Really hot exhaust... could probably toast a piece of bread from my thigh!

I've been riding my VFR around for a while now. I've noticed that the air coming up from my exhaust is quite hot, even for an exhaust; it's hot enough to be extremely uncomfortable and cause my leg to sweat, even when the rest of me is fine.

This may or may not be related, but I'm getting horrible fuel economy. I just got 35 MPG. The bike doesn't seem to have any flat spots or hiccups; it runs smoothly throughout the entire rev range.

The exhaust is stock. I have a new chain and sprockets (stock sizes). I haven't checked the air filter or replaced the plugs since I acquired the bike a couple months ago.

 

I have yet to buy it, but I am eventually going to get some header tape and put on mine. With the aftermarket exhaust that I have, I've been noticing some black marks from my shoe where the pipe goes up to the exhaust. Maybe you can wrap it as well to keep the heat away from your leg.

 

I suppose I could wrap it; I figured there was something wrong w/ the bike. Since it seems to be eating through gas, I thought maybe the two were related.

 

usually cold engines get worse fuel economy than hot.

Are you getting the heat sitting traffic or rolling down the road for 10 miles.

A retarded ignition can give you more exhaust heat and poorer mileage.

A vacuum leak can make your engine run hotter but generally makes the low end rather hicuppy.

Good economy generally involves getting it into top gear as soon as you can do it without lugging it and keeping the speed low.

 

It doesn't seem to matter. I do a lot of highway riding and notice it frequently around 70 MPH, but it happens at slower speeds, as well.

Would Honda do such a thing on a carbureted bike? I've heard of the TRE mod, but I thought that was a fuel-injected Suzuki thing. I read about a bunch of CBR owners doing it w/ no noticeable difference.

The coolant temp doesn't go above 1/2 way up the gauge. I don't think this is the problem.

She seems happy to do highway speeds at 6200 RPM and minimal throttle. Lower RPMs (higher gears) seem to require more throttle.

I never use 6th gear and only use 5th when I'm going well above the speed limit. Running at < 6K RPM seems to require more throttle and provides significantly less acceleration.

 

An older VFR putting out alot of heat around the leg area?? LOL....Next you'll be telling us these things are prone to electrical problems!!! I've owned two 3rd Gens and both of them did this. Almost everyone else I talk to that owns one tell me the same so I assume it to be normal for this model. Both of my bikes put out an amazing amount of heat on the right side especially near the inner thigh. During the winter it's great LOL !!!

Rollin

 

As far as mileage goes there could be lots of other factors. Worn pilot jets can cause an increase in fuel consumption since the diameter of the jet can increase over time as they wear out. Also using aftermarket jets often results in loss of mileage since they are often larger than OEM and the bike would have to be re-tuned to adjust the air/fuel mixture. Also make sure tires are in good condition with the proper air pressure and that you don't have a dirty or too restrictive air filters. Do the exhaust smell rich or do you experience any popping or backfire on deceleration? Is the bike stock or does it have any upgrades/aftermarket components?

Rollin

 

Thanks Rollin, that's all I needed to hear. Maybe I'll wrap the exhaust... the heat is pretty annoying when it's 90 degrees out. I do ride all year (southern VA), but I have an insulated "santa suit" that I wear, so cold legs/torso/arms aren't a problem.

That really only leaves the question of why my fuel economy is so horrible. I'm not an aggressive rider... 33 is pretty awful for taking it easy. She has about 22K mi... I'm thinking I should sync the carbs and adjust the valve lash and take a peek at the air filter. I noticed in the manual that there's a subfilter, too... never heard of such a thing.

My R/R seems to be working. I'm guessing the stocker is on there, but I'm prepared to replace it with one that won't fail as easily. I'd rather not end up stranded somewhere.

• Are there good aftermarket air filters for this bike?
• I haven't looked at my R/R, but I imagine it'll die some day. Can you recommend a reliable R/R?
• Is there a downside to wrapping the exhaust?

 

The tires are in excellent condition. Inflating them to proper pressure was the first thing I did when I brought the VFR to its new home.

The VFR has never popped/backfired. My SV used to do that. It was due to running lean.

The only aftermarket thing I can think of on the bike is the Corbin seat. The exhaust is stock. Nothing on the bike looks modded in any way, but without looking under the tank, I don't know about the air filter.

 

35 mpg doesnt sound too bad for 6000 rpm. My old 86 is making nice torque starting at 4000. Lower mpg means increased heat. Sounds like your bike is normal. You may want to adjust your riding style.

 

Wow, that's dismal. I'm very surprised.

I'm not really worried about getting good fuel economy, I guess... I'm just surprised it's so awful. I thought for sure that these two symptoms indicated something was wrong.

I'm disappointed. On the other two bikes I own, I get excellent mpg. I guess I'll just wrap the exhaust and accept the mpg for what it is.

 

I would agree 35 is not great but it is what it is considering. I have always been under the impression that the vfr has more midrange than many other machines of similar displacement. I am curious why you don't run in top gear at 70. IMO unless you are racing you probably don't need to be in 5th. The highest gear that you can run at any given speed without lugging will usually give you the best mileage. You have to pick, do I want mileage or do I want performance.

Did you check the engine timing? Look for any vacuum leaks or other defects on your intake. Do you have a hole in the exhaust or a bad gasket spewing out fire?

Years ago we used to endurance race a 450 Suzuki and would average about 17-20 mpg at an average track speed of 72-82 mph.

O.T. My current car is an 80's vw diesel and it gets 49 mpg loaded down with people dogs and guns.

Good Luck

 

I've been using 6th gear now on the highway and keeping it around 4-5K RPMs. Fuel economy for the last couple fuel-ups was a little under 31 MPG. Driving at lower RPMs seems to decrease my fuel economy.

 

I recently did a 700 mile trip, from Richmond to Tazewll (RT16), and I averaged 37 mpg, for what that's worth.