Help! Ski won't run right

I rode it Friday and went to ride today and it has like half the power of normal. It gets on plane but not much more thenthat. It's also knocking and dies after a few seconds of idling. The only marina around here doesn't sell bus plugs so I dont know what to do. I'm so pissed too. This was supposed to be my last big day of riding before I start cutting back because of the weather and school
 
Do a compression test before you start tearing it down to determine if your internals are good. If its knocking thats not a good sign. My fx1s lower rod bearing come apart and pieces of bearings passed into my topend and killed 1 cylinder. Hopefully yours didnt do this. Dont run it more than you have to cause if its a rod bearing knocking it can sling a rod through your cases.
 
Do a compression test before you start tearing it down to determine if your internals are good. If its knocking thats not a good sign. My fx1s lower rod bearing come apart and pieces of bearings passed into my topend and killed 1 cylinder. Hopefully yours didnt do this. Dont run it more than you have to cause if its a rod bearing knocking it can sling a rod through your cases.


Better description of symptoms:
Knocking at low rpm. an inconsistent knock.
Barely has enough power to get on plane but it will hold the same amount of power.
Revs much better our of the water
different exhaust note then normal

Its not a consistent knock though, its only at light throttle. Most my tools including the compression tester were at my house and not the lake house so i couldnt do much. Unfortunately i rode it for maybe 15 minutes trying to see what was going on. Here a pic of the plugs, maybe it will give you a better idea of what is up

iphone pics:
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Its frustrating not knowing what im doing... Im not very mechanically inclined but i dont mind wrenching. I just need ideas as what i could check.

On a side note i rode sportfish258's RN with a 951 stroker and man that thing ripped. He said he hasnt completely got it dialed in and i struggled to hold on! I only rode maybe a minute or two but i ws very impressed with the power, also thats the first time ive ridden an RN
 
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If your exhaust sounds funny it could be exhaust is loose. Better hope for that. Open the hood and start it, does smoke come out of the ski? Have you checked your spark? That plug being black and wet doesnt look good. Could've dropped compression on that side for whatever reason. Before you tear into it or anything do a compression test, your looking for somewhat even numbers. If that cylinder with the black plug is low your looking at a rebuild.
 
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would the exhaust being loose affect my performance that much? I did notice both of the gas tank straps were loose so maybe something came undone behind the tank.

So if i check the compression and its even then its a problem that shouldnt require a rebuild? If one cylinder is low ill need to rebuild it though?

As far as a rebuild, how much will that cost me and what will i be replacing? Since ill already be buying parts to fix it is there much i can do to make some more power without breaking the bank? like if i need new cylinders can i buy them already ported or something?

and how do i check the reeds?
 
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An exhaust leak can KILL your peformance. My conversion skis exhaust coupler ripped one time and it would fill the motor comartment with smoke, the smoke suffocates the motor and it cannot run properly unless you remove your hood to allow ventilation.

If your compression is close to even then you wont have to buy a top end, my sn has 1 cyl thats 15 psi off of the other one and it still runs fine its when its like a big difference that its not good and your motor will not run right. But if you have a knock my guess is its your crankshaft, it can be main bearings or rod bearings.

Depending on what pistons you go with the cheapest you can get by on a top end job is $260-$300 including boring. Some curse cheap wsm pistons but I may try some as im not running race gas or stupid power. I picked up a used crank on fleabay for $100 and got a flywheel too in the deal, but used cranks can be a gamble, you might get it in and find out its crap, this has happened to me b4. Otherwise sbt has rebuilt ones for around $200.

You can buy ported cylinders off here pretty reasonable. I just ported my own, I studied Matt Es home porting thread, great info.

When checking reeds look for any chips, hold them up in the light and see if theres light coming through where the reeds should be sealing and make sure the outer metal part isnt bent. Reeds can loose their tension over time and make a motor run crappy off idle.

would the exhaust being loose affect my performance that much? I did notice both of the gas tank straps were loose so maybe something came undone behind the tank.

So if i check the compression and its even then its a problem that shouldnt require a rebuild? If one cylinder is low ill need to rebuild it though?

As far as a rebuild, how much will that cost me and what will i be replacing? Since ill already be buying parts to fix it is there much i can do to make some more power without breaking the bank? like if i need new cylinders can i buy them already ported or something?

and how do i check the reeds?
 
An exhaust leak can KILL your peformance. My conversion skis exhaust coupler ripped one time and it would fill the motor comartment with smoke, the smoke suffocates the motor and it cannot run properly unless you remove your hood to allow ventilation.

If your compression is close to even then you wont have to buy a top end, my sn has 1 cyl thats 15 psi off of the other one and it still runs fine its when its like a big difference that its not good and your motor will not run right. But if you have a knock my guess is its your crankshaft, it can be main bearings or rod bearings.

Depending on what pistons you go with the cheapest you can get by on a top end job is $260-$300 including boring. Some curse cheap wsm pistons but I may try some as im not running race gas or stupid power. I picked up a used crank on fleabay for $100 and got a flywheel too in the deal, but used cranks can be a gamble, you might get it in and find out its crap, this has happened to me b4. Otherwise sbt has rebuilt ones for around $200.

You can buy ported cylinders off here pretty reasonable. I just ported my own, I studied Matt Es home porting thread, great info.

When checking reeds look for any chips, hold them up in the light and see if theres light coming through where the reeds should be sealing and make sure the outer metal part isnt bent. Reeds can loose their tension over time and make a motor run crappy off idle.

Hmm, the more i think about it the more i think it may be an exhaust leak. I started it 1/2 way out of the water but without the hood and it revved fine it seemed but i wasnt really paying attention. Also since the tank straps were loose maybe the water box came loose too. I think my dad is heading to the lake tommorrow so he can check the compression for me. If its good then ill pull the tank next time i make it to the lake. If the compression is low i suppose ill take the ski home so i can figure it out here

thanks for the help, ill update the thread when i find out whats up since you guys know so much more then me.
 
My dad went to the lake and checked the compression and it's right at 150 both cylinders so tomorrow I'll head to the lake and check out the water bow for a leak. Hopefully I can find a set of clean plugs at the auto parts store
 
check your exh hoses for rubs or holes too

Will do. Im just happy the compression is good. Im betting its something behind my tank. Im not sure how but both tanks straps were loose so who knows what happened behind the tank.
Hopefully i can stop at advanced auto parts after school get some new plugs, fix what ever is wrong and ride some!
 

snowxr

V watch your daughters V
Location
Waterford, MI
I think the obvious has been overlooked. NEW SPARK PLUGS. I'd say that black oil covered plug could be fouled. By the looks of that rust you haven't changed the plugs in a long time.
 
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