SLP Piped Viper midrange sputtering

Millinocket Rocket

Millinocket Rocket

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Joined
Mar 25, 2005
Messages
725
Age
57
Location
Sebago Lake, Maine
First season with SLP pipes, jetted to SLP's 0-3000ft. specs, 47.5 pilots, fuel screws 1-3/4 turns out, needles at 4.0, 162.5 mains. When just cruising along it sounds very sputtery even up to 6-6500rpms and won't clean up till you lay into the throttle. Wash looked about right from what I could see, as it doesn't seem to show up well with Blue Marble oil. Plugs are chocolate brown. I'm thinking dropping the needles to 3.5 might clean up that midrange studder?

Also running machined 23cc SRX heads w/2 layers of stock Viper gasket.

Appreciate any insight...
 
Millinocket Rocket said:
Thanks Don, also only getting @7-8 mpg with semi-agressive trial riding! Love to be getting the 10 or so mpg's some others are claiming...
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7-8 sounds about right ESPECIALLY with the new crappy gas ! I've gotten as bad as 4 with mine !
 
pipdviper said:
7-8 sounds about right ESPECIALLY with the new crappy gas ! I've gotten as bad as 4 with mine !
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For trail riding? Ouch- that's awful. Love how it yanks my arms off now, but my buddys stock viper is getting almost double my mpg's.
 
Have I mentioned you should use a different cdi box
next time you come up, if you want to borrow a box and another set of carbs to try, I would love to see what you end up with.
I never found my slp pipes to work very good down low with less than 50 pilots
With an srx box, you might be able to atleast get better mileage up in the higher rpms, not sure if those pipes will let you run lower pilots even with the cdi box change.
let me know if you want to do some experimenting.
 
How does the carb re-venting work like Hauck was doing? I remember hearing he was running like 150 main jets and guys were getting great mileage. I think Mopar1rules knows about this.
 
Journeyman, I do run w/carbs vented to atmosphere, instead of to the airbox. I was running 155 mains, 3.5 needle pos, 50 pilots, and 1-3/4 turns and that was w/ported cylinders, megapower heads, and opened airbox, breathing thru the SLP's. If you guys want to switch from airbox venting to atmosphere venting on SLP pipes, I would start at 150-152.5 mains, 3.5 pos, 50 pilots, and 1-3/4 turns.
 
your not going to get better gas mpg because you changed the venting of the carbs, sure, it will make the carbs richer and youll use a slightly smaller main, but the main jet isnt whats eating up your trail gas mpg. Its the pilot and needle settings. 90% of the time unless your doing nothing but lake running your never even into the main jet soley trail riding.

You cant get away from the large pilots needed because its the pipe design requiring the fuel to accelarate the engine. The stock srx uses a 42.5 pilot, here with a viper the lowest I have ever been able to get away with is a 47.5, thats a huge differance in pilot jets. Your on the gas off the gas in trail riding, never much ever leaving the pilot/needle circuits in the woods.

best thing to do with a piped viper is try and get into a 47.5 pilot, and adjust the needles around 3.5, get your clutching and gearing spot on and youll get 10mpg, wont get any better unless your flirting with detonation in the mid range, sorry but speed cost money, and the money is in gas. :o|

this is why the "srx pipe conversion" is so attractive to many,with the cdi,srx pipes and the small 42.5 pilots, a srx can get 13-14mpg all day long even trail ported with clutching and gearing, yamaha had thier act together on that sled/engine design.
 
Thanks for the replies...I'm thinking just leaving it vented to box, unless there's some real mpg gains there. Scott, won't the 50's will just fatten it up more low end? There's no bog or anything. And won't the srx box lose power? Keep in mind I'm only putting out 95psi center and pto, 100psi mag w/2layers in. Same gasket was 115-120 psi with stock Viper head, using same gauge. Squish is .055-.058....

I'm nowheres near the pros you guys are, but it seems plenty safe to me with the better cooling heads and lower compression? Plugs are more of a dark chocolate color. Also running rear heat exchanger, and SRX base gasket.

I could live with 8,9,10mpg, clean up that sputter and get the midrange sounding smooth again.

