FZRSupport: the FZROnline Archive

Last week I drove my 600 to school and parked it where I always do, the bike started great and ran fine on the way to school. After class and work I went outside to head home. The bike started right up as it normally does, I didn’t give it any gas so it cut off. Started it again with a little choke so she would stay running and this is when I seemed to run into some problems. When the bike started up it sounded more like a two stroke than the normal FZR I am use too. I killed the choke and used the throttle to keep the bike running, still the same thing. Because I noticed something unusual I revved it up to see what would happen. It sounded like it was running very rich because there was heavy hesitation and it had small back fires. Additionally there was a strong smell of gas that I normally do not get. I needed to get home so I got on my way, anytime I would give it gas the bike would again have large amounts of hesitation and would feel very underpowered. I got home and let the bike sit overnight. I took the bike out the following day to try to work out what was wrong. The same stuff was happening as before (hesitation, underpowered, strong smell of gas, back fire) until about 30min into my ride, the bike went completely back to normal, it almost felt like It was running stronger than it was before. She ran smooth with no hesitation and all the power she has ever had. I was very happy that my bike fixed itself but was concerned because I didn’t know what caused it. Well that was last week. Last night I wanted to ride over to a friend’s house, the bike started up just fine, I rolled out of the garage and clutched it as I rolled down my driveway, got to the bottom and the bike died. I went to start it again and nothing. Pulled full choke and she started up for about three seconds (revved up to maybe 1500rpm) then died again. I did this about five times until I gave up because I want to figure out what is going on before I break something.

Are these two problems related?

Could there be something wrong with my choke?

Could this be something electrical i.e. alternator?

Sorry for the book, all help is welcome,

-Thanks, Andrew

Change your spark plugs-sounds as if they fouled. When it went 'back to normal' the fouled plugs probably cleared off allowing it to run right. It could possibly be a bad connection to one of the coils-or one of the coils failing), and removing the old plugs will help you to figure that out (#1 and #4 OR #2 and #3 will show as dirty/fouled if coil function is impeded).


The gas smell is likely just unburnt fuel-doesn't necessarily indicate carb/choke issues.

And, check your charging voltage/condition of battery.

I'm thinking if it's anything you mentioned its a coil, I changed the spark plugs less than 1000miles ago so i'm hoping they are still good. Additionally its a night and day difference, if the plugs were getting fouled I don't think it would be that dramatic or that quick of a change would it? Although a bad connection with a coil sounds that could definitely be the problem, that would explain the hesitation, unburned fuel and underpower right?

AR91RX wrote:I'm thinking if it's anything you mentioned its a coil, I changed the spark plugs less than 1000miles ago so i'm hoping they are still good. Additionally its a night and day difference, if the plugs were getting fouled I don't think it would be that dramatic or that quick of a change would it? Although a bad connection with a coil sounds that could definitely be the problem, that would explain the hesitation, unburned fuel and underpower right?

All correct except that you mentioned in the original post that this started right after you choked an engine that didn't need it. Not "hit a bump", or "had been working near the coil connections....."

Age/mileage on a set of plugs is meaningless. They can foul in seconds. And, yeah, pure fuel fouled plugs will clean off enough to function NOW-but still be prone to resuming fouled behavior once they cool down some. You gotta remember that the coils fire 'waste spark' and are paired. If ONE plug is fouled, TWO cylinders misfire.

Get Autolite 4303s. They are cheap, and good. Throw 'em in and watch the problem disappear...until you over choke it again.

I will do that today for sure. Because I am a noob when I comes to bikes, what exactly did I do/what physically happened causing the plugs to foul when I over choked the bike? Sounds like that is exactly what I did.

-Thanks, Andrew

The 'chokes' (a carried-over misnomer; these bikes actually use enrichener jets) add fuel for starting a cold engine. If the engine ain't cold (and I mean over-night cold-soaked; sitting for a warm summer's afternoon doesn't count), you're adding too much fuel, and you'll foul the plugs.

AR91RX wrote:I will do that today for sure. Because I am a noob when I comes to bikes, what exactly did I do/what physically happened causing the plugs to foul when I over choked the bike? Sounds like that is exactly what I did.

Since it started prior to that, and then stalled...it shouldn't have needed choke-didn't need it stone cold, shouldn't need it after heat has been put into the combustion chambers.

The 'choke' is actually an 'enrichener'-it ADDS FUEL, not 'restricts air'. The fuel the enrichment adds is fairly big droplets (barely atomized) and is therefore quite 'wet'. That wetness short circuits the plug's gap..the electricity doesn't HAVE TO jump the gap....it flows right to ground....THAT is a fouled plug. When the plug tip is warm(but not HOT) that liquid fuel bakes onto the porcelain as basically a lacquer..and at that point it is a toss up as to what has more resistance-the plug gap..or the carbon lacquer. So, when the plug gets hot enough, that gap will be jumped and it will run clean....as soon as the plug temp falls..the fouled plug behavior starts back up.

I've got a pretty good feel for engines, and my FZR-when the temp is decently warm, but it hasn't been started-I will usually start with no choke-if it starts and runs but doesn't want to idle, I will blip the throttle and add about 1/10th choke just to raise the idle. At that point I can walk away from it..grab my jacket and helmet etc.

When an engine starts, idles poor and stalls..it almost always stalls because the mix is too rich and is burning poorly for the cold combustion chamber and spark plug to fire well. ADDING fuel at that point makes the problem worse.

When it is cold cold out...and my engine hasn't started in a while, I throw full choke and don't touch the gas. Then I wait for the idle to climb and decrease the choke. It only takes a minute or two before I can have the choke just barely 'on'.

Summary?:

Use choke only when necessary, and only as much as needed.

And, a spark plug that has been fouled once is more prone to fouling again.

Hey, thank you very much for all the help. This is definitely a noob problem that I had but luckily an easy fix. Now that I know what caused the problem I will make sure to pay more attention when using the “enricher”.

-Thanks again, Andrew

Well I guess I spoke to soon. Changed out the spark plugs last night, as I was doing so I noticed that the old plugs were not fouled at all. Put the new ones in anyway and the bike will still not start. When I first pushed the start it sounded liek it wanted to fire up then nothing, just the motor turning over. Any ideas?

-Thanks, Andrew

could be your valves have tuliped and no one has done them in a while -usually extra starting time will help though

how many miles on the bike?

also, your fuel pump may not be working correctly, they can tend to die on this model bike, do you hear a click sound coming when you turn on the bike?