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CBR600F carb question

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Suntan Sid
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Joined: 07 May 2009
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PostPosted: 10:28 - 23 Oct 2010    Post subject: CBR600F carb question Reply with quote
Due to a running problem I've got the carbs off my CBR.
I've had them apart and cleaned the jets etc.
I'm about to put on a new set of inlet rubbers.
I've got the "Haynes" open and the picture doesn't match my carbs.
It could just be the angle of the photo in the "Haynes" but it does not show the "half moon" shaped things.

Are these restrictors? I'm pretty certain it's a grey import bike so wouldn't be suprised if they were.

If they are restrictors can I just fit the new rubbers without them and if I do will I need to re-jet?

See photo below:-

https://i645.photobucket.com/albums/uu172/Troodos-Pool-Guy/CBR600CARBS.jpg
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Fisty
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PostPosted: 10:31 - 23 Oct 2010    Post subject: Reply with quote
They do look like restrictors, do they come out at all or are they part of the carb casing?
Do they stop the butterfly opening fully?
You say your bike is an import, do you know where from?

I had an F2 in bits some years ago and dont remember seeing them.
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Suntan Sid
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PostPosted: 10:37 - 23 Oct 2010    Post subject: Reply with quote
mr_fisty wrote:
They do look like restrictors, do they come out at all or are they part of the carb casing?

You say your bike is an import, do you know where from?


I've got the carbs on the kitchen table at the moment, those plates are part of the rubbers, moulded in.
The new rubbers don't have slots to fit the plates.

I'm assuming it's a domestic Japanese model, there is no english writing on anything!
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Suntan Sid
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PostPosted: 10:40 - 23 Oct 2010    Post subject: Reply with quote
mr_fisty wrote:
Do they stop the butterfly opening fully?


No, nowhere near them.
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Fisty
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PostPosted: 10:41 - 23 Oct 2010    Post subject: Reply with quote
Hmmmmmmm I honestly *think* they are a restrictor (possibly Honda's own)

They look similar to the ones on a CB500.

EDIT:-

Im 100% sure they are restrictors. Fit the new rubbers and see how it runs. I would guess it was fitted with them and probably not rejetted hence your running issues.
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Last edited by Fisty on 10:46 - 23 Oct 2010; edited 1 time in total
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Suntan Sid
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PostPosted: 10:45 - 23 Oct 2010    Post subject: Reply with quote
I'm going to fit the new rubbers, no choice in that matter, but will I need to re-jet?
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Phoenix
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PostPosted: 11:04 - 23 Oct 2010    Post subject: Reply with quote
Suntan Sid wrote:
I'm going to fit the new rubbers, no choice in that matter, but will I need to re-jet?


How can anyone know unless we know whether the bike was rejetted when the restrictors were fitted? Restrictors don't interfere with the butterfly valves mr_fisty, they just restrict the air/fuel mix than can get down the intake port and into the cylinder.

You should find out what size main jets your CBR should have as standard and then check the size of the main jets in it now, it'll be stamped on the side of the little plug you unscrew from the main jet holder (just to clarify). If they are the same then it hasn't been rejetted and it's possible that the restriction is what is making the bike run like poo. If they are different then i'd buy standard size jets, remove the plates and it might be better.
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Fisty
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PostPosted: 12:53 - 23 Oct 2010    Post subject: Reply with quote
Phoenix wrote:
Restrictors don't interfere with the butterfly valves mr_fisty, they just restrict the air/fuel mix than can get down the intake port and into the cylinder.
.


The ones that were fitted to my imported bandit 400 stopped the buttefly valves opening fully, acting more like a throttle stop.
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Suntan Sid
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PostPosted: 12:57 - 23 Oct 2010    Post subject: Reply with quote
Thanks for the help!
I put the same question up on the CBR Forum.
The concensus there is that they are restrictors and that the jetting would be standard.

"As they are on the engine inlet side they will restrict both the air/fuel mixture going into the engine. So the ratio will remain the same once they the restrictors are removed. Very much doubt that anything would have been changed jet wise and as long as your carbs were balanced before they should remain balanced after. So pull the buggers out and enjoy some"

So I'going to fit the new rubbers without the "restrictors" and see how it goes.

I'll update if anything significant happens.

Karma all round.

Cheers Sid.
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Phoenix
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PostPosted: 13:29 - 23 Oct 2010    Post subject: Reply with quote
mr_fisty wrote:
The ones that were fitted to my imported bandit 400 stopped the buttefly valves opening fully, acting more like a throttle stop.


Are you sure they weren't fitted under the diaphragm caps to stop the slides from opening fully? That's the only other usual method of restriction I know of. I can't see how you'd safely and neatly prevent the butterfly valves opening.
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Suntan Sid
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PostPosted: 15:24 - 23 Oct 2010    Post subject: Reply with quote
Carbs back in, air box and petrol tank back on.
Started after a few seconds, idled ok on choke, let it warm up, idled ok.
Took it for a spin, the pitch of the engine noise seems different, more of a low down rumble than before.
Seems to build revs a bit quicker, and definitely pulls better from low revs.
Didn't have a chance to really open her up, I'll try hat tomorrow.

Restrictors or not, it runs ok without them! Mr. Green
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