ideal throttle response?? wot from idle?

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MrNoFace

New Member
#1
#1
I am just curious what an ideal throttle response is suppose to feel like as in while I'm on my bike idling if i slam the twist throttle to WOT there is a slight hesitation if i twist it as quick as possible *this is while sitting on the bike, and practicing getting out the hole at WOT*, but if I twist it a hair lighter than as quick as possible the response is perfect. Otherwise riding the mini bike the tuning seems perfect, and hit over 60mph on it (wasn't even trying to max out). The response while riding if you slam it to WOT is perfect just not at a standstill. My tuning is spot on, but I am having this one issue *also using a lower rpm stall clutch 2300-2400 engagement*, might change out springs for 3100-3200 engagement, but its just a cruiser really so don't want a high idle/high engagement while i'm riding around.

one thing I don't have is a fuel pump, but I have a stock mounted 6.5hp gas tank. I heard only use a fuel pump if you are using a remote gas tank?? anyone think this might be the issue?

Engine is built about 400 lift 32/28mm valves +.20" over flat top 1.3 billet roller rockers billet 24mm flatslide 15-18ish hp... predator 212cc 13t to 59t with 14.5" tires 4.53 gear ratio with a max torque clutch

24mm pwk with 135 main 38 pilot needle 2nd position from the top

was thinking i might try a 40 pilot, but the a/f is at 1.5 turns out from flush. Going to lower the needle jet to the 3rd position, and see if that helps idle to wot response.
 
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mustangfrank

mustangfrank

Well-Known Member
#2
#2
MrNoFace said:
I am just curious what an ideal throttle response is suppose to feel like as in while I'm on my bike idling if i slam the twist throttle to WOT there is a slight hesitation if i twist it as quick as possible *this is while sitting on the bike, and practicing getting out the hole at WOT*, but if I twist it a hair lighter than as quick as possible the response is perfect. Otherwise riding the mini bike the tuning seems perfect, and hit over 60mph on it (wasn't even trying to max out). The response while riding if you slam it to WOT is perfect just not at a standstill. My tuning is spot on, but I am having this one issue *also using a lower rpm stall clutch 2300-2400 engagement*, might change out springs for 3100-3200 engagement, but its just a cruiser really so don't want a high idle/high engagement while i'm riding around.

one thing I don't have is a fuel pump, but I have a stock mounted 6.5hp gas tank. I heard only use a fuel pump if you are using a remote gas tank?? anyone think this might be the issue?

Engine is built about 400 lift 32/28mm valves +.20" over flat top 1.3 billet roller rockers billet 24mm flatslide 15-18ish hp... predator 212cc 13t to 59t with 14.5" tires 4.53 gear ratio with a max torque clutch

24mm pwk with 135 main 38 pilot needle 2nd position from the top

was thinking i might try a 40 pilot, but the a/f is at 1.5 turns out from flush. Going to lower the needle jet to the 3rd position, and see if that helps idle to wot response.
Click to expand...
Should be able to smooth that out with a flatslide...I'd start with a needle lift to the middle and then 4th position even. My first instinct was pilot as well though.
 
M

MrNoFace

New Member
#3
#3
mustangfrank said:
Should be able to smooth that out with a flatslide...I'd start with a needle lift to the middle and then 4th position even. My first instinct was pilot as well though.
Click to expand...
I am using a 24mm flatslide carb.

I just tried the needle jet position from 1st, 2nd, 3rd, 4th. 1st, and 4th clip were the worst. I had it on the 2nd clip previously, and now I left it on the 3rd (might be slightly better)?

I am still having the same issue though. I can't idle to WOT without a bog or hesitation *hard for me to tell* I think it might be rich on the top end, but I had a 130 main in it previously, and was topping out so upped the main jet to try to get more rpm on top end. Not sure if a fuel pump would help with this?? That might be my next step depending on how my test run goes tonight.....

if top end improves with bigger main I will try to increase the 38 to 40 pilot, and see if that helps after my test run...
 
massacre

massacre

#4
#4
If you are breaking up or having a stumble, you will have to tune your carb which sounds like what you are doing.
Stay with it, you’ll get there.
Are you reading the plug?
 
M

MrNoFace

New Member
#5
#5
massacre said:
If you are breaking up or having a stumble, you will have to tune your carb which sounds like what you are doing.
Stay with it, you’ll get there.
Are you reading the plug?
Click to expand...
Yeah the plug I am using now is 3910x, but got some ngk BP6ES that run a little hotter on the way. If I wot from idle the engine will die (if i snap my wrist as fast as i can). Not sure if its the velocity of air going into the carb without a fuel pump causing a lean condition? Is that even possible if float height is correct? Or if its too rich on the main jet. I think the main jet might be rich, and I need a fuel pump to fix the idle to wot bog??
 
M

MrNoFace

New Member
#7
#7
massacre said:
Sounds you are too rich off idle. Also check your throttle cable and make sure there is nothing fishy there.
Click to expand...
Hmm interesting... I am at 1.5-2 turns out on a/f, but I think you might be onto something. Currently at 38 pilot, but will try out a lower pilot as well. Thanks for the insight.
 
massacre

massacre

#8
#8
MrNoFace said:
Yeah the plug I am using now is 3910x, but got some ngk BP6ES that run a little hotter on the way. If I wot from idle the engine will die (if i snap my wrist as fast as i can). Not sure if its the velocity of air going into the carb without a fuel pump causing a lean condition? Is that even possible if float height is correct? Or if its too rich on the main jet. I think the main jet might be rich, and I need a fuel pump to fix the idle to wot bog??
Click to expand...
If you think it’s running rich, I’m not sure a fuel pump will help.
Fuel pump is usually used if it’s running lean.
 
