need carb help

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sleeper_dave

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Got a new to me 94 vmax 600 ST. going through the carbs.

Machine has SLP pipes and had a cut down head gasket. I will be going back to the stock head gasket.

I set the float height per the book. It was low (higher number when measured inverted).

I went from a 155 to a 160 main jet. I jet all my toys fat because cylinders and pistons are expensive.

Now i'm at the needle valve. They're set on the first notch. One had a plastic washer under the clip, between the clip and the slide, and one had it on the other side. Which way should it go?

Should I set them back to position 3? I haven't had a chance to ride it yet and see how it does. The service manual doesn't have a hell of a lot of info on which way to adjust it. And the reference sheet I have for the pipes says nothing about it.

The needles say 8FLZ2 on them. Are they stock?
 
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Because I don't trust the previous owner to tune it. And there's a giant chunk missing out of one of the pistons, so there's a good chance it wasn't right before.
 
Make sure the carbs are spotless, plus those motors had a NASTY lean condition in the mid range. I like your idea of running rich..

Double check the needle jets - the nozzle as most everyone calls it, if that is the cylinder that burned down, you may want to go to a larger nozzle on that side. On my '96 that I had I think I was running Q-8's in both sides. Have you tried to contact SLP yet to see if you can't get a set up sheet?
 
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if your still utilizing the stock air box, set the needles back to the #3 position. make a mental note between your brain and right thumb to not use the midrange for extended periods. work the throttle constantly.
 
Can someone educate me on needle sizes, markings, and so forth? What does q-8 mean?

This is my first foray into slide carbs. I've become familiar with the super bn carbs on my waverunner though, after burning down 2 motors due in part to a stock lean mid range issue from yamaha!
 
Air box is there but a baffle was removed per the instructions for the pipes.

I found a sheet for the pipes. Stock jetting is 52.5 low, 156.3 high, 1 1/8 turns on air screw. SLP says to run 52, 155, 1/2 turn. At very low temps they say go to a 160 main jet. They say nothing about needle height. Other parts they just say "stock". So the only thing they suggest to richen it up is the air screw change. On these carbs, do the air screws affect fuel delivery at all throttle positions?
 
Q-8 is a mikuni reference # that designates the size of their needle jets. the higher up the alphabet the larger the ID of the jet. the bigger the # also the bigger the jet. Q-6 flows less fuel than Q-8. in order to safely modify that motor w/ pipes &/or porting you need different needles. when bruce schraeder was @ bender's he designed a longer & different taper needle that replaced the stock needle for modified 600 motors. it worked great. i had a bender ported/piped motor in my wife's sled that she put 7500 miles on & never had a problem with. most of those were quebec miles. i believe psi also had their own needles.
bob
 
Q-8 is the needle jet size not the needle designation. you need to do a search on mikuni carbs & familiarize your self w/ them.
i believe the stock needle jet in the '94 600 was a Q-6. so going to the Q-8 would be in the right direction. that's what i ran in mine. you also need to know if the head &/or the cylinders are modified & is the timing changed. also, is the needle you have the stock needle & are the slides & air jets stock. all this makes a big difference.
bob
 
I think the needles and needle jets are stock. I think I'll start with them at pos. 3 and see how it responds in the midrange, and go from there. Hopefully I can get it close without having to change the needle jet. I will pull it and check it though. Maybe it is a Q8 and that's why the needles were dropped to pos 1
 
sleeper_dave said:
Got a new to me 94 vmax 600 ST. going through the carbs.

Machine has SLP pipes and had a cut down head gasket. I will be going back to the stock head gasket.

I set the float height per the book. It was low (higher number when measured inverted).

I went from a 155 to a 160 main jet. I jet all my toys fat because cylinders and pistons are expensive.

Now i'm at the needle valve. They're set on the first notch. One had a plastic washer under the clip, between the clip and the slide, and one had it on the other side. Which way should it go?

Should I set them back to position 3? I haven't had a chance to ride it yet and see how it does. The service manual doesn't have a hell of a lot of info on which way to adjust it. And the reference sheet I have for the pipes says nothing about it.

