Have to double pump throttle to get above 500 rpm

[drake1]

My 787 will not go above 5000 rpm unless I do a double pump with the throttle when it hits 5000. I just rebuilt the carbs with a crap set and the actual mikuni set and same issue. It seems like it needs the second dose of fuel from the accelerator pump to get above 5000 once above it will stay there. My pop off pressure was set to 32 psi since mikuni only has 2 springs, one at 20 and one at 32. Only thing I have noticed is a drip from the exhaust rave cover on the very rear of the water box. Not even sure what that does since it's not a rave but has a same cap any thoughts? Thanks

 

[JeremyD615]

Have you cleaned the RAVE valves? You will also want to address that water regulator, as it controls the amount of water injected into the exhaust pipe. It changes the resonant frequency of the pipe, and has a fairly significant effect on top end power.

 

[mikidymac]

So what spring did you use. There is only 1 spring speced for your ski and it should never be changed to get pop-off. If your pop off isn't within spec something else is wrong and the spring should not be changed to get it within spec.

 

[Ckrawiec]

My '96 water pressure regulator is leaking.....how does it comes apart? I can get the black cover off, the spring comes out but I can't get the rest (the guts) to release.....it spins freely and moves up and down slightly but I didn't want to muscle it or tool it until I know more (and/or have parts). It's dripping, not terribly but annoying me knowing its not quite right. Any ideas....I'm searching for a schematic of that valve as well.

 

[mikidymac]

Just grab and pull, nothing else holds it in.

 

[Ckrawiec]

It was giving me resistance like something was holding it on.....I dared not bust it. There is a hexagonal
"nut" but I think that just holds the bottom of the spring.

OK, in we go....next weekend.....ski is 3 hours away!

BTW...I've read where the clamp inside will rust and release but mine seemed fine...looked like it was all there and still attached.

 

[mikidymac]

THe little spring clamp at the bottom will rust and/or punch a hole in the diaphragm. You really can't see it good until you remove the valve. The top clamp with the screw is usually ok unless the screw falls out.

 

[drake1]

I thought the raves dont come into play until you hit 6000 rpm?

 

[mikidymac]

Are we talking RAVES or Water Regulator?

RAVES come in around 4000-5000 rpm the water regulator gets you the last 500 rpm from 6400-6900.

 

[JeremyD615]

The raves come on as soon as the pressure in the exhaust rises to a high enough level to open the valve. Where that’s at in the rpm band depends on a few different factors, such as where the adjustment caps are turned to and how dirty or clean they are at the moment. They generally kick in below 5000 rpm though.