Surfriding Carb Jetting 701 w/ Powerfactor

Mcarp6

Mcarp6

Location
Southern New Jersey
I currently sold my TNT pipe for a Powerfactor , I will be converting it to a wet pipe as well. I was wondering if anybody has ran a PFP on a 62T setup with dual 38's. If so can somebody guide me in the right direction for a start with jetting? I would assume it's not far from a b pipe jetting.

Thanks,
Mike


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Harbor

Harbor

Location
Stockton
I ran a type 4 dry pipe with 701 and 38's. Should be similar I'd imagine. Also ran it with continues water injection like a pf pipe. Ill have to check my notes for pop off and seat, jets were 77.5L and 140h with aftermarket airfilters. I'll check the other 2 in the morning

Edit: 28 pop off. 2.0 seat
 
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Mcarp6

Mcarp6

Location
Southern New Jersey
Harbor said:
I ran a type 4 dry pipe with 701 and 38's. Should be similar I'd imagine. Also ran it with continues water injection like a pf pipe. Ill have to check my notes for pop off and seat, jets were 77.5L and 140h with aftermarket airfilters. I'll check the other 2 in the morning

Edit: 28 pop off. 2.0 seat
Click to expand...



I was running similar jetting on my TNT V3 and finally got it to run really good.

140/75 2.0's and 95g . Popoff with aftermarket filters 23/25 range

I am going to try it at that first and see how I am doing.


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kevbo

kevbo

Location
dfw
RivMan said:
Not 38's but my OEM 44's on a 701/Wet PFP run well with:

High: 115
Low: 120
Needle / Seat : 1.5
Spring: 95
Popoff: 43
High Screw: 1-1/2
Low Screw : 1-1/2

-Rob
Click to expand...
Those specs would be much too lean for a 62t cyl at 81mm without a restrictive flame arrester. What I'm getting at is, never ask what someone else is running, just tune the carb.
 
Pro-pulsion

Pro-pulsion

Location
Ontario, Canada
I run a Speedwerx dry pipe and have read once or twice that some consider it to be where Power Factor derived the idea. My settings are...

Stock popoff @ about 50psi
Needle and Seats : 2.5
Pilot Jets : 105
Main Jets : 145

Starting point for mixture screws
High : 1 1/8 turn out from lightly seated shut
Low : 1 turn out from lightly seated shut

Adjust as needed according to engine response from there, all engines will respond differently. The fine tuning is up to you to isolate the sweet spots, hope this helps.

This is a quote from John Quast at Speedwerx:

"If you are trying to keep this pump gas(91 octane) safe and you plan on holding it wide open for any length of time, I would keep the 37cc domes. 35cc domes will be too much if your are doing anything other than freestyle.
I would highly recommend changing your CDI box with something that has more timing. I'd recommend a Advent or and EPIC CDI but even an MSD enhancer will give you a boost in bottom end over stock.
As far as jetting goes, the only notes I have with stock 38mm carbs and a ported cylinder is 145 mains, 105 pilots, 2.5 needle & seats with 115 gram (gold) springs. I would highly recommend staying with a dual carb set-up verses a single carb. As far as water routing goes, I attached a copy of our instructions which will have recommend water routing. I'd highly recommend running dual cooling and setting it up like our instructions say."

He also specified at a different time to me that he recommends the water routing mentioned above to be one supply line for the engine and a separate supply line for the pipe.
 
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jo5hi3

jo5hi3

Location
Charlotte NC
Pro-pulsion said:
I run a Speedwerx dry pipe and have read once or twice that some consider it to be where Power Factor derived the idea. My settings are...

Stock popoff @ about 50psi
Needle and Seats : 2.5
Pilot Jets : 105
Main Jets : 145

Starting point for mixture screws
High : 1 1/8 turn out from lightly seated shut
Low : 1 turn out from lightly seated shut

Adjust as needed according to engine response from there, all engines will respond differently. The fine tuning is up to you to isolate the sweet spots, hope this helps.

This is a quote from John Quast at Speedwerx:

"If you are trying to keep this pump gas(91 octane) safe and you plan on holding it wide open for any length of time, I would keep the 37cc domes. 35cc domes will be too much if your are doing anything other than freestyle.
I would highly recommend changing your CDI box with something that has more timing. I'd recommend a Advent or and EPIC CDI but even an MSD enhancer will give you a boost in bottom end over stock.
As far as jetting goes, the only notes I have with stock 38mm carbs and a ported cylinder is 145 mains, 105 pilots, 2.5 needle & seats with 115 gram (gold) springs. I would highly recommend staying with a dual carb set-up verses a single carb. As far as water routing goes, I attached a copy of our instructions which will have recommend water routing. I'd highly recommend running dual cooling and setting it up like our instructions say."

