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Start up deteriorating

Old 09-29-2014, 07:09 AM
Thread Starter
Join Date: Mar 2008
Posts: 1
Default Start up deteriorating

Over the last couple of weeks the startup on my CBR 600 F-Sport (F4i?) has deteriorated. It has always typically started instantly. However one day it took an extra half second, and gradually slightly longer each time. Today it must've been at least 3 seconds, to the point where I'd be worried it wasn't going to start, or would flood or something bad. Adding gas seemed to make no difference. It still starts instantly if I've been out and about on it.

Is there anything obvious I can start to check?

Other info:
The battery is approx 1 year old and always kept on optimate if I'm not using it for more than a few days. Optimate still seems to show it's holding charge ok.
No warnings lights anywhere on dash.
Only aftermarket part is the exhaust, which has been on there for years.
Can't think of any other info that would help.

Any advice appreciated.
Old 09-29-2014, 08:14 AM
Mattson's Avatar
Retired Super Moderator, Tin Star Man & Hurricane Saloon Prospect, ROTM Feb 2015
Join Date: Sep 2011
Location: Vääksy, Finland
Posts: 2,382

Probly a rip in some rubber part that gets gradually bigger -> possible vacuum or intake leak. Have the engine on idle and spray short bursts of motor starter spray around the intake manifold. If your revs peak you got an intake leak. Just don't empty the whole can in there as it will eat rubber if let sit on it, a few short bursts is enough.

Go through your vacuum hoses for rips or tears. And while you're down there inspect the plugs. Might be a valve clearance issue although I heavily doubt it.
Old 09-29-2014, 02:53 PM
Senior Member
Join Date: Jul 2008
Location: Mesa AZ
Posts: 2,001

Its your battery. Took me years and almost 70k miles to figure it out too. Since my bike was about 6 months old I'd have a random hard start. It would crank and crank but only start if I opened the throttle. Also only happened after bike was hot, and was very random. Since it always cranked, I never thought battery. But it is.
Old 10-03-2014, 01:21 AM
Senior Member
Join Date: Jan 2012
Location: Stockton, CA
Posts: 258

im gonna say battery. I once had a replacement battery that wasn't even two weeks old and would have never guessed that the battery was the problem, but after getting a new one problem solved.
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