Honda CBR 250 Forum banner

1 - 20 of 22 Posts

·
Registered
Joined
·
378 Posts
Discussion Starter #1
For those of you that didn't already know, one of the easiest mods to this bike is removing the air box cover to improve the sound. The sound of the intake gets very loud and throaty (less 250 sounding). Almost emulates a better exhaust and I think its louder than the stock pipe.
Here is the question... what effect does this have on A: Performance and B: Fuel Economy. It def sounds 100% meaner but I feel as if it's lost HP and MPG. Anyone try it?
 

·
Registered
Joined
·
681 Posts
There's a thread about this but I don't anyone was really sure about what impact this would actually have on the bike other than the sound. I'm reluctant to try it until I have a better idea what the purpose of the cover really is.
 

·
Banned
Joined
·
1,894 Posts
Think there was a few 'experts' saying completely different things. It will/won't affect performance.

I had mine off for 3 days, put it back on and it felt much better back on, in terms of nippiness and responsiveness, and smoothness and feel. Felt like it was running lean with it off. So have kept it on since then.


An other option would be to drill small holes in it, as many as you want, if you want to cover them up again just use duct tape. Kind of a happy medium.
 

·
Registered
Joined
·
378 Posts
Discussion Starter #4
Felt like it was running lean with it off.
Exactly. It's just hard to believe just opening up another airway would cause it to be noticeably lean. You would think the ECU would compensate. But ya... the throttle response also seems to have suffered. I put it back on but it's raining here so the verdict is still out till I take it out I guess :cool:
 

·
Banned
Joined
·
1,894 Posts
Okay, anyone doing this should reset the ECU.

I've a thread on here about the difference it made after 3 days of riding on a new full system pipe. The ECU doesn't seem to adjust much at all by itself. Descriptions on how to reset it are in the thread.
 

·
Registered
Joined
·
378 Posts
Discussion Starter #6
Okay, anyone doing this should reset the ECU.

I've a thread on here about the difference it made after 3 days of riding on a new full system pipe. The ECU doesn't seem to adjust much at all by itself. Descriptions on how to reset it are in the thread.
I did check out your thread on this... but didn't really get it. Do you leave the biking running then disco the 4 pin thing or just leave the ACC on?
 

·
Registered
Joined
·
96 Posts
I cut two holes in the cover and put it back on, sounds much better. Seems to have helped (at least the butt dyno says so).
 

·
Registered
Joined
·
4 Posts
I tryed taking it off too, and yes better sound (if u like it louder), but took it to the official Honda shop for 1000km check, and they said, Honda garanti is OUT if u do that ! So I put it back on and they where happy. And garanti was back, the owner of the shop told me, well it was only off for 2 days. So DONT take it off ! Get a new exhaust instead, I ordred one already, but will not get it ontil, early September :-(
 

·
Banned
Joined
·
1,894 Posts
I'm currently riding with 8 holes and the ECU reset.

I was previously riding on a full aftermarket exhaust system with the ECU reset to that, but it runs smoother and nicer in it's current mode. Just not as much fun or dramatic. :D
 

·
Registered
Joined
·
256 Posts
What exhaust was it? It runs that much smoother without the aftermarket exhaust? Maybe I should save my money and keep it stock. I sure would like a little bit more "drama" though.
 

·
Registered
Joined
·
19 Posts
I had mine removed and I found that it reaches speed faster and very evenly, so my boyfriend said he didn't have to always think whether I could follow him or not... moreover, he could hear me when I opened the throttle
We went for a round trip today (around 415 kms) and the average fuel consumption was just under 3 liters per 100 kms (MPG??????????) BUT we also added a higher windshield, as suggested by CeeBeeAarr in his post.
Mix of highways, country roads, curly roads...
Altoghether very pleased with the bike and its performance. Soon going for a 3000 kms trip in France and Italy ;-)
 

·
Registered
Joined
·
378 Posts
Discussion Starter #14
I'm currently riding with 8 holes and the ECU reset
Is the ECU reset totally necessary or does it just speed up the "learning". Do you need special tools for it? I have the helm manual and it says i need some special diagnostic tool.
 

·
Registered
Joined
·
282 Posts
Rode mine for couple of hundred K's with the cover off (have 2bros slip-on installed as well) seemed to lose a bit of low end torque, gained a bit at the top end. Didn't like it so put back on. If just looking for decent sound and bit more power slip-on is the way to go imho, doesn't mess with your warranty(according to my Honda dealer anyway) and don't need to reset ECU. (again according to my dealer) Interested if anyone knows diff.
 

·
Banned
Joined
·
1,894 Posts
What exhaust was it?
Namban.

A Thai racing company.

Is the ECU reset totally necessary or does it just speed up the "learning". Do you need special tools for it? I have the helm manual and it says i need some special diagnostic tool.
Yes, my Honda dealer and his wife had after market pipes (Remus and Moriwaki) on for over 2 months. I had mine on for 3 days. We reset all the ECUs and the difference was amazing on all 3 bikes. They then reset them on other customers who had changed pipes and the differences were all reported.

If just looking for decent sound and bit more power slip-on is the way to go imho, doesn't mess with your warranty(according to my Honda dealer anyway) and don't need to reset ECU. (again according to my dealer) Interested if anyone knows diff.
Read above.


I've a thread called something like 'make sure to do if changing the exhaust pipe'.
 

·
Registered
Joined
·
282 Posts
Thanks Redline, checked your posting and as I was trying to point out in my earlier post, I did not change the full exhaust system, just the slip-on muffler. You are correct in your earlier post that a full exhaust sys. change requires an ECU reset, but to my knowledge changing the slip-on does not. All that said I will try an ECU reset and see if I notice any difference. Will post back result
 

·
Banned
Joined
·
1,894 Posts
Thanks Redline, checked your posting and as I was trying to point out in my earlier post, I did not change the full exhaust system, just the slip-on muffler. You are correct in your earlier post that a full exhaust sys. change requires an ECU reset, but to my knowledge changing the slip-on does not. All that said I will try an ECU reset and see if I notice any difference. Will post back result
That's cool, let us know how you go.

My Honda dealer and his wife had two different slip-ons on their bikes for over 2 months before resetting the ECU and it made a great difference to the performance.
 

·
Registered
Joined
·
4,996 Posts
Why would anyone want to remove an airbox cover ffs?

look at the stock intake opening size... now look at how many hundred times bigger it is with the cover off.. WAY off the ballpark.

Ive done alot of experimenting in the past with bikes and best results were stock or opened a few percent at most.
 

·
Registered
Joined
·
282 Posts
Redline did your dealer do many kms with the standard on before adding slip-on, only rode home from dealers with mine(20-30kms) before ditching the original for the 2bros. Don't know if make a difference.
Going to get second airbox cover to drill holes in to experiment, keep original in case need to claim warranty, I imagine drilling holes will void warranty.
 
1 - 20 of 22 Posts
Top