TehXshizzit
#Killer City Rippers
- Location
- H816
Any suggestions on what size? I'm thinking of ordering 140s for the main at least so I can order the lows as well.
What do I need to do to make my 760 64x low end smoother?
- Thread starter TehXshizzit
- Start date
You kinda still haven't said what size you have in there right now, but what you're describing does kinda sound like lean, and since most people with your combination seem to end up somewhere in the nieghborhood of 115 high, 125 low, I would order some 115 high speed and 125 low speed, plus a size or two up or down would be good too.
Then go do jetting. Put the ski up against a dock or strapped to a trailer or somehow restrained so you can let it idle in the water. Turn the low speed screw out until the idle falls off, then turn it in until it falls off, find the point where it idles the highest, if that is more than about 2 turns out (or if you can turn the screw out more than two turns without it falling off), go richer on your low speed.
Very likely, you'll end up about 125, and your high speed will be WAAY rich.
Then go do jetting. Put the ski up against a dock or strapped to a trailer or somehow restrained so you can let it idle in the water. Turn the low speed screw out until the idle falls off, then turn it in until it falls off, find the point where it idles the highest, if that is more than about 2 turns out (or if you can turn the screw out more than two turns without it falling off), go richer on your low speed.
Very likely, you'll end up about 125, and your high speed will be WAAY rich.
I agree with storbecks recommended jetting, I’ve found that you can achieve a good idle but still have off idle hesitation tho if your low speed jet is still too small. I like to ride it from 0-3/8 throttle only and see how it runs, then I make a low speed jet adjustment and go and ride it again the same way and see how it feels.
I usually use the dock thing to get close, then go check response, particularly looking for any hesitation indicating too lean on the low speed. I don't consider myself to be very good at jetting, but this is the basics.
TehXshizzit
#Killer City Rippers
- Location
- H816
So it's stock jets, and I quoted it earlier, but I guess there is a misprint in the book. Looking at the 64x01 and 64x02.
After talking to some other people it should be fronts 135 main and 105 pilot....rear 137.5 and 105 pilot.
I had a guy who has a similar set up say to start at 140s and go from there, so your saying I need to go down to 125 is that more gas or less gas?
After talking to some other people it should be fronts 135 main and 105 pilot....rear 137.5 and 105 pilot.
I had a guy who has a similar set up say to start at 140s and go from there, so your saying I need to go down to 125 is that more gas or less gas?
Attachments
TehXshizzit
#Killer City Rippers
- Location
- H816
When you say 115 high and 125 low, are those jet sizes? Just wanting to be clear. Also probably a noob question but do you guys change jets out at the lake and keep testing??
Also should I test my pop off psi too while I'm changing jets...will that help me get in a ball park of what my lows need to be, and if so what should my psi be? 30ish?
TehXshizzit
#Killer City Rippers
- Location
- H816
Also I was looking at tuning my b pipe. Currently my bottom is sticking an 1/8 inch out and my top about a 1/4 including the threads under the locking screw. I hear you run these pipes pretty hot....mine has never sizzled water before.
Top is shown. In the attachment.
When factory or people say 1/2 out...does that literally mean a half a turn from closed?
Top is shown. In the attachment.
When factory or people say 1/2 out...does that literally mean a half a turn from closed?
Attachments
Ah we need to take a step back to some basics.
Each carb had two jets. A high speed jet and a low speed jet. There are also two screws, a high speed screw and a low speed screw
To put things in the most basic terms, the high speed jet and screw affect high throttle openings, the low speed jet and screw affect low throttle openings AND high throttle openings.
There is also the pop off pressure which affects everything.
So the sequence here is you chose and set your pop off pressure. Do this at home in your shop.
You then set your low speed using the procedure I described earlier, and only then can you set high speed. You have to do the low speed first because it affects the high speed, and you have to keep in mind that high speed is a combined total, so if you make the low speed richer, the high speed also gets richer.
Classic symptom of low speed bring lean is a hesitation when you suddenly apply throttle. There ski will fall on its face almost like you hit the kill switch, if you're really far too lean it can literally stop running. But it is possible to be too lean on the low speed and still too rich on the high speed (probably this is what you have).