He also specified at a different time to me that he recommends the water routing mentioned above to be one supply line for the engine and a separate supply line for the pipe.
Click to expand...

You will never achieve 50 psi pop off with a 2.5 needle and seat........
 
Pro-pulsion

Pro-pulsion

Location
Ontario, Canada
I'm just going by the last numbers I had with stock springs, granted you are probably correct as I have yet to test since changing up to the new n&s's, but basically the point is, Speedwerx recommended 115 gram springs. In 1.5 n&s's they popped at about 55 if I remember correctly. I just assumed they must be close under the assumption that it is the spring tension which determines popoff pressure.
 
jo5hi3

jo5hi3

Location
Charlotte NC
Pro-pulsion said:
I'm just going by the last numbers I had with stock springs, granted you are probably correct as I have yet to test since changing up to the new n&s's, but basically the point is, Speedwerx recommended 115 gram springs. In 1.5 n&s's they popped at about 55 if I remember correctly. I just assumed they must be close under the assumption that it is the spring tension which determines popoff pressure.
Click to expand...

The combo of the seat size and the spring pressure is what determines pop off pressure. With a 2.5 seat and a 115 gram spring, you are probably some where around 20 psi. But with that said the only real way to know your pop off is to check it. Springs vary soo much one might pop at 20 and the other pop at 15.
 
Pro-pulsion

Pro-pulsion

Location
Ontario, Canada
You guys are absolutely right on the combination making the final word and I must apologize for my post being misleading...but also for my previous posting. After re-reading it I thought...crap, that totally did not come out in a way I meant for it to. It was meant with good enthusiasm and intention, not to sound condescending. This full time employment thing really interferes with the ski life sometimes lol...by that I mean break times are too short and trying to get the right thought out via cell phone just doesn't always work in your favor. I vote for 45 min break times, 2 hour lunches and three day work weeks...who's on board with that? :D
 
Quinc

Quinc

Buy a Superjet
Location
California
mikuni_pop_off_pressure_chart.jpg
 
Pro-pulsion

Pro-pulsion

Location
Ontario, Canada
So I did some back to back testing on jetting this weekend and here is what I found...

85 pilots
135 mains
1.5 needle and seats
115 gram springs

results : Great performance but had 2 mini-seize occurrences. By this I mean after wide open throttle runs of more than 10 seconds and cutting the throttle then shutting the ski down, as the cylinders cooled faster than the pistons I believe they squeezed against the pistons locking them up. On a restart attempt only a few minutes after shut down the engine would not turn over. My theory is the 1.5 n&s's are just a shade under being able to adequately supply the fuel demands of the engine after being ported on the exhaust and cases along with having such a massive pipe to support.

Setup 2 :
85 pilots
135 mains
2.3 needle and seats
115 gram springs

Results : Again excellent performance, still easily tuned with minimal adjustment needed, no seizing conditions after a 10 second wide open run and cooling down of the engine.

Setup 3 :

Speedwerx recommended specs
105 pilots
145 mains
2.5 needle and seats
115 gram springs

Results : Much harder to tune, could not clean up certain flat spots near peak rpms, initial tuning resulted in liquid carbon pouring out of the exhaust outlet and very rough idle which again I could not tune out of it without negatively affecting other areas of the fuel circuit such as the overlap of 1/3 throttle transitioning from low to high speed circuits. The power on the top was decent but no better than setup #2, in fact a little lazy by comparison. Fuel economy was terrible too. An hour and a half ride time consumed 2/3 of a tank whereas setup 1&2 would give me respectively about 2 1/2 hours on 2/3 of a tank. My theory, Speedwerx was only going on a start out super rich basis to prevent lean failures and lean out from there. For my ski, setup #2 worked out to be the best performance on all levels.
 
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Air time

Air time

Location
Sydney Australia
Reviving this old thread,I have just fitted a speedwerx freestyle pipe to my 62t 701 with 38s have 145h 80L and 2.5ns what carb adjustments should I start at for the mixture screws?
 
S

Storbeck

Location
Minnesota
Put the adjuster screws in the middle, maybe one turn out each. Then tune.

Nobody on the internet can tell you what the tuning of your carbs will need to be down to the turning of the screws. You're going to have to tune your carbs on your motor in your ski in your conditions. That will probably require you to do some twisting if the screws and changing of the jets.
 
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