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Kevin 89MC
06-06-2011, 02:53 PM
Hey gang. Long time member here, but I haven’t posted in awhile, sadly been way too busy. Got a question about a stall I’m hoping some of the mechanical guru’s on here can help me with. Short story first: it stalls hard in high speed tight corners, but not enough to kill it, as it will keep running and get back up to speed in a second or two. It’s like a series of loud clicks during cornering, almost like a very muted backfire. After it resumes it will run great until the next time I take a hard corner. I think it is a fuel delivery issue, but not sure.

Here is the long story: last fall I foolishly put some questionable gas in when it was almost empty, to get one more slalom set in one evening. It was old lawnmower gas, not sure how old as it wasn’t mine. It ran fine for the last set, but then the next time out it would stumble at most any speed, and would cut out in corners. I figured it needed a carb rebuild, so I got the kit from skidim for my Holley 4160. I had just replaced the fuel filter and water separator 2 years ago, and when I checked them, they looked very clean. The carb rebuild went well, it idled nice in the driveway. First water test it only got to about 37 at WOT, so I thought the secondaries maybe did not open. Second and subsequent runs to WOT all went to 42-43, actually a bit faster than it has run in years. It idles great, and holds all speeds great in a straight line or gentle turns. But in medium to high speed corners, it would cut out.

My thought is there is just barely enough fuel getting delivered to keep the float bowls filled when going straight, but during high speed cornering I am running the bowls dry. As soon as it cuts, speed & angle drop quick, so then the bowls fill up, restoring power. Next I figured I’d check the fuel pickup in the tank and the anti-siphon valve, thinking something got stuck there. I snapped off the anti-siphon valve in the elbow, but fortunately my local Midwest MC had both in stock! Back on the water, and it seems to have helped some. Medium speed tight cornering seems to be better, but high speed cornering still makes it cut.

Because it is such an abrupt cut, I’m thinking it isn’t the fuel filter or mechanical pump. I’m thinking it is not the carb, as it runs good except for a very narrow set of conditions. The floats aren’t really adjustable as far as I could tell, so I’m not sure what there would be to adjust on the carb anyways. I suppose I could just replace the fuel lines and the filter, but I hate to just start replacing things. Anyone have any ideas of what to check next?

Thanks in advance for any help.
Kevin

thatsmrmastercraft
06-06-2011, 05:16 PM
Some random thoughts:
1. Did you replace the floats when you rebuilt your carb?
2. How well did you verify proper float adjustment?
3. Check your coil wire connection and how securely your coil is mounted.
4. Is there enough slack in the coil wire?
5. Points or electronic ignition?

Kevin 89MC
06-07-2011, 10:00 AM
Thanks for the response. To answer your questions:
1. I did not replace the floats, they were not included in the rebuild kit. I did replace the float needle valves. The first time they slid down was not real smooth, but after I moved them up & down a bit they seemed to slide good. Is there a good way to test the floats-or just see if they float in a jar of gas?
2. How do I verify proper float adjustment? I could not find much for instructions. Holley’s website has instructions for checking and adjusting the floats, but most of that seems to apply to the auto carbs with the sight plugs and externally adjustable needles. The new needle valves were the same as the old ones, and the floats seemed to be in the same position with the new ones as with the old ones.
3. Good point about the coil & wires, I will double check all the ignition components.
4. I will make sure there is slack in the coil wire.
5. Boat came with EI when I bought the boat in ’97, When I replaced the plugs a few years ago I checked the cap, rotor,& plug wires, all seemed to be in good condition. However all those components are at least 15 years old, so I should probably do some more testing on that stuff.
Thanks for your suggestions, I will respond back when I check these things out.
Kevin

rjracin240
06-07-2011, 12:32 PM
I am taking a WAG that the fuel float got knocked during rebuild. Have opened up a 4160 that I had received from National Carburettor in order to try and get it to run. So somewhat familiar with it.
Couple of observations that might help diagnose;
Does it matter in what direction you turn to get the motor to lose speed
Not sure if they operate independently of each other......but do you get the same sypmtons if you are running on just primaries or secondaries

Thinking is that if you turn in the direction that the float tab got bent it will cause it to become fuel flow limited. If it does not die in the other direction then this would confirm the tab got inadvertently bent.
If it dies while just the primaries are open in a turn then it would it be safe to say the primary float tab got bent.

Just throwing some thoughts out there to help out!

Good Luck, hope they help.

thatsmrmastercraft
06-07-2011, 12:37 PM
Thanks for the response. To answer your questions:
1. I did not replace the floats, they were not included in the rebuild kit. I did replace the float needle valves. The first time they slid down was not real smooth, but after I moved them up & down a bit they seemed to slide good. Is there a good way to test the floats-or just see if they float in a jar of gas?
2. How do I verify proper float adjustment? I could not find much for instructions. Holley’s website has instructions for checking and adjusting the floats, but most of that seems to apply to the auto carbs with the sight plugs and externally adjustable needles. The new needle valves were the same as the old ones, and the floats seemed to be in the same position with the new ones as with the old ones.
3. Good point about the coil & wires, I will double check all the ignition components.
4. I will make sure there is slack in the coil wire.
5. Boat came with EI when I bought the boat in ’97, When I replaced the plugs a few years ago I checked the cap, rotor,& plug wires, all seemed to be in good condition. However all those components are at least 15 years old, so I should probably do some more testing on that stuff.
Thanks for your suggestions, I will respond back when I check these things out.
Kevin

