Thread: SHO Exhaust Jetworks Mod
02-04-2010, 11:58 PM #1
SHO Exhaust Jetworks Mod
Remove collector from exhaust manifold.
Remove block off plate and gaskets.
Plug original water feed hole in exhaust manifold with 1/4 inch allen set screw. It will self tap into the aluminum very nicely.
Measure water cavity depth on the inside of collector, its 1.2 inches deep, and leaves plenty of room to drill, tap, and install barb fitting for new water supply to the water box..
Locate desired hole location on the 360 degree circumfrence of the collector, making sure to not locate it on top of one of the inner reinforcing webs in the casting.
Center punch, drill hole, and tap with 1/8th pipe thread tap.
Install 1/8th pipe thread barb fitting and jetworks valve.
Use water pressure source supply of your choice. Main feed water line is right below collector, splicing into it with another splice fitting to feed jetworks valve is one of several options.
Reassemble collector on exhaust manifold, make sure and reinstall original block off plate, and new gaskets preferred.
Adjust jetworks valve after installation to desired opening rpm.
Jetworks valves with 1/4 inch outlet are available and would suggest using one that size, that way you wont be putting more water in the water box at higher rpms when the valve opens than the stock system did, as the original water feed hole that is now blocked was 1/4 inch.
Enjoy a drier water box holeshot now.
Sorry for the bad pix, flash died on camera..
02-05-2010, 08:42 AM #2
Dam nice Ross! Did you get to water test after your modding? Bet it made a pretty nice difference.
02-05-2010, 08:45 AM #3
Nice job! this deserves a sticky in the Yamaha 4-stroke section!
02-05-2010, 09:12 AM #4
Awesome! I learn every time I get on this forum.
Thanks for sharing.
I don't see the .25" Pro-Series in the online store. Did you get yours here on GH?
02-05-2010, 03:34 PM #5
How much f a temp difference r u seeing in the exhaust? no areas of the hull bubbling paint off from the inside right? JK JK
What type of performance increase r u seeing? Very cool....
02-05-2010, 04:51 PM #6
This mod has been done to GPRs for many years, just a revised (how to) for the sho motor.
The stock sho doesnt put as much water in the waterbox as the stock GPRs did, but it still should make a difference.
02-05-2010, 05:01 PM #7
- Join Date
- Jul 2005
- Central North Carolina
Ross, The hose you removed and you pluged the pipe what did you do with the hose as it can NOT be pluged off since its the water exit line coming off the water cooled voltage regulator? Thats right guys Yamaha even water cooled the voltage regulator to make it last longer. I assume you instaled a pisser and just let it go over board after it leaves the voltage regulator. Please explain in more detail, Thanks Tommy Jordan
02-05-2010, 05:41 PM #8
Tommy the water enters the exhaust manifold cooling jacket on the lower side of the manifold directly from the main feed line in from pump pressure.
Once it enters the manifold, it then has a topside exit port that feeds the voltage regulator, which is the lower hose to the regulator.
The exit for the regulator is at the number one cylinder exhaust port jacket, which then in turn exits into the cylinder head itself through small holes drilled in the cylinder head cooling jacket surrounding the exhaust port in the head.
There are a total of 6 exits on the exhaust manifold.
One at each of the exhaust ports where the water exits the manifold cooling jacket back into the cylinder head, makes 4 there.
One for the voltage regulator feed inlet, which then goes through the regulator and re-enters the manifold cooling jacket at exhaust runner number one.
I suppose if you wanted, you could dump the water out of the regulator from a pisser and plug the old regulator return in the manifold.
The 6th one is the one i blocked, which feeds the water box its cooling water.
R&Ds cooling upgrade plate simply restricts that waterflow at the 6th exit more than the factory did with a smaller hole in the plate.
This mod eliminates water in the exhaust at low engine rpms when no water is needed, then allows water in the box as heat and engine rpm/pump pressure increase.
The goal of the mod is to prevent water from collecting in the water box at low rpms, and then the motor/exhaust pressure has to push out the excess water from the box on holeshot, robbing horsepower in the process.
So how did i do? Thats a hard one to explain on a forum..
02-05-2010, 08:01 PM #9
- Join Date
- Jul 2005
- Central North Carolina
? I am not sure you have the water flow direction correct but the Jet works should still dry out the exhaust water box at low rpm's. Thats all the sho/fzr/fzs needs is " More" bottom end power to blow the prop out on start off, Tommy Jordan
Last edited by 2fast4u; 02-07-2010 at 02:11 PM.
02-16-2010, 06:02 PM #10
Got mine in the mail today. Add that to the list of parts to install before spring.
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