carb jet question

[tomsl750]

Welcome Bill O. Thanks for joining the site. I've appreciated your help and information in the past. I try to absorb everything you say. I do have a question though. I have a 1995 Polaris 750. I have a waterbox, F/A, and will be installing Boyesen Pro reeds. Will I need to change the jets out for larger ones? I also replaced the fuel lines over this weekend and I seemed to have gotten more RPM's (about 100) is this normal? I was turning 6150 and it jumped up to about 6200-6250. The air was a little cooler, so that may have been it. Just wondering.

[Bryan Glynn]

I can tell you that the RPM change had nothing to do with your fuel lines - I would attribute it to atmospheric conditions.

[tomsl750]

I kind of figured that is what it was, but just wanted to make sure. Thanks for the quick response, Bryan. The weather has been really nasty here in central Georgia. Hope it clears up sometime this week.

[Bill O'Neal]

Tom, thanks for the welcome.

Specific jetting is applicable to your atmospheric conditions and altitude, so I won't go into specific detail as to jet sizes, but normally what happens when you install a freer breathing filter system is that the carbs recieve less signal strength from the motor, a loss of vacume. Watercraft carbs work using the draw of air though them to get the fuel from their feeder passages and into the intake tracts of the motors' cases and clyinders. Due to this drop, is is usually mandatory to lower the pop off pressure a bit to compensate for the lower signal strength. In some watercraft, it is also necessary to enlarge the jets somewhat.
If your watercraft is running pretty rich before the filter swap, then sometimes you can get away with just adjusting the carbs after a filter change. But, I warn you, this could be disasterious in some cases, as more jetting may be necessary.
Always re-jet or adjust to the rich side first when making changes to your watercrafts' motor.
It is much better to be safe, and lean it down later, than to be lean and burn a piston while trying something new.

[tomsl750]

So basically what the two of you are saying is to lower the pop-off (Bryan) and rejet with bigger jets to err on the rich side (Bill). I haven't got the reeds on yet, but have the waterbox and F/A. I am considering on waiting until the end of the season to do the reeds so I have plenty of time and patience.

[Bryan Glynn]

You got it.

[Bill O'Neal]

Tom,
We will be here to help when the time comes, have fun with your ski in the meantime.

[SeaLion]

I agree with Bill on what he posted. Although I had these mods plus more on my 95 SL750 I didn't need to re-jet. My ski stock was way rich to begin with and after adding all the goodies, I ended turning a 1/4 out on the highs from the factory settings. Full throttle chops revealed perfect plugs and I put a ton of hours on that ski and it ran perfect. Still running great for the new owner. What you might consider at least is to open up the highs 1 turn and work down. The stock settings are 1 for the mag, 1/2 for the center and 3/4 for the pto. As you can see, there is room to adjust richer. Wether you will need to re-jet or not for your set up and place of riding, we can't answer that unless we are there to test.

[tomsl750]

Sealion, Still haven't got that waterbox. Can't wait though. It should be here tomorrow around 3pm. Can't wait to get it on. I will test the plugs and adjust accordingly sometime this week if I have a chance. Thanks for the advise from everyone.

[SeaLion]

I forgot to add that in most cases, the Pro series reeds will actually richen the top end and lean the bottom end. You gain carb signal from the reeds. Get the bottom end to hit good first and then work on the top. I still highly recommend getting the 3/8" reed cage spacers because they wil extend the life of the carbon fiber reeds and boost performance. Those spacers work really well on the Fuji engine.

[tomsl750]

I guess I'll break down and get the reed spacers.