Stock jetting and Coffman pipe piping

[3wheelerdude]

I bought a 92 square (650) last fall and took it out on the water yesterday to find out that once in the water it does not rev up like it should. It bogs down quite a bit and wont plane some times.

So last owner says he never ran it on the water after putting the pipe on. So i figured he never rejetted.

Anyone knows what the stock jets should be and what do you recommend with a pipe.


And then what is the routing of the water lines for a 650 with Coffman. When I compare with my Kawi with AM pipe , this seems all wrong,,,, but its my first Yami.

 

[SXIPro]

For a 650 Coffman suggests :2.0 Needle & Seat, a 125 Main Jet, and a 65 gram spring.

 

[3wheelerdude]

For a 650 Coffman suggests :2.0 Needle & Seat, a 125 Main Jet, and a 65 gram spring.

Perfect, thank you.

Can you tell me how to hook up the water lines? I think the previous owner got it all wrong.

 

[SXIPro]

It depends on which Coffman you have. Some have two nipples on the front of the headpipe, some have only 1. Mine only had one. I routed the line from the pump to the exhaust manifold nipple. I routed the line from the head to the nipple on the front(facing the nose) of the headpipe.

I then went from the rear of the headpipe to the stinger, with a 'T' in that line to put a pisser out the side of the ski.

For the Coffmans with two nipples on the front of the haedpipe, this thread has some good info and instructions:

http://www.x-h2o.com/threads/36119&highlight=coffman

 

[Motorheads5]

did you try to adjust the air screw's on the carb we had the same thing with a kawi 650 and a coffmann all we did was adjust the screw's and we did not have to rejet, plug's look perfect, you might try that first.

 

[bassman215]

I have the coffman's pipe with just two fittings on the headpipe, but I had run my line from the engine head to the back of the head pipe and then the front fitting on the headpipe to the stinger w/ pisser. I wonder if is matters, or if I should switch the lines on the headpipe like mentioned above?

 

[3wheelerdude]

Right now its routed like Bassman"s ski, and from comparing with my Kawi this seemed wrong.

Does yours run good Bassman?

 

[bassman215]

I ran it like that for a couple season's with my 650 and didn't have any problems. I recently built a 61x 701 setup that I am running it on and it seems to be fine. I'm no expert though.
When I first bought the pipe I remember calling coffman's and getting the installation instructions faxed to me. That is what I used to route everything. Maybe I did it wrong, but I sure thought I followed the instructions correctly. It's been quite a while back though. I guess it's pretty easy to swap around. Maybe I'll give it a try and see if there is any difference...

 

[gorilla]

i'd run a 140-115 jets and a 2.3n's with 18lbs of pop off pressure.

you should be able to set the adjuster screws and 1 turn out on both to test it with.

with a 701 motor i ran 145-120 jets a 2.3 with 18 lbs pop off.

good luck

gorilla

 

[bassman215]

I've got 140-120 jets with a 2.0 n/s and pop off at 30lbs. I am definitely not "tuned" in though. Gorilla you ran quite a bit lower pop off than I have right now. I'll have to do some playing sometime this week. Thanks for the info.

 

[Mouthfulloflake]

I ran 120/140 1.5 NS, and a65 gram spring.

changed it to 120/145, 2.0 NS and 95 gram spring and its MUCH better.

on the old 650 it was 120/135 1.5, 65gram spring.

 

[bassman215]

Mouth,
Did you ever put a pop off gauge on your carb to see what the actual pop off is?

I can't remember what a 2.0 n/s and 95gr spring is supposed to be by the mikuni book but I think 28psi, but mine checked with a gauge is 30psi. I think I remember that coffman recommeded a 20lb pop off for the pipe on a 650? Not sure though...

 

[Mouthfulloflake]

I didnt test the pop off, just swapped springs and rode it.

2.0/95 gram should be around 25psi according to the mikuni manual.

you could lower yours and go back to the stock spring, that should give you 18psi with a 2.0 seat.

 

[bassman215]

Sounds like my spring is a little stiff!!

I will give a 65 gr spring a try and see what kind of difference I notice...

The 65gr spring is what I ran in my 650 with the same 2.0n/s but with a smaller main jet. I had started with a stiffer spring, but the 65gr ended up a lot better.