Bike Bogging Down While Riding

[Nate4s]

[Back Story]
Hey Everyone! I've been lurking on these forums for a long time (2 years). I started out on a '99 GZ, upgraded to an '02 SV650 (and sold the GZ), and now I JUST bought another '99 GZ for my "winter" bike and for my girlfriend to learn on. It was an MSF bike and has 4.9k miles on it (VERY hard miles, I assume). It was only $440, and I drove it 70 miles home...and I assumed it was in perfect running condition. It was missing mirrors, signals, had a cracked seat, covered in dust/dirt, had vines intertwined into the spokes, has dents in the tank, and the right handlebar side was smashed up. The downside is that the guy I bought it from had it running when I got there - he claimed that the battery had died and he just bought a new one and had just charged it and started it up to make sure it was working for me (that's a HUGE no-no when buying bikes). I tried to start it the next day, and the idle was all over the place and would die if I didn't "maintain" it with throttle - there was gas in the airbox (as well as a huge handful of sand), and tons of sediment in the gas tank. It's running better, but still giving me issues. Just to give you an idea of what I've done/checked so far, here is everything I've done to the bike:

Reupholstered the seat with marine grade vinyl
Put a new plastic bumper on the back (the old one was shattered and couldn't hold turn signals)
Put on some rear turn signals (it didn't come with any)
Put on new throttle tube
Put on new brake lever
Put on new bar ends
Put a new choke cable on (old one was not salvageable)
Lubed all cables
Put in some plexiglass in the speedometer (old one was shattered)
Replaced the speedometer cable
Replaced speedometer bulbs
Reattached the Kick-stand kill switch (had been disconnected)
Put in New Spark Plug
Drained tank, put new gas in (as well as B12 Carb Cleaner)
Put in 2 cylinder head bolts (had an oil leak near the exhaust header because two bolts were missing, and not stripped....really strange)
Completely disassembled carb and cleaned thoroughly
Installed new air filter (with Hi-flo recommended on this site)
Charged battery (with old car battery charger, set on 12v 2amp)

Follow Up
So, after all of this stuff, I start the bike up (with choke, of course) and the idle ranged from 1000 - 4000 (auditory guess) on it's own, and wouldn't settle on an idle speed. If I turned the choke off, it would die. If I touched the throttle, it would also die. I pulled jets and soaked them in carb cleaner (again), and used pressurized spray and air through the holes, and reassembled. All of the cables and hoses were reattached, and I'm almost certain it's not a battery issue (no dimming of lights, everything electronic seems to be working) or a vacuum issue (runs equally well on PRI and ON). After re-cleaning the jets, the bike seems to idle at a constant acceptable speed (with choke and with choke off) and will accept throttle! I rode off, thinking it was miraculously fixed - not quite. I made it 1/4 of a mile, and the engine started to bog down (and made a "ffffffop ffffffop ffffffop..." vacuumy sound, almost the same suctiony sound the "piston valve/diaphram" inside the carb makes when you slide it up and down) - increasing throttle did nothing, neither did decreasing the throttle. I tried to ride it out, as the bike didn't die completely - it lurched heavily (pulsing) before making a single back-fire like pop and immediately going back to a normal engine level. I rode it about 5 miles, and this process occurred 4 more times (with it actually dying once, although it started back up immediately without any issue). The only other noise I've noticed is a suction sound coming from the gas tank cap.

Possible Fixes
My goal is to attempt to drive it around 50 miles or so tomorrow to get the battery charged back up and to see if the B12 will somehow work some magic and solve my issue (but staying close to town in case it completely dies). If it's still giving me this issue, do you think messing with the pilot mixture screw might help (the brass plug is still in there currently)? Would an issue like this arise from valve clearances? Any other thoughts on things I should try? I apologize for the LONG post, but I wanted to give you every detail I could think of (and I probably missed some things I've also done). Thanks in advance for any help! -Nate :2tup:

[Water Warrior 2]

I think you overlooked the obvious. You said the gas tank makes a sucking sound. Betcha the gas cap vent is plugged. You might be creating a vacuum in the tank and the gas will not flow properly to the carb.
Also check the air box drain tube. It should be hanging down from the air box to the bottom of the frame. It should have a plug in it. Pull the plug to drain any mung out and replace the plug. The plug is there to seal the system against unfiltered air from entering the air box and hence the engine. Oh yeah...........Welcome.

