SX/SXi/SXi Pro No power on take off.... NEED HELP!!

[Abbott]

Ok so I need some help!! The ski runs alright and seems to have alright power at the top end speed but has nothing out of the hole. It also doesn’t seem to matter how I adjust the carb I still cant get that snap that it should have as soon as you punch it. Here is where I am so far. I bought the motor and rebuilt it myself had it to have it board out to 1mm over and she seemed to go together just fine. First time in the water she over heated real bad and water was boiling off the head. I got her home and ripped the head off cylinders and pistons seemed just fine so I replaced the head gasket and fired her up. This is where it started to get wild. Almost as soon as I fired her up she took off like a bat out of hell I pulled the tether immediately still kept running at what sounded full rmp. I then pulled the plugs and even with the plugs off it was STILL running at full rpm’s I then stabed the throttle and it chocked itself out. So after this happen I completely took the motor apart and replaced every gasket and even the crank seals! Put her back together and she fired up and seemed to run smoothly. Took her out to the lake and that’s when I was finally able to ride with out any over heating but still has nothing out of the hole almost even hard to get on plane but once on plane and at some speed she will start to take off but I know there is still more top end in her. I ran two tanks of gas through her tuning the carbs a quarter turn at a time and never got any improvement. Never took off on me tho in the water and never had a miss or anything like that. Once I took her out of the water I fired her up to clear out all the water and it once again took off and the kill switch did nothing had to cover the exhaust to choke it out. Anyone ever have anything like this happen or know what it may be???

I pulled the water box out to make sure it was clear and there was a little water in it but not enough that I would think to cause such bad lower end performance. All I can think is that maybe the reeds are bad or the case somewhere has a hairline crack in it??? Any help would be greatly appreciated.

I know that there are some ski guru’s on this site and I would be more then willing to talk on the phone to explain everything in more detail if that would help if anyone can help or has some time reply or send me a pm.

THANKS!!
Andrew Abbott

 

[MikeyB]

We are at a total loss with this thing, the only thing we have come up with is to check out the reeds and reed gaskets. It definitely seems like it has an air leak. He did a compression test last night and has 170psi in both holes. Leak-down test is going to happen next.

When he dropped it in the water over the weekend it was wayyy down on power. Fires up fine, runs smooth, but is just really boggy. Pulled the plugs and they look grey...not black, not white, not brown, but gray. Any ideas would be greatly appreciated.

 

[Sgtlange]

I think a Leak down test is definitely required if you think there is a possible air leak. Also how does the impeller look? Is it cavitating at all? Everytime i've herd of air leaks it usually ment crank seals, but since you replaced those I would be at a loss. Do the leak down and report back to see what your findings are.

Good Luck!
Mitten love.

 

[PWCSAR]

I would be at the leak down stage also, have you re-built the carb/carbs and changed lines etc??? I do recall someone recently who had a pinched throttle cable that was causing a wfo on fire up, but that wouldn't jive with the no low end??

 

[98SXIPRO]

carbs could need a rebuilding... when i first got mine, it was a real dog on the low end, rebuild the carbs and it cleaned it up a bit... i think the stretched out diaphrams in the carbs wernt supplying enough gas to it at low rpm

 

[TigerHWT]

thats exactly what the problem with mine was, i let the ski sit all winter and water was in the carb without knowing and had to rebuild it many times and then finally ordered a carb rebuild kit best 60 dollars spent runs like a bat outa hell now

 

[MikeyB]

He did rebuild the carb, and fresh lines. We did notice that he has a different style ebox in it that has an msd enhancer, maybe something is up there.

 

[Mark44]

Air leak for sure.

Mark4

 

[MikeyB]

We can definitely confirm that it is experiencing detonation. From what I have gathered this occurs when the air/fuel charge is unstable enough to ignite just from a hot spot on the piston; factors that can increase detonation risk are too much timing advancement, too low of fuel octane, too much compression, too lean (air leak?), or improper squish clearance.

I believe he is at +1mm over-bore and I'm wondering how the squish clearance has been affected (and relationship to head domes)?

Here is a summary of where he is at right now: stock timing (no enhancer), 93 octane, 170psi, new lines, rebuilt carb, new head/base gaskets, new crank seals, new carb/reed gaskets, new exhaust gaskets (all new gaskets!!! fresh bore/pistons!)....and the motor tries to run away every time it is started. Pending leak-down test and squish measurement..

 

[Abbott]

I did a leak down test and it seemed to go pretty well. The only thing really left to check would be the crank. I checked to see if the crank is twisted at all and it seems that it may be off by a degree or two but its pretty hard to tell for sure with the crank still in the motor. My uncle runs a crankshaft business and has a fixture to drop the crank in and to quickly see if it is twisted or not. So that is where i am right now and hopefully I will have an answer on the crank here in the next couple days. If it is i am going to have him realign it and weld the pins.

 

[Ron]

I did a leak down test and it seemed to go pretty well. The only thing really left to check would be the crank. I checked to see if the crank is twisted at all and it seems that it may be off by a degree or two but its pretty hard to tell for sure with the crank still in the motor. My uncle runs a crankshaft business and has a fixture to drop the crank in and to quickly see if it is twisted or not. So that is where i am right now and hopefully I will have an answer on the crank here in the next couple days. If it is i am going to have him realign it and weld the pins.

How bad does it bog when you take off? Can you barley get up on plain?? Think a bearing in the pump is bad and dragging down the motor??? just a thought. Keep us posted.

 

[Abbott]

I dont think it has to do with he pump because the ski ran great before the kid i bought it from blew the motor up. The pump and everything is the same only thing different is the motor.

I do have a question about the timing mark on the flywheel.. I set up a Dial indicator to find tdc of one piston spun the crank 180 to check and make sure the pistons are 180 apart and they seemed to still be 180 apart. The question that I have and i though was a little weird was that then i had the piston closest to the fly wheel at tdc the timing mark on the fly wheel was not at tdc it was maybe 10-15 degrees off??

I also double checked the jets and i have a 150 and 115 forgot to double check the needle and seat but i know the spring is a silver spring.

 

[Ron]

Mine had a slight bog, like a rich blubber. I fixed it yesterday. my low speed screws were 1 to 1.5 turns out. I put them both at .5 turns out and it is much smoother and responsive.

 

[Abbott]

Do you know what jets and needle and seat you have in your carb??

 

[Ron]

As far as I know its stock, i pulled them apart, one said 72 the other 40 I believe. .. . .. . I do not know if that is correct. It has the dual 38 keihns.

 

[Hagan]

If its a timing issue maybe the crank key broke? Thats what happened to me anyway.

 

[Abbott]

I do not think it is a timing issue i believe i just need to play around with the jets. I think that high speed jet i have in it right now it to high (150) i am going to try jumping down to a 145 then maybe a 140 to start and then go from there. I plan on also getting a smaller low speed jet also right now it is a 115 and i am going to try a 110 or 100 and then fine tune from there