Is it true that venting to atmoshere only affects main jets?
 
mrviper700 said:
your not going to get better gas mpg because you changed the venting of the carbs, sure, it will make the carbs richer and youll use a slightly smaller main, but the main jet isnt whats eating up your trail gas mpg. Its the pilot and needle settings. 90% of the time unless your doing nothing but lake running your never even into the main jet soley trail riding.

You cant get away from the large pilots needed because its the pipe design requiring the fuel to accelarate the engine. The stock srx uses a 42.5 pilot, here with a viper the lowest I have ever been able to get away with is a 47.5, thats a huge differance in pilot jets. Your on the gas off the gas in trail riding, never much ever leaving the pilot/needle circuits in the woods.

best thing to do with a piped viper is try and get into a 47.5 pilot, and adjust the needles around 3.5, get your clutching and gearing spot on and youll get 10mpg, wont get any better unless your flirting with detonation in the mid range, sorry but speed cost money, and the money is in gas. :o|

this is why the "srx pipe conversion" is so attractive to many,with the cdi,srx pipes and the small 42.5 pilots, a srx can get 13-14mpg all day long even trail ported with clutching and gearing, yamaha had thier act together on that sled/engine design.
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i never said that you would get better mpg w/venting to atmosphere. also, where i ride, i'm on the main jet alot. its pin it to the bars, let off for turn, then back to pinning it. if you have a viper jetted "safe", w/some nice piston wash going on, you won't see over 8-9mpg. my viper when it was stock, best it ever got was 10.5mpg and that was stock un-aggressive clutching, and it would average 9.7-10mpg. a piped viper will not get that, unless its the srx pipe/cdi conversion. also, out of the 5 srx's i played w/over the years, never ever got 13-14mpg. always averaged 11.5-12.2 mpg and that was stock jetting and stock clutching on 2 of them and altered clutching on the other 3, so if you properly jetted it up for the port work, you would never see that 13-14mpg and that 12mpg is gone too. i get anywhere from about 9-10.5mpg w/my ported srx. maybe if you rode the sled like a grandpa, you would see that 12mpg, but then you should probably just get a bravo, if you plan on going that slow.
 
I never found the venting change to affect anything other than after 1/4 throttle, that is where it started to show up.

I used 50 pilots to end up at a similar ends as you have. I had a lean bog transfering through, 1/4 to 1/2. I might have been able to take it out by lifting the needles but I also had an idle hang up problem I could never seem to get rid of without the 50 pilots.
All I can guess is that as I would let off the gas the larger pilots would add enough extra fuel to keep the idle from hanging up, kind of like flipping the choke after the fact.

I doubt you would see a power loss running the srx box since the extra timing is too much and heat is being controled by using raw fuel as a coolant.

Like I said, I don't think your going to get down to the stock srx pilots with those pipes but I am pretty sure your wot is going to require alot less fuel.

Think of it this way, a srx with 140hp and at speeds on the beds from 80-100, i have got 12mpg, with slp pipes as I remember, I was around 7-8mpg with those speeds on my viper which again, had roughly 140hp. Even if I believed the hype and said a piped viper had 150hp. Tthat mean I am using 33% more gas to get less than .7% hp increase. There is no way that extra gas is being used for power, the math just doesn't add up.

Free to experiment. give me a call when your up if you want to mess with it. Shop is free to use on the weekend for fun stuff like this.
 
mopar1rules said:
i never said that you would get better mpg w/venting to atmosphere. also, where i ride, i'm on the main jet alot. its pin it to the bars, let off for turn, then back to pinning it. if you have a viper jetted "safe", w/some nice piston wash going on, you won't see over 8-9mpg. my viper when it was stock, best it ever got was 10.5mpg and that was stock un-aggressive clutching, and it would average 9.7-10mpg. a piped viper will not get that, unless its the srx pipe/cdi conversion. also, out of the 5 srx's i played w/over the years, never ever got 13-14mpg. always averaged 11.5-12.2 mpg and that was stock jetting and stock clutching on 2 of them and altered clutching on the other 3, so if you properly jetted it up for the port work, you would never see that 13-14mpg and that 12mpg is gone too. i get anywhere from about 9-10.5mpg w/my ported srx. maybe if you rode the sled like a grandpa, you would see that 12mpg, but then you should probably just get a bravo, if you plan on going that slow.
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well,..you might need to look at your clutching/tuning setups if your srx gas mpg is that bad, I do them all the time and get 13mpg, ported,clutched and geared! I again remind you this is trail riding, this what the thread is about,not down a lake all day........ any sled ran wide open constantly wont get gas mpg.

