Where to go from here

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Chrisx88

Location
Rochester Ny
We built this blaster for spec. My son has done great on it. Never really rpm tuned it. Did some plug chops and got a nice color and sent it. Now that his riding is getting faster, i really set out to tune it by rpm today. Problem is, i cannot get it over 6680rpm.

62T/61X
Ada head 180psi
Boyesen pedals on stock cage
Dual 44 (Dont remember jets, i got a kit from Watcon) - Screwed high screws all the way in to 0 turns to get highest rpm of 6680
Hooker 10/16
JC Racing 2" set back
Bpipe, blaster chamber
Jet maniac WB
MSD, Turned all the way up.

I know my next move should be to take prop to maybe a 17 or 17.5, but i wanted to get some insight from you all. The ski runs great. Bottem end jumps out. Gets to top end really quick then just flat.
 
JetWash

JetWash

Location
Irish Hills, MI
more pitch isnt going to equal more rpm .
need to know jetting. also..
screw settings on head pipe? an hoprfully its hot.
is first couple inches of chamber sizzling?
how much water is going into stinger?
what rideplate? why you ask...i can tell you i gained 2+mph with a plate switch an almost 100 rpm cause it rode alittle drier.
 
kevbo

kevbo

Location
dfw
You should be able to find peak rpm before the carbs top screw is completely closed. Usually they will start losing throttle response as peak rpm is obtained. You end up a little rich of peak when it runs best. Make sure that the pipes bottom screw is open just enough to keep the chamber from getting too hot. The pipes top and middle screw should be closed tight. I would expect 6700rpm with an unported 61x cylinder and 6900 or more with a 62T.
 
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Big Kahuna

Big Kahuna

Administrator
Location
Tuscaloosa, AL
as Jetwash mentioned and same as Kevbo, getting the pipe tuned is a big thing for top end, first inch or so should sizzle. If you go up in pitch, your RPM's will actually go down most likely. Tuning a motor for racing is not just about RPM's, it is about peak speeds also unless your to the point of tuning for specific race courses, Then you already have your motor tuned perfectly and you are tuning for smooth water conditions, rough water conditions, tight course, open course etc etc.
 
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Chrisx88

Location
Rochester Ny
115/125 Jetting
pro water craft ride plate
Pipe was sizzling, i opended top screw a little, no more sizzle.
Water going into stinger? Not sure, havent touched jetworks flow control yet.

John at watcon said it sounds like im running rich still. Im going to pull head and check piston wash tomorrow.

Can anyone explain why when i took water from pipe (turned screws in) i lost RPM?
 
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sturat

Location
WA state
Chrisx88 said:
115/125 Jetting
pro water craft ride plate
Pipe was sizzling, i opended top screw a little, no more sizzle.
Water going into stinger? Not sure, havent touched jetworks flow control yet.

John at watcon said it sounds like im running rich still. Im going to pull head and check piston wash tomorrow.

Can anyone explain why when i took water from pipe (turned screws in) i lost RPM?
Click to expand...
that sounds overjetted to me. I typically run reverse jetting at 100 high 110 low (give or take one size up each) with 2.0 n/s and 80g spring on dual 44s for kawi 750 engines and have great results. Based off the mods you listed you're probably closer to those numbers.
 
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Chrisx88

Location
Rochester Ny
Thanks for all the input. With our last race weekend being so close, i didnt want to mess with much. I did try the pipe out a ton and got 6600rpm. Good enough for this last weekend. My son has been proving himself as is on ski. I will rejet and see what i get before it gets too cold to ride.
 
TheBuzzard

TheBuzzard

Location
the jetski grave yard
If you got the high screws closed, you need to put smaller mains in there and see if the rpm go up. Since the low jets contribute to overall fuel at top end, just turn the lows in and see if you get more rpm. Quick way to see if it's too much fuel
 
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Chrisx88

Location
Rochester Ny
TheBuzzard said:
If you got the high screws closed, you need to put smaller mains in there and see if the rpm go up. Since the low jets contribute to overall fuel at top end, just turn the lows in and see if you get more rpm. Quick way to see if it's too much fuel
Click to expand...
Will do that fri afternoon at race site, appreciate it.
 
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Chrisx88

Location
Rochester Ny
Update on this.

By doing more tuning of pipe, and closing low screws some we were able to get 6800rpm. I left it there and let my son finish last race weekend in Sylvan.

44's are off now and we are going bigger.
 
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