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5th gen starter valves sync INCORRECT for last 22 years


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Hi there!

 

I know, its a bit strange to find incorrect procedure in workshop manual 22 years later. But no one did it, and I want to share my story now.

According to 5th gen manual, 3rd cylinder vacuum pressure should be dropped to 20mm compare to 1st. Most of us read it as dropped DOWN, and translated manuals have it mentioned as LESS vacuum for 3rd and 4th.

When I got my bike, it had flat sync for all cylinders. I did full maintenance some time later, through workshop manual, include starter valves synchronization. In very first day after, I noticed some surging when low throttle, it was a bit twitchy during city riding. Very uncomfortable to keep some speed at low throttle opening. Most of internet discussions about nervous VFR had tips about PAIR blocking and other redneck mods. Some of them suggested to always keep revs over 4k, because VFR doesn't love low revs... That's true, but I had very smooth bike before maintenance, even on very low RPM.

 

First - I adjusted flat sync back. It helped me a lot, motorcycle became very friendly again. Then I did it opposite to manual. It means 3rd cylinder adjusted to 20mm MORE vacuum than 1st, and 4th 10mm more than 1st. And the bike is smooth as butter. Even better than flat, and MUCH smoother than official way.

 

From here I want to explain why it helped. In service manual for 5th gen, they showed fuel injection diagrams. It has independent maps for each cylinder. On these graphs you can see - 3rd cylinder get lowest fuel portion, 4th a bit more, and 1+2 even more. I checked it with injector opening time frames. Diagrams are true, 3rd cylinder has less fuel than 1st on idle. For same mix ratio, fuel/air, we should feed less air into 3rd cylinder. It means we need close starter valve a bit, as result we will have MORE vacuum.

 

It looks like they forgot to explain, what means "dropped". If your vacuum gauge has movement from right (0) to left, more vacuum will drop indicator down... If it is gravity meter, less vacuum will drop level down. There is no right description, more or less vacuum you should set with word "dropped".

I'm pretty sure, they had some problems with that description, and maybe complains about flat is working better than described way. And finally they removed it from manual for next generations...

 

2.png.0d17a4e661198b41d7f4662f62e35bd8.png

vfr_inj_time.png.c9c5ff3fdd2159a75ff3107e467eb6b3.png

P.S. I installed ABS brake system to my 5th gen VFR, with very minor modifications. If it would be interested - let me know)

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Well researched post Jkson! When I had my 5th gen I did what I thought was right and dropped the liquid level in the gauges by 10 and 20mm for 3 and 4, which is setting less vacuum in those cylinders. I never thought to do it the other way.

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Yeah, most of us read it as dropped down, less vacuum. And it is very common issue with VFR 800 any generations - hesitations, surging, jerky on small throttle opening. Many, many topics about it. When vacuum is ajusted lower or even flat, 3rd and 4th cylinders have lean mixture. Its a reason why PAIR blocking helps a bit. Because PAIR allow to intake a bit fresh air into cylinders from exhaust port. When you block it, you make your mixture reacher on idle and low revs.

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Always read it as more & have had super smooth engine, must be my logical brain & from all the diving pressure training, where less is more. I keep a note on the inside of my vacuum gauges box so I never have to think about it 👍

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Thanks Jkson, gonna give this a shot.  About to check into my recently-new-to-me Gen5's sync and see where it is... it's OK but could be improved.  My buddy's VFR seems better, I'll also compare to that one.  All makes sense to me.

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In that case I have done mine incorrectly. I followed a guide with pictures and that shows a Carbtune with 3 and 4 displaying less vacuum. (The more vacuum you have the higher the steel rods rise up the tubes).

Thanks for pointing this out too!

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I have a electronic VacuMate, same readings as Carbtune without the fluctuating mechanical bits.  Put both on the VFR yesterday, sync was off but not too bad, had lumpy idle.  Adjusted to the manual, idles way better, and going to go for a spin....... then I will re-tune to Jkson's method and go for a similar spin...... updates later.

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Update, I adjusted my sync to jkson's suggestion, #3 20mmHg higher and #4 10mmHg higher.  My VacuMate has a tach function that senses pulses, and I found it important to readjust (tweak) idle to 1200 rpm or vacuum readings spread more... of course, the VacuMate is very sensitive.  I tried a CarbTune as well, but the resolution is much coarser with those moving parts.  My cooling fan kicked on, and that will throw things off, so recommend you let it cool down again so the fan doesn't come on.