[Nate4s]

Thanks for the welcome and tips! The airbox-draintube-plug was removed when I drained the previous sewage out of there...It literally looked like a string of seaweed (covered in sand too, of course) and I replaced the plug immediately.

I've read a few other posts talking about the gas cap vent being plugged...but I have no idea where this plug is located (assuming it's on the gas cap somewhere) and how to go about unplugging it. Is there an easy way to check if it's plugged? I could just disassemble it entirely like I did for everything else...like the petcock - I just don't want parts to explode out of it and accidentally lose one. Unlike a few other posts on this forum, I'll be sure to stick it out until the end and provide concluding statements when it's all fixed up! Thanks again!

[Rookie Rider]

Very nice detailed explanation, welcome to the forum. What took you so long ?

[Nate4s]

Very nice detailed explanation, welcome to the forum. What took you so long ?

I (unfortunately) made the assumption after selling my first GZ that I would probably not acquire another...and so I never joined to forum the first time around. I should have known that a fun, no frills bike like the GZ would continue to appeal to me. Thanks for the welcome! I'm off to "unplug" the gas cap vents and try to ride all the quirks out of it. If you don't hear back from me, I've probably died in a GZ related accident (it stalled uphill on a 15% grade yesterday...I'll try to drive it on kinder terrain today). :roll:

[mrlmd1]

You could go for a ride with the cap in place but loose (try not to lose it) and see if it still bogs down.
The best way to see if this is the problem is to go for a ride and when it stops, quickly remove the cap and hear if there is air rushing into the tank by the sound it makes. The problem is that you need the key to get the cap off, you can't do this while you are riding. The vent is basically in the cap - see if you can clean out a little hole somewhere in the cap, maybe around the gasket. I no longer have the GZ so I can;t give you any more info on it, except that it's in the cap.

[Nate4s]

Well, I disassembled the cap and cleaned all the gunk out. I also tried running the bike with the cap slightly ajar. Unfortunately, the bike is giving me the same issues it was giving me yesterday. It starts, but the idle is all over the place (2-4k rpms) and it won't accept ANY throttle (so adjusting the idle screw doesn't make a difference). When I go to turn the throttle, the there is a strange noise - I don't know how to describe it other than "foop foop foop foop, etc" - it almost sounds like someone is beating on a rug (you know, like when you're cleaning it outside) at a high speed. It's a really low, dead/muffled sound and it takes over the higher pinging sound the idling makes.

Any thoughts on what to check next? Thanks!

[alantf]

You do know that the carb is the Achilles heel of the GZ, right :) I'm no mechanic, but it sounds like you still have carb problems, even after cleaning it out. Sounds like you have to strip it down again, and clean it again. The carb is the only bad part of a good bike. :2tup:

[Nate4s]

You do know that the carb is the Achilles heel of the GZ, right :) I'm no mechanic, but it sounds like you still have carb problems, even after cleaning it out. Sounds like you have to strip it down again, and clean it again. The carb is the only bad part of a good bike. :2tup:

Alantf,

I've read about 25 posts where you've suggested the same thing and you've been right in the end...so you're probably right again. Do you have any suggestions for a deeper clean of the carb? I took EVERYTHING apart the first time I did it...and hosed everything off with a horribly toxic carb cleaner. Just out of curiosity, do the passageways beyond the jets get clogged? If so, how do I access/clean them - I want to make sure the carb cleaner isn't going to eat away at any seals or gaskets in there...so I don't just want to submerge the carb unless it's safe. Thanks!

[Rookie Rider]

Maybe a small dead animal or something small, stuck in your exhaust someplace. Just a thought.

[Nate4s]

Maybe a small dead animal or something small, stuck in your exhaust someplace. Just a thought.

It seems to be producing a normal amount of pressure out the exhaust, but I'll do my best to check for dead animals none the less.

