My ski cuts only when I snap the throttle hard.

[Chris Pausch]

Pretty stumped on this one. I recently built my first am ski. Gen 2 bob.

When I snap the throttle from low rpm to full it cuts out but doesn't stall. The rpms galop a little but won't pick up. When I pull the throttle to 80% it hits hard and if I pull it to 100% a little softer than a snap it hits hard to.

My engine is a 61x/61x, Php freestyle ported cylinders, ada head 175lbs, limited b pipe, boyesen power reeds, lightened flywheel, OEM spark arrestor with only 1 screen, advance my timing 1/8" on the stator, ocd rpm ignition mod set to 7800 rpm.

Zack at PHP recommend a 120 pilot jet, 147.5 main and a 95g spring. Ive tried 2 sizes smaller springs. The first size down it got better but was still there so I went down again and it didn't do much. It ran best at about 3 turns out on my low speed so I put a 125 pilot in it and it runs best at about 1 2/3 out on the low speed screw. I still have my choke butterfly in.

I almost feel like I might be chasing an issue that is not carburetion because no matter what carb adjustment I do its always there. Any ideas?

 

[River Rat]

Random question but is your gas tank vented?

 

[Vumad]

Did your try the 127.5

 

[Roseand]

What's the condition of your throttle butterfly and shaft seals?
I also have never had any luck with 120 pilots on single 44 ported 61x cylinders. I've always used either a 125 or a 127.5

Sent from my SM-G920V using Tapatalk

 

[Pro-pulsion]

^^ what he said.

I tried to setup an SBN44 on a 61x/61x last year and found that it wasn't enough carb for a B-piped engine. Switched over to the Buckshot SBN46 the guy had for his back up as he thought the Buchshot was giving issues. After setting it up on the Buckshot he never looked at the 44 again. A little food for thought, I have found that the intake gaskets on these 61x intakes to be a different animal, there are one or two little alignment pins pointing on an angle toward the cylinders. If the gasket catches a pin upon install it will tear or oblong that hole and cause an air leak. It is also very very easy for the gasket to fold over at the outer edge too during install and be missed...ask me how I know lol. No amount of carb modification will correct an air leak.

 

[augustaf]

Back in the day, when 61x/61x ruled, I was not smart enough to get the stock 44 to work with the usual mods. Solved that problem by using a 46mm. I recall using 127.5 pilot 'cause the 125 was not large enough.

 

[yamanube]

Have you tried going down on the main?

 

[WB1994]

Ive set up many B piped 61x's with 44sbn's and never had an issue.

 

[Pro-pulsion]

Back in the day, when 61x/61x ruled, I was not smart enough to get the stock 44 to work with the usual mods. Solved that problem by using a 46mm

Heyyyyy....you tryin to say sumtin ere?

 

[Chris Pausch]

Random question but is your gas tank vented?

Tank has a check valve on it, and yes in the right way lol

 

[Chris Pausch]

What's the condition of your throttle butterfly and shaft seals?
I also have never had any luck with 120 pilots on single 44 ported 61x cylinders. I've always used either a 125 or a 127.5

Sent from my SM-G920V using Tapatalk

Butterfly looks fine. Are you talking about the seals on the shaft the butterfly connects to? I will have to check those.

 

[Chris Pausch]

If there was an air leak at all, even a small one, wouldn't it have a hard time running at idle and not reving up. It starts and idles fine.

So it sounds like you guys think I need to try some different jets, I'm gonna have to order some. I will get a 127.5, any others I should order while I'm at it?

 

[WB1994]

120 pilot and 147.5 main is correct. 145 main is what factory pipe recomends. It looks like your popoff is too high. He told you to use a 95 gram spring which is what factory pipe recomends but your running one screen. Drop your popoff.

 

[Pro-pulsion]

The Blaster I worked on was fine during idle, perhaps there wasn't enough demand to force it to leak? Either way I only noticed that it was running strangely at 2/3 to full open. I at first thought reeds, I pulled the carb off and the started my way in toward the reeds when I noticed the gasket was the problem. Changed it out and reinstalled the 44, tested and it was ok but the Buckshot was certainly better so I opted that he stay with that. He said it came with it on there when he bought it, when it started acting up he figured the carb was the problem as the Buckshots do have a reputation for being dirty to tune and keep tuned sometimes so he tossed on the 44. The entire time the primary issue was the coil that went faulty.

 

[yamanube]

I'd give a 145 main a shot, I'm running the same setup and it runs very well with the Factory Pipe recommended jetting.

 

[kevbo]

Too much pump load will do the same thing.

 

[Chris Pausch]

Too much pump load will do the same thing.

Can you explain that a little more? I have a 144 solas mag with a new 9/15 hooker.

 

[Chris Pausch]

120 pilot and 147.5 main is correct. 145 main is what factory pipe recomends. It looks like your popoff is too high. He told you to use a 95 gram spring which is what factory pipe recomends but your running one screen. Drop your popoff.

When I rebuilt my carb the kit came with 4 springs. One (the biggest one) appeared to be the same size as the 95 I ordered. Then there was one a little smaller, and another a little smaller, the last one I had looked to be the same size as the other smallest one I have. I have tried every size I have. Which I think is two sizes down from the 95. The first drop down got better but the second didn't do anything.
What do you think the pressure should be roughly. I'm thinking about making a tester out of a bike pump.

 

[WB1994]

The only thing i can tell you is to get a tester and figure out what the preasure was when you started (origional spring) and work your way down. Its going to be a combination of popoff and pilot.

I made a popoff tester you can plug into the compressor. Got the 30psi guage for cheap off ebay and any regulator will work. I can creap the psi up real slow if wanted and hold preasure wherever you want.

 

[Chris Pausch]

So I made a makeshift tester and I'm getting almost 30 psi with my 95g spring. The other two are about 23 psi and 18 psi. I put a new 1.5 needle and seat in when I rebuilt the carb. it pops off clean then leaks down a few psi before it seals back up. Is this normal? Any idea where the pop off should be.