Changing Jets at the lake is exactly what you'll probably have to do, it will probably take a few tries to get it right, and I would encourage you to do since expirementing to get a feel for what the changes do.
Get familiar with this manual, and search around for since if the zillions of threads on jetting. Bed aware that but everybody agrees on exactly how you should go about it, but if you get familiar with the basics then go do some playing with it yourself you'll get it.
https://www.google.com/url?sa=t&sou...FjAAegQIAhAB&usg=AOvVaw3OX3f9bU2_M-mVnlkW8VhS
Each carb had two jets. A high speed jet and a low speed jet. There are also two screws, a high speed screw and a low speed screw
To put things in the most basic terms, the high speed jet and screw affect high throttle openings, the low speed jet and screw affect low throttle openings AND high throttle openings.
There is also the pop off pressure which affects everything.
So the sequence here is you chose and set your pop off pressure. Do this at home in your shop.
You then set your low speed using the procedure I described earlier, and only then can you set high speed. You have to do the low speed first because it affects the high speed, and you have to keep in mind that high speed is a combined total, so if you make the low speed richer, the high speed also gets richer.
Classic symptom of low speed bring lean is a hesitation when you suddenly apply throttle. There ski will fall on its face almost like you hit the kill switch, if you're really far too lean it can literally stop running. But it is possible to be too lean on the low speed and still too rich on the high speed (probably this is what you have).
Changing Jets at the lake is exactly what you'll probably have to do, it will probably take a few tries to get it right, and I would encourage you to do since expirementing to get a feel for what the changes do.
Get familiar with this manual, and search around for since if the zillions of threads on jetting. Bed aware that but everybody agrees on exactly how you should go about it, but if you get familiar with the basics then go do some playing with it yourself you'll get it.
https://www.google.com/url?sa=t&sou...FjAAegQIAhAB&usg=AOvVaw3OX3f9bU2_M-mVnlkW8VhS
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Yes, literally screw all the way in until the screw is bottomed out then turn back half turn it three quarters turn it whatever setting people are describing.
Same thing with the mixture screws on the carburetor, when people say "one turn" they mean they screwed it all the way in and backed it out one turn.
On the pipe obviously you have to loosen the jam but, do the adjustment on the screw, then tighten the jam but while being careful not to turn the screw.
To clear it up a little more, main=high and pilot=low.
- Location
- Charlotte, NC
open the top screw of the pipe for better bottom end. theres no set number of turns, its gonna be set based on how you want it setup. the farther open the screws, the more bottom end and cooler the pipe will run, the hotter and less water, the less bottom end, midrange youll have in exchange for more rpms. 3/4 turn open is just a recommended setting. you could end up with more water than that. you can run the ski, open the screw, ride again and keep opening until you feel a noticable powerloss at high rpm, then back the screw in 1/8 turn. im running a 62t engine in a superjet with a c4 chamber and it felt best with the top screw at 1 turn open all others closed.
- Location
- Charlotte, NC
question, why set up with reverse jetting? larger pilot with smaller main.
People call it reverse jetting but reality it’s just jetting. Set the low speed jet where the bottom end runs the best then set the high speed up for best top end pull and if the low speed jet is bigger than the high speed then that’s just how it is.
@TehXshizzit On the b pipe, close top 2 screws and set the bottom one so the beginning of the the chamber (right after the coupler) sizzles just a bit(usually around 1/2-3/4 turn out). This is setting for max power, I’ve seen people start just jacking with the top screw thinking it’s automatically just going to add power. You need to get your base line set first and get the pipe up to temp. Temp is key and if it’s too cold it won’t work much at all. Once you set your temp you can start opening your top screw for better low end response. Open about 1/2-3/4 turn.
