HX Carb Headaches

[Shane0306]

Hi guys, so i picked up a HX about 9 months ago, the kid i brought it off said the carbs needed attention, they did, the N/S were leaking in both carbs.

I brought a rebuild kit throught either SBT or WSM fixed and cleaned them up, set everything to factory settings including pop off.

Meanwhile i went over the engine, it was obvious it didnt have many hours on it, the ski looks brand new, bilge, engine/exhaust paint everything. I did a top end rebuild and went over everything anyways.

After that was done i put a good 15 hours on it, it was running well but the carbs were not ideal (running really rich) giving me a slow ramp up from idle to WOT
As it was too rich, i didnt worry too much as i knew i was doing mods before dialing it in.

I have just installed a maxiloader intake grate, skat trak 14.5/22.5, ADA high comp head 36cc domes (170psi in the jugs)
Stock exhaust pipe and carbs, stock F/A’s but i did remove some screens in accorance with a write up from group K

I took it out for a ride last weekend in hopes to tune it trying to follow the mikuni manual
I just want a reliable tune, with a crisp throttle i also spend alot of time wot so i know staggering the jetting is a good idea.
It still seems very rich im not getting the performance i know i should be getting, super boggy, black sooty plugs... surely i dont have go lower jet size than stock?? I was expecting to go UP jet sizes?

Any thoughts? Cheers.

 

[mikidymac]

Your problem is the aftermarket carb kits. Get rid of the junk and replace with genuine mikuni kits and needle and seats.

 

[Nemisis]

Also check that oil pump alignment marks are correct.

 

[Shane0306]

Nemisis good suggestion although oil pump was calibrated with rebuild i will check up on it again.

Mikidymac, i cant find a genuine mikuni 1.2 size needle and seat online at mikunioz, they have every other size though, i will call them tomorrow to confirm, the seadoo oem parts finder states its a Pointeau brand N/S???

I can change to a 1.5 N/S but i have no idea what i will have to do in terms of changing jets and pop off.
Im also interesting in adding an accelerator pump once this is all worked out, i see you were writing about it in another post.

 

[mikidymac]

You can get them on amazon for $15, Mikuni Needle and Seat Valves - 1.2 786-35018-1.2.

Also there is no reason to add accelerator pumps.

 

[dieselndoo]

Put the original spring back in. If the oem diaphram is still "soft", reuse it. If your using the diaphram that doesnt have the red nipple to it, then bend the needle arm down some. Little lower than carb inner plate. Use a razor blade to confirm. Use original seat and install new oring. Set l/s screw to 1 turn out, h/s screw to 0

 

[Shane0306]

I ordered rang Mikuni, they said anything other than genuine mikuni is rubbish, i ordered 2 rebuild kits, 2 N/S and 2 springs (i think 80 gram)

They also said on a 38mm carb theres no need for accel pumps, if its dialed in its dialed in i guess?

 

[mikidymac]

Yes, the stock carbs work just fine without accelerator pumps.

It's not just the o-rings that go bad on the needle and seats as the tip will wear and deform over time and leak or stick so they do need to be replaced. Also just bending the arm to get the aftermarket diaphragms not to leak is not the correct fix and will just bandaid the problem with them being too stiff.

Do it correctly or not at all.

 

[dieselndoo]

A/M diaphram peg is longer than the oem, hence bending the arm

 

[mikidymac]

A/M diaphram peg is longer than the oem, hence bending the arm

I realize that but it is also the fact that most of them are made of stiffer rubber that can mess with the proper function and fuel flow also. It's not just the tab that sticks out that is the problem is what I am trying to say.

 

[Shane0306]

So after a carb rebuild with mikuni parts, it all went back together nicely, i can tell the difference its much snappier, but its still loading up which i have just realised is due to the oil injection, its in calibration but it just seems to be pumping too much in? If i rev it in the driveway i can’t see the cars parked behind it.

Either i have done something wrong or there is an issue with the injection pump, does anything know of anything that needs to be replaced every now and then regarding the injection pump

 

[mikidymac]

THere is nothing to replace on the pump but you should replace the small 3/32" oil lines from the pump to the intake.

Make sure the alignment marks are aligned when the idle is set and the engine is off.

What oil are you using?

If everything is correct it is probably a leaking crank or rotary shaft seal causing your over oiling and not the pump.

 

[Shane0306]

I will change the lines, i’ll add it to the to-do list.

The alignment marks are sweet, the idle is set to 1500rpm in water / 3000 out or water as per manual.

Using the yellow bottle XPS synthetic oil.

Ahhhhh, yeah that would make sense wouldnt it, i just had the bloody engine out too, thats about the only thing i didnt check, i might do a bottom end pressure test and see what comes of it, thanks.