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Question about syncing the starter valves. Do I need to remove the airbox?


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Hello helpful forum. I just bought this awesome '98 VFR 800 last week (49 state version), and I've been riding it every day, all around like a happy crazy person. I just love this bike. Wanted the legendary VFR for a long time. Anyways, I have the symptoms of what I've found is likely because of the starter valves drifting out of sync over time. The bike does have 56,000 miles at this point.  I have the factory service manual and I looked up the procedure to sync the intake valves, and I've done a lot of research on this job actually and it looks totally doable. Here's the thing though: all the YouTube videos that show this type of job, the person has the whole airbox removed before they begin the sync process. But in the factory manual it just says you just prop up the fuel tank, unplug the PAIR valve, unplug the 4 vacuum hoses to the starter valves, idle the engine, and start adjusting. Can you actually get to the starter valve adjusters without removing the airbox? That would be nice, since there's only about a million hoses, sensors, clips and fasteners that need to be removed to take the whole airbox off.

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Yes you certainly can do the SV synch without removing the airbox on the 5th gen bikes, and I did just that on my 99; I think on the 6th gen VFR (02-12) you do have to pull the airbox because the SV's are located in the V rather than on the side. Accessing the SV adjusting screws is a little tricky but I used an open ended spanner for the job, IIRC 7mm was just right. 

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1 hour ago, Terry said:

Yes you certainly can do the SV synch without removing the airbox on the 5th gen bikes, and I did just that on my 99; I think on the 6th gen VFR (02-12) you do have to pull the airbox because the SV's are located in the V rather than on the side. Accessing the SV adjusting screws is a little tricky but I used an open ended spanner for the job, IIRC 7mm was just right. 

Correct Terry, 6 and 8gen requires airbox to come off. Lucky 7gen owners don't have SVs.

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13 hours ago, Terry said:

Yes you certainly can do the SV synch without removing the airbox on the 5th gen bikes, and I did just that on my 99; I think on the 6th gen VFR (02-12) you do have to pull the airbox because the SV's are located in the V rather than on the side. Accessing the SV adjusting screws is a little tricky but I used an open ended spanner for the job, IIRC 7mm was just right. 

YEESSS!!!! Thank you, this is great news. Ok now I feel really good about doing this job now.  That's so awesome that I don't have to remove all that crap and remove the airbox.

 

Also, I thought I'd share a link to an affordable, highly-reviewed sync tool that I found on Amazon. It's only about $58 after shipping, and it's called a "Motorcycle Carburetor Vacuum Synchronizer Adjustment Tool" https://www.amazon.com/dp/B073XQNPB3/?coliid=IIWTNOPBCI2QM&colid=2E58O191L483G&psc=1

 

One more nitpicky/nerdy question for you: Why does the vacuum between the 4 cylinders drift out of spec so far in the first place? I mean my bike has 56k miles so just about anything can happen in that time, but what could change the airflow through those starter valves so drastically from normal use?

 

While we're on that topic, why have the picky starter valve system in place at all? Why not just have a set screw that keeps all 4 throttle body butterfly valves cracked open just a little bit for idling? Do most fuel-injected motorcycles have a starter valve system in addition to the main intake butterfly valves?

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If/when you get that tool, make up a wee manifold to join all four together, use a vacuum pump to ensure each are reading the same, at say low-mid-high vacuum, note any deviations, include those deviations in your actual readings.

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5 hours ago, raYzerman said:

If/when you get that tool, make up a wee manifold to join all four together, use a vacuum pump to ensure each are reading the same, at say low-mid-high vacuum, note any deviations, include those deviations in your actual readings.

Good tip,

 

Also go to a local fish shop and buy some air valves, about a $1 each, which will allow you to adjust each vacuum line to stop the needles bouncing whilst you use it during the synch process.

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On 6/9/2020 at 8:38 PM, Grum said:

Correct Terry, 6 and 8gen requires airbox to come off. Lucky 7gen owners don't have SVs.

Grum, 

On 7g's does that mean they have an ECU controlled idle air control valve like a typical car?   Wouldn't that be nice!   No more low idling when climbing in to higher altitudes.  On Pikes Peak my 6g would barely remain running. 

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18 minutes ago, Cogswell said:

Grum, 

On 7g's does that mean they have an ECU controlled idle air control valve like a typical car?   Wouldn't that be nice!   No more low idling when climbing in to higher altitudes.  On Pikes Peak my 6g would barely remain running. 

Hi Cogswell.

7gen has throttle by wire so the butterflies are fully controlled via the ECM and throttle body motor so no need for SV's, no doubt similar to what cars have had for quite a while. Hopefully the 7gen would handle your Pikes Peak situation far better than the 6gen.

