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Discussion Starter #1 (Edited)
Let me start by saying, I have gathered info from lots of forums trying to solve this, and 3 days of "search, debug, search another term, debug, ect."

This is my second Bird, both 1997. I still own both. I was sideswiped on the first in light traffic, totaling the bike. Sad day, but I have a good parts bike now. motor is still good. (ranting sorry).

Here is the issue, old bike had about 30k miles (stock +KN air filter), most flawless bike Ive ever ridden.
Test rode my "new" bird, only has 10,900 miles! Rode exactly the same. It was a breath of fresh air after the crash.

I rode the new bird from middle of PA to middle of Ohio where I live. Flawless. Rode it to work.... Flawless.... and then I decided this time I wanted the factory pro +4 reluctor wheel. This is where it all started. Install was a breeze, pulled the tank, air box, put new E3 plugs in, put K&N filter in, put the +4 reluctor in and did an oil change. I got on the bike after warming it up assuming no trouble would arise. Cruised out past the city limits (3 miles) and opened her up... up to 4k rpm seems normal and she fell on her face, fumbles up to 6 or 7000 and about shreds the rear tire (well it will pull the front up actually but it spun in a wet patch earlier today doing debugging) same symptoms in all gears and seems limp passing 135mph but nevermind top speed right now that might have been perception.

I was shocked? to say the least, would the reluctor ruin the mid but help the tippy top that much to both extremes? NOPE! I took the wheel right off SURELY it cant be this bad.

Stock reluctor acted the SAME way.
Back to stock plugs these E3s are trash!... same symptoms
Stock filter (all stock at this point)... same symptoms.... I threw in the towel for 2 days work of checking and double checking...
afterthought Amid trials the idle started breaking up too. could not clutch out at 2500rpm, it would kill it.


Today I set back to the original quest. I compared EVERYthing to the old bike for reference, checked coil resistance, stator puts out 13.8 volts, petcock is good, and reassembled the mod package (+4 adv, E3 plugs, K&N filter). I put my hand over the airbox inlets (fairings off) to feel the vacuum the bike had... revved it up and it didnt hang at 4-5k rpm. Thinking LEAN and using only what I have in my personal parts bins I took the stock 140 jets from cyl 1 and 4 OUT and put in the center 142 jets from the old bike. so it is now 142, 142, 142, 142. Smoothed out a bit. but I feel like I am reaching at this point.

It still breaks up, mid range bad, rips hard at a very specific range up top and idle is smooth again thats for sure. all mods installed (+4 adv, E3 plugs, K&N filter, 142 jets) but it pops out the exhaust off throttle, you can even see a few flames at night. I know a lot of other bikes that ive seen do this with no poor symptoms but I just dont know what happened.

What throws me the most is that it was perfect until I took it apart and even going back to stock, its dead at 4 or 5k rpm. Its mad at me, I know it!

Am i just in need of a rejet? I dont believe so. Not with the stubborn symptoms.

Thanks for reading my novel! you guys are the best.
 

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  • Check your other bikes carbs. The carbie hates any meddling with airbox and pipes. If you go to a high flow filter your guaranteed itll need a rejet. Check to see if the needles have been shimmed. Also check the air bleed hole sizes in the slides. Also check the needles. These are usually all altered when trying to compensate for aftermarket air filters and slip ons. Also check and make sure you didn't knock out the air deflectors. They are the little plastic shields at the front and back between the frame and the airbox. There should be one in front and behind the airbox intake horn.
 

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Discussion Starter #3
Plastic deflectors are present and accounted for. Pilot jets on both bikes were stock 140/142/142/140. I did change the new bike to all 142's and as i mentioned it seemed to help. So you think its all tuning at this point? The next knee jerk would have been "Buy a jet kit" for me.

Also, I have video of this in action. The bike does the same thing in a neutral "free rev". Sounds like it only takes air in at 4k and then comes back.


This second video is my friend riding because I needed someone else to feel what im feeling while riding. You can also hear the popping en the exhaust.
 

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Yes
Thinking so. Check slides and needles. The fact that it got better fattening up the mains tends to make me think the same. You could do a 2nd or 3rd gear plug chop check. Then pull the plugs and read the color. it's an old school technique. Here's a link to a page with different ways of doing it.
 

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Never worked on a carbie but is the pickup coil air gap adjustable. Any mechanical advance. Reluctor wheel magnetized. Pickup wiring good and connector fully seated and pins clean.
 

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Had similar problem to-day with my fi K75 was breather pipe from crankcase to air box dislodged (by me). Bad effect was pretty megga. You had air box off so check all vacuum pipes are ok and nor cracked and I mean also the small ones going to the pet cock etc. It looks very much like lean mixture due to an air leak could be difficult to find but go back over what you have done it is possible was caused by your self.....at least it usually is with me. Good luck.
 