I noted a much less lumpy idle at the new settings, and went for a shakedown ride, some highway and a lot of stop and go in town.  Clutch action was much smoother, did not have to play throttle/clutch games nearly as much.  Overall much better, and some time ago I was thinking of a new clutch pack next winter, but no longer is that a concern for me.

So, highly recommend you try those new settings.  I'm happier, thanks jkson for the analysis.........

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I have gone for a couple more rides and must say it is better now...  with engine warm, can feather the clutch out without any throttle input on a level surface, rpm drops to say 7-800, bike moves and hasn't hinted of stalling, it would before... so, quite pleased.

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You are welcome! Few days ago I repeated official and mine way. Just to be sure, one more time. It is definitely smoother and bike has more torque on low rpm, with #3 and 4# more vacuum. 

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  • 2 weeks later...
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On 6/26/2020 at 4:19 PM, Jkson said:

Hi there!

 

I know, its a bit strange to find incorrect procedure in workshop manual 22 years later. But no one did it, and I want to share my story now.

According to 5th gen manual, 3rd cylinder vacuum pressure should be dropped to 20mm compare to 1st. Most of us read it as dropped DOWN, and translated manuals have it mentioned as LESS vacuum for 3rd and 4th.

When I got my bike, it had flat sync for all cylinders. I did full maintenance some time later, through workshop manual, include starter valves synchronization. In very first day after, I noticed some surging when low throttle, it was a bit twitchy during city riding. Very uncomfortable to keep some speed at low throttle opening. Most of internet discussions about nervous VFR had tips about PAIR blocking and other redneck mods. Some of them suggested to always keep revs over 4k, because VFR doesn't love low revs... That's true, but I had very smooth bike before maintenance, even on very low RPM.

 

First - I adjusted flat sync back. It helped me a lot, motorcycle became very friendly again. Then I did it opposite to manual. It means 3rd cylinder adjusted to 20mm MORE vacuum than 1st, and 4th 10mm more than 1st. And the bike is smooth as butter. Even better than flat, and MUCH smoother than official way.

 

From here I want to explain why it helped. In service manual for 5th gen, they showed fuel injection diagrams. It has independent maps for each cylinder. On these graphs you can see - 3rd cylinder get lowest fuel portion, 4th a bit more, and 1+2 even more. I checked it with injector opening time frames. Diagrams are true, 3rd cylinder has less fuel than 1st on idle. For same mix ratio, fuel/air, we should feed less air into 3rd cylinder. It means we need close starter valve a bit, as result we will have MORE vacuum.

 

It looks like they forgot to explain, what means "dropped". If your vacuum gauge has movement from right (0) to left, more vacuum will drop indicator down... If it is gravity meter, less vacuum will drop level down. There is no right description, more or less vacuum you should set with word "dropped".

I'm pretty sure, they had some problems with that description, and maybe complains about flat is working better than described way. And finally they removed it from manual for next generations...

 

2.png.0d17a4e661198b41d7f4662f62e35bd8.png

vfr_inj_time.png.c9c5ff3fdd2159a75ff3107e467eb6b3.png

P.S. I installed ABS brake system to my 5th gen VFR, with very minor modifications. If it would be interested - let me know)

This is gold. I don't like to ride my 5th Gen on heavy traffic as it acts exactly as you describe at low speeds. I'll try your recommended settings. Thanks!!

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Having just got my Gen5 a few months ago and never previously owned a fuel injected bike I found it to be very challenging on initial throttle opening and it has surprised me a couple of times. It is also a bit hard to start from cold. After reading this I ordered A Digi-Sync and will tackle this job tomorrow. I haven’t done any intake mods yet except for a K&N filter so it will be nice to know I have the correct baseline for reference.

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  • 3 weeks later...
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So just to make sure I'm correct. I have a MotionPro Sync pro, which attaches to the the top of each tube pulling the fluid up. So if #3 and #4 need to be dropped, each valve needs to be closed more than, #1 and #2 to reduce vacuum, in turn lowering the fluid level vs #1 and #2 at idle?    

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gig, I think we're saying just the opposite, raise 3 and 4 vacuum, not drop it.  You can try it both ways for yourself and the difference should be apparent.  Let us know what  you find.

