Poor throttle response on new sbt 657x

[Rebuilt657x]

ok, I installed this motor over the summer last year, The motor starts and runs, and idles fine. It has poor throttle response, very slow out of the hole, and doesn't have the whip like acceleration that the 657x should have. So I changed the rotart valve again I thought I had the wrong one before, and it ran a bit better. THe carbs have been rebuilt. I'm about to break it out for this season and try again. My question is what could be causing this problem?? I'm thinking maybe I need to replace the cover on the rotary vavle, maybe its not tight enough to make a good seal. Then I thought that maybe theres something in the exhaust thats causeing it since the ski sat a year before I got the new motor for it? I"m looking for any info on where to start to figure this out! I want the ski to perform as strong as it used too.

[Bill O'Neal2]

Re: Poor throttle response on new sbt 657x

You could have any number of problems. I would start by rechecking the pop off pressure in the carbs and making sure the high and low speed carb adjusters were properly set. A Sea Doo will run like crud if it is too rich. Highs set at zero turns out, lows set at between 1.5 and 1.75 turns out ( adjust as necessary). Are your sparkplugs wet and dark, like it is running too rich?

Look at all of the exhaust couplers and hoses and their clamps. Anything loose or have a hole in it? Is there smoke under the seat when you run the motor? Maybe a hole rubbed through the bottom of the muffler?

Have you clipped back the sparkplug wires to get a new connection at the sparkplug boots?

Is the charging system working correctly? Are you getting about 14.5 VDC at the battery at 5500 rpm?

[Rebuilt657x]

Re: Poor throttle response on new sbt 657x

bill, I had you rebuild my carbs last summer, so I think for the most part they are correct. I didn't clip back the plug wires, or check the voltage. although the ski never looses a charge, and when running it it runs fine all day with out battery issues. I remeber it was running rich before the carb rebuild, but to be honest I haven't checked them after the carb rebuild it was towards the end of the summer and after I got the carbs back in and it still struggled, I kinda gave up on it for the year. I"ll have to break it out this year and see if I can see smoke inside. would oil injection have any issue with this aswell?

[Bill O'Neal2]

Re: Poor throttle response on new sbt 657x

Ok, recheck the low speed adjusters to see if they are properly set. Clip the plug wires.

Are the sparkplugs wet and black?

Are you talking about poor engine performance of is it cavatating when you say it is sluggish?

[Rebuilt657x]

Re: Poor throttle response on new sbt 657x

I'll have to pull the plugs and check, but the ski has been sitting all winter so I dunno how accurate they will be reading them now. Cavatation I assume you mean the pump just spinning and not grabbing water?? This is like a bogg you grab full throttle it takes a while for it to rev up and move. Its not like my other xp where its break neck quick and not boggy at all. Once you get it moving it lacks that 2 stroke power band where you feel increase in each movement of the throttle.

[Bill O'Neal2]

Re: Poor throttle response on new sbt 657x

Ok, That sounds like the carbs are too rich. It is possible that the carbs are not adjusted correctly, or the needles are leaking. Anything is possible.
Maybe you got the rotary valve timed wrong? Or if you changed the position of the stator, it could be retarded timing?

[Rebuilt657x]

Re: Poor throttle response on new sbt 657x

humm, I put the stator I"m pretty sure right back in the same place I think, (IS that the thing on the front of the motor that charges the battery?? I'm not exactly sure what the stator is) I wasn't aware that that had anything to do with timing... maybe thats it. I think the rotary valve is correct I used the degree wheel and all, but its worth a check. Also I thought maybe it was the cover for the rotary valve maybe that needs replaced...

[dsolie]

Re: Poor throttle response on new sbt 657x

If you open up your front cover, you will see a scribe mark on the ring of your stator, as well as a mark on your case. You want to line those up. You will have to remove your flywheel to get to the stator. It can be done with the motor in the boat too.

The stator hold a plethra of items that your boat needs in order to run. It handles when when and how your boat sparks, as well as the coil for the charging of your battery.

[Rebuilt657x]

Re: Poor throttle response on new sbt 657x

ya, I know what part it is now. Well I know its charging the battery, so I know thats working, maybe it is off time a bit, I dont remeber honestly how I put it in. I thought I put it right back in the way it came out. I dont remeber the scribe marks though. I guess I'll try remove the cover and look, although I'm thinking it might be easier to pull the motor out again, and go through it that way... :emoticond

[Bill O'Neal2]

Re: Poor throttle response on new sbt 657x

Yes, in the longrun, if you do not have all the proper tools, pulling the motor may well be the best route to take. You could also double check the RV timing. It seems people screw up that alot.

I would pressure test the carbs first just to see if the needles and seats are leaking. You can do this by blocking off the return line and pumping about 15 psi into the inlet nipple. It should hold that 15 psi for several minutes. If it leaks, that is why it would be rich.

I'm sure if we rebuilt the carbs, we tested them before shipping them back, but it never hurts to double check them if you are experencing a problem that could be the fault of the carbs.

I think if you aligned the marks on the stator as you were susposed to do, you would have remembered doing it.......

[Rebuilt657x]

Re: Poor throttle response on new sbt 657x

ya, I guess I"ll pull the motor again, sucks, but ohwell. Any performance mods I can do to the motor since I'll be pulling it out, that are reliable and make a difference?? If I need a new exhaust, Id rather go aftermarket any suggestions?

[Bill O'Neal2]

Re: Poor throttle response on new sbt 657x

That motor comes with a fairly good aftermarket type Westcoast Exhaust on it from the factory.
A slight bump in compression helps.

[Rebuilt657x]

Re: Poor throttle response on new sbt 657x

Just have to change the domes or head to bump the compression?? What do you recomend?

also, would the oil injection have anything to do with it?? seems to be working properly, and the marks are lined up. I guess I could get the oil block off plate, but mixing is a pain in the butt. Plus my other ski still runs great with oil injection.