[mrlmd1]

Make sure the vacuum line leading to the petcock isn't cracked or leaking - maybe you have a gas flow problem or a vacuum leak, and make sure the plug is in the bottom of the carb drain. Check also to see that the air box/cleaner is firmly attached to the carb and the boots attached to the carb are intact and tight.

[Nate4s]

mrlmd1,

As far as I can tell, there isn't a vacuum leak (PRI and ON run the same) - the hose is attached and in good shape, and there are clamps on both ends. As far as I can tell, the carb boots are securely attached and not leaking air either - is there a more factual way to check for air leaks? I wish I had another carb to borrow and try out so I could potentially rule everything else out...

[raul10141964]

carbon buildup on the slider can prevent it from open

[blaine]

is there a more factual way to check for air leaks? I wish I had another carb to borrow and try out so I could potentially rule everything else out...
You can spray some WD-40 around the boots.If you have a leak the idle will increase.I to think you missed some openings when you were cleaning the carb.Did you remove the M.j. when you were cleaning? If not there several small openings that control fuel delivery when the needle lifts as throttle is applied.
:) :cool:

[Nate4s]

is there a more factual way to check for air leaks? I wish I had another carb to borrow and try out so I could potentially rule everything else out...
You can spray some WD-40 around the boots.If you have a leak the idle will increase.I to think you missed some openings when you were cleaning the carb.Did you remove the M.j. when you were cleaning? If not there several small openings that control fuel delivery when the needle lifts as throttle is applied.
:) :cool:

Excellent information - although it might be impossible to tell if WD-40 is responsible for an idle increase when my idle is currently so sporadic. I took out all of the jets (if M.J. stands for Main Jet), and thought I got all of the nooks, crannies, and crevices. Do I need to do anything special to clean the areas underneath where the jets screw into? I'm really hoping this is just a carb issue...and not something engine related.

[blaine]

Some times if using compressed carb cleaner,it needs to "soak" awhile to get full effect & desolve stubborn residue.I'm pretty confident that another cleaning will fix your problems.Did you remove the plug over the idle mixture screw,so you could remove it to spray some cleaner in the jet.If it is dirty it will effect from idle on up.Also make sure diaphram is seating properly & not leaking.
:) :2tup:

[Nate4s]

Some times if using compressed carb cleaner,it needs to "soak" awhile to get full effect & desolve stubborn residue.I'm pretty confident that another cleaning will fix your problems.Did you remove the plug over the idle mixture screw,so you could remove it to spray some cleaner in the jet.If it is dirty it will effect from idle on up.Also make sure diaphram is seating properly & not leaking.
:) :2tup:

Thanks! I'll give it a try tomorrow and report back. :techy:

[Nate4s]

Alright. I found 2 things!

1). There is a hose that attaches to the carb but I can't find out what it's purpose is (NOT: fuel line, vacuum line, or float bowl drain) - it is completely plugged shut - full of spiders and cocoons, just like the rest of the bike. I will replace this.

2). The tip of the Pilot Jet Screw is completely snapped off. The brass plug blocking the pilot screw was blocked off, so the previous owner probably didn't break it. The tip is still sticking in the carb body.

IS THAT IT?! Did we find my issue? Now I just need to wait for a new pilot screw to come in... (I also just bought a second carb off ebay for $60...)

[blaine]

Not sure what hose you are referring to,but the tip broken on the pilot jet screw is your main problem.
:) :cool:

[Nate4s]

There is no explanation of what that hose is on the parts fiche. Do you have 4 hoses plugged into your carburetor (not counting the choke cable as a "hose")? Float bowl drain is on the bottom, top-right-front is the vacuum hose, top-left-back is the fuel hose, and the hose in question is on the top-right-back of the carburetor. Mine runs back over the battery and points down towards the ground - it's almost a foot long. What does it do? Maybe it was supposed to suck up spiders/cocoons and I just didn't know any better... :lol:

[blaine]