M

MrNoFace

New Member
#11
#11
Tom S. said:
Accelerator pump?
Click to expand...
My carb does not have an accelerator pump it is just the 24mm pwk off amazon 24mm flat slide clone basically.

I tried dropping the pilot down to 35 from 38, and seemed to help a bit as well. The lowest pilot I have is 32, but I am going to take it on a test ride right now, and see how she does.
 
M

MrNoFace

New Member
#12
#12
that was my worst run yet lol... only hit 57.5 mph 135 main/35 pilot/needle in 2nd with 4.53 gear ratio...

when i had 135 main/38 pilot/needle in 2nd with 5.0 gear ratio hit 60.8...

hopefully i can break that 60.8

just tried 135 main/40 pilot/needle in 3rd position 4.53 gear ratio, and hit 59.2 mph... little better.. starting to think its leaning out up top due to lack of fuel... going to try a walbro fuel pump see if that fixes any of my issues, and going to raise stall on clutch to 3100 so I can increase my idle rpm.
 
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M

MrNoFace

New Member
#15
#15
SAS289 said:
I don't know how a fuel pump would help with an off idle stumble. At idle the carb should have plenty of fuel ready.
Click to expand...
It idles perfectly, but if i snap the throttle to wot it hesitates then starts going. I am going to just change out the engagement springs from 2300 engagement to 3100 engagement that will get rid of the hesitation/bog from idle to wot... played around with the idle/air screw/pilot seems it's as close as it's going to get. Going to see if the fuel pump helps before I change out the clutch spring.

minibikin' said:
Where's the ignition timing? I'm not a fan of a plug you cannot gap and read. I would go with the NGK personally.
Click to expand...
32 degrees of timing, and I am going with the NGk plug as well.

I think it might be a fuel delivery issue.. that's why I think the fuel pump would help at least on the top end. Plug chop says its lean after WOT run. Going to run the pulse off the valve cover.
 
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mustangfrank

mustangfrank

Well-Known Member
#16
#16
You're not going to empty the float bowl/uncover the jets off-idle. Check float level and post some pics of the side view with tank elevation and hose routing to carb, including fuel tap at tank.

Your off-idle issue is pilot jet IMHO, I would leave a main that works well with the needle clip in the middle and tune the 0-1/4 throttle first.
 
M

MrNoFace

New Member
#17
#17
mustangfrank said:
You're not going to empty the float bowl/uncover the jets off-idle. Check float level and post some pics of the side view with tank elevation and hose routing to carb, including fuel tap at tank.

Your off-idle issue is pilot jet IMHO, I would leave a main that works well with the needle clip in the middle and tune the 0-1/4 throttle first.
Click to expand...
That's what I thought before I did a test run.

Now I think my pilot is correct, my needle is correct, but my main jet at 135 is too rich, but I was getting a lean condition at WOT/60 mph due to fuel delivery issues... So that's why I think the fuel pump will help with the lean condition up top, and dropping the main to 130/125 will probably get rid of the idle to WOT bog.. I'll report back. Thank you.
 
M

MrNoFace

New Member
#18
#18
got the walboro pump fuel in its awesome.... Here are pictures of how I set it up/got it mounted. I have a t-running from the pump to carb, and back to gas tank for any extra supply... Drilled a hole in the gas tank lid for a vent hole... will eventually add a line coming out the top of the vent hole....

idle to WOT is not an issue anymore.... works perfectly now, however the float bowl does overfill at idle, and is there a common fix for this? Re-route the overflow line back into the gas tank as well??

Well here is how it is set up currently. Would be perfect if I can figure out a proper way to re-route the excess gas coming out the vent for the bowl.

I think it's the needle/seat, but I just think the pulse running off the valve cover is too strong for the needle. Would rather an easier fix like a line re-work or something similar than to mess around, and find the right needle..... Thanks for the help.

Currently have a 24mm pwk flatslide with 120 main, 38 pilot, and gold needle in 3rd position (at 100ish ft elevation 50-60% humidity)

What would the correct needle/seat be for this application? I also could slightly close off the fuel shut off valve to not overload the floatbowl... but i want this done right....

minibikepump.jpg
t-line-re-route.jpg
 
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massacre

massacre

#19
#19
My fuel pump takes the pulse from the intake manifold, and there is no return line back to the tank.
But I use the square fuel pump and not the round one.





Kinda hard to see here ^^^
Fuel lines are blue. Fuel pump has 3 nipples.
One nipple faces forward, goes to fuel tank.
Two nipples face rearward, one is for vacuum pulse, the other goes to carb.
I’ll see if I can find a better pic.
But the square WMS (walbro) fuel pump is a simpler setup with less connections.
Also, I route crankcase AND valve cover to catch can.
Fuel pump is looking for vacuum, valve cover is not vacuum.

I would send the valve cover to the catch can, and take the pulse from the intake manifold and see if that works any better. Just my two cents.
 
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