Viper Fuel Pump, 3 outlets only need 2

Y

Yamablue

Member
Joined
Mar 7, 2004
Messages
221
Location
Ham Lake, Mn
Anybody see a problem with blocking off one of the fuel outlets on the viper fuel pump? I have a Polaris 38mm rack and it only has 2 inlets. I had a little 2 into 1 manifold made up a few years ago, but I can find it and I can't find the needed fittings anymore. Do yo think the viper fuel pump can keep up on the volume from only the two outlets or not? I'm having a real hard fitting a T in there to combine two lines in a different manner than I did before.
 
The polaris pump is similar to the yami, both Mikuni, but I'm using the std viper pump and have been with these carbs, just can't find my fuel line adapters.
 
I am running the Polaris XCR 800 TM 38 carb rack on my SRX with the TPS.
I made a little manifold so I run three fuel outlet lines off the SRX pump and convert it to two for the XCR carbs.
You have to use the Polaris TPS as it rotates the opposite direction of the Yamaha one.
You will have to reverse the grey and red wires on the TPS wiring. I just removed the two outer wires on the connecter that plugs on to the TPS and switched them. The centre wire is green and it is the TPS output to the CDI.
 
Bob, the 38s are not new to me, just putting them back on. I have the tps taken care of. What are you running for jetting and needles, out of curiosity?
 
Yamablue said:
Bob, the 38s are not new to me, just putting them back on. I have the tps taken care of. What are you running for jetting and needles, out of curiosity?
Click to expand...

My sled is not stock...and I run Power inc pipes...With the XCR 800 carb rack, I have had a heck of a time getting the jetting dialed in..when it ran good off idle and mid range...it was lean at 3/4 throttle...when it was good at 3/4 throttle, it was fat down low!
I finally changed the slides to 3.0[stock XCR are 2.0] and then I could get it dialed in.
Here's what I am currently running:
Mains: 360
Needles: stock XCR 800 position 3
Pilots: 55
Fuel screws: 1 1/4
Air jets: .8
Vents hanging...NOT in AIRBOX
This jetting has been safe in my sled right down to -28c

I also had a few other issues running the 38s
- Because I use so little throttle for most riding conditions, my oil consumption went from 40:1 to 100:1 !!! even with all the slack taken out of oil pump cable so it was maxed out at full throttle...I now add oil into fuel tank every time I gas up to ensure I am geting adequate oil to the engine.
-the throttle travel is much greater with the 38s so the TPS is also rotated further , on my sled, this created too high of voltage out of TPS to CDI at full throttle[4.5 volts rather then stock approx 3.0 volts] this resulted in a bog when wide open not unlike overly rich jetting would create.

Since you have been running these carbs you probably have already dealt with and sortred out the side effects created with the bigger carbs...it was a bit of a challenge for me to sort out as I was starting from scratch.
 
Hmm, never noticed a bog at wot, but I have a different timing curve in mine. I haven't run these with stock cylinders, I had race ported cyls before. I ran 410 mains, 50 pilots, stock needles at 4, std air jet, std slide. I run CPR pipes and spun the motor to about 93-9400. I'll only spin it to 9100 with the stock cylinders. It did run rich down low.
 
If I remember correctly, it was vented to the belly pan. I was richest at full than 3/4 throttle. Thinking of thinning out some needles to suit my needs.
 
I found these XCR 800 38s EXREMELY sensitive to sycronization...but since i have had them fairly well dialed in[3000+ miles this season] I really like them. Throttle response + top end is great and my fuel economy couldn't get much better. On the last ride I did on groomed trails cruising I only used 19 litres on a 80 mile leg. Thats 16 mpg US and 19 mpg Canadian!
 
Went through the syncro stuff and I'll agree, very sensitive. The mileage was the big reason I wanted to put them back on. Even when I had the carbs set rich, I got better mileage than the pipes and stock carbs,and in some cases better then the single pipe and stock carbs. Maybe if I could get my hands on some SRX carbs with the different nozzles and needles, by CPR pipes would MPG better. Thanks for your input about your setup.
 
Yamablue said:
BTW Bob, what did you do about the TPS?
Click to expand...

I am still trying to sort the TPS issue out on the TM 38s.
I tried running two TPS, both actively wired to the CDI..one fixed on the airbox set for idle voltage as per Yamaha specs...the other variable on the carb rack set for the normal full throttle voltage...that did not work.
I now have a bit of a bush league solution...not my typical method..LOL
I have one TPS fixed on the airbox set at 3.0 volts.
I have a second one in the normal position on the carb rack that varies with throttle opening and is callibrated for idle like a normal TPS.
The variable one works great for trail riding but for high speed full throttle runs it provides way too much voltage to the CDI...So...I installed a selector switch connected to the green output wire from both TPSs. For normal trail riding I have the variable TPS on carb rack selected[95% of the time]. When I have to run my buddies across the lakes or drag race ect..I select the fixed TPS.

Works for me...for now
 
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