haven’t had any issues after hauling the kart in a trailer for over 2 hours and I have kept the fuel tank level low. I keep the fuel level below 3″ which is well below the top of the float bowl.
ThanksOctober 15, 2013 at 7:39 am #12858
I’ve never had the problem you’re experiencing and I’ve run a pump-around for the last 3 seasons on my Honda. You’ve taken care of the rebuild, so my only other suggestion would be to check the tank vent line to ensure you’ve got an open line. Also changing your fuel filter if you haven’t already.
You mention heavy springs in the clutch. As in heavier than stock? My Honda is the easiest of the three motors I’ve had to launch (Suzuki RM125 and TM Moto). The clutch should be smooth to engage and disengage. Maybe try a different gearbox oil? I have tried several and the Royal Purple made a huge difference mid-season this year. Of course it will take some practice to be consistent, but she should be able to get there early next season. Learning to grab the clutch and/or keep her foot in it during a spin is another area to learn to not stall.October 15, 2013 at 6:26 pm #12956
things to check… The pulse line and the pumps themselves can fill up with oil and you may have not enough fuel. You should see almost a constant stream of fuel coming out of the carb and a constant stream in. Fuel filters, plugged jets and at least two vents are next. Which carb? Pwm or pwk? My pump around works well and usually start my kart by spinning the rear tire by hand.October 16, 2013 at 1:34 am #12965
Hoses and filter are new. Jets have been cleaned and problem has existed with other jets installed. All four vent hoses are in place. Tank vent is good and I have even tried to start the motor with the tank fill cap off to make sure that wasn’t the issue. I will go through the pumps again in the next couple days. Carb is a PWM.
ThanksOctober 16, 2013 at 8:37 am #12994
One more thing that can help – knowing how to apply throttle when restarting. I helped someone recently that kept stomping on the gas as if an accelerator pump was there and would get the motor started. Asked them to just apply 5% gas and leave their foot there and their motor started in about 10 feet of pushing. Usually there’s a throttle position that works for most carbs but you kind of have to figure it out. Seems like the PJ carbs can be pretty bad about this…even if it’s not relevant to your situation.
hth, laOctober 16, 2013 at 9:49 am #13001
Another simple thing to check: make sure your spark plug is not wet. If you stall with the throttle open, it’s possible to have a cylinder full of unfired mixture.
-billOctober 16, 2013 at 6:31 pm #13033
pwm has an idle adjust built into the choke knob. Turn all the way open to start and dial back to warm up. Just remember to close all the way before driving so the engine doesn’t actually idle. It makes shifting easier if there is no motor load in the trans.October 19, 2013 at 7:57 pm #13203
I rebuilt the pumps a couple nights ago. I was able to detect a small amount of leakage through the valves of the return pump. On the stand that night I started and stopped the kart numerous times without issue.
I brought my daughter out to an industrial park to check it out today. It started on the first pull. After warming the motor I shut it off and push started it with my daughter. This was the last time it would start without issue. We ran the car through the gears and then stopped/restarted it roughly 10 times. Every time, the motor would not start unless I blew through the vent lines to force fuel back to the tank. The motor would then start in gear immediately or after continuing to push in gear for a short time.
Would it make any difference if the pumps were mounted lower than the carb. Since there is no float, could fuel be running down into the bowl when the motor if off.
ThanksOctober 25, 2013 at 9:39 am #13778
Sounds to me like your return pump can’t keep up or is pumping the wrong way. Did you rebuild it with new diaphragms and seals? Can you swap the two?
Pumps should be higher than the pulse line if possible so any oil can drain back to tank but honestly I’ve seen all scenarios work. High fuel levels can cause issues too.October 29, 2013 at 5:56 am #14134
I found this on the SRS web site that says something about height of pump assy. maybe this will rule some things out.
I have a couple of spares if you want to try, I would say shipping would be less than 10 bucks. you could rule out the pump rebuild and know if it is working correctly.
Also I have a pump around system. If I let someone else drive the kart and it stalls I have to change the plug due to them lugging the kart around at lower RPM’s and then if they spin they tend to floor it with out pulling the clutch in. I can usually tell if it is flooded because when you push start it the engine sounds just like you have the throttle wide open while pushing. BAAAAA deep sounding.
I found that out the hard way, I adjusted the throttle to much “open” and about never got the kart started again.October 29, 2013 at 8:45 am #14150
My pumps are as high as they’ll go on the seat. Ran it this weekend with no issues. lumbered around in 3rd gear video taping my son, let a newbie drive it for a while and didn’t foul up the plug. Never have had an issue flooding the crankcase ever. If you want a picture of the setup let me know.October 30, 2013 at 6:14 am #14302
I appreciate everyone’s comments. I think I’ve checked and double checked everything that’s been suggested(New fuel lines, reposition fuel lines, carb vents, clean jets, rebuild pumps, fuel pick-up, tank vent ok, keep low fuel level in tank). Short of replacing the carb, I’m not sure what to do next. Unfortunately cold weather is starting to set in and there are no more events. I hate to leave the problem unsolved but I will need to bring the motor in for the winter and pick back up with this in the spring. Thanks BrianNovember 25, 2013 at 5:08 am #16511
I’ve experienced the same sorts of issues on other people’s karts with the pump around. Not sure how to get around it. One unorthodox solution, which I use on my kart is to install a mikuni 1.8mm float needle seat(from, I think a VM34/39) to deal with the fuel pump pressure, and a boyesen “super bowl” to deal with the sticky float issue.
I bought the kart this way and I haven’t had a single non user induced problem out of it.
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