Low Topspeed, possible causes and solutions? - Honda CBR250R Forum : Honda CBR 250 Forums
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post #1 of 23 Old 03-13-2017, 03:01 AM Thread Starter
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Low Topspeed, possible causes and solutions?

I am generally unable to break 80mph on my motorcycle unless slope or winds are in my favor (even then the gain is only 3-4mph). I tuck in as best I can, as getting above 73mph is very difficult for me otherwise.

I have looked over my previous posts and have reviewed many of the prior threads on top speed and I keep coming across people hitting 90-100mph without too much difficulty. The speed limit for I-10 and I-20 (which I do use on occasion and are the most practical options for travel in the area) is 80mph. Being able to just barely go the speed limit on a heavily used and vital route kills a lot of the enjoyment while riding.

I will freely admit that I am big, at 270lb and 6'1", but some of the posters have gotten speeds higher then mine with bikes nearly as weighted down or more so then mine.

I was new to riding when I got the bike. I never inquired if the previous owner did the 600mi service check and am still running the original chain and rear sprocket on the bike (~10000mi on odo). I've noted that even after cleaning and lubing the chain there are a number of tight spots and kinked areas.

So all that said here are my questions:

1) Would out of spec. valve clearance cause a lower then normal top speed? (Bonus question: how would the internals look after 10000mi of out of spec valve clearance?


2) How much power would a worn and/or stiff chain rob transferring power to the rear wheel?

3) Would there be any other causes for a lower then average top speed?


For the record, I use 86/87 octane gasoline, have changed out the airfilter already, change the oil every ~3000mi, and keep my tires at ~30psi. I typically average 50mpg-55mpg.

2013 Black CBR250R ABS, forced to haul my 6'1 270lb butt.

Last edited by TestBacon; 03-13-2017 at 04:48 AM. Reason: gramar
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post #2 of 23 Old 03-13-2017, 08:36 AM
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I hate to say this but the bike is very marginal for the Interstate riding that you are discussing.

I rode an equivalent powered bike and the low 80s are about all that one can expect, and I have 100 pounds less mass and wind resistance.

I really think that you need a 500-650 cc class bike to comfortably ride those roads, and would recommend selling or trading the bike in on a more freeway-friendly motorcycle, rather than trying to improve the performance of your CBR250R..
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post #3 of 23 Old 03-13-2017, 10:41 AM
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The items you mentioned could have an effect on top speed, especially the valves and chain condition, but you may just be asking too much from the little CBR because of your size.

A bike with more torque, like a 650 twin, would give you a lot better all-around performance.

I would have the valves checked, replace the chain, and run a strong fuel system cleaner like Techron Concentrate (1oz per gal) through it if you aren't in a position to upgrade right now.

As far as getting top speed goes, you would need to keep the engine spinning as high as safely possible (redline) before making each shift, especially before going into top gear. That's going to give you all you will get, but because of the relatively low power, and additional aero drag from your size, I wouldn't expect to see anything near 100 mph.

I don't think even in the best conditions with a small rider the little CBR is going the crack an honest (actual - not by the speedo) 100.
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post #4 of 23 Old 03-13-2017, 11:06 AM
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Quote:
Originally Posted by jkv357 View Post
I don't think even in the best conditions with a small rider the little CBR is going the crack an honest (actual - not by the speedo) 100.
Indeed. Over here Honda says the CBR250 has a top speed of 140km/h (87mph). I don't think I've ever been able to go faster than that and I weigh ~75 pounds less than the OP.

If cruising at 75mph isn't a viable option then a bigger bike might be needed.
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post #5 of 23 Old 03-13-2017, 11:54 AM
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At 6'2" and ~210lbs anything over 85 took a while for the bike to creep up to it with the +1 front sprocket.

You might want to look into getting a -1 front sprocket with your new gears & chain. Your MPG will suffer but it might help you get through the wind barrier. (Disclaimer: I have no idea how much this will lower your top speed)

Definitely do a valve adjustment, we need all the power out of the 250 we can get so we feel every drop in HP, at least near the top.

