SXR Just past half throttle thru full throttle seems about the same...?

Matt in Houston

Matt in Houston

Location
Atascocita
I was out riding around on the SXR about an hour ago and I have noticed that from perhaps just past 1/2 throttle through full WOT the top speed and acceleration seems to be about the same. I forgot to turn on my phones GPS to clock my speed but maybe I will tomorrow. I am thinking it is a little slow running at WOT. Anyway, the ski seems to have no other issues. It doesn't hesitate or bog, or anything like that. It feels strong in the low and mid, and is very smooth up top, but it just seems like it should still be accelerating.

The ski has always done this I believe. I've only had it for about a month now and I am new to stand ups. The guy I bought it from had some aftermarket flame arrestors installed on it, and he said he didnt mess with the carb screws. I also have done the +6 degree timing mod. I am running 93 octane with kawi oil on a 50:1 mix. I am thinking it needs about 1/8 a turn on both screws to add more fuel since it is probably breathing better.

Am I on the right track, or could this be something else?

Thanks,

Matt
 
mthomps

mthomps

Location
Cleveland
^^^It might...

If you feel the need to mess with it though tie it to the trailer and throw a sand bag or cynder block on it to keep the pump in water and hold the boat 3/4 to wide open and experiment with the high speed screw(s) very slightly.
 
Cross

Cross

X
Location
WA
Check the jetting in the carbs. They are jetted a little lean for most areas from the the factory. Adding flame arrestors can make this even worse.
 
OCD Solutions

OCD Solutions

Original, Clean and Dependable Solutions
Location
Rentz, GA
Does the motor REV but the ski doesn't really go any faster? What impeller are you running? I ask because I had a 9/15 in one of my old skis and it was way too short. It would run the impeller out around half throttle and just rev from that point. I upgraded to a 10/16 and the ski came alive with bottom, mid and top where all I had before was solid bottom end. If the ski is new to you, the old owner may have swapped out the impeller.
 
Matt in Houston

Matt in Houston

Location
Atascocita
Thanks for all the suggestions...The ski has the stock impeller. I think I will GPS it first and see what my top speed is and then go from there. If a few people say that's how SXR's are and my speed is up to par, then I doubt I will mess with anything.


I should be able to GPS tomorrow so I will report back then.

Thanks!

Matt
 
djkorn1

djkorn1

kidkornfilms
Site Supporter
Location
Cleveland Ohio
Richin up the top end...If it gets better keep doing it until you've got the most out of it...Too much fuel can't hurt it. Too lean can.
 
mthomps

mthomps

Location
Cleveland
Just be careful...I always have to try to mess with stuff. I freaked my self out on my latest ride because i just had to mess with my screws...Luckily I got it back to the way it was..remember where you started at the very least!
 
Matt in Houston

Matt in Houston

Location
Atascocita
mthomps said:
Just be careful...I always have to try to mess with stuff. I freaked my self out on my latest ride because i just had to mess with my screws...Luckily I got it back to the way it was..remember where you started at the very least!
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Yeah that is what's looming in the back of my mind. I am the type that sometimes breaks something trying to fix something...know what I mean? Don't know why, its just always been that way. In the end it always gets fixed but it takes me longer since I had to also fix whatever it was that broke along the way. Good news is I get to learn a lot more than I thought I was going to.

If its not bad weather tomorrow I'll take it out and GPS, and if its not in the mid-high 40's then I might attempt to richen it up a bit. I have a stubby cone so I wonder if that will take a little off the top anyway. But I also have the advanced timing and a R&D plate so maybe it wont make that much of a difference.
 
mthomps

mthomps

Location
Cleveland
Yes I do know what you mean! I recently took off my stock exhaust to get to the bendix and I didnt have which destroyed exhaust gaskets. Cost me a day of riding because I sat with two others making gaskets for four hours.

I dont know what the stock carbs on sxr are but mukinis sbn manual states if you have open air filters carbs will need adjusted/rejetted. They will make you lean. Hell just try it. If Dj says its fine than its fine.

I can tell you though my 650 superjet top speed in owners manual states 37-38 mph and that's exactly what mine does...AND 3/4 to full throttle is almost exactly the same.
 
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kevbo

kevbo

Location
dfw
Super_Slow_Jet said:
Say they make full power by half throttle.... If you run it at wot would it lean out or would it only suck what air it needs to?
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A carb that is too large and/or too much pump load will make them more difficult to tune. Oversized carbs work well for freestyle throttle blipping when part throttle mixtures are set extremely rich. Tuning them for general use can be challenging.
 
T

Texan33

Yacht Wakes Hunter
Location
Texas
My 11' SXR kinda did the same thing the past two seasons. It was not from 1/2 throttle to full. It was more like 3/4 to full. I checked the spark plugs and they were dark brown-ish.
 
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