Jetting help

[nick20555]

OK guys, I'm finally to the jetting part of my build. I got jetting suggestions before for my 35mm air striker that said
50-52 pilot
155-162 main
CEL needle
#6 slide
I got all of those and leak tested so I went to start jetting it and I'm only on the pilot/air screw. I started with what I was suggested (50) but couldn't get my rpm to change unless the air screw was almost completely out (8 turns probably) so I've went all the way down to a 45 and now my rpms are climbing at around 4 turns out so I'm thinking a 42 or 40 is what it's telling me but for my mods that sounds crazy low. Can someone throw out their input please. I'm running:
240 cylinder ported by KOR
170 psi head
+3 crank
Vito fat basted pipe
vforce 4 reeds
cfm airbox with uni filter
And of course the keihin 35mm PWK air striker carb

 

[nick20555]

Oh and I'm around 400 feet elevation with 60-70 being the average temp right now

 

[nick20555]

Update: I put in a 40 in and peak rpms are at 4 turns out. Before with the 45 I was only able to get the rpms to start climbing at 4 turns (not peak). I'm on my way now to buy a 35 and I'm really wondering why so low

 

[Awk08]

Update: I put in a 40 in and peak rpms are at 4 turns out. Before with the 45 I was only able to get the rpms to start climbing at 4 turns (not peak). I'm on my way now to buy a 35 and I'm really wondering why so low

i'd say no to the 35, something else is going on.

I run a 48 @ 1.5 turns in my 200cc KOR engine @ 1800' elevation
a 240cc @ 400' elevation should require richer jetting than me, and has been listed in other jetting threads as needing a 50 or even 52 for an engine of that tune and elevation.

have you checked the float height ?
the proper height and how to adjust it are in here......
http://www.blasterforum.com/threads/float-heights-and-how-to-adjust-them.50565/

are you slightly increasing the rpms with the idle screw before trying to adjust the airscrew ?
it needs to be higher than the usual idle for a good screw response when tuning

are you allowing 20 seconds or so between 1/2 turns to allow the engine to respond to the new AFR turning the screw feeds it ?

 

[Awk08]

also......
is this a new carb ?
used but properly cleaned ?
new filter with too much oil on it ?

somethings funky for sure, no way pilot down into the 30's

 

[nick20555]

also......
is this a new carb ?
used but properly cleaned ?
new filter with too much oil on it ?

somethings funky for sure, no way pilot down into the 30's

It's a new carb, new filter but not too oily.
I did it step by step from the sticky. Increased idle, waited for response, half turns at a time.

I had a 50 in it at one point and like I said earlier, the only response I got from the motor was when the air screw was about to fall out. I can put the 52 in and see what happens.

I tested the 35 and don't seem to get any engine response except bogs hard at half turn out. The 40 had optimal rpms at 4 turns. I'm kinda lost.

 

[nick20555]

I never checked the float height since it's a new carb but I guess that's the only thing left to do

 

[speedyslyder]

i want to see it on quad pic?

 

[nick20555]

Well there was something I thought strange when I replaced the slide and needle. The needle had wiggle room side to side. Is that normal? Could that effect my air screw setting even though they are 2 different throttle ranges?

 

[Awk08]

The 40 had optimal rpms at 4 turns.

I once had a race team owner tell me they ran a 38 pilot in their race quads in flatland ohio, but i'm sure they threw at least new rings in before every race ?
thats an aweful small pilot for that elevation.
I was hesitant to let that info out, as it goes against what 99% of us have experienced on here.

Well there was something I thought strange when I replaced the slide and needle. The needle had wiggle room side to side. Is that normal? Could that effect my air screw setting even though they are 2 different throttle ranges?

thats normal, and makes it hard to get the slide down in without using your finger to guide the needle into the needle jet if not perfectly level

I never checked the float height since it's a new carb but I guess that's the only thing left to do

get that checked, the fuel level in the bowl effects all jetting ranges.
it's in the link i posted above

 

[nick20555]

I once had a race team owner tell me they ran a 38 pilot in their race quads in flatland ohio, but i'm sure they threw at least new rings in before every race ?
thats an aweful small pilot for that elevation.
I was hesitant to let that info out, as it goes against what 99% of us have experienced on here.




thats normal, and makes it hard to get the slide down in without using your finger to guide the needle into the needle jet if not perfectly level




get that checked, the fuel level in the bowl effects all jetting ranges.
it's in the link i posted above

I'll see if I can check it sometime tomorrow.

