Bogging???

#1
My minibike will go full throttle if I accelerate calm but when i wanna go full throttle at a stop it dies

pwk28 carb
45 idke
150 main (tried multiple jets)
 

Thepaetsguy

Well-Known Member
#2
My minibike will go full throttle if I accelerate calm but when i wanna go full throttle at a stop it dies

pwk28 carb
45 idke
150 main (tried multiple jets)
Can you adjust the clip on the needle? When you slam the throttle open all that does is open a massive hole for air to flood in and a few small passages for fuel to flow through. Your going wide open quick and allowing all the air in but not enough fuel quick enough. move the needle clip down one or two notches and that will raise the needle in the slide. now when you crack the throttle the needle is already raised two notches and it immediately lets enough fuel in.
 
#3
Can you adjust the clip on the needle? When you slam the throttle open all that does is open a massive hole for air to flood in and a few small passages for fuel to flow through. Your going wide open quick and allowing all the air in but not enough fuel quick enough. move the needle clip down one or two notches and that will raise the needle in the slide. now when you crack the throttle the needle is already raised two notches and it immediately lets enough fuel in.
Alright i’ll try this today thank you
 
#5
How about some details! Like what engine, what has been done etc. It must be a larger engine if you are running a 28mm carb. I haven't road tested this one yet but it is a 28mm PWK on a 224cc.
Awesome bike!!!!! You turn out some top notch riders.
I noticed the "small engine cams" sticker, and was wondering, what's your opinion on those cams??? And why they pull so much harder when compared to others with the similar specs. all things being the same, of coarse. I've only used 4, 1BMJ, and 3 customs, and always had to go to a higher gear, by 1:1 or more. That's by no means a problem, lol. Ive noticed the tillys, ducars, and preds around here running the popular selling 265 cams, with lighter weight riders, doesn't even come close to Tim's BMJ or any of his smaller duration cams.

Didn't mean to high jack the thread. The sticker jus caught my eye.
 
#6
I just replaced the original engine in that bike that was a old greyhound 196 with BM sr and it was Fast. This is a Tillotson build 224cc with a dyno 356 cam. All my other karts and mini's are isky's, BM jr and sr as well as a custom grind in a engine not yet used. I have no idea if this new engine will be any faster than the old one but I'll let you know when I test it. I love the ISKY grinds for the clones.
 
#7
I just replaced the original engine in that bike that was a old greyhound 196 with BM sr and it was Fast. This is a Tillotson build 224cc with a dyno 356 cam. All my other karts and mini's are isky's, BM jr and sr as well as a custom grind in a engine not yet used. I have no idea if this new engine will be any faster than the old one but I'll let you know when I test it. I love the ISKY grinds for the clones.
Yea, I would like to know the results. Also would be interested in the specs of that custom cam, and what you came out with on the IVC, in crank degrees. I'm a believer in the isky cams. That lil 225/.300/104 cam, makes a low CR 196cc hit like a wreckingball around 3300 rpm.
I'm gonna back out and let you guys get the OP's slide carb fixed.
Thx again for your input and keep up the great work. Pics of builds and head work are much appreciated.
 
#10
Please tell us what else has been done to your engine. Is it a stock engine with this carburetor on it? Is the governor still in the engine? Did someone replace the flywheel with one of those shiny ones?
no it’s carb and exhaust only the govenor is still in it but it doesn’t seem to do anything and no it’s a cast flywheel i’m jus having issues with the carb
 
#13
Saw your video in the other thread about the idle. So are you familiar with the sequence of tuning the carburetor? First step is to get the idle working before moving on to anything else. Looks like your carburetor is not a pwk but a copy. Is it a nibbi or a makuni or other? I have quite a few of those and the 3 different ones I have used all ran OK without touching them. Now your engine seemed to idle then drop, first thing would be to adjust the idle mixture screw. Have you done that?
 
#14
Saw your video in the other thread about the idle. So are you familiar with the sequence of tuning the carburetor? First step is to get the idle working before moving on to anything else. Looks like your carburetor is not a pwk but a copy. Is it a nibbi or a makuni or other? I have quite a few of those and the 3 different ones I have used all ran OK without touching them. Now your engine seemed to idle then drop, first thing would be to adjust the idle mixture screw. Have you done that?
yea i adjusted it didn’t seem to do anything , i thought it wasn’t sealed well and had a air leak so i re tightened the boot but that didn’t do anything
 
#19
The slide height and the idle air screw both work together. If the slide height is adjusted it allows more or less air in, then the idle mixture will change so the idle mixture then needs to be readjusted in that order. Now if you played with both and it made no difference then you need go no further till that issue is fixed. First do not keep adjusting things and changing other things not related to the idle. So if you focus on the idle you have only a few things that could be causing the erratic idle. First pull the sparkplug and make sure its not black or fouled. Best to start with a new plug if in any doubt or you will be chasing your tail. Next make sure you do not have a air leak. Next step is to remove carb from the rubber spigot (you do not have to take off anything just get it off so you can eyeball the back of the slide to see how high it is from bottomed out. it should be opened. it should not be opened more than 3/32 of an inch. I'm not sure about your pilot jet size as that could be an issue. I would have to go look at one of mine as I don't remember what my sizes are on mine. The main jet does nothing for getting your idle set so ignore that for now until you get the idle issue fixed. If anyone else had used a 28 on here they can chime in on the correct size that worked for them.
 
#20
I just pulled off my carb which is idling fine took a pic of the slide height and checked where my air fuel mixture screw was set and it was at 1.5 turns out. I dod not remove the float bowl and jet so I do not know what pilot it has. So start with setting your slide height so it looks like mine and set air fuel to 1.5 turns as a starting point. That still does not explain why you have a eratic idle I suspect either fouled plug, air leak, or fuel flow issue.
 

Attachments

Top