Rear cylinder not firing
03-26-2007, 02:07 PM
#1
Josh
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Rear cylinder not firing
Well, for the last 6 months i have been having problems with my rear cylinder not firing. Originally i thought it was just the spark plug geting fouled, but i now believe for some reason i am getting an air bubble in the fuel line going to the rear. has anyone had a similar problem? Does anyone know a fix for this? It is driving me nutz, because my bike will be running just awesome and then i will restart her and all the sudden just one cylinder. I have plenty of spark, i have tested that. I used to be able to just run her hard for about 10 minutes and then the cylinder would kick back in, but now i have to take the tank off and remove the fuel hose. When i do, a good amount of fuel leaks out, so i think the line is full and not actually going into the the carbs. Any assistance would be awesome. Thanks!
03-26-2007, 02:44 PM
#2
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that is a hard scenario to imagine: I don't think it works like that. Those lines are big going to the carb and the fuel is stored in the float chamber so unlikely that is the issue. You can always check if fuel is in the float by simply opening the flat-screw on the bowel: for the rear carb its facing out left side easy to reach.
I would think the problem is somewhere else in the carb if you are sure its getting spark when it misfires. Simplest thing is to remove and clean well, check the diaphragm and float mechanism. Perhaps a sticking float or partially clogged jet. Have you ever tried lightly tapping the bowel when it won't run? if its stuck in the up position and shutting off fuel you should get a dry bowel when you check the flat-screw and sometimes tapping with the handle end of a screwdriver will dislodge the float. then you know it need cleaning. if that isn't it, check the spark and then clean carb if that is OK would be my approach.
I would think the problem is somewhere else in the carb if you are sure its getting spark when it misfires. Simplest thing is to remove and clean well, check the diaphragm and float mechanism. Perhaps a sticking float or partially clogged jet. Have you ever tried lightly tapping the bowel when it won't run? if its stuck in the up position and shutting off fuel you should get a dry bowel when you check the flat-screw and sometimes tapping with the handle end of a screwdriver will dislodge the float. then you know it need cleaning. if that isn't it, check the spark and then clean carb if that is OK would be my approach.
03-26-2007, 03:51 PM
#3
Josh
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Update: Ok, i will add a little info. Originally i thought the plugs were fouling. So i would take the rear plug out every time it was running on one cylinder and i would use a wire brush to clean it up. Truthfully it always looked fine, but for some reason it always seemed to work. Well yesterday i did it and it dawned on me that alot of fuel was in the line. It would kinda spew out. That is why i am thinking there is a backup in the system, but simply taking the hose off of the tank and putting it back on after releasing the fuel seems to fix the problem for a few startups. Then it happens again. Also this only happens when it is cold out. If you have any ideas, please let me know. Thanks!
Also, about 1100 miles ago i cleaned the carbs. I know that i am running a little too rich due to larger jets, but other then that, the bike runs pretty awesome when it is getting fuel
Also, about 1100 miles ago i cleaned the carbs. I know that i am running a little too rich due to larger jets, but other then that, the bike runs pretty awesome when it is getting fuel
03-26-2007, 06:26 PM
#5
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If the plugs fouls, replace it. Only way to be sure of the plug. Buy some cheaper plugs until you get this figured out.
And I just thought of something. (I know, a rarity.) Those light up plug wires the chopper guys use would be real handy at seeing if the coils are firing. That is if the wires can be removed from the coils.
And I just thought of something. (I know, a rarity.) Those light up plug wires the chopper guys use would be real handy at seeing if the coils are firing. That is if the wires can be removed from the coils.
03-26-2007, 08:33 PM
#6
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03-26-2007, 10:18 PM
#7
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I'm going to have to agree with most of what was recommended, particularly opening the bowl drain screw right after this happens. I also recommend the next time it happens to open the fuel filler. If you hear a sucking rush of air and the bike immediately runs fine after that then your problem is a clogged vent line. Blow the vent line out from top down, never from bottom up.
03-27-2007, 03:08 AM
#9
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One more easy thing to try is swapping your coils front to rear. If the problem moves to the front cylinder then your coil is bad. I was having a intermitent problem similar but different to yours. Everything pointed to a fueling problem but it wasn't Sparks always tested good but would drop the rear cylinder when I would give it to her.
03-29-2007, 03:03 AM
#10
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See how you go with the fuel. If that is not the problem, then look at spark. One lesson I learned with spark is that often the system will work fine at idle but break down under load. Hard to diagnose when this happens.
You can check your coils to see if they are still within spec, and another set of plugs would be a good idea too.
You can check your coils to see if they are still within spec, and another set of plugs would be a good idea too.
03-29-2007, 01:05 PM
#11
Josh
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Ok, so i am still a little baffled. It does seem that it keeps fouling the plugs. Just about every time i have to pull the plugs out and clean them and reinstall them before i can ride. It is like there is just way too much fuel getting on the plugs and it kinda covers the plug so mucht hat it wont spark. When clean they spark just fine. Is it possible that i am just trying to ride her too early in the season? It is like about 45 degrees when i try to start her. I do remember most of my problems have happened and occured when it started getting cold at night last summer. Maybe i just dont know something. Any advice would be awesome! Thanks!
