Yet Another Stage 3 Kit Attempt..

Hey guys, thanks in advance for checking out my first post. I currently own a 1986 Xj700 with around 6400 miles on it. Shes in great condition, so I decided (it being my first bike and all) that instead of just flipping it for a couple hundred bucks profit, I'd dump half a grand into it and bring it down to florida next year. So, the mod's began. I took out the airbox, and put on some K&N pod filters(Which I hear is a pain in the ass to tune), coupled that with a MAC performance 4 into 2 exhaust, and finally I took apart the carbs and installed a Stage 3 Jet kit from Dyno Jet.
So here it comes....
Now the bike wont idle. Its bogs down and dies whenever you give it gas. Im thinking its either
A. The E clip on the needle should be moved up one groove, maybe the bike is getting too much fuel(DynoJet reccomends 3 grooves form the top, so Im thinking of moving it up to 2 grooves)??
B. Pilot Jets could be clogged? But i really dont think so. The bike ran TITS before I did the work, and even afterwards, it doesnt have a hard time idling once it gets hot. The carbs were squeaky clean as well.

So I guess my question is, for anyone who has been brave enough to venture into the world of XJ700 Stage 3 kits similar to my own, what worked for you? Did you ever have a similar issue to my own?

Also, I have NO IDEA how the hell im gonna Synch these carbs. Ive probablly done 20 hours of research into the YICS system, and its hasnt helped one bit. Ive seen advice ranging from "Dont bother" to "The bike wont run at all unless the YICS system is correctly calculated for".
So I guess after I get the carb adjustment correct, I was just going to bring it to a mechanic to get the carbs synched in correctly, But now I really want to do it myself. I heard you need a 4 gauge manometer(optional YICS Tool), but my question is, How do you actually make adjustments to the carb vacuum? with the fuel mixture screws? Any help would be appreciated guys!

 

I built a homemade yics block off tool tool for five bucks and a homemade nanometer for seven. You adjust butterfly screws for vacuum and fuel mixture for lean/rich running. That's as far as I am on my stock bike.

 

Great Ill take a look at a couple diagrams and see where the butterfly screws are. Thanks

 

I did the dynojet stage 3 kit on an xj650, aside from being nervous as all hell drilling out the holes on the pistons/slides it wasnt too terrible. That included switching to pod filters and chopping the headers off at the bend at the bottom of the bike(yes I know its not terribly good for the valves and sounds like a nascar at RPM). In any case, after much fooling about with tuning I ended up moving the E-clip down a notch from position 3(note I mean 1 notch closer to the needle, not away from it) which will lift the needle and help richen everything up. At an idle it would bog like crazy and stall all over the place unless you gave it gas very slowly or opened up the idle enrichment circuit. Checked my spark plugs and they looked to be running a bit lean. After adjusting the E-clip the engine literally woke right up and ran extremely well. A full carb sync later the thing was kinda scary with how responsive it was.

Try choking the engine and then give it a rev, if it does not stall and actually seems to run properly your likely too lean at an idle. If it still wont idle very well or still stalls give it a try with moving the e-clip 1 position away from the needle from position 3. Just make sure you monitor your plug condition relatively often through and for a while after making changes to watch for too lean and too rich indicators.

 

Did you "bench synch" your carbs before you put them back on the bike? If not, that would be a great starting point. Here's how:

http://xjbikes.com/Forums/viewtopic/t=6 ... ching.html

Now slap them back on and do your vacuuml synch. You can make a very effective manometer for under ten bucks with some clear house, trannie fluid, a piece of wood, and maybe a couple zip ties. Search the forum or google for "homemade manometer" and you'll get the idea. Then the process is almost the same as the bench synch above but you connect the manometer hoses to the vacuum port on the top of your carb-to-engine boots and make VERY SLIGHT adjustments while "blipping" the throttle until the fluid levels match up on either side of the manometer.

 

Those "butterfly screws" are the ones referred to as "synch screws" in the bench-synch tutorial link in my last post.

 

Guys thank you so much. each one of you have literally answered my questions perfectly, and saved me hours of fumbling. The only question, Ive heard of making your own YICS tools, by taking a coat hanger, rapping a cloth around it, and spraying that down with a Vapor repellent like Marvel Mystery oil, any thoughts?? Also, where is the YICS port located?

