Modern fuels: carbs versus fuel injection

[hizzo3]

As far as race results where carb bikes run with efi.

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[SilverBullet]

Originally Posted by Meriden

I guess I'm not afraid of ethanol in fuel and routinely leave small gasoline engines, and lately a car, to sit for months at a time without fuel related problems. In fact I'm always surprised when a generator that I've let sit for two years fires right up on the fuel left in it's tank. Sure there are problem with varnish and corrosion in some cases, especially antique bikes stored for years, but I think that there is a hysteria surrounding fuel as well. I believe it was OU that did a study of long term storage of gasoline and E10 and determined that as long as the engine had the proper sealants and gaskets not much prep was needed. I posted the link on ADV about a year ago, if I can find it I'll post it here.


I am a complete convert to fuel injection and consider it far less troublesome than carbs. For example when I changed exhaust and didn't have to re-jet. No work is needed to go riding in higher elevations. Fuel efficiency is better. Cold start is simpler and faster. I'm not saying EFI is perfect, but I'd much rather clean a throttle position sensor plug than chase those tiny jets around a workbench.

Results vary on carbed bikes. When I bought my 4 cylinder Voyager it had a slight idle issue. Seafoam first tank and then Berryman's B-12 next took care of it completely. Rode the bike every other day for six months without problem. Then it sat for 3 months straight and would not start at all after. Big big job to take the carbs off and clean the pilot jets. Well at least I thought they got clean enough, bike would start but just barely when cold. So I have another full weekend job to take it down again, this time will replace the jets with new ones (should have done first time). Jets can gradually clog over time some without any symptoms and then take a hard fail.

Of course precautions can be taken to prevent this. Drain carbs after each use, shut off petcock (if you have one) and run out the gas, use Stabil, etc.

But with EFI none of this is needed. Easy choice. I doubt if I will ever buy another street legal bike with carbs.

_

[Johnf3]

Originally Posted by JadeRider

Wow, pretty awesome stuff. Thanks y'all. In this case I am considering a KTM 950, which is being offered here. I am guessing is a bit more modern.

FI is great, no doubt. I will give you specific feedback on the KTM, since I own a carbed version and ride with a buddy of mine that has a 2010 FI version.

First, the CV carbs like the 950 use are really good. The vacuum slide they use actually compensates a bit for altitude changes. I have had mine well over 12K in Colorado with the exact same jetting I run with at 3K and the bike ran great. Fi bikes do compensate for altitude changes, but they are not magic. You WILL have a HP loss at high elevations with FI just like you do with carbs.

The FI system on the KTM Adventure is not the highest tech system. My carbed version consistently pulls harder than my buddies FI 990. Others report the same thing. His FI bike gets slightly better mileage, but the 950 has more tank capacity since the fuel pump is not inside the tank like it is on the 990.

When looking at KTM Adventures, basing your decision on whether on not it has carbs or FI shouldn't make or break the overall decision. The carbs work really well on this model, and the ethanol issue is not one, unless you let your bike sit for six months. Short periods of time up to a month or so won't hurt anything, and if it bothers you than turn off the fuel and let the carbs run dry.

Base your decision on condition of the bike and value. Buy the best one you can find 2006 or newer and you won't have any issues.

Here is a specific story that happened to both of us in Big Bend two years ago. Completely factual. Both my 950 and my buddy's 990 got a dose of bad gas thanks to watery gas out of a barrel that Trail Riders of Houston supplied on their Dual Sport run at a refuel spot out away from Terlingua. The 990 uses an in tank filter sock that plugs up almost instantly when exposed to bad gas. We limped back to the hotel in Study Butte and spent the next four hours tearing out his fuel pump /filter and trying to clean it out enough with carb cleaner bought at the little convenience store to get it running. We finally did, although it only lasted through the next day. On my 950, I drained the tanks (didn't even have to drain the float bowls) and got the bike started and running without issue once I filled it with good gas. Took 10 minutes.

[hizzo3]

Fuel filter bypass with an inline is on my lists for sure. Not sure why OEMS insist on the in tank style. Cheaper?

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[Maintainer]

Had both: F.I. hands down. They are easily tunable via a PC III and laptop with no fuel bowl to gum up. or manual chokes.

Carb bikes are technologically prehistoric relics.


I own a carbureted bike now and regret it.

[JMZ]

I would also say FI. Unless it is as simple as my XR. I can have the carb off , pliot jet cleaned and back on in about 20 minutes

Unlike Meriden , I HATE ethanol . I do believe that if you keep the tank full it will help .

[hizzo3]

Btw, those who are looking to convert carb to FI, micro squirt is a good alternative.

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[DFW_Warrior]

Originally Posted by poser

The ethanol in fuel will gum up a carb in just two or three weeks. Of my dirt bike sits for just a few weeks, I've got the pull the jets and clean them.
FI doesn't seem to be bothered by it as much.

Number one, be sure to drain the bowl when you park it. Number two, always ride a two-stroke as having pre-mix for whatever reason seems to keep the gas better, for longer. I've had 4 month old gas in my YZ and it still starts on the first kick. Granted, it is a Yamaha and not a KTM.

[Donsgreentrophy]

After recent issues with my triumph, 4 carbs and no shut off valve, i will not buy another carbed bike unless it is a single with an easy to work on carb, and a shut off valve.

[poser]

Originally Posted by DFW_Warrior

Number one, be sure to drain the bowl when you park it. Number two, always ride a two-stroke as having pre-mix for whatever reason seems to keep the gas better, for longer. I've had 4 month old gas in my YZ and it still starts on the first kick. Granted, it is a Yamaha and not a KTM.

