No POP in PopOff test ... Just hiss..

[BMANN06]

Okay, so here's the story. I have 2 rebuilt engines in my speedster (lower end bearing seizure) anyways I wanted to have my carbs rebuilt. So i took them to a shop to get rebuilt (at thetime the job seemed over my head). K well that was a terrible idea; my boat would flood like hell after stopping and would be next to impossible to start thereafter and i lost midrange and top end performance. I've done some reading and asked some questions and discovered that my carbs we not rebuilt properly. The tech didn't do the pop off test after discarding my old springs:rant:

So i've decided to perform the test myself; here's what i got. When i get up to around 60lbs the valve opens and i hear a hissing definatly no pop! I have to open the valve with my thumb to get it to fully open. I probably need a lower weight spring (i think) any idea where to find these? Am i likely order a new rebuild kit to get this sorted? Any help is super appreciated, and I'm not going to bother chasing the shop down; they aren't touching any of my toys ever again!

 

[Dr Honda]

do you have the carb(s) off? If you do... do you have the diaphragm cover off? I'm assuming you do since you say you can push the arm.

OK... look at the nipple in the center of the diaphragm. Is it red, or silver? If it's silver... that's your hard start/flooding issue. The import rebuild kit's SUCK. If it's red... there may be other problems. (like the pivot arm is not level with the carb body)

To get a clean pop-off... you will want to lift the needle, and put a few drops of oil down in it. (make sure it gets to the tip) This will help seal the needle, and should give you a clean "pop."


FYI... your settings should be:


pop-off 38
main 142.5 MAG, 145 PTO
Pilot 67.5
Low 1-1/2
high 0

 

[BMANN06]

do you have the carb(s) off? If you do... do you have the diaphragm cover off? I'm assuming you do since you say you can push the arm.

OK... look at the nipple in the center of the diaphragm. Is it red, or silver? If it's silver... that's your hard start/flooding issue. The import rebuild kit's SUCK. If it's red... there may be other problems. (like the pivot arm is not level with the carb body)

To get a clean pop-off... you will want to lift the needle, and put a few drops of oil down in it. (make sure it gets to the tip) This will help seal the needle, and should give you a clean "pop."

Hi Doc,

Yah i've got the carbs off (as per your instruction in a different post) I've got the diaphram off too. The there is a RED nipple on the diaphram so i'm hoping this is good. I have sprayed some WD-40 in the needle to lube i can get some oil in there to try that. I have done this test about 10 times on this carb. I have heard a "pop" twice at 44 psi.

Should the arm be flat? because my is bent kinda sorta like a V. Should i straighten it out and get it level with the body?

As always thanks..

 

[BMANN06]

FYI... your settings should be:


pop-off 38
main 142.5 MAG, 145 PTO
Pilot 67.5
Low 1-1/2
high 0

What is meant by:

main 142.5 MAG, 145 PTO ??

 

[dsw222]

What is meant by:

main 142.5 MAG, 145 PTO ??

142.5 main jet for the mag side carb, 145 main jet for the PTO side carb... each of the carbs takes a different size of the main jet

 

[Dr Honda]

yep... what he said.


You should be able to get a pop everytime... but, after the oil "pops" out... you will have to put a little more oil down there. (re-oil for each test)

Personally, I don't like WD40 for this. I haven't ever heard of this problem... but I feel that kind of oil (plus it's propellant) could damage the rubber tip on the needle. I like good old machine oil. (something I can control, and drip in)


Yes... when the arm, spring, and needle are assembled into the carb... the arm should be flush with the body. You can bend it slightly up or down to do a fine adjustment on the pop-off pressure. (changing the spring for large changes) If your arm is bent down too far (more than 1mm from level) that is a problem. At that point... the diaphragm can't push the arm open enough for good flow at full throttle... and it would make it hard to draw fuel at low vacuum situations. (like starting cold)

 

[BMANN06]

K .. it pops now!!

Well the gear oil certainly made an improvement. Got it out to do the pumps .. I can get it to pop everytime. BTW that stinkin' gear oil tastes about as bad as it smells.

So I've trimmed my springs a couple hairs here and there and can get a consistent PoP every time at 39 PSI. I'm going to assume this is close enough?

 

[BMANN06]

Ahhh .. Makes sense!

142.5 main jet for the mag side carb, 145 main jet for the PTO side carb... each of the carbs takes a different size of the main jet

Thanks DSW22

 

[Dr Honda]

You shouldn't stretch or cut your springs. :banghead:

Cutting the spring will get your pop-off numbers... but the spring itself is still too stiff, and won't allow the needle to open properly.

 

[BMANN06]

Clarification pls?

You shouldn't stretch or cut your springs. :banghead:

Cutting the spring will get your pop-off numbers... but the spring itself is still too stiff, and won't allow the needle to open properly.

K i'm pretty sure i can get the shop that rebuilt these to hook me up with some springs. So just so i'm on the same page, I need to get springs that get a pop off around 38psi without any modifications to the springs? Have I got this right? On a side note: I have a 2006 yamaha R6R where my valves tick on a cold start; after warmup seem to stop? Is it time to adjust these valves? I've got about 24K on the bike. Prolly shouldn't be posting this but figured I could slide it in and get your opinion LoL.

Thanks Doc,

 

[Dr Honda]

K i'm pretty sure i can get the shop that rebuilt these to hook me up with some springs. So just so i'm on the same page, I need to get springs that get a pop off around 38psi without any modifications to the springs? Have I got this right?

Yes. It can be a little higher, or a little lower... but not magnitudes. I know race guys who get crazy on the pop-off thing... but honestly... it's not that big of a deal, as long as you are close to spec. The only thing is if the pop-off is too high you can go lean. Pop-off is to help balance the internal vacuum to the restriction of the intake. (that's why you normally drop the pop-off with less restrictive filters) On my Polaris... it has a "K&N" style filter from the factory, and I run 18 psi on it.

On a side note: I have a 2006 yamaha R6R where my valves tick on a cold start; after warmup seem to stop? Is it time to adjust these valves? I've got about 24K on the bike. Prolly shouldn't be posting this but figured I could slide it in and get your opinion LoL.

Thanks Doc,

Are you sure it's not just the injectors getting loud?

Normally on an R6 engine... the valves start to stretch, and the gap closes up. Then you get hard starts. (no sound is heard)

Also... there is a cam chain adjuster... it could be warn, or the chain can be stretched. (it's ugly when they break)

I think there is a chain driving the oil pump on that engine... check it to see if it's slack.


Finally... when was the last time you serviced the clutch? you could have a broken spring in the basket.


If it was my bike, and I didn't know exactly where the tapping was coming from... I would start with removing the valve cover. Check the valve clearance, and check the chain. I would also remove the adjuster to check it compleatly. (I don't remember if that one had a manual, or hydro) It may be stuck.


I know on the modern 4 stroke MX bikes... all the auto adjusters are crap. We remove them, and replace with a manual adjuster. Basically, when you install it... you make it finger tight, start the engine, and slowly turn it in until the cam chain goes quiet. Any more that that, and you will stretch the chain.

BUT... since this is a SeaDoo forum... PM me if you have any more bike questions.

 

[BMANN06]

got some new springs

Hey Doc,

I've got some new unmolested springs. With the PTO side (pump) side i've got a popoff of 42psi. And the Mag side is 40psi.

These numbers going to work. Or should i keep finding more springs. BTW thanks for the advice on my bike. And uhh errr understood no more yamaha questions in the seadooforum.

:cheers:

 

[Dr Honda]

Your spec is 38 (+-12) So... I'd say you are fine with those numbers.