SX/SXi/SXi Pro Would a bad voltage regulator/rectifier cause my engine to not rev up?

[Radcon15]

I have an issue with a 750sx where my engine isn't revving up over 3000 rpm. I can't even get it on plane. It just feels like it's on a rev limiter. I've replaced EVERY electrical part on my ski with a brand new one except for the regulator/rectifier. Replaced CDI with a new msd enhancer, replaced ignition coil with a new one (and replaced cables on original as it is still good), and replaced the stator TWICE with brand new ones from sbt. No luck. It's not a fuel problem as I've already rebuilt and retuned my carb.

Any help at this point is appreciated, I feel like I've almost got this but I'm about ready to give in and drop it off at the dealer.

 

[OCD Solutions]

What plugs are you running and what's your gap set at?

 

[Radcon15]

BR8ES, didn't mess with the gap, theyre at .025, also tried some equivalent champion plugs (I don't run them) and had the same results

 

[Radcon15]

Any ideas? I'm completely stumped by this. I literally threw my multimeter across the room

 

[Vumad]

When did it start. Does it ski d like its on a rev limiter or does it sound all boggy or just die or what? What all have you checked and what is the history leading up to.

 

[Radcon15]

It starts each time like it normally should, no issues starting at all. It's when I give it gas it just acts like it's on a low limiter. (I disconnected my temp sensor inside the ebox too btw). It just started it one day and I could get out of it by restarting it a couple times. Then it hot worse each time and now it's always doing it. It doesn't get boggy or anything, it just goes up to 1/4 throttle and anything more just sounds louder (open intake noise) but stays at the same rpm.
I've disconnected the heat sensor, changed the flame arrestor, changed ignition coil, rebuilt carburetor, changed the cdi, changed the stator, changed fuel lines, resealed the gas tank to hold pressure, replaced intake manifold gaskets, made sure there's no exhaust leaks from the factory pipe, and the result, nothing. Still dies the EXACT same thing. That's why I'm wondering about the voltage regulator. It's the one thing I haven't replaced.

 

[OCD Solutions]

At this point I would say to change it, what could it hurt and what's left anyways. You've already changed out everything else that I would have suggested.

 

[Dutchie]

Sorry but what has the voltage regulator to do with this problem ??

Did you check your compression, are the seals of the engine still in place ? The reedvalves ok ?

did you messured the resistance of the spark plug lines ?

what did you rebuild of the carbs? 100 % all new parts ? did you check every channel in the carbs for flow / buildups of junk e.c. )

Disconected the kill switch already with a bypass ?

Can it rev up out of the water ?

Tried the ski without the hood on it ?

There is more to a ski then the stators e.c.

Greetings,

 

[Radcon15]

Compression is 150/150. Checked the reeds and all are perfect. Coil is reading 4.6 ohms across the spark plug leads. Carb is rebuilt 100% with parts from SBT. The engine runs and doesn't die and seems to run perfect at low rpms so I don't think it could be a kill switch issue. It won't rev up out of the water either, just sits at the same rpm, that's what leads me to believe it's electrical.

Thanks, I hope I get this finally fixed

 

[Dutchie]

Is there enough flow from the exhaust ? Not that the waterbox or something is clogged ?

 

[Radcon15]

Nope, checked the waterbox and lines. I just don't get what it can be at this point, it ran perfect and just started getting worse. I've gone through everything I can think of except the flywheel and woodruff key (can't get the flywheel bolt off)

 

[4SeasonsPower]

I would be willing to bet its your carbs. I know you said you rebuilt them, but I would go back and double check your work and possibly swap your SBT kits for Winderosa kits if they are Keihin or Genuine Mikuni if thats what your running for carbs. Everybody makes mistakes so its very possible a component was installed improperly or you missed a seal or o-ring somewhere. Been there, done that and turns out I'm not immune to mistakes either Since you have replaced every electrical component with a new one and verified engine compression it would lead me to believe its a fuel problem.

Also crack the hood open while trying to run wide open to verify 100% your not missing an exhaust leak somewhere or a hood vent issue.

 

[Radcon15]

I'll check them again, it's just weird to me that it would act the exact same way and just get worse even after fully rebuilding them. I'll throw some on from my 650 and see if it changes anything

 

[Radcon15]

Well... Switched the carbs... No change. Still the same results. Any other ideas? Would weak flywheel magnets cause this? Or could it be timing related..

 

[Radcon15]

Well I think I've ruled out any chances of it being a fuel issue, I've pressure checked the tank, switched carbs, even held it wide open while it acted like it's being limited and poured gas down the carb throat and still no difference. I'll check compression again, but I really think it's electrical.

 

[OCD Solutions]

But what's left electrically? If you swapped out all the components, maybe it's time to inspect the harness. I've seen it before where a buddy installed Tubbies and one of the screws went into the wiring harness. It took awhile to find and the results were similar to yours.

 

[Radcon15]

I'll check through the harness. I did recently have the ski apart to take the weights out of the front and install tubbies. But the only wiring up there is for the start stop switch, should I try a new voltage regulator? I'd hate to throw money at another part just to find out it made no difference. It doesn't make sense

 

[OCD Solutions]

It never hurts to have a complete spare ebox so any money you spend now on components is still a good investment. I just got caught without a spare CDI and lost 2 weekends of riding.

I've only fried one regulator and the ski wouldn't run at all. I don't think they go bad often but the effects when they do could be pretty erratic.


Do you have a service manual for your ski?

 

[Radcon15]

Alright, I'm going to tear at it more this weekend. Is there any chance that a sheared woodruff key would cause this? If there is a chance, then I'd pull my engine out this weekend and get the flywheel off to check things out. There's literally only 3 more things left to check, woodruff key, flywheel, voltage regulator. The engine was just rebuilt last year and ran perfect.

 

[Dutchie]

It's hard for us to help true the internet haha

But if u are sure that is it i sould go for it. Jess i would take off my flyweel and inspect it ! Key's usually dont jump but if it does the timing will be off.

Greetings,