03-29-2007, 01:17 PM
#12
Josh
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It does seem that it is running way too rich, i am going through the manual to see what i can do to change that. Umm, has anyone had a similar problem 2 me? I get horrid gas millage, about 18 around town. It does have an aftermarket jet kit, but not super big. Anyone have similar problems? I cleaned the air filter last fall when i was having the problems and it didn't seem to change anything. I have 1100 miles on the oil change, so that should be fine also. I know that if i could lean the mixture she would run better.
03-29-2007, 02:14 PM
#13
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If you're getting 18mpg then there's definitely something awry. Pull the carbs. Check the float valves and clean out the passages. Check your idle jet. Should be #45. You might have a #50. That's part of the problem. The idle mixture screws should be about 2 turns out (unless you have major mods). Problem here is they are "D" shaped heads on those. You'll need to borrow a tool from your Honda dealer or find someone with the FactoryPro tool (from a jet kit). Lastly, your mains are dependant on mods and altitude so that's going to be the hard part. Either dyno tune or use somebody elses numbers with mods and altitude close to yours.
03-29-2007, 02:23 PM
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Should be around 30 or so, depending on your right wrist. I had my RLOD come on at 90 miles on the track. That's about 20mpg, WFO about 80% of the time.
RLOD stands for Red Light of Death, BTW.
RLOD stands for Red Light of Death, BTW.
03-29-2007, 02:29 PM
#17
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I'm confused. It does sound more electrical now. And your first post said even when you changed plugs they in truth looked fine to you. now your say they look fouled. can you just describe what they look like? And finally, has this bike ever run well for you all around (idle, throttle etc) or is this an inherited problem and you don't know what baseline is and what current mods are? That information clearly given might help us try to help you.
03-29-2007, 09:48 PM
#20
Josh
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I'm confused. It does sound more electrical now. And your first post said even when you changed plugs they in truth looked fine to you. now your say they look fouled. can you just describe what they look like? And finally, has this bike ever run well for you all around (idle, throttle etc) or is this an inherited problem and you don't know what baseline is and what current mods are? That information clearly given might help us try to help you.
The bike ran very well until it started getting cold at night last summer, but good gas mileage, i mean anything near 30, that hasn't happened really ever. I think 27 was the best of all time. I am one of those dorks who checks his mileage every single time he fuels up. I have been just dealing with it, but last tank was 18.7. I actually drive like a grandma, i don't accelerate very fast. I mean i do to start up, but i rev usually only to about 5k, maybe 6, never more then that. I am going to snap a few pix of what she looks like and hopefully i can get some more ideas. Thanks everyone for their input!
03-29-2007, 10:15 PM
#21
Josh
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Here are a few pix of the area.
Lots of oily sludge in here.
I don't know if these will help, but i thought i would at least take them. I appreciate any other suggestions.
This is what i know, the carbs are definitely out of sync, the valves should be adjusted within about 3000 miles, and i get horrid gas mileage.
Lots of oily sludge in here.
I don't know if these will help, but i thought i would at least take them. I appreciate any other suggestions.
This is what i know, the carbs are definitely out of sync, the valves should be adjusted within about 3000 miles, and i get horrid gas mileage.
03-30-2007, 05:36 AM
#23
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were the needles stock when you removed the slide? is there a clip to adjust them? You have to remove the plastic device inside the slide - you can see it in picture 1 above. Use a screw from the carb top and partially thread it as a holder into the threads on that hard plastic part and you can wiggle it loose and up. THere is at least 1 small washer and spring at the bottom so don't lose anything. Your this far, take the carbs off and remove the lower bowels and see what size the main jet is (it will have a number and a "K" symbol or no symbol which will help tell if its stock or after market.
03-30-2007, 08:16 AM
#24
Josh
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were the needles stock when you removed the slide? is there a clip to adjust them? You have to remove the plastic device inside the slide - you can see it in picture 1 above. Use a screw from the carb top and partially thread it as a holder into the threads on that hard plastic part and you can wiggle it loose and up. THere is at least 1 small washer and spring at the bottom so don't lose anything. Your this far, take the carbs off and remove the lower bowels and see what size the main jet is (it will have a number and a "K" symbol or no symbol which will help tell if its stock or after market.
03-30-2007, 08:17 AM
#25
Josh
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Yes, most definately there is a gas ordor, i never ever have to use the choke also. She most definately is running rich.
03-30-2007, 08:19 AM
#26
Josh
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I am going to go and tear the carbs off and start a cleanup, i have a feeling that she is simply not getting enough air into the carbs. Does anyone replace all the gaskets and rings they tell you to replace in the carbs?
03-30-2007, 08:29 AM
#28
Josh
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i was talking about the small o-rings and things they tell you to replace during the carb uninstall in the manual. i dont have my manual near to say what i am exactly talking about. it is in the shop.
03-30-2007, 08:51 AM
#29
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no, you don't have to disassemble the carbs entirely. Just remove the main and pilot jets clean them and be sure all air passageways are removed. Be sure the choke cables are working probably and not stuck in the open position also and the float height - apparently its not adjustable. And check the mixture screw to see how far out it is turned.
03-30-2007, 09:47 AM
#30
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Watch for the oval needle seat, I have the feeling that Honda engineers have overlooked the needle to seat rubbing made worse by the low RPM pulsing needle movement. This makes the needle leak, it have been seen in other threads.