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On 6/26/2020 at 4:19 PM, Jkson said:

 

P.S. I installed ABS brake system to my 5th gen VFR, with very minor modifications. If it would be interested - let me know)

That is one hell of a "one more thing."  What is the short version of how you pulled that off?

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The confusion comes from peoples misunderstanding of basic arithmetic. Basically you have Positive 2,3,4,5 and Negative values -2,-3,-4,-5. Where people go wrong is not understanding that -50 as a reference, then -40 is NOT -10, its -90 ! 
 

So on my post-it note, cylinder 1 is not adjustable & is the reference cylinder. On my guage below that usually measures around 200mm you can see below the needle on the left inner scale. Cylinder 2 should be adjusted = to #1. Cylinder 3 should be 220 on my gauge & cylinder 4 = 210mm. These are vacuum figures (negative) in mm/hg. 
 

Hope that makes sense. 

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6741C985-72ED-49FD-AB4C-68E362A602A1.thumb.jpeg.5412c85cbcb289c08780506e22143b7d.jpeg
 

The 6th gen swapped headers 1 & 3 around, so all headers are closer to same length, so a flat vacuum setting will work best for them. 

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On 6/27/2020 at 4:54 PM, interceptor69 said:

How difficult is it to adjust the starter valves?

Sent from my SM-G975U using Tapatalk
 

Fairly simple. You need a couple of gauges, I prefer to use just two, that I calibrate on cylinder #1 which is the reference & not adjustable. On the 5th gen you need a magic screw driver, I use a piece of old wiper blade SS reinforcing strip about 5" long with a 3/8" blade at one end at 90degrees & another in the opposite direction on the other end a couple of inches long for a handle. Lift the tank, then on each side of the airbox there is a rubber vacuum hose for throttle body. 
Start engine & let it come up to temp 80c. Then adjust the idle to 1200-1300rpm. Connect gauge to #1 as reference, then other to #2 adjust so  #2 is the same as #1. Check idle is stable every time you make an adjustment. Repeat for cylinders 3 -20mm/hg & 4 -10mm/hg compared to #1 reading.  Don't let engine get to hot, if fan cones on wait until it cycles off before doing more adjustments. 
 

If you think they are currently off, then rev engine once at temp then do it again once starter valve  are set correctly, you will be amazed at how smooth & fast it revs ! 👍😎

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I did this a few weeks ago and found that they had been set flat, adjusting them to the correct offsets definitely helped with smoothness off a closed throttle. I was really pleased with the Digi-Sync as well, great customer service and a nice piece of hardware for a decent price, the tach function is a nice bonus.

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I did this a few weeks ago and found that they had been set flat, adjusting them to the correct offsets definitely helped with smoothness off a closed throttle. I was really pleased with the Digi-Sync as well, great customer service and a nice piece of hardware for a decent price, the tach function is a nice bonus.
Where did you buy your Digisync?

Sent from my SM-G975U using Tapatalk

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I bought it straight from their website; https://thedigisync.com/

They responded quickly to requests and changed shipping method to accommodate my current hatred of USPS and Canada Post.  I got the 6 cylinder one for maximum future utility. It would be nice if it had the option to change units, but it's easy enough to convert your targets to the units on the device. I found the tach function very handy.

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Could someone explain or list the correct settings for the starter valve sync so in 'laymans' terms so as I can tell my mechanic buddy what the recommended settings are? It's probably simple to figure out from the original post but I'm not sure of it, thanks.

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10 hours ago, Saoirse said:

Could someone explain or list the correct settings for the starter valve sync so in 'laymans' terms so as I can tell my mechanic buddy what the recommended settings are? It's probably simple to figure out from the original post but I'm not sure of it, thanks.

"Then I did it opposite to manual. It means 3rd cylinder adjusted to 20mm MORE vacuum than 1st, and 4th 10mm more than 1st. And the bike is smooth as butter. Even better than flat, and MUCH smoother than official way."

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Just curious, are these settings relevant to a 6th generation, i synched my 2003 the other day and set all 4 cylinders the same, but i still have what i call a stutter just off idle, the motor acts lean at low rpm to me, i am used to carbureated engines, i had an 1987 vfr 700, which was a super  machine, very friendly to work on and tune, does anyone know the exact reason for setting 5th generation engines with different vacuum readings, im wondering if 6th gen. would benefit from a different setting,  anyone have any input?

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