NeverSeenDatV4

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.

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.

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.

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.

Yes! A fellow snap-crackle-pop enthusiast! Cool, I don't feel like such a weirdo anymore. I knew there were more of us out there. I know man, it's awesome. I mean I don't like some exhausts because the exhaust note is just too harsh, too raspy, too unrefined. There's a certain noise level that I will just draw the line and say, "Nope, that exhaust sounds like shit. Too loud and obnoxious." But that being said, I always love a lot of crackle-and-pop on decel. Just a matter of personal taste I guess. It's surprising so many other people try to completely eliminate those sounds though, isn't it??? To me that would be like being in love with aged, triple-cream brie cheese, yet they can only eat the soft middle and throw away the whole rind. The rind is awesome too. Ok so we just need to find someone out there who's devised a way to "Make Exhaust Crackle Great Again" lol and tell us how to modify the bike somehow. Maybe modifying the PAIR valve system to inject more air into the exhaust manifold? Maybe doing an ECU tune where it adds a little more fuel on decel? How about adding a manual trigger on the grip that disrupts the spark, letting unburnt fuel get into the exhaust manifold...

I just bought a 5th gen VFR two weeks ago. 1998. I think the PAIR and flapper valves are stock, and I don't think there's any kind of power commander or ECU tune on the bike. I have this peculiar disease. My disease is: I actually love the sound of a whole bunch of serious popping noises from my exhaust on deceleration/overrev. The more the better. Anyone else out there like that too? My exhaust is not stock; I have a Two Brothers slip-on that I LOVE. I totally love just about everything about this bike and it's hard to think of ways to improve it, but if I could just have my gurgling popping sounds the way I like, that would be great. If the PAIR system has been disabled, maybe re-enabling it would give me my popping sounds back? Maybe adding some type of ECU tune that makes it extra lean when the throttle is closed?

Hello forum. I love my stock hydraulic brake and clutch master cylinders, but I'd like a much shorter and much fatter lever for both. Something similar to the "shorty" style levers you see on dirt bikes. Something designed to be squeezed with one or two fingers instead 4 fingers. Has anyone seen levers like that available, especially for my 5th gen VFR800?

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?

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.