juddery/sluggish below 3k

Hi,


Im new to the forum and its just a qu out of curiosity. I have always had new bikes and most have been inline 4, although my Aprillia was an RSV4

Got my old mans vfr at the moment, just curious are they all sluggish and hesitant below 3k? Once past there it pulls really well and is fine.

Just feels like it needs a good tune/remap?

 

Yep, the VFR's V4 likes to be above 3,8K rpm especially in the higher gears.

 

Thats cool, I had a feeling that was the case, any good easy ways to improve it?

 

Manford welcome to the forum!

Some things to consider: What year is the bike, how many miles are on it and has it been ridden in recent years? What is the exhaust system?

The first things that come to mind are to attend to all standard maintenance. How many miles are on the spark plugs and air filter? Has it sat with old gas? Tune the starter valves which are the source of air input at <5% throttle. Check the charging voltage against the spec. Particularly if it is an aged bike, inspect the vacuum hoses carefully for leaks.

If everything checks out than as John451 verified you may be noticing the general engine character. It does need to be revved for reasonable take-offs. A fueling computer with a custom tune might smooth out the throttle response, but this would not make it generally faster.

 

Welcome aboard and congrats on keeping the VFR in the family!

There are lots of things that could be done to help with the low RPM stumble, but the reality is these bikes simply don't like being below 3k, plain and simple.

 

Bikes only got 17k on it, 99 I think from memory. I've been using it past week or so, so all fuel in the system should be good and clean. It does have stainless headers, original collector box rotted away and remus can.

Can you plug into the bike and read the afr?

Had an issue with vac lines on the car, was quicker and easier to replace than fart around trying to find a leak, also if all new you hopefully can be 100% they are all good. A pin prick thats only open when under vac is almost impossible to find in isolation.

 

Hi Manford.

I almost turned around and brought the bike back to the seller. I thought there was something wrong too.
After a few miles of ridding it I got it to smooth out. Shifting was a little different too. I posted "How do I ride this thing?" shortly after. Got good advice. I'll see if I can find it.

 

Reading AFR: Only from certain aftermarket hardware in combination with an O2 sensor. If you list any fuel controller hardware here someone should be able to answer this. Typical placement is under the seat.

The stock 1999 does not have an oxygen sensor. Double check the year on the frame sticker. If it is a 1999 and you see an O2 sensor in the exhaust, that is aftermarket and most likely runs to a fuel controller.

The header is a hint to your question: It is typical to lose low-end power with headers in exchange for higher mid and max rpm flow. That change may make the bike even more dull down low than it already is.

Good advice on vacuum lines!

 

http://vfrworld.com/forums/showthread.php/48395-How-do-I-ride-this-thing

RobVG here is your thread.

 

Thanks Knight.

Scuba's advice was spot on, "Just Pinch it.....and roll on. She like it hard....!"

 

I'm not sure if things were different across the pond, but as Knight said, the 99's did not have the catalytic converter and 02 sensors. Those came out in 2000 (again, here in the US).

Check into that header a bit more. If you happen to have a "real" SS header (and I think 2 Brothers was one of the few companies that made them), that's like seeing Bigfoot riding on his unicorn to go and wrestle with the Loch Ness monster. I know - I had one on mine.

 

Ya know thats all good stuff those guys have thrown out.. my experience has been depending on what gear I'm in, if I'm puttsing along say 2nd or 3rd at 1500 then bring it on it's actually not to bad, almost wheelie popping, if I'm in 4 and above doing 1500 it's like ok I'll go but... easier to imprudently drop a gear then off to the races, the V4 torque curve is a wonderful thing here with the VFR it's so smooth and wide makes riding these really fun.

 

Maybe this is a dumb question lol but what is "pinch it"? I know pinch bolts and a pinch flat but then I fall short...

 

LOL this is hilarious, but I am not sure what it means.

 

Analogous to slapping it on the ass...

 

You shouldn't ever have the clutch out on a VFR below 3k RPMs (better yet, 3,500). The engine just doesn't produce any power there and you'll be lugging it.

 

LOL, its basically just implying that while some folks will go to their grave believing something (as in they've seen bigfoot, unicorns or nessie), others will insist it never exists. Either way, it would be a rare beast to witness.

I was implying that having a true Two Brothers Stainless Steel header is a rare thing, indeed. And that I honestly had one on my bike.

 

In other words, they're made out of stainless steel with a high percentage of pure unobtainium in the alloy...

 

If you expect impressive acceleration from anything below about 3000 rpm in any gear but 1 or 2, the VFR doesn't do that. But you could switch the front or rear sprockets to better suit your riding style and needs.

 

Much as others have said; Yeah. Over 3.5k for most riding. 2k+ is fine for low speed or moving around in stop-start traffic. I tend to keep mine below 4.5k when riding in the city.