Factory Spec 2 Pipe on 787 - 92 octane safe?

[sdunkle]

Hey guys, I am new to here and to owning a jetski in general. I got a great deal on a 97 GSX with a seized 787 engine. I am getting it rebuilt and going 1 size over factory. The specs include open flame arrestors and a factory spec 2 pipe with water injection. The jets are 150 and 152.5 mains and 70 pilots (per Factory's recommendations) with a primer kit and choke plates removed. As far as I can tell the impeller and intake grate are stock. The question I have is what octane fuel are you guys running with similiar setups? I called a couple places that rebuild these engines, including the shop rebuilding mine and have gotten mixed answers. I have been told anything from I need to go up to 175 mains and 75 pilots to you can't run that pipe without race gas so I wanted to see what people were actually running and what worked. I realize humidity, elevation, air temp, etc have a big effect on performance but I am mainly trying to figure out if the configuration I have is a safe base to fine tune from. I don't want to melt it down right away due to the pipe causing too much heat and detonation. I am really looking for reliability.

Thanks guys,

-Shannon

 

[Dr Honda]

Factory pipe spends a lot of time jetting. So... run their specs, and adjust if needed.

As far as the fuel goes... as long as you didn't bump the compression... you will be fine with mid grade. (89) That is... unless Factory Pipe recommends 92.

 

[sdunkle]

Thanks Doc. I will give that a shot.

The manual does call for 92 octane. Once I get the motor back, I will get everything adjusted and report back!

Also, Dr. Honda, I also pulled one of your other posts about reinstalling an engine into a GSX....Excellent info and I am going to use it when I put this back together, Thanks!

-Shannon

 

[Spimothy Leary]

yes i definitely think you need 92 or better, 89 is not recommended at all.

 

[Dr Honda]

Thanks Doc. I will give that a shot.

The manual does call for 92 octane. Once I get the motor back, I will get everything adjusted and report back!

Also, Dr. Honda, I also pulled one of your other posts about reinstalling an engine into a GSX....Excellent info and I am going to use it when I put this back together, Thanks!

-Shannon

I run 89 in my 800. No issues. The thing with a 2-stroke is that the adjusted compression ratio is low because of where the ports are opening. With stock compression, and ignition timing... 92 isn't needed.

Just an FYI... my lawn equipment, and large model aircraft (with "gas" engines) I run them on Coleman camping fuel (white gas) That stuff is only 65 octane. It runs great, and smells like a BBQ.




****EDIT****


I just check the seadoo manual, and it says the 800 is good with 87.

But... like I said before... if Factory pipe wants you to burn 92... then do it.

 

[mikidymac]

Stick with the 92 as Factory requires. You will be turning a lot more rpm's with that setup and the increased heat especially in the PTO cylinder can cause detonation. Factory does a lot of dyno testing on their pipes so stick with what they say. This setup becomes more complicated than just the compression requiring the added octane as you are venturing away from the stock settings. Also make sure you are getting a good quality rebuild. Some of the bargin ones are not going to last with your setup.

 

[boattechguy]

i just talked to my partner who used to race seadoos and he says that more than a ten degree change in air temp causes u to retune the jetting. kinda sounds like a pain to me!!

 

[modblaster]

Hey guys, I am new to here and to owning a jetski in general. I got a great deal on a 97 GSX with a seized 787 engine. I am getting it rebuilt and going 1 size over factory. The specs include open flame arrestors and a factory spec 2 pipe with water injection. The jets are 150 and 152.5 mains and 70 pilots (per Factory's recommendations) with a primer kit and choke plates removed. As far as I can tell the impeller and intake grate are stock. The question I have is what octane fuel are you guys running with similiar setups? I called a couple places that rebuild these engines, including the shop rebuilding mine and have gotten mixed answers. I have been told anything from I need to go up to 175 mains and 75 pilots to you can't run that pipe without race gas so I wanted to see what people were actually running and what worked. I realize humidity, elevation, air temp, etc have a big effect on performance but I am mainly trying to figure out if the configuration I have is a safe base to fine tune from. I don't want to melt it down right away due to the pipe causing too much heat and detonation. I am really looking for reliability.

Thanks guys,

-Shannon

the factory pipe spec 1 or Rossier is good save for 92 octanes (to 7100 rpm and rossier you can raise your rpm to 7300 rpm save for gas pump).......the factory pipe spec 2 will eat your piston for diner...factory pipe spec 2 = 100 octanes
ask to bill o neil

 

[IDoSeaDoo]

What about a Spec I Factory Pipe? I have that, water injection, R&D flame arrestors, bored NOVI carbs with huge jets (like in the 160's I think), head that gives 180psi compression and MSD ignition enhancer as well as a R&D ride plate and 17/23 SkatTrak impeller. Will I have to buy 100 octane gas? What if I limit my RPM's to 7000? I haven't put it together yet... I have a motor that I will put a new top end on and put all these parts on this winter. What does it mean to have a "FRESH MOTOR"? The one I'm rebuilding has new bearings on the CB shaft and on the ends of the crank. I have not replaced connecting rod bearings, only the wrist pin bearings... Should I bore it as well?

Thanks!