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Good point Carler, Mike check carb boots make sure they are tight. Did you pull them? How pliable were they?
 

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Discussion Starter #8
Carb boots are on my list today. I replaced the 5/32 vacuum lines (case to petcock) and the one from the valve cover diaphragm to the tee on the carbs (and both 1 inch sections of line after the tee). Here is my problem with jetting, I already returned the bike to stock and it showed the same symptoms, so I believe I altered something critical upon assembly/ disassembly.
 

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  • Ok then go back to stock again but verify everything is setup to factory specs for timing and alignment. Fire it again and let us know. If you have access to a vacuum gauge. I'd check each cylinders readings to see if theres any differences. Keep us posted. We'll get it sorted just be patient and methodical.
 

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Discussion Starter #10
Started taking the bike apart again last night, but had some other things take priority. Probably won't get back to it until Sunday. I'm working two 12 hour shifts back to back.

Really appreciate the immediate help and responses. I'll be right back. Stay healthy.
 

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Discussion Starter #12
I think I found it! I did not realize this had a single vacuum line between only two carbs. And it was split bad.

Replaced and assembling now.
129020
 

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Good catch check the rest of the lines as well. Save you from popping them back off again.
 

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Discussion Starter #14
It's not the problem....

I got really curious. So we zip tied a rag around the left side snorkel. Took it down the road and man did she go. No popping or dead spot.

So my friends... How did it go lean. And how did go lean in 100% stock configuration. And why on Earth did creating a miniscule barrier in front of just one snorkel eliminate the problem.

I still have 142 jets across the board. It seems smoother.
 

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Are all 4 of the air dams in place?

Did you blow out all the passages reverse flow in the carb bodies?

Blocking off one port tells me your still a tad lean. Try shooting carb cleaner at the boots between the carbs and head then at the airbox. You could have cracked boots
This can happen at the sharp bends in the boots and be practically invisible to see.

You can also hook up a synch gauge or vacuum gauges and watch them as you spray. The needle that jumps when you do is likely the one leaking.
 

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Discussion Starter #16
I did the spray while running trick to no avail. Blew the carbs. Might have to redo that. The air dams are all there. And it happens while stationary in free rev. It will literally hang at strictly 4-6k and free up and rev to 11k like normal.

Bottom line is the bike isn't getting enough fuel. It won't even get enough fuel while stationary in free rev so its not a ram air problem. Vacuum actuation has been ruled out, and this bike does not have evap (built in 1996) so there are only 5 sections of the tiny vacuum line, all which have been replaced.

1 is from valve cover diaphragm to tee, 2&3 go from the tee to the carb and air restriction valve. 4 is from the intake manifold to the petcock. 5 is between carb three and four.

Fuel tank vent line is not blocked.
Fuel flows from the tank into the bowls freely and the bike started quickly even with previously emptied bowls.

So.... Maybe there is still something in a passage. Would you agree nothing else stands in the way?
 

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Tending to agree with you. Last thing to check in the tank would be the in tank strainer. Make sure it's 100% free and clean when you look at it does it look varnished any at all.

Is it doing any popping when it hangs or is it just lagging? Can you clear it like you did with the road test? If so then try tipping a bit of choke and see how it reacts. If both of those cure it you are probably right in that there is a still blocked passage. Did you get some Yamaha Cumbustion chamber cleaner it'll dissolve just about any kind of crap in there. There may be one other possibility. If you run gas with even 10% ethanol and it has sat for anymore than 2 or 3 weeks and you have a lot of humidity. This stuff can create a black crud that is like a diamond it will be very very fine and will cause blockage headaches. So again try back blowing stuff. Took me 3 times once when I worked on a V45 Sabre to get it all out. Also you may want to go into a totally black room and shine a very bright small penlight flash light at the diaphrams and check especially where it meets the slide joint.Gently pull it as you shine the light to look for tears or breaks.
 

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Discussion Starter #18
I can't pull it all the way out, it stops and hangs there. Wiped it off and it seems cleaner. When I pulled it out it seemed to have fuel in the strainer still like it was held in with surface tension.

129022
 

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That should come completely out wioth little to no resistance. Can you get a light in from the filler neck and see the top of it. Hmmm was the fuel caught inside the strainer or are you talking that it was on the outside surface. If it's the latter that's ok. Still kind of suspicious that it won't drop completely out. If you end up tearing it trying to get it loose don't panic. Juat get an inline strainer from and auto parts store and splice it into the line before the carbs.
 

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Discussion Starter #20
Well, I set the tank up and ran fuel lines to a Jerry can, sucked the petcock open and it rapidly pours gas out.

Not sure if this means anything as I scour this information. If the bike is (we will say cold) and you fire it up on choke, if you twist the throttle at ALL it kills the bike.

As I mentioned, flow from the tank is NOT an issue. You could empty the tank in minutes.
 
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