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On 6/10/2020 at 8:16 PM, Marooncobra said:

Good tip,

 

Also go to a local fish shop and buy some air valves, about a $1 each, which will allow you to adjust each vacuum line to stop the needles bouncing whilst you use it during the synch process.

The issue of the vacuum gauge needles swinging wildly above and below the correct vacuum pressure reading, is solved easily by closing each valve gently with your fingertips (there's a valve knob below each of the 4 gauges for this purpose), until the needle isn't moving anymore. This is shown and and addressed clearly in the videos. You're necking down the flow of air through the vacuum gauges, so that the pressure evens out. The vacuum air is being forced through a pinhole at that point instead of a large tube, and smooths the reading out very well. No need to go buy anything else or modify/complicate the vacuum gauge tool.

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On 6/10/2020 at 3:03 PM, raYzerman said:

If/when you get that tool, make up a wee manifold to join all four together, use a vacuum pump to ensure each are reading the same, at say low-mid-high vacuum, note any deviations, include those deviations in your actual readings.

Is there a process to synchronize not only the starter valves but individually adjust all 4 main throttle valves too? I would guess if the starter valves and drift out of spec the main throttle bodies can too.

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I'm pretty sure the butterflies are factory set and there is a warning in the service manual to leave them alone. 

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On 6/13/2020 at 2:58 AM, NeverSeenDatV4 said:

The issue of the vacuum gauge needles swinging wildly above and below the correct vacuum pressure reading, is solved easily by closing each valve gently with your fingertips (there's a valve knob below each of the 4 gauges for this purpose), until the needle isn't moving anymore. This is shown and and addressed clearly in the videos. You're necking down the flow of air through the vacuum gauges, so that the pressure evens out. The vacuum air is being forced through a pinhole at that point instead of a large tube, and smooths the reading out very well. No need to go buy anything else or modify/complicate the vacuum gauge tool.

Rgr. The set I have didn’t come with valves hence the visit to the fish shop.

 

cheers

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If I recall the gauges must read some very low pressure for the starter valve adjustment on the 5thgen. My old motion pro mercury vacuum carb sync tool I used on my 2nd gen 86 VFR was useless. I may have to get a set of these if they do read in lower lower increments. Great tips here.

Question. What are symptoms related to a starter valve system that is out of sync.?

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57 minutes ago, VFR Capt.Bob said:

If I recall the gauges must read some very low pressure for the starter valve adjustment on the 5thgen. My old motion pro mercury vacuum carb sync tool I used on my 2nd gen 86 VFR was useless. I may have to get a set of these if they do read in lower lower increments. Great tips here.

Question. What are symptoms related to a starter valve system that is out of sync.?

The rated intake vacuum at idle is 200-250mm Hg according to the service manual. I had no difficulties with my SynchPro or the Morgan Carbtune.

 

Out of synch starter valves may give hard starting, stalling or a rough idle.

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On 6/17/2020 at 12:27 PM, VFR Capt.Bob said:

If I recall the gauges must read some very low pressure for the starter valve adjustment on the 5thgen. My old motion pro mercury vacuum carb sync tool I used on my 2nd gen 86 VFR was useless. I may have to get a set of these if they do read in lower lower increments. Great tips here.

Question. What are symptoms related to a starter valve system that is out of sync.?

The symptoms that are observed in other threads is that the bike's throttle response is too aggressive off idle, as when taking off from a stop, making it hard to smoothly and consistently launch the bike. Also, people report that starter valve vacuum out-of-sync issues causes a low-RPM vibration through the engine (think, less than 3k RPM). I hope this is what's contributing to my vibration issues that I've felt at low RPM. The reviews of this motorcycle online often include a description of how "buttery smooth" the engine on this bike is, and that's funny because this engine doesn't seem very smooth at all to me. It's not buzzy or vibey compared to some inline-4 or inline-3 motorcycles that I've ridden, but this bike is far from "buttery smooth", especially under 3k RPM, and especially at more than slight throttle openings. I saw one review where they said they can accelerate cleanly from 1k RPM! What??? Lol not on my bike you can't. If you are under about 2500 RPM my bike chatters and chugs so hard you feel like you're going to shake something apart. It's worth mentioning that I've adjusted the chain perfectly and still feel the same vibrations at low RPM. 

 

I will sync my SVs pretty soon, and report back here on any changes to throttle response and engine vibrations. I just got my sync tool in the mail yesterday. VERY high quality, by the way, most impressive for a $39 tool from China. It's larger and heavier-duty than I expected, with gauges that are nice and large, like maybe 5 inches in diameter for the gauge faces.

