Poor MPG and Throttle Hesitation - Honda CBR250R Forum : Honda CBR 250 Forums
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post #1 of 38 Old 07-15-2017, 01:46 PM Thread Starter
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Poor MPG and Throttle Hesitation

Not sure if I have an actual problem as yet or if I'm just dealing with a bad tank of gas from the last fill-up, but I thought I'd throw the symptoms out there for some comments and suggestions from the more tech-savvy here.
On my last long ride last weekend I experienced a noticeable lag in throttle response. Every time I'd roll on the throttle, especially from a stop, I noticed a slight hesitation before power delivery (although it's still there and still noticeable on occasion even in the higher gears). Much different than the snappy response I usually get on my 2011 CBR250R. It almost felt like the engine was cutting out for a nano-second or fueling had flooded for a heartbeat before power returned to normal. I also noticed that I was going through gas at a much faster rate than normal. On the next fill up I added B-12 Chemtool to the tank, thinking it might be all that was required, but it hasn't made any difference at all. I'm still getting the hesitation and still using a LOT more gas than usual.
Think it may be a TPS problem? I have less than 7000 miles on the bike, so a clogged fuel filter seems unlikely, as does a problem with the fuel pump itself. I'm not getting any stalling or failure to start at all, so I'm leaning in the direction of a failing TPS.
What do you guys think? Are there any "known" problems like this that you're aware of, or am I in for a detailed "investigation" to determine what's causing this? A "search" of past threads on the subject hasn't produced anything useful.

Last edited by TrueFaith; 07-15-2017 at 07:50 PM.
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post #2 of 38 Old 07-15-2017, 02:42 PM
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https://www.reddit.com/r/250r/commen...alling_issues/

Is this it? Did the battery die recently and all of the "bike logic" get reset?

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post #3 of 38 Old 07-15-2017, 07:48 PM Thread Starter
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Quote:
Originally Posted by jsonder View Post
https://www.reddit.com/r/250r/commen...alling_issues/

Is this it? Did the battery die recently and all of the "bike logic" get reset?
I'm not experiencing any "stall" issues at all and the bike has never failed to start on the first crank. It never even threatens a stall in any gear, coasting or otherwise.
I dunno, maybe I just haven't given the fuel injector cleaner time to work. I just added my second tank today with B-12 and I'm still getting the same hesitation and greater fuel usage, but perhaps I haven't run enough treated fuel through the injectors yet to make a difference.
I'll see if another hundred miles tomorrow shows any promise, but so far it's been giving me a lot of indications that I may have a throttle position sensor problem.
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post #4 of 38 Old 07-15-2017, 08:23 PM
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Try Chevron Techron Concentrate next time. 1 oz per gal.

According to a friend that's a ME and works in auto emissions testing - it's the best at cleaning deposits from valves and combustion chambers.
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post #5 of 38 Old 07-16-2017, 12:53 PM Thread Starter
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If I get no result from the B-12 Chemtool I will definitely try Techron in the next tankful, although you would think that using even a lesser fuel injector cleaner would have at least some noticeable result if deposits in the EFI system were the problem.
Still, I have used Techron in my cars in the past with almost magical results and it is without a doubt the most recommended EFI cleaner among every mechanic I know, so it's worth a try.
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post #6 of 38 Old 07-16-2017, 05:03 PM
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Completely drain out the old gas might also be an option if you think it could be bad. Condensation is going to sit at the bottom, so it's going to stay there unless you run the tank dry or drain it.

Gas with ethanol will go bad quickly and also hold/absorb water more than gas without.
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post #7 of 38 Old 07-16-2017, 06:50 PM Thread Starter
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Excellent idea. Between storing the bike with Sta-bil added during the winter and running fuel system cleaner through it this week you'd think moisture at the bottom of the tank would be highly unlikely, but it would certainly eliminate one item on the list in isolating the cause.
80 more miles put on the bike with B-12 added today still hasn't led to any noticeable difference in the symptoms.
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post #8 of 38 Old 07-17-2017, 08:53 AM
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Probably the easiest thing to do at this point, and something to cross off the list.

Let us know what happens.
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post #9 of 38 Old 07-18-2017, 02:37 PM
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B-12 chemtool is the strongest stuff I've stumbled across for in-tank additives. Acetone is a great cleaner, and B12 has a good bit of it. So it's better as a quick cleaner instead of something that is going to sit in the tank for a week or more since it's not too happy to play with plastics. Techron fuel injector cleaner is kind of crap in my opinion, so if you use the Techron, make sure it's system cleaner as it is much more concentrated. The B12 is more solvent based, and will clean the nastier grime out of the ends of the injectors better and helps to remove some moisture if present.

In my experience, if it's a fuel nastiness problem and B12 doesn't help you, no additive will.
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post #10 of 38 Old 07-20-2017, 12:16 PM Thread Starter
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Quote:
Originally Posted by cbrlocal View Post
B-12 chemtool is the strongest stuff I've stumbled across for in-tank additives. Acetone is a great cleaner, and B12 has a good bit of it. So it's better as a quick cleaner instead of something that is going to sit in the tank for a week or more since it's not too happy to play with plastics. Techron fuel injector cleaner is kind of crap in my opinion, so if you use the Techron, make sure it's system cleaner as it is much more concentrated. The B12 is more solvent based, and will clean the nastier grime out of the ends of the injectors better and helps to remove some moisture if present.

In my experience, if it's a fuel nastiness problem and B12 doesn't help you, no additive will.
Thanks for the head's up about the B-12's acetone content. Are there any plastic parts to the fuel pump that could actually be damaged sitting in a tank treated with B-12 for a week?
I'm about halfway through this second tankful treated with B-12 and I'm sure not noticing any improvement of the symptoms as yet. The throttle hesitation and excessive fuel consumption are just as pronounced as when I started. A little odd that while it's completely noticeable, it's also very consistent, not getting any worse or better to any degree either way.
Really starting to wonder if the problem is actually mechanical rather than a dirty fuel system.
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