The problem is much less since I've been using Stabil regularly.

Don't be hate'n cause you're jealous You know you want to drink the orange kool-adie

[TwoSmokeDS]

I think I'm starting to understand. The carb haters are the street bike guys with multiple carbs buried underneath all the metal and plastic. The carb lovers are the single carb trail bike guys who can take out the carb and disassemble it in 5 minutes.

[hizzo3]

EFI conversion on a CBR250RR

Interesting to see some of the issues being run into on the conversion.

[KenH]

Originally Posted by TwoSmokeDS

I think I'm starting to understand. The carb haters are the street bike guys with multiple carbs buried underneath all the metal and plastic. The carb lovers are the single carb trail bike guys who can take out the carb and disassemble it in 5 minutes.

Pretty much.

Each technology has its plusses and minusses.EFI provides more precise fuel metering under varying environmental conditions with varying fuel qualities. Carbs are more easily serviced in the field. EFI is complex, heavy, and requires specialized electronics to diagnose and tune. Carbs do not require an electrical energy source. EFI repairs can cost as much as a good used carbed bike. EFI can provide better throttle response and a wider powerband. Either can make horsepower.

On the ethanol issue, read the signs on the pumps carefully. They say "may contain up to 10% ethanol. That allows an ethanol content between 0% and 10%. Many small business owners provide fuel with a lower than 10% ethanol content because they believe they will sell more fuel to people who see better fuel efficiency from a lower ethanol content. Corporate-owned stations tend to pump the full 10% in pursuit of subsidy dollars. Also, it is not uncommon for E10 to be mixed with an inaccurate dose of ethanol, or even a double dose. We've measured 17% ethanol in fuel sold as E10. No carbed bike in the world will run well on fuel with ethanol contents ranging from 0% to 17% without adjustment. EFI bikes handle the varying fuel quality relatively well

Considering the widely varying fuel qualities riders have to contend with today, I'll lean towards EFI on my next road trip bike, though the modified carbs on the CB550 are providing good service under the limited altitude range I'm currently riding. They are tuned slightly rich for E0 (what I prefer to run) on a hot summer day. Should I have to run E10, they'll be a bit lean, but not so lean as to cause damage. A couple times I've had to run E10 on trips, and I can actually feel the fuel mixture change as the ethanol content gradually changes in the carbs. There's a small increase in power as the mixture goes from 0 to 5% or 10 to 5%, then the power drops back off as the ethanol content approaches the other extreme. It's a compromise tune, but that's the best I can cope with varying fuel qualities. The carbs probably wouldn't do so well on a trip to Colorado, what with a 10,000+ feet change in altitude. On the other hand, 5 minutes is all it takes to rejet Tdub's carb for any altitude, including the ride up Pikes Peak.

.

[Meriden]

While we consider clogged jets and flooded carbs just a part of the game, we paint EFI as being hard to repair and troublesome in every case. Recently I had problems with EFI on a fourteen year old bike. I diagnosed the problem with a test light and repaired it with a wire brush. Sure, on some bikes test equipment can be expensive, sometimes more than a jet kit. Most of the time it's a bottle of injector cleaner.

It's comical, the few times I've laid my Challenge over dirt riding people quickly remind me to pick it up before it floods or leaks. It doesn't flood or leak fuel. You don't choke it, prime it, cycle the kick starter, or fiddle with the reserve. It just goes and tunes itself ever couple of turns of the crank.

Out of the four bikes that completed the ET450 Dirty Butt last year two had carbs and two had EFI. I don't recall us having problems with any of them. Later that year I did 126 miles along the Rusk to Moscow section on two gallons of gas riding the same G650X Challenge (of course I was going a lot slower.)

[RollingJ]

You know, if somebody gave me a crf250l or a wr250r, I think I would be okay with FI.

[Donsgreentrophy]

Originally Posted by TwoSmokeDS

I think I'm starting to understand. The carb haters are the street bike guys with multiple carbs buried underneath all the metal and plastic. The carb lovers are the single carb trail bike guys who can take out the carb and disassemble it in 5 minutes.

Exactly!

[focus frenzy]

Originally Posted by hizzo3

Fuel filter bypass with an inline is on my lists for sure. Not sure why OEMS insist on the in tank style. Cheaper?

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it is a high speed electric motor, they put it in the tank so the gas will keep it cool.

GM vehicles have/ had a tendency to eat fuel pumps if they were run with only low gas levels or especialy if they were run out of gas.

[focus frenzy]

[quote=DFW_Warrior;1066240]Number one, be sure to drain the bowl when you park it. Number two, always ride a two-stroke as having pre-mix for whatever reason seems to keep the gas better, for longer.

some two stroke oils have fuel stabalizer mixed in already!

I have a gallon can of pre-mix for my weed eater that is over a year old and it is still good.

[trainman]

It's fuel injected for me from now on, I don't buy bikes to work on, farkles, yes, but carbs no.

John

[KenH]

Different strokes for different folks. I can't afford a $9000 toy. I have carbs on all my bikes. If I could afford a KTM or BMW, fuel system technology wouldn't be a consideration. There are a lot more important things that contribute to riding enjoyment than fuel system technology. I've seen more rides ruined because someone showed up with inappropriate tires or sprocket ratio or some other lack of planning and/or preparation for the riding conditions than from anything else mechanical. Still, I've seen more rides ruined by overconfident riders than everything else combined. Whjatever you have, ride it!