FX-1 Vibrates with RPM increase

[NSRSSR]

Hi guys,

I have an FX-1 with a 650 engine in it (bought second hand with the smaller motor but has been running fine for 4 years now).

This past weekend, the ski has a vibration that comes on as the prop picks up speed - I say prop picks up speed as the vibration is there whether the ski is going fast, or if I am pinning the throttle while coming out of a 180* turn or want to quickly pick up speed on the ski itself.

I haven't had the ski apart yet, and a couple local guys have mentioned either a bent/chipped prop, bent driveshaft, or pump bearings are on their way out.

Ski seems to run fine at lower RPM (idle, putting around) but when throttle is at 60% or more, the vibration can be felt by my feet through the tray, and in the throttle lever on the handlebars.

I'm comfortable wrenching on the ski but just wondering what the easiest things are to check first, before I dive into removing the ride plate and investigate the pump. Also - can I top the ski on its side, or will gas come running out of everywhere? All the work I've done on the ski so far has been when it is sitting in its upright position...

 

[Sanoman]

Hi guys,

I have an FX-1 with a 650 engine in it (bought second hand with the smaller motor but has been running fine for 4 years now).

This past weekend, the ski has a vibration that comes on as the prop picks up speed - I say prop picks up speed as the vibration is there whether the ski is going fast, or if I am pinning the throttle while coming out of a 180* turn or want to quickly pick up speed on the ski itself.

I haven't had the ski apart yet, and a couple local guys have mentioned either a bent/chipped prop, bent driveshaft, or pump bearings are on their way out.

Ski seems to run fine at lower RPM (idle, putting around) but when throttle is at 60% or more, the vibration can be felt by my feet through the tray, and in the throttle lever on the handlebars.

I'm comfortable wrenching on the ski but just wondering what the easiest things are to check first, before I dive into removing the ride plate and investigate the pump. Also - can I top the ski on its side, or will gas come running out of everywhere? All the work I've done on the ski so far has been when it is sitting in its upright position...

Sounds like you already know what to do..So what is stopping you?
Empty the gas tank.Get the ski on its side,carb(s) side up.Remove the ride plate and then the pump.Look at the prop and driveshaft to see if there is damage.Everything you remove will not require any new parts.Thats the best advise l think anyone can give you.The only real way you can figure out what your issue is...It’s tuesday,Get busy!

 

[streetroc]

If the motor mounts were loose or worn the engine may have shifted in the mounts and thrown off the alignment with the midshaft coupler. I've heard that can cause a lot of vibration. Have you had any really hard jumps or falls lately?

 

[NSRSSR]

If the motor mounts were loose or worn the engine may have shifted in the mounts and thrown off the alignment with the midshaft coupler. I've heard that can cause a lot of vibration. Have you had any really hard jumps or falls lately?

No real hard jumps or falls on flat water - there are a couple surf boats at the lake I ride at, but so far the landings have been pretty smooth.
As my confidence grows on the ski, the amount of time spent at 3/4-WOT has increased - alot less feathering/putting around and more throttling out of corners, u turns, etc.

 

[streetroc]

No real hard jumps or falls on flat water - there are a couple surf boats at the lake I ride at, but so far the landings have been pretty smooth.
As my confidence grows on the ski, the amount of time spent at 3/4-WOT has increased - alot less feathering/putting around and more throttling out of corners, u turns, etc.

Have you already checked the prop and drive shaft for damage?

 

[NSRSSR]

Have you already checked the prop and drive shaft for damage?

No damage on the prop or driveshaft this weekend.
What I did find though, is that the entire motor rocks back and forth inside the hull. There’s probably 1” or so of deflection I can create if I push on the side of the motor east and west.
Exhaust pipe clearance to the side of the engine bay hull is easily 1”, but the stock spark arrestor is rubbing on the hull.
I’m thinking motor mounts? The ones in this ski look like they are OEM, but before I take the engine out to replace the mounts, is there anything else a guy should check before hand?

 

[streetroc]

No damage on the prop or driveshaft this weekend.
What I did find though, is that the entire motor rocks back and forth inside the hull. There’s probably 1” or so of deflection I can create if I push on the side of the motor east and west.
Exhaust pipe clearance to the side of the engine bay hull is easily 1”, but the stock spark arrestor is rubbing on the hull.
I’m thinking motor mounts? The ones in this ski look like they are OEM, but before I take the engine out to replace the mounts, is there anything else a guy should check before hand?

Stop riding it immediately before you destroy the bearings in the coupler and mid-shaft. You most likely need new motor mounts and if it is rocking back and forth that much you have probably broken something completely. You should be able to tell once you get it all apart. The engine has to come out so go ahead and start disconnecting the cables and wiring harnesses. It's not too bad to pull an engine, you can do it in an afternoon. While you're at it this would be a great time to get to the correct 701 61x motor and ditch the 650.

Keep in mind that the alignment of the engine to the mid shaft coupler is measured in fractions of a millimeter and it has to be very precise. Make note of any shims in the motor mounts when you pull the engine so that you can put them back on the correct mounts. You'll need to get a shim gauge to reinstall the engine and align it properly. You can get one for about $5 at an auto parts store and it isn't hard to do but it is time consuming. Plan on an hour or two of tightening motor mounts checking clearances and then redoing it over and over again until you get it right. There is a 10min video on YouTube of the correct way to align an engine.

