Another accelerator screwup

[rj45lanman]

Looks like I've fallen victim to the torn orange accelerator pump valve. I barley touched it and it ripped off. So I guess I'm removing the pump and fuel line going to it...

It seems that census on the forum is to change the low-speed jet by 5#'s. Since I have the 951, I believe my stock size is 80 so I'll try going with an 85.

I used to do this work on Holly jets but also drilled them to larger sizes. Has anyone here drilled these out? If so, do you know the bit size?

 

[rj45lanman]

After running to Northern Tool and Harbor freight to purchase a small assortment of drill bits from .5mm to 3.0.
I broke out the micrometer, did some measuring and found the best fit bit.

Measuring .315" which equals 8mm
(Jet size 75 -> 80). So with the accelerator pump disconnected, I'm going to drill my primary jet to .315 inches to bump it up by 5.

I'm going to start with 1.5 turns out on the low speed screw and make sure my pop off pressure is at least 20lbs (currently 18).

Anyone have any recommendations before I button this up?

 

[Venturian1]

After running to Northern Tool and Harbor freight to purchase a small assortment of drill bits from .5mm to 3.0.
I broke out the micrometer, did some measuring and found the best fit bit.

Measuring .315" which equals 8mm
(Jet size 75 -> 80). So with the accelerator pump disconnected, I'm going to drill my primary jet to .315 inches to bump it up by 5.

I'm going to start with 1.5 turns out on the low speed screw and make sure my pop off pressure is at least 20lbs (currently 18).

Anyone have any recommendations before I button this up?

Personally, I wouldn't drill out any jet. If that wasn't the problem, now you have to buy a new one, and hopefully its available.
Deviating from stock, and expecting it to run better, is like assuming you are smarter than the engineers that designed the carb. You should
double check everything else, and don't forget the carb base gasket and rotary valve, & oring. you may have a vacuum leak.

 

[etemplet]

Perhaps you're missing a zero in your number. I don't think you can drill a jet that small and have it work. Better off buying the jet you need and avoiding any mechanically induced issues.

 

[gp1200x]

I would pull acc lines and clean the bores into the throat. At times I have seem mine clogged with a greenish paste from the brass corrosion from sitting. Replace hose lines while at it. I only use thick green carb base gaskets on my 951 and 800 and not the thin gray gaskets. I've had problems with carb heat stroke using cheap thin gaskets but my heads were reworked from stock. The thick green base gaskets with the metal insulation in the center is the way to go but harder to find. I think they are 50mm with the additional alignment holes in them.

 

[Venturian1]

I am curious about this "carb heat stroke" you mentioned, gp1200x, I didn't think these engines got hot enough. My 720's get warm, but not hot. Never saw an operating temperature in any of the manuals. but am very curious what that temp should be!
Maybe your 951 and 800 are different.
Gaskets with metal in them are usually found in automotive exhaust gaskets, no? I have yet to see a Seadoo 2-stroke exhaust gasket with metal in it, not even on the exhaust manifold where it connects to the cylinders.

 

[gp1200x]

I just reinstalled my 951 pipe (removed to get the carbs and reed cover off) and that gasket (I orderd several since I had to redo it) has a thin metal sheet in the center. You can actually see it on the edges too. This is where the infamous water leaks ocurred that could destroy the 951 engine since it is right above the carbs. I don't know in that case if it is to insulate heat or to reinforce the gasket (probably) to keep it together. I always use a red silicone on this gasket on both sides and wait a full day before testing it for water leaks. As far as the carb gaskets are concerned, in the early 2000s I had my top end reworked on both my 800 and 951 and was told which plugs to use for higher temps. I had a few issues were the engines ran wild and I couldn't control the rpms and it didn't appear to be lean carbs. Rebuilder told me to make sure I was using the thick green gaskets on the carb base. Never had the issue again once I changed them so who knows. I also used them on my gp1200 waverunner which also had headwork done. I was told to make sure to use them on that engine but those carbs sit much closer to the actually heads/cylinders. The gp1200 and 951 green gaskets I have are thick and use a center thin metal sheet however my 800 gaskets are thick but missing the metal in the center. May reorder them. Don't know about your 720 but I always use the thicker gaskets just to eliminate any chance of an air leak too at the carb base which could also have caused my rpm issues. I don't install my carbs with only a thin sheet gaskets just to be on the safe side since I don't want another rod through my case. Stock engines probably came with the thin sheet carb base gaskets.

 

[mikidymac]

The exhaust gaskets are reinforced to prevent blowout and should go on dry, not with silicone. If you have damaged mating surfaces then a little ThreeBond 1211 will help seal them. The only exhaust gasket that gets silicone is the copper ring and that uses Ultra Copper RTV.

The green carb gaskets have nothing to do with being reinforced, they are just a softer paper for better sealing and have nothing to do with heat. The best thing to do with them is a very thin coat of ThreeBond 1211 to hold them in place.