Low RPM running problem
#1
12-18-2017, 04:04 PM
Low Throttle position running problem
OK,
So I'm hoping this isn't a valve clearance, although this is my oldest cbr I've had fireblade and blackbird etc and well it's not a ZXR Kawasaki and it's older but it's only got 31K on it.
Since I've had it, I've noticed it drops onto three on very partial throttle, idle is OK, but clearly not entirely in sync, feels as if the pilots are holding it.
On any very partial throttle opening it'll run on three anything more than a partial throttle, say the first five or so degrees or less even of twist and it's running on all four... In fact it's entirely throttle position dependant.
You can short shift the bike to over pull a high gear and it'll pull clean with no missing.
However open the throttle in idle and give it a few degrees of twist and it'll drop onto three and flatten its tone, twist harder all four cut in and it revs out.
Depending on how might throttle is required it maintain speed it may drop to three on a low speed cruise...
However any increase past this "dirty" few degrees of throttle and its clean.
The bike is also doing 50mpg with 80mph 20mile motorway cruise each day.
My gut reaction is that there is a carb behind a low throttle opening... And the pilots are holding up the idle. Or perhaps a coil... Sticks? Don't even know yet on this engine... Maybe even a plug.. I'm loathed to consider a valve, as it's so so throttle dependant and slow clean, although not entirely in sync, at wider throttle openings...
The bike starts easily, doesn't smell of fuel, pulls very well and sounds great on the throttle and feels like it's giving full power for its age at the top..
What are your thoughts guys?
So I'm hoping this isn't a valve clearance, although this is my oldest cbr I've had fireblade and blackbird etc and well it's not a ZXR Kawasaki and it's older but it's only got 31K on it.
Since I've had it, I've noticed it drops onto three on very partial throttle, idle is OK, but clearly not entirely in sync, feels as if the pilots are holding it.
On any very partial throttle opening it'll run on three anything more than a partial throttle, say the first five or so degrees or less even of twist and it's running on all four... In fact it's entirely throttle position dependant.
You can short shift the bike to over pull a high gear and it'll pull clean with no missing.
However open the throttle in idle and give it a few degrees of twist and it'll drop onto three and flatten its tone, twist harder all four cut in and it revs out.
Depending on how might throttle is required it maintain speed it may drop to three on a low speed cruise...
However any increase past this "dirty" few degrees of throttle and its clean.
The bike is also doing 50mpg with 80mph 20mile motorway cruise each day.
My gut reaction is that there is a carb behind a low throttle opening... And the pilots are holding up the idle. Or perhaps a coil... Sticks? Don't even know yet on this engine... Maybe even a plug.. I'm loathed to consider a valve, as it's so so throttle dependant and slow clean, although not entirely in sync, at wider throttle openings...
The bike starts easily, doesn't smell of fuel, pulls very well and sounds great on the throttle and feels like it's giving full power for its age at the top..
What are your thoughts guys?
Last edited by BikeJake68; 12-18-2017 at 04:21 PM. Reason: Correction
#2
12-18-2017, 04:23 PM
#3
12-20-2017, 04:54 AM
Senior Member
Hi Jake, sounds from your post like you haven't had the bike too long.
That's always a problem with an old bike, because you don't know how well maintained it's been.
If it was me I'd be looking at the carbs first, quick check there are no air leaks and then maybe take them off for a good clean and balance.
As you're going to be in there, you could give the coils a quick look over too, might be as simple as a spark-plug lead not seated properly. My old 1000F was a bugger to get the plug leads on properly, they'd feel OK but on fire-up she'd be running on three
That's always a problem with an old bike, because you don't know how well maintained it's been.
If it was me I'd be looking at the carbs first, quick check there are no air leaks and then maybe take them off for a good clean and balance.
As you're going to be in there, you could give the coils a quick look over too, might be as simple as a spark-plug lead not seated properly. My old 1000F was a bugger to get the plug leads on properly, they'd feel OK but on fire-up she'd be running on three
#4
12-20-2017, 03:44 PM
Hi Jake, sounds from your post like you haven't had the bike too long.
That's always a problem with an old bike, because you don't know how well maintained it's been.
If it was me I'd be looking at the carbs first, quick check there are no air leaks and then maybe take them off for a good clean and balance.
As you're going to be in there, you could give the coils a quick look over too, might be as simple as a spark-plug lead not seated properly. My old 1000F was a bugger to get the plug leads on properly, they'd feel OK but on fire-up she'd be running on three
That's always a problem with an old bike, because you don't know how well maintained it's been.
If it was me I'd be looking at the carbs first, quick check there are no air leaks and then maybe take them off for a good clean and balance.
As you're going to be in there, you could give the coils a quick look over too, might be as simple as a spark-plug lead not seated properly. My old 1000F was a bugger to get the plug leads on properly, they'd feel OK but on fire-up she'd be running on three
Are these coil sticks or twin coils with a wasted spark or?
I'm sure it's carbs my mates one of these had done 100K on the same engine pistons and rings and valves were still un touched.
Could be an air leak or one behind or pilots
But I doubt it's that.... As pilots holding idle reasonably steady
#5
12-20-2017, 05:10 PM
Senior Member
Hi Jake, I'm not exactly clear what bike you're riding at present, might be a good idea to put that in your signature, then it will be displayed on all of your posts ( I just did it myself 
).
Personally I'm convinced it will be a carb issue, but until you take a look-see, it's just guesswork.
).Personally I'm convinced it will be a carb issue, but until you take a look-see, it's just guesswork.
#6
12-20-2017, 05:17 PM
Hi Jake, I'm not exactly clear what bike you're riding at present, might be a good idea to put that in your signature, then it will be displayed on all of your posts ( I just did it myself ).
Personally I'm convinced it will be a carb issue, but until you take a look-see, it's just guesswork.
).Personally I'm convinced it will be a carb issue, but until you take a look-see, it's just guesswork.
#7
12-21-2017, 09:48 AM
Senior Member
No worries Jake, if you don't get any joy when you take a look at the carbs, it might be a good idea to post your problem in the specific F3 section here :-
https://cbrforum.com/forum/cbr-600f3-17/
These guys will have first hand knowledge of your bike and any common problems with it.
Good luck with your investigation, need any more help just ask.
Merry Christmas
https://cbrforum.com/forum/cbr-600f3-17/
These guys will have first hand knowledge of your bike and any common problems with it.
Good luck with your investigation, need any more help just ask.
Merry Christmas
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