 

I've read about others stuffing the YICS port with oily rags & from what I've heard it works fine.. I've never used the tool or blocked the port. I synched my carbs without blocking & it worked fine. My bike was purring like a kitten so if you want to do it without blocking it will definitely get you at least very very close. There are differing opinions out there as to whether blocking the YICS port will provide any additional benefit when you synch.

The Yics port is on the back side of the "jugs" kind of below the carb-to-engine" boots (if my memory serves me correctly). It kind of looks like a tube molded into the backside of the motor and has a large bolt plugging either side.

 

Then I wont bother with it(YICS) for now. Heres the plan though:
1. Take carbs off, move the e clip up one position just to try and get the bike running for the vacuum sync.
2. Bench sync the carbs before I put them back on.
3. Put the carbs back on after I am happy with an extremely precise bench sync, use a 4 gauge Manometer to get the fine adjustments.
4. Adjust air and mixture screws after 5-10 min rides, making minute adjustments until it runs and sounds good.
5. Check spark plugs after each day of riding, ensuring that conditions are not too lean or too rich.
Sound Good??

 

Only if your valves are already in spec.

RE: Blocking YICS: You CAN get a decent sync without blocking YICS if you're lucky. HOWEVER, the YICS system can and will also "mask" a slightly out-of-sync condition. This will give you a "nearly synchronized" motor whereas with YICS blocked (and therefore the intake tracts isolated from each other) you will get a much more accurate, "unmasked" sync. I've played with sync both ways myself to reach this conclusion.

There are 3 SYNC screws on the throttle linkage, one each for carbs 1, 2 and 4. Number 3 has no sync screw per se; it is "home base" so its adjuster is the main idle knob. The linkage for #1 and #2 is "Siamesed" so any adjustment made to #2 will bring #1 with it.

There are 4 PILOT MIXTURE screws, one on each carb. Set your pilots at 2 1/2 ~ 3 turns out to start; and don't start tweaking mixtures until you have a solid vac sync.

When doing the vac sync, you sync 1 to 2; then adjust 2 to bring the pair into sync with 3. Then adjust 4 to 3.

AFTER THE VALVE CLEARANCES ARE IN SPEC.

 

One issue though. I decided to just make my own manometer, so the bench syncing isn't necessary. But, those carbs in that tutorial aren't like mine. Mine have slides, not the butterfly plates like those carbs. In my situation, where would the carb synch screws be?? Thanks You!

 

Yes it is. The bench sync provides a baseline that makes the vac sync go much more smoothly.

Unless a PO installed aftermarket carbs, you have throttle plates. They are on the engine side of the carb. If you do indeed have cable-opertated slides they're usually adjusted using the idle screw for each carb. Have a careful look at the carb bodies (yes all of them. I've seen the mixing of brands more than once) for a makers mark and/or model number.

 

okay ill make sure to do a bench sync first then. Illl check on the engine side of the carb, but I really do dubt that I have throttle plates. Neither me nor my friend remember them being there last time we stripped the carbs apart. Thanks again for the input.

 

Where I am right now:
Everything went surprisingly smooth thus far. Altough its a pain to keep adjusting the needle height in the carbs, its good practice I guess. This morning I got it all back together with the clip set one position higher on the needle, and its definitely running too lean. It was laggy and unresponsive, didn't run right at all. After work, Ill take off the carbs and adjust the needle 2 positions down and see if that sounds any better. Also, right now im just messing with the needle height, so is it alright if I put off mixture adjustments and vacuum syncing until after I get the bike running nice with just a bench sync? Thanks for the responses guys

 

HAVE YOU CHECKED THE VALVE CLEARANCES YET?

You should leave the mixture screws at a "default" setting (2.5 ~ 3 turns out) until after the vac sync;

and you won't truly get it running correctly until you do the vac sync; the bench sync is only to get it running well enough to vacuum sync.

 

This is why i took my pods off, and put the airbox back in.... I have a mac 4-2 as well.... with the pods, i spent months messing around + never got it right....

 

Yeah as of right now it just wont start cold. Maybe its just a mixture issue? it was running beautifully yesterday, but today I go to start it and it stalls all over the place and wont even run after a bump start. Any ideas?