951 XPL Tuning issues

[skeletor88]

I have a 2000 XPL that, no matter what I do, I cannot get to run properly. Please bear with me.

Ski has been sitting for about 2 years (was fogged and run on the hose every few months then re-fogged).

Took it out for a run and it ran like a pig - barely able to get above idle. So I decided to rebuild the carbs (which I have done before without issues), but this time I changed the springs (and no I did not check the pop off pressure before doing this. Yes, I'm an idiot!!)

Anyway, after mutliple jet changes, needle and seat changes and different pop off pressures, I continuously had the issue of the ski running fine up to about 4000rpm but then it would die completely as though it had run out of fuel.

So, I pulled the fuel pickup (in the fuel tank) apart and cleaned it, cleaned the fuel filter, replaced the fuel lines (no its not connected to the fuel selector) and rebuilt the carbs again using the following;
The accelerator pump was disconnected years ago and I am at sea level so the setup is to suit this.
Low speed screws - 1.5 tuns out
Lows - 100
Highs - 165
N/S - 2.0
Pop Off - 21 psi with a 95G spring
High speed screws - closed

Problem is now the thing is really hard to start, idles for a second or two and then the engine runs away, requiring me to pull the chokes to stop it. Sounds lean to me. But have no idea how to fix it.

I know that tuning is an art - and I clearly have no talent in this area and I have run out of patience. I have 2 stock XPL's (both now have tuning issues) and a twin piper in bits. Please help an old fool as the pwc mechanics over here will not touch 2 strokes and the local guru is, well, on another planet nowadays. I have nowhere to turn and, despite the push to upgrade, struggle at finding a ski that is as much fun as these, especially in the surf.

[Myself]

Stock flame arrestor? Accelerator pump working? Low speed jets should only need to be 85-90......and that's with the acc pump disabled. Pull carbs again. Start with flashlight and mirror and check the reeds. Also check that the RAVE line with check valve is OK, and the pulse hose is OK.

[Pacer]

Double check your fuel pump. Make sure that you don’t have a pin hole in one of the rubbers, or the check valves. Check your pulse line from the motor and make sure you don’t have and air leak. Hard to start and then running away is lean, lack of fuel, low fuel pressure. Make sure the arm that opens the needle is level with the valve body. New diaphragms? Ethanol fuel can make them stiff and they won’t fully open the needle.

[GPR Ace]

If you have flame arrestors and no accelerator pump, try 95 lows and instead of 95g springs try the black 80g springs.

[skeletor88]

Thank you everyone for your input. I found the issue - I had somehow pinched the large O-ring on the Mag carby. so the hard starting and engine run away is now sorted. However, am now having the issue where the engine runs perfectly at idle and just off idle. If you let it idle for, say 10 seconds, then jam the throttle wide open, the engine quickly climbs perfectly to 7000 rpm.

However, if I slowly accelerate to 4000rpm (I am assuming just over Qtr throttle), and try and keep it there, the revs will quickly die until the engine stalls. Sounds like a lean condition to me.

Would changing to an 80G spring and lowering the pop off to about 18psi affect this?

[SURFnTURF]

You need to have it running with no air leaks before any tuning is done
If your running free flowing air filters,no pumps
95 lows 1.5 turns open ,165 highs closed
2.0 N/S with Black spring
with pumps 90 lows open 1.5 turns,165 highs closed
Pop off should be 20-21 psi, the black spring will give you this

Always check the adjustment screw o/rings, they go hard and deform and will lean the engine out

[skeletor88]

SurfnTurf, thats exactly what I am running. Tried the 80G springs and replaced the adjustment o-rings even though they were done when the carbs were rebuilt. Checked the rave valves and reeds. All good. Ski starts and idles perfectly at about 1200rpm in the water. Slight bog upon slow acceleration then accelerates nicely as you open the throttle. At just over 4100rpm the ski starts to die. If I close the choke butterflies a little the engine climbs to 6000rpm without any throttle change. Clearly feels like a lean condition. But how??????? And why FFS??????

I am stumped and to be honest, over it. No one wants to work on two strokes anymore. So, after 20 years I just want to get rid of the damn things now, but cant let them go with this issue.

I have one more question before I set both of the skis on fire. If the needle and seat was open because the rocker arm was set too high, what would that do?

[Myself]

I have in the past chased a midrange/transition bog issue. I looked over everything else and decided it was carb issues......even though the owner rebuilt them already. What I found was the anti-siphon flapper on the back of the jet covers was very stiff. Thicker plastic than the oem. I didn't find anything else suspicious at all. I swapped those out to the thin oem ones and the problem was solved. When that one was experiencing the bog you could pop the choke 1/2 way as you rolled on the throttle and quickly let off the choke and it would open right up to full speed every time. That's when I decided to open the carbs.

[skeletor88]

I have replaced the anti- siphon valves when I rebuilt the carbs. I will pull them down again and replace them again. Can't hurt I guess. Will also have a look at the check valves as I have been told that they have a little bit of green paint (or whatever) on them and the painted side must be up. Don't know how it would make a difference, but will check.

[Mentzel]

sounds like the accelerator pump is not working. The accelerator pump shoots fuel into the carb when accelerating. It is common for the diaphragm to go bad over time. If it is not working ski will idle but die when you hit the throttle. They are jetted very lean for emissions reasons. You can remove accel pump and increase pilot jet size to compensate. Some of the diaphragms are no longer available so that maybe your only option.

The accelerator pump is mounted on side of carb and connected with mechanical linkage. There is no reason to take it apart during carb rebuild unless you suspect a problem.