Start with a new cap and rotor. Not likely your problem, but it will be soon.

thatsmrmastercraft
06-07-2011, 01:18 PM
I am taking a WAG that the fuel float got knocked during rebuild. Have opened up a 4160 that I had received from National Carburettor in order to try and get it to run. So somewhat familiar with it.
Couple of observations that might help diagnose;
Does it matter in what direction you turn to get the motor to lose speed
Not sure if they operate independently of each other......but do you get the same sypmtons if you are running on just primaries or secondaries

Thinking is that if you turn in the direction that the float tab got bent it will cause it to become fuel flow limited. If it does not die in the other direction then this would confirm the tab got inadvertently bent.
If it dies while just the primaries are open in a turn then it would it be safe to say the primary float tab got bent.

Just throwing some thoughts out there to help out!

Good Luck, hope they help.

No doubt there is some racing background there. May just be the secondary float set low.

To check the float adjustment, pull the top off the carb and hold inverted. Float tops should be parallel with the gasket surface of the carb. The needle should move freely in it's travel. Floats should be replaced as this could be your problem. Buy blue reusable gaskets in case you end up taking this apart again. Only buy Holley parts.

1redTA
06-07-2011, 02:31 PM
could the tank be low enough on fuel the pick up is sucking air? maybe the fuel line is getting pinned during turns

thatsmrmastercraft
06-07-2011, 03:39 PM
JimN had mentioned in another thread that some fuel line will delaminate and the inner can collapse and restrict fuel flow. This is another small replacement that doesn't cost much and you won't ever regret doing it.

slushpup
06-07-2011, 09:52 PM
Have you dumped all the old fuel out? Ethanol is the worst thing in the planet for boats and sleds, dump as much fuel as you can, If you have a spin on filter and its new this season,unscrew it dump the fuel thats in it and use it again, If it's last seasons filter replace it.Start off with fresh high test fuel,This will help the octane with any old fuel in the system,Add stabilizer (Startron is my favorite it's got enzymes) also check your pump pressure,I have seen fuel pumps do odd things in a turn ,I think it will limp along providing just enough fuel to run but in a turn it starves the carb. IMO its a fuel problem pull the doghouse and have a passenger verify that the secondaries are opening, 4160's are a great carb till they screw up. If all else fails pull it apart again and check for a chunk of crud that has shown up since it's re-build.

Kevin 89MC
06-10-2011, 11:01 PM
Problem solved! Turns out it was the fuel filter (or water-fuel separator, I replaced them both). Figured I'd stay with the simple (and relatively inexpensive) stuff first, actually I should have done that before diving into the anti-siphon. I had just replaced both of them 2 years ago, the filters in to that point were from at least 1996, possibly original, got a lot of life out of them. I had checked them earlier and they looked pretty clean, but with that bad gas I put in, it makes sense that the filters held onto a bunch of stuff, but still letting some through to the carb.
Thanks for everyone's suggestions. The boat ran great, except for a new hopefully minor overheating problem. I'll research that first and start a new thread if needed.
Kevin

woobiedmd
06-11-2011, 09:25 AM
Glad it worked out. I have a '88 Prostar(same engine) and am having similar problems. I am still waiting for a rebuilt caarb from National. I replaced the racor filter in the fuel/water separator. You mention a second fuel filter. Where is it located? I have only changed one filter ever, could be part of my problem. Thanks!

northof52
06-11-2011, 10:41 AM
.....i'm having similiar stuff with my '90 prostar......stall during a hard turnaround (sputters) then kicks back in like no problem......

slushpup
06-11-2011, 12:16 PM
Problem solved! Turns out it was the fuel filter (or water-fuel separator, I replaced them both). Figured I'd stay with the simple (and relatively inexpensive) stuff first, actually I should have done that before diving into the anti-siphon. I had just replaced both of them 2 years ago, the filters in to that point were from at least 1996, possibly original, got a lot of life out of them. I had checked them earlier and they looked pretty clean, but with that bad gas I put in, it makes sense that the filters held onto a bunch of stuff, but still letting some through to the carb.
Thanks for everyone's suggestions. The boat ran great, except for a new hopefully minor overheating problem. I'll research that first and start a new thread if needed.
Kevin

Those spin on filters are way better than the old Raycor paper ones.That and the EI upgrade are almost required on the older boats.

Kevin 89MC
06-12-2011, 09:48 PM
Yep, that was my symptom. The other filter is right below the mechanical fuel pump, port side on engine, toward the front. You will see the flex fuel line going in, then the hard fuel line up to the carb. There is a screw on the bottom of the filter canister that keeps tension on a strap bracket which holds the filter canister up to the bottom of the pump. This filter is the cheap one, about $10 at ski dim or your local MC dealer. The one on the bilge starboard side is about $30. Yeah EI is a huge upgrade, mainly from a maintenance standpoint.
Good luck to you both, gotta love this board!
Kevin