break in vs. jetting

[SharkB8]

I have my freshly rebuilt motor ready to go.

The engine builder prepared the carb to his standard jetting for that configuration of motor/porting/head/pipe and said I should be roughly in the ballpark but I will need to go through the whole process of adjusting the screws to get it right.

Since there are no competent pwc shops in my area, I will guess I will attempt this myself using my new Pet tach and the instructions I printed from the Group K web site. The process might not be brain surgery but it does require plenty of WFO runs.

As I understand it, the jetting process usually starts well on the safe side (overly rich) where the ski will barely get out of its own way.

So this is where I'm confused, in light of #.0's break-in advice here.... I can't ride it to break it in until its jetted, and I can't fully jet it until its broken in.

Surely this can't be an uncommon occurrence, to build a motor from scratch and have to both break it in and jet it.... how is it done?

 

[750sx1992]

Bump for Interesting question.

 

[Matt_E]

What did your builder say?

With my engine, the jetting was no different for break-in vs regular operation.
If your builder is half-way competent, the jetting you have will be pretty close.
Simply fine tune it during the first tank and break it in at the same time.
It's not overly complicated.

 

[crammit442]

I wouldn't that that break in advice as gospel either.

 

[SharkB8]

What did your builder say?

With my engine, the jetting was no different for break-in vs regular operation.
If your builder is half-way competent, the jetting you have will be pretty close.
Simply fine tune it during the first tank and break it in at the same time.
It's not overly complicated.

The builder said its not overly complicated. But then they have a four-page document on their web site explaining how to do it. :-0 (the jetting, that is)

 

[Matt_E]

I think your jetting will be pretty close to what you need.
Fine tune it during your first tank and ride.

 

[Kennay]

The builder said its not overly complicated. But then they have a four-page document on their web site explaining how to do it. :-0 (the jetting, that is)

Group K?

 

[SharkB8]

Yup, Group K. I have no complaints about their work. I'm just not very confident in my own jetting abilities.

I tried it once and floundered through the process and I'm still not sure if I got it right - it seized up tighter than a bull's arse with flies on it, but it turned out to be the wear ring that seized, not the engine.

So with the added complication of what appears to be an intricate break-in procedure, I thought I'd drop a line here asking how other people do it - jet then break in or break in then jet, or both at the same time.

 

[Waternut]

Well you have to get the engine fairly close for break in. If it's too far off it either won't plane off, won't start, won't run, or worst of all...it'll sieze up after a few minutes.

Breaking in an engine is still a heavily debated topic so depending on how you break it in will determine how you should tune it. If groupK tells you what jets to use, that would be considered close enough in my book to not do damage to the engine.

I recommend you read up on tuning a carb so you have some knowledge when you get out on the water the first time. That way when there is some kind of hesitation, bog, sputter, etc. you'll have ideas. Chances are, you won't know the difference between a bog or hesitation but if you know which adjustment screw does what, you can give that screw a small turn and see if the problem gets better or worse and go from there.

 

[nokfir]

people usually have pretty different views on engine break in......some say ride it hard right away, others so take it easy..i stay in the middle

 

[Matt_E]

Yup, Group K. I have no complaints about their work. I'm just not very confident in my own jetting abilities.

I tried it once and floundered through the process and I'm still not sure if I got it right - it seized up tighter than a bull's arse with flies on it, but it turned out to be the wear ring that seized, not the engine.

So with the added complication of what appears to be an intricate break-in procedure, I thought I'd drop a line here asking how other people do it - jet then break in or break in then jet, or both at the same time.

You're making this too complicated.
Drop it in the water and start running it.
Fine tune as needed.
Ride, and don't go wide open for another two tanks.

 

[SharkB8]

Sounds good. I'll give it a try... as soon as my SBT break-in premix arrives. : - )

And yeah jfw I pretty much have both the Group K jetting articles memorized.

 

[tom21]

You're making this too complicated.
Drop it in the water and start running it.
Fine tune as needed.
Ride, and don't go wide open for another two tanks.

exactly!