There is no explanation of what that hose is on the parts fiche. Do you have 4 hoses plugged into your carburetor (not counting the choke cable as a "hose")? Float bowl drain is on the bottom, top-right-front is the vacuum hose, top-left-back is the fuel hose, and the hose in question is on the top-right-back of the carburetor. Mine runs back over the battery and points down towards the ground - it's almost a foot long. What does it do? Maybe it was supposed to suck up spiders/cocoons and I just didn't know any better... :lol:
Mine never had that hose.But on carbs that have a hose like that,It is a vent/over flow hose & must remain unrestricted & open or the bike will not rev with bogging.Not sure if that is what yours is,but is what it sounds like.It been almost 3 years since I had my G.Z but I would have remembered a long hose like that.
:cool: :)

[alantf]

[attachment=0:1o6yml86]b17.JPG[/attachment:1o6yml86]

Has your bike got one of these? On my European GZ, this is a crank case ventilator, and that accounts for the extra hose, although it goes to the petcock, not the carb, with an extra tee piece.

[Nate4s]

Has your bike got one of these? On my European GZ, this is a crank case ventilator, and that accounts for the extra hose, although it goes to the petcock, not the carb, with an extra tee piece.

Nope! Although I kind of wish I had one of those...I'll take a photo at some point, just for fun.

[Nate4s]

FIXED!!! I installed the new air mixture screw (pilot jet screw) and a piece of fuel line to that previously clogged other line....and now it starts, idles, and drives like a normal GZ! Thanks for the help everyone!

I do have one more issue. My speedometer had a cracked housing (the white plastic part under the chrome), was missing the glass, and the cable had sheered off inside of the speedo-cable housing. I actually pulled the entire speedo apart (which is actually extremely difficult - I had to bend the metal from the front of the housing to get to the internals) to put a new piece of "glass" (actually plastic) in it, and glued the cracked housing back together. I got a new speedo cable and lubed the mechanism on the front wheel, but it's reading what appears to be 10mph off - not a percentage, just a linear 10 mph. Any thoughts on what could be causing this huge discrepancy? It say's I'm going 17 mph in my driveway...which I've never achieved on my other GZ or SV650. Thanks again!

[jonathan180iq]

I have an old stationary bike that has the same speedo problem. With fixed gear, mechanical speedometers, once that happens, unless you want to take the whole thing apart and find the spring that has been stretched out of shape or the gear that has jumped it's cog, you just need to replace it.

However, honestly, just do the math in the head and live with it. I mean, it's a $400 bike that now runs like a champ. You can tell everyone you've hit 90MPH on the GZ with no problem and you technically wouldn't be lying. :)

I'm glad you got this sorted out, man. There is nothing better than knowing that the reason the bike is working at all is because of your handy-work. It's what makes a $400 bike priceless.

[Nate4s]

However, honestly, just do the math in the head and live with it. I mean, it's a $400 bike that now runs like a champ. You can tell everyone you've hit 90MPH on the GZ with no problem and you technically wouldn't be lying. :)

I'm glad you got this sorted out, man. There is nothing better than knowing that the reason the bike is working at all is because of your handy-work. It's what makes a $400 bike priceless.

I suppose I don't have any real issue with it. You're correct about it being a successful $400 purchase! I'll make my GF drive around with me and get some actual comparison numbers for the most common speeds in town. The only reason I wanted it to be within "normal" GZ spec was because my girlfriend likes to make any excuse possible to not want to drive it. Oddly enough, she's the one who wanted me to buy it for her and claims to REALLY want to learn how to drive it. O_o

[jonathan180iq]

Women.....

I would say something derogatory or slanderous, but let's face it... We need 'em and love 'em anyway. ;)

[DAN]

Once I had an oddball problem with the engine reving and dying, would not idle, acted strangely. It turned out that I had left the fuel selector in "PRI" and the carb overflowed into the air box (reved on the fumes then died) and excess fuel filled the crankcase oil. An oil change and airbox flush cured the problem. Moral of the story; don't leave the fuel selector in "PRI". --Dan--

[Water Warrior 2]

A cheap easy way to know your correct speed is to use a bicycle speedo. They are more accurate than the OEM unit and you can mount it where you like.