 

[E350]

streetroc is 100% correct.

FYI, I am old and weak with torn up shoulders and biceps tendons from years of whitewater kayaking so I found this device to be especially helpful when removing and replacing a complete engine all at once.

https://harborfreight.com/1-ton-capacity-foldable-shop-crane-61858.html

(I bought the 2-ton version because I may have to pull the 7.3 PSD out of the van, but the 1-ton is more than sufficient for a jet ski engine.)

The engine has a hoist ring on top, so the hoist is pretty straightforward to use. (Although, I have no idea how you could actually pick cherries with it.)

You can also remove an engine in pieces manifold by manifold if you prefer. But for a swap, the hoist is best.

 

[streetroc]

I have done it both ways and pulling a complete engine with the manifolds still attached is definitely easier. You can do it with or without a hoist, that is up to you. I don't think it's particularly hard to pull it by hand but I lift weights regularly and I'm in pretty decent shape. I'd say a complete engine only weighs about 50-60lbs, maybe even less than that. I just straddled the engine bay and grabbed it by the intake and exhaust manifolds and lifted it out. Just make sure that you unbolt the the e box from the firewall and disconnect the cooling lines that go to the underside of the exhaust manifold.

 

[NSRSSR]

Update: a whole wack of stuff was wrong.

When I bought this ski, the guy I bought it from had swapped in a spare 650 motor he had kicking around as I couldn't afford his built 701. Turns out he had used different length bolts, some were missing, others had stripped the cast bolt holes on the motor bed plates, basically everything that had been installed had rattled loose. The motor mounts were tight, but the bolts holding the motor to the bed plates were not.

I took this opportunity to find a known good 701, and a coffman pipe and MSD enhancer to swap in. Thanks everybody for the replies!

 

[Stavissimo]

Nice, this happened to me once but turned out to be an annihilated midshaft due to the idiot that put my motor in without aligning properly.

 

[NSRSSR]

Nice, this happened to me once but turned out to be an annihilated midshaft due to the idiot that put my motor in without aligning properly.

This is sorta off-topic now, but I am preparing to put the motor back in. Did you use a set of feel-er guages to figure out the shim thickness you needed when reinstalling your motor?

 

[Stavissimo]

Used the alignment tool from cold fusion I believe and as for the shims I had to start from scratch because the asshole who installed put too many. watched a few videos on somewhere on YouTube

 

[DrewOregonian]

This is sorta off-topic now, but I am preparing to put the motor back in. Did you use a set of feel-er guages to figure out the shim thickness you needed when reinstalling your motor?

Get a cold fusion alignment tool to verify your driveshaft is aligned properly before installing your engine. Should also verify the depth of your driveshaft into your engine bay. You can see where it should be on my build. FX1 Tom21 build.

For alignment of your mid-shaft coupler to engine coupler you’ll want to use a straight edge to make sure they are aligned properly. Shim engine accordingly.

You can buy the tool from @JetManiac

 

[NSRSSR]

Sorry, I should have added more detail - I borrowed a friend's Cold Fusion alignment tool and confirmed the driveshaft is aligned properly. Midshaft housing has been installed and sealed to hull.

@DrewOregonian - when using the straight edge, are we talking straight across between engine coupler to midshaft coupler, without the rubber bushing installed between the two?

I know I will need to purchase shims, but at $10+ a shim, non-returnable and a week+ shipping away from my local Yamaha dealer, I'd like to only have to order once!

 

[DrewOregonian]

Sorry, I should have added more detail - I borrowed a friend's Cold Fusion alignment tool and confirmed the driveshaft is aligned properly. Midshaft housing has been installed and sealed to hull.

@DrewOregonian - when using the straight edge, are we talking straight across between engine coupler to midshaft coupler, without the rubber bushing installed between the two?

Yes. You just want them square/inline/centered with each other.
This is done without the rubber dampener first. Once you know you’re shimmed properly. You install dampener and shims in correct place.

You also one both joint relatively close. To each other so you have proper load bearing on the coupler itself.

Below are my aligned ada couplers.

You can also get your shims from @JetManiac
I wouldn’t buy poop from a Yamaha dealer. Maniac will ship faster and have more knowledge on everything you need.

I know I will need to purchase shims, but at $10+ a shim, non-returnable and a week+ shipping away from my local Yamaha dealer, I'd like to only have to order once!

 

[NSRSSR]

You also one both joint relatively close. To each other so you have proper load bearing on the coupler itself.

What do you mean? ^^


How do these pictures look for coupler alignment? I can slide the motor forward to make the front to back clearance between the two couplers within the 2-4mm spec, but I am not sure if the alignment side to side and top to bottom alignment is within spec. I am going to get a feeler gauge set and see if the deflection clearance (distance "a" in the shop manual) is within spec of 0.5mm.

 

[DrewOregonian]

What do you mean? ^^


How do these pictures look for coupler alignment? I can slide the motor forward to make the front to back clearance between the two couplers within the 2-4mm spec, but I am not sure if the alignment side to side and top to bottom alignment is within spec. I am going to get a ************ gauge set and see if the deflection clearance (distance "a" in the shop manual) is within spec of 0.5mm.

I need to proofread better before hitting reply. Sorry to confuse you.

Get some feeler gauges and get your couplers 2-4 mm apart as shown in manual. Use your straight edge as shown in manual as well.