Hello all,

I've been plagued with this issue (if it is an issue) for a while now and was wondering if I have a problem or not.

The video below is a video of me starting my bike from a cold start and trying to rev it after a few seconds. When revving, the bike sputters a little and I was wondering if this is normal or not.

The bike started and idled normal this time, but usually, when I start the bike from a cold start the bike's RPM is low and it takes about 15 - 30 seconds before the RPM hit the usual idle RPM (1300 - 1400 RPMs).

The bike is 2004; has around 6K miles on it. I have a Jardine slip on that was cut to a shorty. I changed the FPR last year. Haven't changed the air filter or spark plugs.

Trying to narrow down what the problem is and fix it.

Now, if this is normal, then great, but I would like to get opinions if this isn't normal. I know that like most vehicles, a small amount of warmup is necessary, but I've seen a lot of motorcycle riders be able to start their bike from a cold start and rev it immediately.

After the bike warms up for about 30 seconds to 1 minute, everything is normal.

The only other thing I can think of that is sometimes problematic that could be related is if I am out riding and cruising and if I want to open the throttle real fast with a quick turn of the wrist, the bike sometimes hesitate (similar to how it hesitated when I was revving the throttle in the video). I can usually recover by dropping to a lower gear or just let the bike take a few seconds to get to speed or not open the throttle as fast.

Any ideas?

Thanks.

The first rev starts at 13.

2004 Honda CBR F4i revving stutter at startup - YouTube

 

Well it shouldn't be hesitating when you rev it. I don't rev my bike until it's been warming up for a few minutes while I'm putting my gear on. Once it's warm it should not hesitate when you get on the throttle, that I'm certain of. Have you tried running some fuel injector cleaner through it like techron concentrate? At 6k miles the spark plugs and air filter should be good.

 

At first I was thinking it's running too lean, but seeing the black color of the exhaust indicates rich. It's almost like the injectors aren't opening at the same time as the throttle body (causing the lean stumble) and then over compensate (causing the black smoke and rich condition). Do you have a power commander or some other sort of fuel enrichment/tuning device on the bike?

 

I haven't used any fuel injector cleaning. I am very wary as to the safety and effectiveness of such products like fuel additives and such. However, if there is good enough experience with such a product, I would be willing to try it if there won't be any negative after effects and if it would help my problem.

 

No power commander, no fuel enrichment/tuning device, nada.

The only performance mod that is on the bike is an aftermarket Jardine exhaust that I cut into a shorty.

 

Another thing I forgot to add is that after subsequent starts (even if like 15 minutes later) the bike will do the same thing, just slightly less intense. After about a 1 minute, just like at the end of the video, the bike will respond normally to blipping the throttle.

 

did the fault start when you put the exhaust on ?????

injection bikes have air flow meters that is controled by the ecu the exhaust can mess it all up unless its remaped to the ecu , it will make it run rich on tick over and weak on high revs , try your standard can and see what happens,

carb bikes are easyer to put after market cans on ( and you can ajust the carb set up easly )

 

The Jardine RT-1 was on the bike when I got the bike back in 2008 (or 2007, can't remember now). Everything was fine then. I don't have the OEM can as I bought the bike with the Jardine on it.

I can't say that I remember if it was when I cut the exhaust to a shorty, but it could very well have been right after that.

I guess I will need a shop to remap the air/fuel ratio to the ECU? Any idea on how much that could cost?

 

I'd try running a couple tanks of fuel with Chevron Techron (sp?) in it, and if that doesn't help, then I'd take it to a shop.

 

It's perfectly safe to run techron concentrate through the fuel system that is what it's made for, check the bottle or website for the necessary does per gallon.