Different Pop Off ~ WTF?

wildman326

wildman326

Who else?
Location
Kansas
Any one get different pop off readings on duals set up the same way? Then switch needle and seat from one side to the next to repeatedly get one side that is higher?

I put in the new butterflys, verified that all internal gaskets were good, and just for fun decided to check pop-off. On 44s with 2.0 n/s and 95 gram springs one side popped at about 24 and the other changed from 28 to 34.

I switched all parts that were relevant back and forth and one of them (the same one) had a higher pop-off regardless of what guts it got.

How much wd-40 do you put in to test pop off? Where do you put it?

I need to re-run all these tests again a little more sober, but I know I was befuddled.

This pop of testing is messy $#!+. Blew wd all over the place (once or twice)
 
keefer

keefer

T1
Location
Tennessee
I always use wd40 because it is handy and cheap. I always manually open the seat and make sure the underside is wet. I then make sure that the N/S assembly is submerged in WD40 every time I pressure test. To avoid the mess I just lay a heavy paper shop towel over the carb so it won't spray all over everything.
 
wildman326

wildman326

Who else?
Location
Kansas
And you've got reliable/accurate results?

I tried a million different things - wd in the return, wd in the in-let, wd in the needle, filling the needle area with wd then pressurizing the pump to below popoff level then depressurizing it to suck wd into the seat - whew. Hope the wetting the needle is all I need to do.
 
'Crockett

'Crockett

Freelance Smartass
Tweak the pivot arms slightly until you get the same reading on both carbs, slightly up reduces pressure . . . slightly down increases pressure.

This is why a popoff gauge is so important to proper carb tuning . . . . it's the only way to know both carbs are matched.

Just for the sake of argument I will say this though: A buddy of mine is great with carb tuning . . . a real natural born tuner . . . his stuff always hauls ass. . . . .

He has never owned a popoff gauge as far as I know !
 
john zigler

john zigler

Vendor Account
Location
wisconsin
'Crockett said:
Tweak the pivot arms slightly until you get the same reading on both carbs, slightly up reduces pressure . . . slightly down increases pressure.

This is why a popoff gauge is so important to proper carb tuning . . . . it's the only way to know both carbs are matched.

Just for the sake of argument I will say this though: A buddy of mine is great with carb tuning . . . a real natural born tuner . . . his stuff always hauls ass. . . . .

He has never owned a popoff gauge as far as I know !
Click to expand...

crockett nailed it.

i always adjust the lever height.

zig
 
oxnard111

oxnard111

Creative RE Purchasing
Location
so Cali, Ventura/Oxnard area
'Crockett said:
Tweak the pivot arms slightly until you get the same reading on both carbs, slightly up reduces pressure . . . slightly down increases pressure.

This is why a popoff gauge is so important to proper carb tuning . . . . it's the only way to know both carbs are matched.

Just for the sake of argument I will say this though: A buddy of mine is great with carb tuning . . . a real natural born tuner . . . his stuff always hauls ass. . . . .

He has never owned a popoff gauge as far as I know !
Click to expand...

Did your buddy tune the ski I got from you? B/C if he did I can vouce, the tunning he did on my ski is perfect. No flat spots and plugs come out looking nice.
 
wildman326

wildman326

Who else?
Location
Kansas
OK. Anybody know what size drill bit will make a 2.0 seat? I bent the poop out of that damn thing and have concluded that the 2.0 seat is worn and therefore making more contact than a new one would.
 
Matt_E

Matt_E

steals hub caps from cars
Site Supporter
Location
at peace
No. I don't know what it is, but I am pretty sure that a 2.0 Seat does not have a 2.0mm hole.
 
'Crockett

'Crockett

Freelance Smartass
When in doubt . . . . . new needle and seat. . . . . .

It's not worth messing with and they aren't that expensive. The viton tip of the needle gets a groove in it and it increases the seat area and makes it pop at a higher pressure. Buy a couple of new springs too. If the springs are old the metal fatigues and they will become work hardened . . . . that will change the spring rate.

The carbs functioning properly is the key to the successful operation of any 2 stroke motor . . . this is not a place to skimp in my opinion.



oxnard111 said:
Did your buddy tune the ski I got from you? B/C if he did I can vouce, the tunning he did on my ski is perfect. No flat spots and plugs come out looking nice.
Click to expand...

Nope . . . Believe it or not when we got that set of duals for it those were the jets that were in them ! . . . . . all I did to them was replace the needles and seats add the F/A adapters and taper bore them. I bolted them on and ran it just to see where it was and what changes need to be made . . . . I couldn't believe it . . . . they were perfect !

I've never gotten lucky like that before . . . or since !
 
SkiDaddy

SkiDaddy

Just Havin' Fun!
Location
Orange City, FL
I was adjusting mine last night, while waiting on jets. Same setup, new 2.0 N&Ss, 95 gram springs, one spring would always pop at exactly 25, other springs (I have 5 "95 gram" springs) at 22 -23 even bending the lever. So I put both levers on 1 shaft & bent them flat & as close to each other as possible. Still one spring higher that the rest, so I figure batches of springs must vary from other batches.

I ended up using two 22 PSI springs (as the initial starting point).
 
john zigler

john zigler

Vendor Account
Location
wisconsin
SkiDaddy said:
I was adjusting mine last night, while waiting on jets. Same setup, new 2.0 N&Ss, 95 gram springs, one spring would always pop at exactly 25, other springs (I have 5 "95 gram" springs) at 22 -23 even bending the lever. So I put both levers on 1 shaft & bent them flat & as close to each other as possible. Still one spring higher that the rest, so I figure batches of springs must vary from other batches.

I ended up using two 22 PSI springs (as the initial starting point).
Click to expand...

what brand kits / parts are you using?

zig
 
addicted

addicted

Location
nj
wildman326 said:
OK. Anybody know what size drill bit will make a 2.0 seat? I bent the poop out of that damn thing and have concluded that the 2.0 seat is worn and therefore making more contact than a new one would.
Click to expand...

A 2.0 is 2.0mm. Just like jet sizes. The seat isn't going to wear out. Just the viton tip. If you have a needle from a 1.5 n&S, try that, the groove will be in a different spot. If that fixes it, you found your problem.
 
wildman326

wildman326

Who else?
Location
Kansas
I agree that the best thing to do would be purchase new parts, and I agree that they are not very expensive, but I have such a collection of parts that it just kills me to spend money on parts.

I don't have my cylinder back yet, so I think I can wait until my buddy gets back in town.
 
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