SRX Needles And Nozzles?


Please don't do that!

I know you recently purchased that brand new Viper engine. I sure hope you didnt expect good fuel mileage. I get 9 or 10 mpg and all the SRX and Apex riders in my group think its hilarious. Their has been some of discussion lately about vented to atmosphere or air box and I hope you've been keeping up on your reading. Also several guys on here have 780 motors with posts on jetting. I think you may want to search for info or post your questions and include riding conditions, kind of fuel your burning, engine details, compression, airbox stock or gutted to get some idea of what others are running for jets.
 
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carbs

Stock srx jetting will be way too lean for a 780 piped viper.Do you have stock carbs or bored carbs.
 
Fact of the matter is srx needles and nozzles worked perfect for me on my piped viper. 2 burndowns with stock needles and jets.
 
780 Jetting

In my 780 with SRX needles and nozzles vented under hood (not in the air box) I ran 150, 150, 152.5 mains most of the time unless it was real cold I went to 152.5, 152.5, 155. I have been told that vented VS non vented is worth about 10 numbers on the main jet. The pilots were 50, 50, 52.5. Gas mileage still sucked.....but most people don't get a big bore for the gas mileage do they?

Madmatt
 
780

Thanks for chiming in. I'm not concerned about milage. What i do want is jetting as close a possible, I hate running it fat. I'm running the air box stock, with 4 TPI's on top ,two 3 " flow rites cut into the dash, 300' elevation, -5 to -25 C,run 91 to 94 octane. ( have octane booster but not sure if it's needed).My other posts show my sled setup! So it sound like a good way to go with the SRX needles and Nozzles. Any other comments?

Thanks Steve
 
Viper 780 jetting

Viper 780 jetting. All riding in quebec, trail fuel, bored carbs, gutted box, vented to atmoshere, klotz oil set at 23.5 freeplay, 12.1/2 to 1 compression
153.8 153.8 156.8
4th 4th 5th
2 under 2 under 0 under
52.5 52.5 55
all fuel screws 2 3/4
It would seem with this jetting I would be rich. The piston wash is small pensil eraser size in the corners on the piston.
 
Mac 780

Mac, that's with Viper brass right? Those # would make sense with mine if you are running Viper brass and I'm running SRX brass which is inherently richer.

Madmatt
 
Viper 780

Matt, nope incorrect. SRX needles and nozzels. When I first started with the 780 I used to run leaner. Although I havnt seized since the big bore I am wearing out pistons every 2k to 2500 miles. I've been slowly increasing my jetting with hopes of making this motor live a little longer. One other change this year is the addition of Mega Power heads that MrViper has recently machined for me opening them up from 700 to 780 size. Same low compression but a different squish angle. Maybe he will chime in and explain if he sees this. This is an attempt to make this motor run cooler. Everyone on this board reports the Mega heads flow the most water.
 
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Its the balance between the slide cut away and the low speed response, its not nearly as important as increasing the nozzle and needle flow. Easier to obtain a good qualty idle with the leaner slide. The pilot jet in a piped viper has to be pig rich due to the pipes design, the needle the same rich setting as per the pipe and some extra ign timing in mid section of curve, but it still boils down to each engine is going to be differnt specs due to the porting and in my opinion the head set up has more to do with the engines fuel drinking tendencies then the other componets. To the best of my memory there are not any viper pipes on the market in which you can run leaner then a 47.5 pilot jet, right theres the gas pumping thru the motor along with rich needle settings.Mian jet selection has alot to do with the actual engine set up.

Srx nozzles and needles will help a piped viper live longer!
 
Mr Viper, Could you please explain what we could do to our Viper head design that would make our sleds burn less fuel. I hope what ever is... you did it to my heads. Thanks
 
Head work

Yes Mac, I believe he did that to my megapower heads last year. He's got some secrets that work very well. You are right, that jetting does seem rich with SRX brass. Whatever works for you!!!

Madmatt
 
nozzles, ie: needle jets, are the long brass tubes, between the main jet and the floor of the carb body (needle slides into it). ski
 
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