no problem on a piped viper either,but 10mpg is as good as it gets, if your only getting that on a stocker, you again need to look at your tuning setups/track tension, general set ups/skills.
 
mrviper700 said:
well,..you might need to look at your clutching/tuning setups if your srx gas mpg is that bad, I do them all the time and get 13mpg, ported,clutched and geared! I again remind you this is trail riding, this what the thread is about,not down a lake all day........ any sled ran wide open constantly wont get gas mpg.

no problem on a piped viper either,but 10mpg is as good as it gets, if your only getting that on a stocker, you again need to look at your tuning setups/track tension, general set ups/skills.
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nope, don't need to look/check over a thing....its all good. SAFE jetting against poor fuel and cold temps w/aggressive clutching that loads the motor, will yeild lower mpg. i'm regeared as well too. i could get 13mpg as well, but it would have to be jetted so lean, that the motor wouldn't survive very long. not to mention if i had aggressive clutching in it, that i would probably have lean bogs in the throttle range somewhere, as i would be loading the motor too hard, for the amount of fuel being pumped thru the jets. i also noticed that engines tend to act more torquey, when fuel is being thrown at them. also, i run the trails around by me and not lakes. like i said, i pin it to the bars, hold it, then let off for the turn and back in it, so i will NEVER see 10mpg+ anymore. even when i rode my old '99 srx 700 mildly, i never got over 12mpg w/that thing. i've never seen a piped viper get 10mpg. hell, my stocker would hardly get that! there is people posting on here every year, about how their piped viper burnt down, and some of them had jetting that i bet was getting them 9mpg, so 10mpg and engine surviving sounds real questionable to me.
 
BETHEVIPER said:
I never found the venting change to affect anything other than after 1/4 throttle, that is where it started to show up.

I used 50 pilots to end up at a similar ends as you have. I had a lean bog transfering through, 1/4 to 1/2. I might have been able to take it out by lifting the needles but I also had an idle hang up problem I could never seem to get rid of without the 50 pilots.
All I can guess is that as I would let off the gas the larger pilots would add enough extra fuel to keep the idle from hanging up, kind of like flipping the choke after the fact.

I doubt you would see a power loss running the srx box since the extra timing is too much and heat is being controled by using raw fuel as a coolant.

Like I said, I don't think your going to get down to the stock srx pilots with those pipes but I am pretty sure your wot is going to require alot less fuel.

Think of it this way, a srx with 140hp and at speeds on the beds from 80-100, i have got 12mpg, with slp pipes as I remember, I was around 7-8mpg with those speeds on my viper which again, had roughly 140hp. Even if I believed the hype and said a piped viper had 150hp. Tthat mean I am using 33% more gas to get less than .7% hp increase. There is no way that extra gas is being used for power, the math just doesn't add up.

Free to experiment. give me a call when your up if you want to mess with it. Shop is free to use on the weekend for fun stuff like this.
Click to expand...

Thanks for the offer, I'd def. take you up on it but getting up there right now wouldn't be too easy timewise.

I see what you're saying now about the pilots. I thought you meant a low end bog when you stab the throttle off the line, but it sounds like it's part of my studder when going from pilots to needles. I guess I should have tried 50's today when I had the carbs out to adjust needles to 3.5. Seems to have cleaned up midrange a bit and sounds smoother. I'm gonna ride around here tomorrow and see how she goes, check wash and plugs.

Is the SRX box plug and play, or is there some wiring mods needed?
 
Hum, I saw an immediate increase in gas mileage when I went back to venting to the box. Went from about 110k tank to around 140k.Same trip, same conditions, same riding style? I've been watching my numbers closely for years.
 
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