Carb experts needed, Please!: 700 VES Set-up

[gtfoxy]

I have a fairly indepth question I am hoping someone can give me an answer to.

I am almost done putting together a 02/03 700 VES Engine for a 03 SKS. I have a set of carbs off a 01 800 XC SP I was going to use.

After doing some research I found the 01 800 carbs utilize a piston valve with a 2.0 cutback and a J8-9EFY02-61-3 Jet needle in the 3rd possition.

Begining in 01 the VES 700 and subsiquent 02+ 800 VES utilize a 1.5 cutback piston valve and a J8-9DFH10-57 jet needle (800s were in the 3rd possition, 700s in the 2nd).

All of which used the same P-8 Needle Jet, so that is a constant.

Also, a change from a .7 Long Pilot Air Jet in the 01 800 carbs to a .9 Long Pilot air jet in the 02+ VES 700/800 carbs.

I understand the 2.0 cutback will allow for a leaner air fuel ratio at part throttle than the 1.5 (provided the same needle is being utilized) but I am not familiar as to the metering differences of the different jet needles.

It appears for some reason, depending on low speed fuel delivery of the J8-9DFH10-57 jet needle, they wanted to richen up the VES engines a tad. Or perhaps this needle has a lesser flow at lower openings and they compensated by allowing less air to enter at these throttle openings, thus maintaining the desired 14:1 A/F ratio.

My question lies in, can I utilize these carbs with a needle change to the correct J8-9DFH10-57 needle while still utilizing the 2.0 cutback piston valve, making a change to the correct main jets for my altitude? Or can I increase the main jet and live with it being a little fat at the top end to keep it from baking a cylinder at part throttle? However, a leaner midrange and subsiquent slightly longer plug life and perhaps snappier throttle response would be nice.....

Or another option, leave the jet needles that came with it in, drop them to the 2nd possition and use the VES jetting differences for the 700/800's as a guide as to how to jet for this 700. (I have heard some say they actualy think the non-ves's felt more snappy down low, granted that could be purely a qualitative analogy, but given this apparent calibration difference it may be somewhat accurate.)

Do the VES' require a more robust mid range fuel map for something like valve cooling or lubrication?

Is the change from a 1.5 cutback for the factory calibration to a 2.0 cutback going to make that much of a difference? Or is it so much of a difference I should just sell these and start with 01+ VES Carbs with the proper cutback, needles and air jets? Needles and Air jets are relatively inexpensive, but piston valves are not.

I will try and see if I can compare the needle charts at the dealer tomorrow to see where the metering differences between the Jet needles really are.

Any advice would be greatly appreciated!

 

[gtfoxy]

Anyone?

 

[hesse]

what ignition are you running 02 700 or 03 as they had some changes in them?

 

[sled_guy]

You need to get the needle chart and compare the needles. The RMK even in '02 used the 2.0 cutaway. And then in '03 the RMKs went even richer on the needles than in previous years and dropped main jet size.

Cutaway is really only going to affect off idle performance. The disadvantage there is that you don't have an air screw on those carbs but jets so changing isn't that easy. But you do have fuel screws so you'll be ok with the 2.0 cutaways. You may end up with a needle position change to compensate for it, but you'll just have to see what off idle performance is like.

As for needles, the '02s were lean in the midrange (on RMKs at least) and required big main jets to even be close to reasonable. Worked ok at altitude but at sea level keeping the midrange cool was near impossible. Some people suggest that this contributed to the problem with the corners of the valves melting at prolonged midrange riding. I don't buy that fully because I've seen the same thing happen on '03 and newer 800s with the richer needles.

But for sure putting in the richer needles made jetting much crisper because the mains could be dropped dramatically (on an 800RMK it's like 6 jet sizes). But at the same time the carbs were switched to both fuel and air screws so adjustment in the part throttle range was easier.

So what all does that mean. I personally would suggest you get the '03 and newer needles. They are the richest possible. I'd use those and jet to the '03 700RMK specs for everything except air screw obviously. I'm going to guess you'll end up at 1.1 on your air jet from the .9, but you'll just have to play that by ear.

Is that confussing enough?

sled_guy

 

[gtfoxy]

Thank you so much for the attention and response.

