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Discussion Starter #1 (Edited)
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.
 

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Discussion Starter #3
https://www.reddit.com/r/250r/comments/2zjs6q/cbr250r_dying_andor_stalling_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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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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Discussion Starter #5
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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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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Discussion Starter #7
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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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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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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Discussion Starter #10
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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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.
The Concentrate is the only one to use. The regular Techron Fuel Injector Cleaner is not the strong stuff.

I don't know how it compares to B12, but I do have pretty good info that it does what needs to be done.

That may not be it at all, so if you aren't getting any improvements I would check the condition of the air filter and snorkel opening for obstruction, and possibly check the plug. It's usually uncommon, but I have heard of the CBR having plug failures. It's in here somewhere...
 

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It's usually uncommon, but I have heard of the CBR having plug failures. It's in here somewhere...
The one on my bike was changed during the 24,000km (~15,000miles) service which is just half of it's expected lifespan (not that I had noticed any problems before or experienced any improvements after the rather expensive swap...). Maybe something was wrong with it, maybe I was just ripped off.
 

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I switched to iridium plugs when I did the valves at about 15K miles. I'm lazy, it was a simple precaution. ;)
 

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Discussion Starter #14
I'm not anywhere near 15k and the air filter was just replaced 2 months ago (with a new OEM one). The snorkel appears to be perfectly normal also with no obstruction.
Checking the plug was way down on my list of things to check because of the relatively low mileage, but it wouldn't hurt to pull it and see if it's anything but normal in appearance.
Thanks for the suggestion.
 

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Any recent mods or service work. Valve adjustment?
I used a small amount of fuel additive once and it decreased my fuel economy for three tanks. Never again.
Depending on how you ride, running a strong fuel system cleaner in the CBR may prevent some serious issues.

The CBR appears to have unusual engine problems when ridden lightly and not revved. Deposits build-up in the combustion chamber and intake valves and lead to detonation, burned valves, and engine damage.

None of this has been proven absolutely, but everything I've encountered here over the last few years suggests that deposits could be the cause.

I can't say I've ever noticed any mileage drop from running Techron, but it could be possible. Not sure how it could continue after the treated gas had been consumed though.
 

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Depending on how you ride, running a strong fuel system cleaner in the CBR may prevent some serious issues.

The CBR appears to have unusual engine problems when ridden lightly and not revved. Deposits build-up in the combustion chamber and intake valves and lead to detonation, burned valves, and engine damage.

None of this has been proven absolutely, but everything I've encountered here over the last few years suggests that deposits could be the cause.

I can't say I've ever noticed any mileage drop from running Techron, but it could be possible. Not sure how it could continue after the treated gas had been consumed though.
You never empty the tank, you refill with some fuel still in it to cool the fuel pump. Think of it as a serial dilution.
 

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The CBR appears to have unusual engine problems when ridden lightly and not revved. .
Well I can debunk that completely. I am the lightest riding, lowest revving owner ever. Fully 1/3 of my 46,000 trouble free miles would be with the clutch in and coasting since I always ride with PulseNGlide. And I ride through town at 4,000 rpm and clutch in coast up to the stop signs.
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It took three, 2 gallon fill ups to finally rid my tank of a normal dose of BG fuel treatment so my fuel efficiency could return. I did my spark plug at 30,000 just because I was adjusting the valves and it still measures a tight .035"/ .889mm. I might check my valve clearance again soon. it has been 16,000 miles.
 

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Well I can debunk that completely. I am the lightest riding, lowest revving owner ever. Fully 1/3 of my 46,000 trouble free miles would be with the clutch in and coasting since I always ride with PulseNGlide. And I ride through town at 4,000 rpm and clutch in coast up to the stop signs.
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It took three, 2 gallon fill ups to finally rid my tank of a normal dose of BG fuel treatment so my fuel efficiency could return. I did my spark plug at 30,000 just because I was adjusting the valves and it still measures a tight .035"/ .889mm. I might check my valve clearance again soon. it has been 16,000 miles.
What is the explanation for carbon build-up, engine meltdown, burned valves, scored cylinders, etc, especially when ridden gently then?

I can't see how running a strong fuel system cleaner can be blamed for numerous tanks of poor fuel economy.

Try Techron next time (if there is a next time).
 

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You never empty the tank, you refill with some fuel still in it to cool the fuel pump. Think of it as a serial dilution.
To get the full benefit of the cleaner you need to fill the tank, add the cleaner, and run until the tank is low - but obviously not dry.

I don't think overheating of the pump is a problem as long as there's fuel in the tank. A hot pump would cause vaporlock in certain situations, which I don't believe is an issue.
 
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