The needles say 8FLZ2 on them. Are they stock?
Click to expand...
Dave I did a Google search and found this...
http://www.startinglineproducts.com/instsheets/09-600.pdf

Hope this helps you.
 
Sxr700Bandit said:
Dave I did a Google search and found this...
http://www.startinglineproducts.com/instsheets/09-600.pdf

Hope this helps you.
Click to expand...

Yep, I found that too. That's what i'm working from so far. The odd thing is that it's recommending stock or even smaller than stock jet sizes (stock is 156.3, the machine had a 155 in it). i stepped it up to a 160 which is good for colder temps than what I normally ride, according to that chart. I will ride below -20 very rarely, if ever.
 
sleeper_dave said:
Yep, I found that too. That's what i'm working from so far. The odd thing is that it's recommending stock or even smaller than stock jet sizes (stock is 156.3, the machine had a 155 in it). i stepped it up to a 160 which is good for colder temps than what I normally ride, according to that chart. I will ride below -20 very rarely, if ever.
Click to expand...
Well the factory usually jets the machines a bit rich so there are minimal engine failures(cheap insurance for them), and the high performance guys and performance orientated people are the ones who change the jets and lean out the mixtures because you gain power when you are closer to the "ragged edge". You may have an issue with the sled breaking up/missing at top end as a result of overly rich jetting and your plugs will look either a wet black or have a weird spotted effect due to having so much fuel in the combustion chambers.

Does your sled have a Q-8 in one carb and a Q-6 in the other?? When I did my sled with GYT twins I went with both Q-8s for a safety factor as I would rather change plugs than pistons. My sled ran great that way, plus I had to richen the needles one more notch than what was reccommended as my sled would serge when holding the throttle at a steady speed in the mid range, also with you going a little richer on jetting you may be playing it safe in a good way as todays fuels are for beans- If you know what I mean.
 
sleeper_dave said:
Yep, I found that too. That's what i'm working from so far. The odd thing is that it's recommending stock or even smaller than stock jet sizes (stock is 156.3, the machine had a 155 in it). i stepped it up to a 160 which is good for colder temps than what I normally ride, according to that chart. I will ride below -20 very rarely, if ever.
Click to expand...


Fairhaven still has ice and getting snow as we speak so get up there and test a little.

I'll be around all day Saturday and am closer to SCS if you want to stop by. The river looked iffy earlier in the week but my neighbor stopped by on his ATV Wednesday night via the river. It saw a bit sloppy but ridable. PM me if interested.
 
Which river?

I went across the black creek on Monday and it was iffy. Went across the Clinton river before the thaw and it was okay, but there were some iffy spots by the point over by belle maer.

Once I get the motor back together I hope to get it out a couple more times. I'm out of town all week for work this week though, and probably going skiing tomorrow, so that leaves little time for fixing or sledding. trying to get it fixed today (putting a top end in it). Haven't ridden this one at all, been riding an '84/'85 Phazer (turned a blown up '85 and a wrecked '84 into one sled).
 
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How do I check what size needle jet I have? I'm assuming I have to remove the "main nozzle" and look for identification marks. How the hell do I remove this? The manual just says "remove". Is it pressed in? screwed in?
 
sleeper_dave said:
How do I check what size needle jet I have? I'm assuming I have to remove the "main nozzle" and look for identification marks. How the hell do I remove this? The manual just says "remove". Is it pressed in? screwed in?
Click to expand...

n/m I figured it out. It's a slight press fit. A couple of taps and it came right out.

Mag side is a Q6. About to button that one back up and get into the PTO side. Mag side is the burnt down cylinder.

My changes are going to be main jet up from 155 to 160, needle from #1 to #3 with washers under the needle, and float height raised to spec. Should be richer throughout the mid and high range. I'll keep an eye on it and adjust again later if need be.

edit: PTO side is a Q6 also. Carbs are done. Synchronizing these things is weird, hard to tweak the eccentric to get them exactly the same. I'm not even going to bother trying to sync them with a vacuum gauge. Already had to trim some feeler gauges to sync them on the bench.
 
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