Soot is a sign of running rich, or of incomplete combustion. When you put on less restrictive pipes, you leaned the system out, and solved it by upping the jet to richen it up enough to run in good balance.

I'll bet you're seeing a combination of 1: More choke/warmup time 2: Heavier throttle hand due to enjoying the sound of your new pipes 3: running warm plugs in cold weather - check your manual - there's spec's for that.

Engines run more efficiently in cold weather due to greater air density - and winter gas generally contains more energy per volume than summer blend gas (if there's actually a difference in your area). All other factors aside, there should be no change, or a slight improvement with winter gas vs summer blend.

It could be as simple as your air filter has become dirty after a long season too...so many reasons for variance in fuel economy.

 

Cold alone should, in theory, deliver higher MPG as it leans out your mix. (More oxygen molecules per cubic foot of air.) But that could lead to a power loss for which you compensate with more aggressive throttle usage.

A factor: Winter blend fuel delivers different MPG. Changeover at refineries takes a while to show up at pumps and it varies by station so there is no actual date you can go by.

Then there's the whole issue of ethanol; it has a third less energy per gallon than gasoline so it delivers lower MPG. e10 (10% ethanol) delivers 3% lower mpg. For that to change suddenly, though, you'd need to have switched from e-free (There isn't really any such thing here anymore.) to an ethanol blend. Even if you didn't change stations, they may have switched without your knowledge.

If the range decrease is a problem, look into the fuel tank punch mod. It doesn't affect MPG but should get you another ten miles of range.

 

I like the theroy of the cold leaning it out and lossing power and me having a heavier throttle because of it. The air filter is brand new.

So is the 10-20 miles im loosing a tank be a concern now? Or should I wait till summer and see what it does?


Also can incomplete combustion because by running to lean? To give the extra soot im seeing?

 

Also can incomplete combustion because by running to lean? To give the extra soot im seeing?

ALL of the symptoms you have so far described points to a RICH running bike. My guess is that since you say you rejetted and the bike is a 750 you are probably jetted a little on the rich side. Hence the soot and bad MPGs. Soot can also be a sign of air leaks. IMO, most 750 jet kits are too rich. especial on the pilot jet.

 

that's lousy mileage for sure. Don't know what your problem is but I get 160 miles at least before I hit reserve. Average almost 60 MPG. That's with the stock setup

 

Ever since a I got it I averaged 115-120 before hitting reserve . But I also have a big fairing bags and a trunk

 

JK - I don't think you're getting bad mileage for your setup. I only get about 100-120 out of my 750 Spirit without windshield & trunk, but I believe I'm a bigger guy than you.

What's your parking situation?

 

Im sorry but I dont know what you mean by parking situation. But why would it droop like that? Is it just from whhat was mentioned earlier?

 

Do you have a climate controlled garage where you park? Or is it outside? Air temp isn't going to kill your mileage like that, but the temperature of the engine would.

 

No at work its parked outside at home in the garage the walls are insulated but no heat in there pretty much cold all time.

 

Cold weather changes also lower tire pressures...could be a factor.

 

Im pretty good at keeping the tires inflated to proper psi

 

Try pushing it some of those miles. I bet you would get better mileage that way...:mrgreen:

 

PUSH BOOGER PUSH!


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The only thing that makes sense to me is if your getting a higher percentage of ethanol in the fuel now with winter here. It drops the mileage in my Toyota from 23 to 21.

 

again - put in the proper spark plugs for cold weather - the spark plug spec's are right in the service manual. Here's a link - it's on page 1-9 Honda VT750DC Shop Manual

 

not to question you or the manual but is that for the aero or spirit? i only ask because neither ngk website or advance auto says that plug that the manual says to use in cold temps fits the aero. both sites say it doesn't.

 

Yeah - that's not the right manual...my bad, bro. If manual says to use a 6, use a 6.

Maybe this will put it into perspective - On the spirit from the link above, spec's recommend an 8 for normal, and a 7 for cold and a 9 for extended high speed.

you're using an 8 in a bike that the engineers recommend a 6 for normal and a 7 for extended high speed riding...might get away with that in warm/hot temps, but in cold temps, your deviation from spec is going the wrong direction regardless....make sense?

 

This thread puts the spark plug thread in perspective. Running a cold plug in the cold.....:???:

 

Yes - because cold air is denser, causing the mix to lean out, which causes a rise in plug tip temperature, you go with a plug with a colder heat range in cold weather.

 

vito i thank you for your help i now understand better. ill be switching to DPR7EIX-9 for 2 tanks see if there is a difference (probably won't) then ill try DPR6EA-9 and see if thats any different ill probably rejet again seeing as ive been needing to up my needle 1 clip i put my pipes on used dynojet stage 1 kit and from what ive learned on here from another member my needle clip should be raised 1 more notch my main should be fine same with the screw but my mid range lacks some power and plugs show lean so i need to raise up my needle clip one more to the 3rd notch make it a tad richer but i do appreciate all the help with the correct plug and helping me understand WHY and what the difference in the heat ranges.