- Location
- Charlotte, NC
reverse jetting just doesnt seem to make a lot of sense. running higher popoff then running a huge pilot jet with a small main jet. ive never had to set one up that way to get it to run right.
adding water to the pipe isnt really adding power, its just changing where the power comes on and is made. the op is saying he doesnt have much bottom end. opening the top screw will help with that. do a degree. but it sounds like he has carb tuning issues to work out first before messing with the pipe. every ski ive had with a factory pipe always ran better at least to me with the top screw open and some middle screw cracked open. when i put a blaster chamber on my x2, i opened the bottom screw 1/2 turn, didnt like the way it ran, then started opening the middle cause that particular headpipe didnt have t handle screws and i couldnt get an allen on the top to open it without removing the headpipe. it didnt have any bottom end either and opening the middle screw didnt help much. going to the t handle screws, i reset them all with just the top open. ended up with 1.5 turns out on top and it runs and accelerates much harder and still has solid top speed. the closer the water injects to the exhaust ports, the more dramatic affect on the power range it will have.
the pipe tuning youre talking about sounds more like for a bouy chaser. if the pipe is too cold then it will have great bottom end but wont rev out entirely. its all about what type of riding youre doing.
adding water to the pipe isnt really adding power, its just changing where the power comes on and is made. the op is saying he doesnt have much bottom end. opening the top screw will help with that. do a degree. but it sounds like he has carb tuning issues to work out first before messing with the pipe. every ski ive had with a factory pipe always ran better at least to me with the top screw open and some middle screw cracked open. when i put a blaster chamber on my x2, i opened the bottom screw 1/2 turn, didnt like the way it ran, then started opening the middle cause that particular headpipe didnt have t handle screws and i couldnt get an allen on the top to open it without removing the headpipe. it didnt have any bottom end either and opening the middle screw didnt help much. going to the t handle screws, i reset them all with just the top open. ended up with 1.5 turns out on top and it runs and accelerates much harder and still has solid top speed. the closer the water injects to the exhaust ports, the more dramatic affect on the power range it will have.
the pipe tuning youre talking about sounds more like for a bouy chaser. if the pipe is too cold then it will have great bottom end but wont rev out entirely. its all about what type of riding youre doing.
Quinc
Buy a Superjet
- Location
- California
I would start with 110 Main jet and 125 Pilot jet 24psi pop off.
How to check pop off:
How to rebuild your carb
there is a thread on here somewhere that goes over how to adjust your bpipe screws and why etc
How to check pop off:
How to rebuild your carb
there is a thread on here somewhere that goes over how to adjust your bpipe screws and why etc
- Location
- Charlotte, NC
read factory pipes website they give a great explanation. also depending on what chamber ltd or mod youre running will affect the bottom end. the limited is 1.5 inches longer and will have a little better bottom than the mod chamber.
That combination of jetting is pretty normal for oem Yamaha 44mm carbs. I'm running a similar motor and I don't remember exactly what's in there, but it is something like 125 low speed 105 high speed. Any leaner on the low speed and it stumbles, any richer on the high speed and it's too rich. I agree completely with max boost it's not "reverse" jetting, it's just jet the thing to the way it runs best. It's not like there is some "forward" jetting combination that would run right and somebody is choosing the reverse combination, it's just the correct jetting.
I suggested to the OP a richer high speed because A: it's best to start on the rich side, B: he's not running the stock flame arrestor, C: he doesn't have the larger bore or porting. and D: most people seem to be a little richer on the high speed than my combo.
For what it's worth I also have an 898 with SBN 46's and that needed a slightly lower number on the high speed than the low speed too. Again it's not like I said "I'm going to choose reverse jetting" I just jetted it to make it run right and ended up with a smaller number on the high speed.
I suggested to the OP a richer high speed because A: it's best to start on the rich side, B: he's not running the stock flame arrestor, C: he doesn't have the larger bore or porting. and D: most people seem to be a little richer on the high speed than my combo.
For what it's worth I also have an 898 with SBN 46's and that needed a slightly lower number on the high speed than the low speed too. Again it's not like I said "I'm going to choose reverse jetting" I just jetted it to make it run right and ended up with a smaller number on the high speed.
Quinc
Buy a Superjet
- Location
- California
There are a few great threads on here with waxhead and others that are much smarter then me that explain the benefits.
- Location
- Charlotte, NC
yeah im running a single 46 on a ported sp750 in a x2. im running 25psi popoff (2.0) n/s with 95g spring, 125 pilor 155 main. obviously different setup entirely. im guessing the dual 44s and 46 are jetted that way, not the singles. possibly cause the larger dual carbs weakens the signal to the low speed circuits requiring larger jetting on the pilots than mains.