Patiently waiting until I can ride again
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post #6 of 23 Old 03-13-2017, 12:10 PM Thread Starter
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Thank you all for the replies. I going to go after this incrementally. I ordered a set of sprockets and a new x-ring chain last night; will track down a fuel system cleaner; am going to search for a set of tapered feeler gauges and get around to doing a valve check.

In between "fixes" I'll do a few test runs on the bike and more importantly work on losing weight! There are actually some larger bikes on Craigslist right now that are in my meager budget. Main issue is that 2 of the 3 would STILL probably have a difficult time pulling 80+mph with my butt on them. Just for the record the bikes are a '97 Yamaha xv535, a '94 Kawasaki KLR650, and a '96 Suzuki GS500.

2013 Black CBR250R ABS, forced to haul my 6'1 270lb butt.
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post #7 of 23 Old 03-13-2017, 02:39 PM
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Originally Posted by TestBacon View Post
Thank you all for the replies. I going to go after this incrementally. I ordered a set of sprockets and a new x-ring chain last night; will track down a fuel system cleaner; am going to search for a set of tapered feeler gauges and get around to doing a valve check.

In between "fixes" I'll do a few test runs on the bike and more importantly work on losing weight! There are actually some larger bikes on Craigslist right now that are in my meager budget. Main issue is that 2 of the 3 would STILL probably have a difficult time pulling 80+mph with my butt on them. Just for the record the bikes are a '97 Yamaha xv535, a '94 Kawasaki KLR650, and a '96 Suzuki GS500.
That's all pretty old school, and you aren't going to gain that much. What's your budget?

Check out a SV650n if you are in the $2000 range. Plenty of torque and good on the hwy. 1999 to 2002 are carbed and known as "1st Gens". 2003 to 2008 are F.I. and are "2nd Gens". After that they went to a "Gladius" that not many people cared for (me included). Last year they brought back the SV name, but the bike is closer to a Gladius with different bodywork.

I have both 1st and 2nd gens.

More SV info - svrider.com

My youngest boy recently bought a 2009 Ninja 500R with 2400 mi for $2000 as well. Not a bad bike either. Small fairing and more power. Not quite as much power as a SV, but available in better condition for less.
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post #8 of 23 Old 03-13-2017, 03:13 PM
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As a side-note, on a smaller bike it can be beneficial to use a non-o-ring chain. It's not going to survive as long as an o-ring chain, but it has significantly less internal drag and will roll a lot easier. It's also a lot cheaper.

Just keep it lubed and you'll benefit from more acceleration and mpg.
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post #9 of 23 Old 03-13-2017, 04:26 PM Thread Starter
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Quote:
Originally Posted by jkv357 View Post
That's all pretty old school, and you aren't going to gain that much. What's your budget?

Check out a SV650n if you are in the $2000 range.
I was hoping to keep any purchase to under $2000 after tax, insurance, and registration with the state. All of the Sv650 I've seen near that price range have been salvage or no title and beaten to hell. The xv535 is $1300, gs500 $1000, klr650 is $1600.



Regarding chains, already ordered the x-ring chain. I don't remember where but I recall being told that sealed chains are better for rough roads.

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post #10 of 23 Old 03-13-2017, 04:48 PM
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I was hoping to keep any purchase to under $2000 after tax, insurance, and registration with the state. All of the Sv650 I've seen near that price range have been salvage or no title and beaten to hell. The xv535 is $1300, gs500 $1000, klr650 is $1600.

Regarding chains, already ordered the x-ring chain. I don't remember where but I recall being told that sealed chains are better for rough roads.
Decent SVs are out there under (EDIT: around) $2000, but you have to be patient - and quick.

My thoughts on the ones you listed - xv - nope, gs - nope, klr - maybe. The klr is going to have the torque, but not get you much more on the hwy than the CBR.

We looked at a GS500E before buying the Ninja 500, and I wasn't impressed. Looked really cheap-o and not much performance for the size and weight.

It took us a while to find a good Ninja 500, the first couple were overpriced and beat. Eventually we found a clean one. Their book value is $3000, but that's not going to happen. $2000 for a clean late-model one is realistic. Less if it's less than great.

O-ring chains are better in poor conditions because they are sealed, but in normal street riding it's not so much of an issue with regular maintenance.

Last edited by jkv357; 03-13-2017 at 05:20 PM.
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