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Old 10-17-2012, 03:43 AM   #1
nguyen925
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Issues with throttle, CBR F4 1999 carberated engine

So here's the situation, bike was perfectly fine before I took it through traffic on my way to UH from Sugar land. Once I got there I managed to park to drop off some lab reports. When I got back bike had issues started.

Things that should be noted, I purchased the bike from a seller off CL and I have since charged the battery. I don't have any issues getting the engine to turn over and start. It occasionally acts up after warming up and main issue that day was the engine would die unless I would open the throttle up (which only resulted in the RPMS reaching 2-3k) and it would immediately die if I let it go.

So far I've replaced the airfilter with a K&N air filter and tried cleaning the spark plugs. Not much of a difference if any at all. Here's a video of the bike on. Engine making some odd noises.

Please click on picture to load video, thanks.

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Old 10-17-2012, 08:16 AM   #2
Patrick
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Sounds like a vacuum leak.
When you replaced the air filter did you reconnect the 4 small vacuum lines to the air box?
Are they also still connected to the carb manifolds?
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Old 10-17-2012, 09:30 AM   #3
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I'll see if I can come by right after work to take a look. I don't have anything planned really, just le gym.
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Old 10-17-2012, 09:45 AM   #4
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Quote:
Originally Posted by Patrick View Post
Sounds like a vacuum leak.
When you replaced the air filter did you reconnect the 4 small vacuum lines to the air box?
Are they also still connected to the carb manifolds?

The smallest things make a world of difference!
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Old 10-17-2012, 06:18 PM   #5
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I disconnected them when I removed the air box and replaced them the exact same way they came off. I wonder if there's a leak in one if those lines. Thanks guys, and Josh I'll text you when I get home. I'll keep it updated in case someone else needs this as a reference.
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Old 10-18-2012, 04:21 PM   #6
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so I got to taking the gas tank again and I was testing the airflow from the 4 small hoses that connect to the bottom of the air box and it seems the air is sputtering. it doesn't seem like a constant or smooth run flow.
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Old 10-20-2012, 02:10 AM   #7
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So I turned it on today and had no issues, took it for a spin from Sugar Land to the Heights (40 minute ride) then rode back (another 40ish minutes with traffic) and still had no issues. Didn't have any engine hesitation or any other problems I was experiencing before. I'm going to play it safe though and ride only within the area in case I break down or something. :/
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Old 10-29-2012, 04:57 PM   #8
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please keep us informed. Maybe you adjusting those tubes did the trick. Patrick was spot on if anything else!
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Old 10-30-2012, 02:12 AM   #9
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Yeah after Patrick gave me that helpful advice I was more careful with adjusting everything. I think the issue might have been related to my spark plugs so I ordered and replaced my OEM NGK sparks with some NGK Iridium sparks and I also put in a K&N airfilter (which sounds extremely nice btw). After riding for a bit I've had no issues.

Funny though, I've been smelling gas in my garage for awhile now and I was wondering where it was coming from and so I cut a small portion of a water bottle off to place under where the gas tank connects to the fuel filter and I saw it was leaking there. I then took off the gas tank (pro at it now because I've done it countless times so far) and I took apart the fuel reserve part under the gas tank and seems someone decided the fuel tank didn't need an O ring. It turns out my bikes been leaking gas roughly about 3-4 ounces every 3-4 hours slowly. I temporarily solved the issue by getting one of those o rings from the hose spouts (screw onto water hose) while I'm waiting for my parts I ordered online to replace what I'm missing.

I also replaced the clutch lever and that thing that holds the clutch lever down. The previous owner thought using a MOTOCROSS part was adequate which was very usable until I hit traffic ( only allowed me to use 2-3 fingers off my hand to clutch in ). So far so good!
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