Ok, a few notes;
1. the 02 700/ 800 both utilized the 3rd clip position.

2. I am currently utilizing an 02 Flywheel and CDI. I had a bear of a time finding an 18deg 03+ Flywheel so I had to settle. I plan on adding PERC and will pick up a 03 Flywheel at that time.

3. Do the 02 Carbs utilize both fuel and air screws?

Here is where I stand now, I just purchased another set of carbs, these for the 02 700, So now I have two sets. I can use either pair. I do have the 01 carbs listed on Ebay so I need to make a decision, you tell me....

Using the 01 Carbs, here is what I was planning;
1. Go to a 1.0-1.1L pilot screw (as you said) to richen up idle-1/4throtle
2. Drop pilot jet to 35
3. Jet according to my altitude/temp going 1-2 jet sizes larger for a compensation of the leaner 2.0 cutaway (this would begin increasing it's metering cycle while the Plot circuit would be decreasing.) I know this would lend to a tad richer top end and would not be ideal, but a compromise.

I am assuming do to the drastically smaller main jet size, in the 01 800 carbs, they were set up in a similar fashion to the 03 tunes (higher flowing needles with smaller main jets).

I will have enough of a time calibrating my clutching and do not really want the headache of dealing with major tuning issues right off the bat. At least, in my opinion, if I start with the 02 Carbs I have a much better foundation for a solid factory tune. I am not going to be trying to "rethink" what the factory did.

That being said, now, should I still run the 03 needles (J8-9DGN05-57) with the 1.5 cutaways in the 02 carbs like my SKS would have came with and jet accordingly to my location or because of my older Flywheel/CDI leave them alone? Not sure if a few degrees of advance either way would make that dramatic a difference in combustion efficiency and temps, but I could be wrong.

Needles; I went to the dealer today and looked at both the 02 Performance and 02 Deep snow manuals and none had the needle charts in them, so I have no basis for comparison in that respect. That is, unless, someone happens to have access to them from another source.

Let me know what your game plan would be. I am at just over 1,000 ft and do not do any mountain riding. It is mainly 50/50 trail and off trail.

I understand, ultimately in the end, plug and piston checking along with EGT info is going to be the determining factor as to where I end up for a final tune. Starting with a known baseline tune that would at least be as good as a factory 02 VES 700 calibration would be a good starting point. Once there I can gather data and have a basis for comparison, thusly giving my changes, and corresponding data, a relative quantitative relevance.

 

[sled_guy]

Flywheel difference may make for some pipe heat issues, but you'll be fine I'm betting.

I would use the '02 carbs you bought and jet to '02 SKS specs across the board. Even when you go to the '03 flywheel it won't make any difference there. Just use the stock jetting charts for your starting point on the '02 SKS and I would think you should be pretty close.

sled_guy

 

[gtfoxy]

Why does the 02 SKS use 8 jet sizes smaller(420's vs 500's) with the same needle and needle jet?

I was looking the RMK specs over and they use the 2.0 cutaway w/J8-9DGJ02-57 needles, 350 jets. Like you said they have the air jet screw but what else is different?

Are the air screws something that can be added?

 

[sled_guy]

8 sizes smaller than what? The '03? You can't add the air screws, carbs are different and air passage is in a different location.

sled_guy

 

[ivar]

02 SKS were in the Gen2 chassis, w/ different airbox etc. Not sure what other differences.

1 more thing that may confuse matters is that the 01/02 xc had a larger air box than 03 and later sleds.

 

[gtfoxy]

The 02 SKS jetting 420's vs 02 XCSP 500's.

Hmmm, very interesting.....

Now I am totaly confused.... now I have to tune it for my airbox.... man this is working out to be a major pain. So what now, I have to go find some 03 carbs?

I guess I am going to be doing a lot of plug reading once the engine gets broken in....

I was plannig on adding the SLP intake kit w/ some add in 2" filters.....

 

[ivar]

the second set of carbs you got, were they from a 02 SKS or 02 XC?

 

[gtfoxy]

They are off a 02 700 XC SP. I will be taking them apart today to see how they are calibrated.

I currently have the 01 800 carbs on the engine waiting to fire it up. I dropped the pilot jets and readjusted the pilot screw to be a little leaner. But I will probably drop the 02's in as soon as I get it running. Kinda want to see how it runs both ways....

