400TWIN w/ YICS ?? 82 xs400j

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DeeDoubleU

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OK I know what yics is, what is does, ECT.

There is no port to use to block off the system to sync. the carb's on the 400 twin dohc w/yics.

I noticed with the vac. gauges connected that the gauge readings on decel would get stable enough to get a reading and would change with adjustments, So I got them as close as I could during decel and tweeked a little more by ear/and exaust temp.

I'm close runs pretty smooth, pulls good, idle to 6000rpm, but I get some stumble/cough/spit, slight not bad,on tip in/accel above 6250rpm.

My ? is. Does anyone know the factory proceedure for sync. on this model?
Or your own personal trick?
Or do you think I have another issue?

Thanks in advance for any info.......DW :bike:
 
I don't think I understand - YICS is basically the really loopy air intake system they used. All that plastic. Nothing to do with balancing carbs.

Each carb boot has a nib you can use to balance the carbs. I've done it several times. YICS doesn't make it any different.
 
I could be wrong here, But what Ive gathered from every thing i can find to read on this, there's a port between each intake port in the cyl. head that causes a swirling effect, for a more complete combustion.

On 4 cyl models theres a plug in the side of the head you remove and a yics tool is inserted tighted up and blocks off these port where you can get a steady reading on a vac gauge.

google image (yics shut off tool)
The vac gauges on my 400 twin at idle or any steady rpm the needle bounces like I got burnt intake valve. but I have excellent comp. and plenty of power.

Again I could be wrong, I'm not familiar at all with this bike, I do have knowledge/expirence with swirl control valves and ports ect. and the concept on auto application.
 
your right, there is a way to balance the yics and you need a special (read expensive) tool to do it with.

I just read online a how to, can't remember where i found it
 
Air gauges tend to bounce a lot if they don't have thumb screw in line to slow the vacuum down. Mercury gauges or a manometer work much better.
 
DoubleDee, you taught me something today. I didn't know YICS had anything to do with the engine.

That said, I've still just synched my bike with a little ATF fluid and about 10 feet of rubber tube. Works like a charm.
 
I started to throw together a manometer to sync mine , But I have a very nice set of matched vac gauges so I used them. Bent; I been turnin wrenches for 30yrs and I think I learn something new every week still.
 
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