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post #1 of 12 Old 06-29-2006, 10:55 PM Thread Starter
 
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Stupid Carbs

OK, I need suggestions.

Here's the scenario:
The bike accelerates fine. It has plenty of power. It isn't fouling plugs.

At cruising speed though, with the bike at 4500 - 5000 RPM the bike will stumble if a quick throttle response is administered. The stumble immediately clears up? (If this were the only problem I would attribute the problem to a carb charicteristic.)
If you drop the throttle in 3 - 6th gear and then grab it again (semi-agressively) the stumble is very noticeable to a point in which it seems to try to shut the bike down.

I am running the stock keihin carbs that came on all CBR900RR bikes. I removed the aftermarket jetting because I thought the bike was flooding and choking down. I am now running 115 main jets on the outside and 118 on the inside, which is the stock application. (This change made no difference at all in the bikes hesitation and stumble)

As for the things that I have changed on this bike: Full Micron System and a K&N filter as of right now. The 120 main jets have been changed if you have been reading thus far.

I have pulled and completely cleaned the carbs themselves. There was a small amount of dirt, but not enough to cause a problem. There were no clogged jets.

*Could the Throttle Position sensor cause this problem? If so, would it hurt to just disconnect the sensor all together?

*The carbs don't seem to be out of sync, but could this be an issue?

I need suggestions guys.
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post #2 of 12 Old 06-30-2006, 9:54 PM Thread Starter
 
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Re: Stupid Carbs

Back to the top for you
bump
bump
bump
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post #3 of 12 Old 06-30-2006, 11:40 PM
 
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Re: Stupid Carbs

All the really smart cats are recovering from Grattan. Give it a couple days and you should start getting suggestions.
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post #4 of 12 Old 07-01-2006, 12:33 AM Thread Starter
 
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Re: Stupid Carbs

Quote:
Originally Posted by seamus
All the really smart cats are recovering from Grattan. Give it a couple days and you should start getting suggestions.
Seamus, that comment could be used against you. By the way, have you have 11,000 RPM problems at the redlight lately?
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post #5 of 12 Old 07-02-2006, 10:18 PM
 
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Re: Stupid Carbs

When did you notice it started stumbling? Any type of changes to the bike, or just randomly started happening
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post #6 of 12 Old 07-02-2006, 10:24 PM
 
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Re: Stupid Carbs

Check for an air leak. My SV suddenly started running badly at full throttle on Thursday, and I found one of the carbs had popped out of the elastic boot connecting it to the cylinder. Maybe using the rev limiter as a tach wasn't such a good idea?


BTW, Stegen is our 11K wonder, Seamus is, by all reports, the biggest man in North America.
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post #7 of 12 Old 07-02-2006, 10:30 PM Thread Starter
 
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Re: Stupid Carbs

Nope, the bike has been doing this for a while now. I left it alone and was focused on Drag Racing. Now that the Drag Bike is gone this is my toy again. I thought when I rejetted the bike it would stop. That's what I get for thinking.

I've already checked for every airleak possible. I also pulled the needle jets and checked the springs. All is good there.
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post #8 of 12 Old 07-02-2006, 11:03 PM
 
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Re: Stupid Carbs

you mentioned syncing the carbs, why not sync them anyway. it won't hurt anything.

if you can't convince them, confuse them.
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post #9 of 12 Old 07-02-2006, 11:03 PM
 
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Re: Stupid Carbs

Quote:
Originally Posted by Custom900
Seamus, that comment could be used against you. By the way, have you have 11,000 RPM problems at the redlight lately?
Quote:
Originally Posted by CBRVFR
Stegen is our 11K wonder, Seamus is, by all reports, the biggest man in North America.
Yeah, what he said. Minus the biggest man in North America comment. I did some trimming down over the last two months.

I'm no carb expert, just didn't want you to think people were ignoring you. Knew the list of Grattan attendees included the majority of the technical experts here.
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post #10 of 12 Old 07-03-2006, 10:57 AM
 
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Re: Stupid Carbs

If you can find the specs, you will be able to check the TPS (throttle position sensor) for proper ohms, also check for the volt reference and ground at the connector to ensure they are within specs. Or, just swap it out with a buddies tps. I would try to snyc the carbs as well, even if that doesn't fix your problem (which it kinda sounds like it would), your bike could most likely use it anyway. If that doesn't work, let us know.

Last edited by LUCIDDREAM57; 07-03-2006 at 11:21 AM.
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post #11 of 12 Old 07-03-2006, 11:14 AM Thread Starter
 
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Re: Stupid Carbs

Yeah, I'm gonna sync the carbs as soon as I get back into the shop again. It definitely can't hurt.
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post #12 of 12 Old 07-03-2006, 1:03 PM
 
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Re: Stupid Carbs

I'd put a little more restriction on the air filter (aka stock) and see if that helps.
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