I justwant to say thanks again to you guys for the help! I greatly appreciate it!

 

[ivar]

I would think both the 01 800 setup and the 02 700 setup would work, maybe raise the needle 1 notch just to be safe. The stock mains should be more than rich enough on both, but especially the 02 7/800 needle is on the lean side in the midrange.
The smaller air box on the 03 will affect jetting some, but should be compensated by the carbs being vented to the air box.

 

[gtfoxy]

I found out my airbox won't work the way it is with the 01 carbs, I guess the 03's have a longer inlet flange. SO I bought a set of 03 XC SP 800 carbs now also.... yep, that's right, I now have three sets of carbs....

I do have some boots to put on, and if they fit I will run what is on the engine until I get the 03 carbs.

Any sugestions now..... Is the 02 CDI timing map going to change my required calibration? I will keep my eye out for the 18* Flywheel and 03 CDI.

 

[sled_guy]

Man, you have me so confussed I don't know what you have.

CDI/timing won't affect your calibration.

sled_guy

 

[gtfoxy]

I had to put on the air box boots to reach the carbs. Luckily I had a set laying around off an older XC.

I wanted the 03 Carbs si i would have the maximum adjustability, not to mention the longer inlet flanges to match the airbox.

How about this, can I run an 03 CDI and advance the timing to 18* initial. Also, does anyone know the difference between a XC and Pro-X CDI? They are different part numbers. Does the Pro-X make more power through more aggressive timing curve? Or do they have DET sensors?

 

[rocket]

The XC and Pro-X CDI modules are "slightly" different, but not enough to make any real difference. As far as mixing the '03 CDI and '02 flywheel, you "might" be able to do it, as the difference in the amout of offset between the ignition trigger and flywheel key is only 4 degrees. There may be enough adjustment in the stator to get your base timing set correctly. If there is, you should be ok. However, if your goal is to have reverse as well, I don't know what sort of side-effects there might be. If you want to be safe, just run the '02 ignition parts until you can find the flywheel you need for the reverse system. Keep an eye out, they are available periodically. As far as your jetting questions go, the throttle slide cutaway only has significant effect in the 1/4-3/8 throttle area. If the slide is "close" to what is correct, you can tune around it by adjusting the air jet (or air screw) and perhaps a pilot jet size change. One other thing I'll mention: With your jetting questions, you never did mention your application - altitude you ride at, what chassis you're putting the motor in, any other mods to the engine, etc. That information will help all of us offer better suggestions.

 

[gtfoxy]

Rocket, I appreciate the input, thank you. I did mention it is a 03 SKS and I am at 1,000 ft elevation. I ride here and in the UP, that's about it. I would be close to the base calibrations or maybe a jet size or two leaner in the 0-3,000ft calibration.

I built the engine with Wiseco M series pistons. As of today it is all stock with only gearing and clutching changes. I have a SLP can coming so that will be on shortly. I may add a SLP intake kit and some boyesen reed pedals, other than that, not too much.

I would like the most out of a stock application for ease of tunability and longevity. I look at different stock components because I would like to get the most possible power and tunability with stock components. Exhample, if an 03 Pro-X CDI will give me 1, 2 or 3 more HP at a very minimal cost and an adjustment in timing, it is worth trying. I could try incremental timing adjustments. I figure if they can run on 89 octane then 1 or 2 degrees more timing should be possible with 91 octane. Basicly I am trying to maximize the combination.

I see the pipe is a different part number than the XC/SKS, but I do not know if it is something like a tuning difference in the pipe like tuned for a higher RPM range, or something astetic like a diple or something to clear higher strut tower.... someone should know.

 

[sled_guy]

The pipe differences are only so they fit the chassis. The higher shock towers on the Pro-X need a different pipe bend.

sled_guy

 

[gtfoxy]

The pipe differences are only so they fit the chassis. The higher shock towers on the Pro-X need a different pipe bend.

sled_guy

Thanks guy, I thought it might be something like that.

Does anyone know the progression of power raings from the first VES 700 through to 2005. I know the 04+ had decompression ports but were there any changes in the ports that made a difference in power? From what I have been told it was about 2-3HP but I can't seem to find any confirmation.