650/X-2 Completely new 650sx ported engine. High compression head. Need advice for break-in

[Proptimus Prime]

Hey guys, this winter tore apart my old 650 motor and have replaced every part with any upgraded parts I could get my hands on. I bead blasted and powder coated just about everything I could.

Bottom line
My new motor is a ported cylinders with new sleeves on a stock bore with a high compression head and is 210 psi front and 207Psi rear. I have a dual intake manifold and two Buckshot Mikuni 44s. I was thinking about breaking in the motor with just the single but I don't have any idea what to do with jetting and fuel octane past 180psi. Could someone please offer me some advice?

I tried to break in the motor today with 92 octane and a single Mikuni buckshot 44, I didn't check the compression before I tried. I figured it HAD to be under 180.
I ran a 50/1 ratio of Maxima super M. The settings on the carb are as follows...
N/S 2.3
Spring color- Normal silver
Low Jet - 120
High Jet - 125

Running a Solas 13/18 pitch impeller also.

I got the ski to idle by adjusting the low speed knob. I had to idle and then slowly pull the throttle to get up to a speed where I could stand. Top speed felt like my friends bone stock machine. Maybe a little slower. Pushing the primer button while holding the throttle down gave it a lot more speed for a few seconds.

Can someone please help me get in the ball-park of what gas octane/ jets/ pop off pressure I need? I was running a single but i have matching buckshot mikuni 44's and a R&D 44 mikuni dual intake manifold. I just thought it would be better to break in the motor with a single because i've never used duals before.

Any advice anyone? Please?

 

[element3488]

Get a pop off tester and the mikuni tuning guide.

 

[JetJunky]

For breaking it in I would go a lot richer on the mix, like 32/1 for a least half a tank then run 40/1

 

[Seanc]

Why do you think your compression would go down? 180 is pushing it on pump without a really good tuner. What's your altitude? And from the sounds of it your running way lean fix that before all that money and time is a big paper weight

 

[Proptimus Prime]

Why do you think your compression would go down? 180 is pushing it on pump without a really good tuner. What's your altitude? And from the sounds of it your running way lean fix that before all that money and time is a big paper weight

My altitude is 702 ft (214 m) " Minnesota"
My older motor was 165 and I knew it was going to go up with a fresh top end and stock bore i just didn't think it would go past 180. I didn't check it before I went out. I figured i would only have to tune the carb a little bit. lolol Clearly i was horribly wrong.

 

[Proptimus Prime]

I just really have no idea where to go from here.
I have a new motor with 210 compression and i have 2 carbs and a single and double intake manifold.
I don't know about jetting, and everyone is telling me different premix ratios.
I am so unsure about what to do it's ridiculous!

 

[element3488]

first tank of gas half mixed 32/1 the rest 40/1 for all future tanks.
Run a single carb. Dual is going to be unnecessary and harder to tune.
the mikuni tuning guide will help with jetting to achieve a proper pop off pressure.

 

[kevbo]

I just really have no idea where to go from here.
I have a new motor with 210 compression and i have 2 carbs and a single and double intake manifold.
I don't know about jetting, and everyone is telling me different premix ratios.
I am so unsure about what to do it's ridiculous!

Your jetting is for dual carbs. A single carb manifold delivers much lower vacuum pulse to the carb so larger jets are needed. Be sure about the spring, a 2.3N/S with a 95 should work well, an 80 may be better. Your 120 pilot could be too lean (depending on popoff pressure) for best response, the engine should sputter some around 1/4 throttle. Your main jet will probably end up larger than anyone would guess. Start with a 180 and the top screw open 3 turns. You want to experience low power from too much fuel instead of too little. Remember that the main jet and top screw feed the same circuit. Close the top screw until some power is restored and burn a couple of tanks. It is easy to toast a fresh top end on full throttle runs so always start rich of peak power.

 

[kevbo]

I just really have no idea where to go from here.
I have a new motor with 210 compression and i have 2 carbs and a single and double intake manifold.
I don't know about jetting, and everyone is telling me different premix ratios.
I am so unsure about what to do it's ridiculous!

Your jetting is for dual carbs. A single carb manifold delivers much lower vacuum pulse to the carb so larger jets are needed. Do you have a 65gram or 95G gram spring? A 2.3 with a 95 should work well, a 65 is very low. Your 120 pilot is probably too lean for best response, the engine should sputter some around 1/4 throttle. Your main jet will probably end up larger than anyone would guess. Start with a 180 and the top screw open 3 turns. You want to experience low power from too much fuel instead of too little. Remember that the main jet and top screw feed the same circuit. Close the top screw until some power is restored and burn a couple of tanks. It is easy to toast a fresh top end on full throttle runs so always start rich of peak power.

 

[Proptimus Prime]

Awesome! thanks everyone for your advice. I will take that into consideration. Wish me luck this weekend!