Another red flag that had me concerned was that the idle screw does absolutely nothing to change the idle speed. My only way to adjust my idle was with the throttle cable adjustment which I'm pretty sure is the wrong way to go about your idle.

 

[Awk08]

I'll see if I can check it sometime tomorrow.

Another red flag that had me concerned was that the idle screw does absolutely nothing to change the idle speed. My only way to adjust my idle was with the throttle cable adjustment which I'm pretty sure is the wrong way to go about your idle.

i use the throttle cable to adjust my idle on my PJ, but it has that stupid choke knob that turns for idle adjustment, no idle screw

but your idle screw should be working
take it off and see if it is actually lifting the slide ?
that could be your whole problem here ?

 

[nick20555]

i use the throttle cable to adjust my idle on my PJ, but it has that stupid choke knob that turns for idle adjustment, no idle screw

but your idle screw should be working
take it off and see if it is actually lifting the slide ?
that could be your whole problem here ?

Alright, next chance I get, I'll be checking my float level and investigating why my idle screw isn't doing anything. I didn't know what the idle screw actually does to the carb to alter your idle, that's why I hadn't messed with that yet. I would have checked my float level as well but when I tried to tilt my carb like you're supposed to do, my float would be all or nothing. I couldn't get it to just barely seat. And I also thought that since it was a new carb it should be at the right height but now that I think about it, a very large amount of fuel drained out every time I tore the carb apart to adjust my jets.

 

[nick20555]

I'm not at home to work on the blaster right now but I thought I'd ask to see if you guys have advise. I read the how to on the float adjustment but does anyone have any suggestions on tools or something that make taking the measurement easier? I know the 35mm air striker has a 16mm float height so luckily that is literally a hair more than 5/8 inch so that makes an easy mark but the actual measurement taking I can foresee being a PITA! I'm already most likely going to be taking a metric measurement in inches so I don't really want compounding error when adjusting the float height.

 

[Awk08]

printable rulers
http://www.vendian.org/mncharity/dir3/paper_rulers/

print it out, glue or clear tape it to a popscicle or other stick ? or just make a 16mm mark on a flat thin anything.
measure from where the gasket would sit with gasket removed, not the outer lip, to the highest point of the float with the carb held on a 45 degree-ish angle, so the floats don't push in the spring loaded pin in the float valve.

if it's off the 16mm
bend center tab down into carb to raise measured float height
bend up to reduce measured float height

less is more, only bend a little at a time as the tangs little movement is multiplied to the floats

 

[nick20555]

printable rulers
http://www.vendian.org/mncharity/dir3/paper_rulers/

print it out, glue or clear tape it to a popscicle or other stick ? or just make a 16mm mark on a flat thin anything.
measure from where the gasket would sit with gasket removed, not the outer lip, to the highest point of the float with the carb held on a 45 degree-ish angle, so the floats don't push in the spring loaded pin in the float valve.

if it's off the 16mm
bend center tab down into carb to raise measured float height
bend up to reduce measured float height

less is more, only bend a little at a time as the tangs little movement is multiplied to the floats

thanks, I'll get on that when i get a chance and keep you posted. I'll probably get back with an questions I have about the idle screw as well

 

[nick20555]

OK I got around to it and my float height is right and my idle screw does move the slide up but not very much. That is probably why my idle is not responding to the screw.

I got the 50 pilot back in it and the rpms are still climbing at 4 turns out. I really don't want to blow my new motor up by running lean. I have no idea what's going on with it.

 

[nick20555]

As of right now I just left the 50 in it and have the air screw turned out just passed the point where it bogs so around 2 turn. It's not ideal throttle response but not bad either. I went ahead and did a half throttle plug chop just to see if I'm in the ball park on my needle but don't have anything handy to cut the threads so I can show you guys a pic

 

[Awk08]

so is the idle screw increasing rpms as it is screwed in ?
you say it's only lifting it slightly ?.... enuf to increase rpms to beyond a normal idle ?
if not, what would it take to get the idle screw to lift the slide further ....longer screw ? lose the nut and go with a spring for retaining it's setting ?

 

[dirtysquared]

I had a similar problem with a 35 pwk on my banshee. It ended up being a bad slide.

No matter what I tried , I could not get the engine to respond to the airscrew. Finally after messing with it for a week, I took the carb out, and looked inside and could see that the slide was not closing all the way.

Just something to check or ponder.