Just gone 701 to 753 with porting..

Big Kahuna

Big Kahuna

Administrator
Location
Tuscaloosa, AL
Every Setup Is Different....................


Where Geek Was Running His Porting (sport Port I Believe) And 38's He Was Running About 75 Low 135 Highs.

I Was Running Tlr Porting With 38's With 105 Lows And 135's (give Or Take A Few Points On The Highs)........... Other Than That, We Had The Same Setup...........

No Two Are Alike, That Why Nobody Can Tell You What Will And Will Not Work.
 
ski4

ski4

gonzo
Location
cleveland
this is where i have to say

THANK YOU JIMMY
i had acess to every jet, needle and seat etc
what a time and money saver

matt is right, you need a lot to try with and just experiment till the motor gets what it wants to eat.

oddly i am still running rich?????????????????????????????
 
T-bone

T-bone

brraap....thats so 2002
Superjetjim said:
Matt E - yes they are twin/dual stock 38mm Carbs - thanks for your help so far.. I take it richening up the screws with same jets as when it was 701 (and had all the other items already fitted) would not allow enough fuel to flow to cover the extra 53cc?.. I'm over simplifying this by the sounds of things... take the porting allows for loads more fuel too?

I'm a newbee at all this carb setup!!
Click to expand...


think of the hole thing as an air pump.....now that you have increaced the volume it will handle you will have to increase the flow to handle it. rejetting is amust .
 
Matt_E

Matt_E

steals hub caps from cars
Site Supporter
Location
at peace
Personally, I would leave the N&S and springs the way they are for now.
Start by adjusting your idle & low speed adjuster.
Then try sticking in bigger pilots (100) and see what it does.
If it's worse than before, drop the pilots down gradually until the low end is good.
Look at the Mikuni tuning manual, become familiar with it, and tune.
This will take a while.
Once the low speed circuit is adjusted right, move on the the high speed circuit.
 
Superjetjim

Superjetjim

X-
Finally got it sorted and OMG its pulling like a train!..:biggrin:

Well it turned out to be a couple of faults elsewhere that resulted in the lack of hit low down... the jetting/carb settings weren't a million miles off.

1) Firstly the 1 x way valve on the tank was knackered = no tank pressure from the pulse line and no fuel pressure at the carb - hit full bore and it struggled to fuel its self initially.

2) Next we put the ski on the scissor stand and ran the ski with the air filters off while looking down the carbs - as the revs increased to where the flat spot was (also at the point of maximum vibration) the rear carb atomiser ring suddenly started gobbing huge chunks of fuel into the intake - the front carb was atomising the fuel perfectly. Swapped the needle and seat for a new one (same size) and it stopped.

Hey presto - the problem was sorted.

Final settings

135 Top (2 turns out)
80 Pilots (1 3/4 Turns out)
95 Spring1.5 N/S

List of things found to be faulty:

Factory B header pipe top jet hole was totally blocked up - cleared blockage
Rear carb Needle & Seat badly worn - replaced
One way valve faulty on fuel tank

BIG THANKYOU to Chris at ATP (Air time Products) for his skill, patients and knowledge - these guys really know there stuff.:You_Rock_Emoticon:

Hope this post helps someone that maybe in a similar dilema..

Jim
 
W

waxhead

wannabe backflipper
Location
gold coast
From my playing with 38s
thats sounds very close to the figures i have found to work well
( if that matter)
have fun with your ski
 
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