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29 minutes ago, NeverSeenDatV4 said:

 The reviews of this motorcycle online often include a description of how "buttery smooth" the engine on this bike is, and that's funny because this engine doesn't seem very smooth at all to me. It's not buzzy or vibey compared to some inline-4 or inline-3 motorcycles that I've ridden, but this bike is far from "buttery smooth", especially under 3k RPM, and especially at more than slight throttle openings.

Totally agree with this. I remember my first ride on the 86 VFR and I was suprised at the uneven pulsing at low revs compared to my previous VF bikes with the 360 degree cranks. My 800 was more of the same, and really wasn't happy below 3000 rpm either. By contrast I also have a VTR1000F and that is quite happy at lower revs, so go figure. 

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On 6/24/2020 at 1:46 PM, Terry said:

Totally agree with this. I remember my first ride on the 86 VFR and I was suprised at the uneven pulsing at low revs compared to my previous VF bikes with the 360 degree cranks. My 800 was more of the same, and really wasn't happy below 3000 rpm either. By contrast I also have a VTR1000F and that is quite happy at lower revs, so go figure. 

Yeah the ol' low-RPM shudder of this engine.... It's funny none of the professional reviews talk about this. I think this is just normal for this engine. Thanks for adding your two cents on the subject. I feel I understand it pretty well now and I synced my starter valves properly, replaced the chain and adjusted it properly, and the issue is still there so I'm just going to ignore it. With 12K RPM to use, it's not a big deal keeping it above 3k all the time anyways. Just part of the character of this engine. I still love this engine. The low-RPM shuddering doesn't ruin the experience or anything, that's for sure.

 

That's awesome you have a VTR1000 too. I'd love to see what one of those is like, especially compared back-to-back to this VFR800.  I love those VTRs because they're small, light, must handle great and sound INCREDIBLE.

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16 minutes ago, NeverSeenDatV4 said:

That's awesome you have a VTR1000 too. I'd love to see what one of those is like, especially compared back-to-back to this VFR800.  I love those VTRs because they're small, light, must handle great and sound INCREDIBLE.

The VTR has lots more torque and does indeed sound mean, but it is not the sophisticated engine that the VFR is, and sounds kind of agricultural at idle (mainly clutch chatter I think). Its is not much different in weight to the VFR but feels longer and lower and corners well with some decently modified suspension, and has endless ground clearance as well. The riding position is a bit "locked in" with lower bars/higher pegs and a short seat, mainly the leg room is what lets it down. It also only has 16L so realistically 13L before the low fuel light is on, compared to the VFR which has about 18L usable and goes much further between fills. 

IMG_4018.jpg

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5 hours ago, Terry said:

The VTR has lots more torque and does indeed sound mean, but it is not the sophisticated engine that the VFR is, and sounds kind of agricultural

Agricultural? Ooh, that stings 😉 They do sound pretty good with a set of Yoshimura RS3 cans

 

5 hours ago, Terry said:

Its is not much different in weight to the VFR

I've owned 3 VTRs in between my various VFR750s & VFR800s and found the VTR to feel much lighter than any VFR. The low bars, high pegs are an issue if you weren't born this century.

5 hours ago, Terry said:

only has 16L so realistically 13L before the low fuel light is on

Ah, yes, the infamous RLOD. The VTRs biggest shortcoming is it's lack of range. I found that on trips the mileage is not much less than my VFRs, but combined with the small tank the range was maybe ⅔ of the VFR. Fwiw, of my VFRs the 6th gen has the greatest range, then the 5th gen, and lastly the 3rd gen.

 

Here's a pic of my last & favourite 2005 VTR1000F.

 

 

D2D10826.JPG

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On 7/10/2020 at 4:50 PM, Lorne said:

Agricultural? Ooh, that stings 😉 They do sound pretty good with a set of Yoshimura RS3 cans

 

I've owned 3 VTRs in between my various VFR750s & VFR800s and found the VTR to feel much lighter than any VFR. The low bars, high pegs are an issue if you weren't born this century.

Ah, yes, the infamous RLOD. The VTRs biggest shortcoming is it's lack of range. I found that on trips the mileage is not much less than my VFRs, but combined with the small tank the range was maybe ⅔ of the VFR. Fwiw, of my VFRs the 6th gen has the greatest range, then the 5th gen, and lastly the 3rd gen.

 

Here's a pic of my last & favourite 2005 VTR1000F.

 

 

D2D10826.JPG

That is one pretty bike, we never got those colours here. My bike was ex Japan, and may have lived part of its life near the sea (or possibly in the sea) as there was a fair bit of corrosion present and dodgy paintwork. Like the Millenium Falcon it may not look like much but she's got it where it counts! And I did say "agricultural" compared to the jewel that was the 5th gen. It runs beautifully smoothly. 

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