Rebuilt 787 motor vibration

[danduta]

Just finished putting my 1996 GSX together after a motor rebuilt by SES.
I am breaking it in.
Just ran half a tank of 1:40 premix.
The motor seems rougher and there is more vibration then before the rebuilt.
Is this to be expected? Should it smoothen out with more wear and after the break in?
Any thoughts would be appreciated.

 

[Austrian Rotax]

A noticable rougher vibration than normal can be associated with an imbalence in your carbs. Are the carb butterflies in sync? Did you clean or better yet rebuild your carbs? Did you try new plugs? Ive heard about aircraft engines running rough because of an imbalence in dual carbs.

 

[LouDoo]

Did you align the motor to the pump?

Lou

 

[toddfw2003]

motor alignment

 

[Seadoobuddy]

Alignment or motor mount problem.

Can you grab the motor and while shaking it quite does it move a lot?
No, that's good.
Then it's probably the alignment that's the issue

 

[Mekanix]

Alignment,
carbon seal jumping all over the place
Counter balance shaft not aligned properly.
Carbs not in synch.
Rich mixture of oil or fuel.

Remember the carbs need to be synched every time you install them because there is enough slop in the carb bolts to allow them to be up to 5 degrees off!

The way I do it is to turn the idle way down, Off actually. and back the bolt out a bit more.

Then install the link arm and make sure its loose. Tighten it until it just starts to take up the slack and then lock it down. That way both butterfly's are completely closed and when the mag carb moves so will the pto.

Then just dial up the idle to 3 turns from seated and it should be pretty close.

It does get a bit better when your done mixing the oil. Straight gas smooth's it out a bit.

 

[danduta]

Thanks for all the advice.
I did not sync the carbs given that I did not touch or change anything there.
As far as alignment goes I marked the position of the motor very carefully. The rear mounts stayed on the body...only had to remove the front mount.
The pump shaft and PTO seem to line up. In fact there was slight side to side movement.

What is the easiest way to align the motor to pump?

 

[LouDoo]

The best and only way, IMO, to align the motor is with an alignment tool. [MENTION=43374]Coastiejoe[/MENTION] has one he "rents" at cost to members.

Lou

 

[Coastiejoe]

If you have checked all the basics, spark plugs, wire connections, fuel filters ect ect.. Then you should do the alignment. Even if it isn't the alignment causing the vibration, out of alignment issues can get expensive fast. It puts lateral torque on the shafts which wear the splines at a great rate and it will off-center the impeller. It only hast to be 10-thousands off for the impeller to have an issue with the wear ring and it will cause earlier cavitation as well.

Here is the link to my alignment tool if you so desire, (thank Lou).
http://www.seadooforum.com/showthread.php?69943-Alignment-Tool-Rental

 

[danduta]

Sounds like I definitely need to align things properly.
I will likely need to buy the tool. I have 4 boats in total so it makes sense to have the tool. The dealer here is close to useless and expensive too.

 

[danduta]

It would be nice to rent the tool (thanks much) but shipping to Canada would end up costing as much as the tool.

 

[Coastiejoe]

It would be nice to rent the tool (thanks much) but shipping to Canada would end up costing as much as the tool.

I agree,,, crossing the line always costs substantial funds...

 

[Mekanix]

but the damn thing cost nearly 350 to buy it from our local dealers here

Best ive found was from winnerscircle canada @ 315$+shipping

 

[Mekanix]

It would be cheaper to have a rod made that you could use your jet pump with as the guide.