First bike... always smells like gas?

Greetings everyone. I just bought my first motorcycle, an '82 seca 650. It's been a blast riding it around for about a week now, but have noticed something which I wasn't sure about. Apologies if this is a noobish question, I'm new to motorcycles.

When I ride, it always smells like gas. It's like I'm always at a gas station. The bike only had 5600 miles on it when I bought it (and apparently sat around in a shed for a long time). I have since filled it up, but it smells just as bad as before. When I'm at a stoplight, I have to keep the engine revved slightly or it'll die. Any ideas what could be causing this? Is this normal? Should I check something?

Thanks for helping a motorcycle noob!

 

Could be many things but I would start at the carbs. Are they clean and the fuel line is it in good shape no cracks or anything?

 

Welcome to XJBikes from the Boston Mountains of NWA

Danger Will Robinson!!!

You should not be smelling gas. When these bikes are properly maintained the only thing you should smell is the lovely odor of 99.9% burnt hydrocarbon. I highly advise you to park your bike and begin a maintenance odyssey on it. You are flirting with disaster for your bike and yourself!! Trust me on this-I don't want to sound like Debbie Downer but it's true.

How old is your bike? 29 years right. Consider that when leaving the factory in 1982 your bike was expected to have regular maintenance performed on ALL of it's critical parts. Now some of that has been done, but I'm betting a bag of money that some/most hasn't been done. And you can't know what is needed unless you either do it all yourself or make sure it isn't needed yourself.

Much like flying at 10,000 feet-when you're riding on two wheels at 65mph and surrounded by 4000lb lead sleds you can't afford a catastrophic failure of any kind. Brakes, tires, motor, etc. will all need attention. And in your case you might watch your bike melt into the pavement if you keep riding. Much advice will follow and no-one is telling you wrong, follow the advice.

Start checking at the top of your tank-Is your cap sealing? Then move down to your petcock (where the fuel comes out) is it leaking? Pull off your side panel and look in your air box, fuel in there? Open your oil filler cap and put your nose right on the opening smell fuel?

 

Debbie is right. Someone will scream check your rear brake and you should.

 

Hehe....Debbie is right. That's funny!

theadbrewer is right too. Do a search on here for Delamination and scare yourself, and he's right about your carbs too. Look them over carefully for fuel leaking from the mated surfaces or the bottom where there are drain ports.

 

Okay, thanks for all the info. I will park my bike until I have a chance to check that stuff out. The guy I bought it from never actually rode it, but did clean the carbs to get it ready to sell.

I'll post what I find here. Thanks for the help.

 

It's a "mobile molotov"!

 

WATCH OUT FOR THAT OLD GUY WITH THE OXYGEN TANK WHO WANT'S A LIGHT FOR HIS SEEGAR!!!!

 

When I first got my Maxim, I noticed the smell of gas as well. It took a bit of checking but when the big was running I finally noticed a spritz of gas coming out the back of the petc0ck. A rebuild fixed that problem. Hopefully this helps or of anything gives you another place to look.

 

yep start with petcock, an easy check is to pull the fuel line from the petcock and see if gas flows (make sure it is not on prime) - it should not. If it does you could be overfilling your bowls and/or leaking gas into the crankcase. also as MM suggest check the Airbox for the gas smell as well. could be float settings too.

 

FINALLY. Here you go:

You most likely have a stuck float, but as maybe4 pointed out, it could also be float level adjustment, depending on how knowledgeable the "carb cleaning" practitioner was.

If it only does it when the bike is running, then your petcock may be ok. The biggest concern is gas filling up the crankcase, diluting your oil, and damaging the engine.

Immediately open your oil filler plug, stick your nose in the hole and sniff. It should smell only of toasty oil; if it smells strongly of gasoline STOP RUNNING THE MOTOR until it's dealt with.

This is especially a concern if you have a (vacuum operated) petcock issue ALSO, so that the stuck float(s) have a constant supply of fuel to pour into the motor.

It could also be that the fuel supply tube o-rings have dried out and it's just peeing gas wherever it can. My 650 Seca came with that issue.

 

Okay, I have an update. Sorry for the delay.

You all scared me about brake delamination and the whole mobile molotov thing, so I decided to have a pro take a look at it. I'm all for DIY, but not when an amateur mistake could lead to Very Bad Things.

I had the bike shop do a full safety check, and also inspect the gas smell issue. What the guy said is that the carbs "need to be rebuilt," (for $400 plus change) because they're flooding and drenching the plugs. He didn't seem to think it was urgent per se.

So I drove it home, then to work the next day. It ran fine to and from work (about 30 miles round trip). The day after, I drove to work, but on the way home about 5 miles in, it lost all power. I was starting from a stop light, and all of a sudden my rpms just dropped as I revving the engine. I turned the engine off, and was able to start it up just fine. With the clutch in, I could rev to 3000+ rpms, but the minute I dropped into gear and tried driving, it would lug, drop to 500 rpms, then normalize again once I pulled the clutch. I couldn't drive in gear without the engine dying.

During the time it broke down and now, I tried running the engine for brief periods. The usual pattern is it would start up just fine (as long as it had been sitting for several hours), and make it about 2 miles before having the loss of power issue.

I had a friend help me get it home, and checked the airbox for fuel smell (nothing). I also pulled the plugs out, which were coated black with soot (not sure if that's normal or not--I cleaned them off with a dry toothbrush).

On the recommendation of a friend, I also put a thing of carb cleaner in the tank and started running the engine. It took a while to get started, but once I did, I took it out and noticed the usual pattern (it'd get about a mile or two before losing power). But this time, I popped it into neutral and let it run for a minute. The engine was running choppy, but all of a sudden it started revving on its own from about 1000 to 3000 rpms, then stabilize smoothly back to 2000. At that point, I was able to ride for another couple miles before the power loss. I would shut off the engine for a bit, then start it up and let it idle in neutral for a bit, where it would rev on its own, then run smooth for another couple miles. I did this a few times and overall it seems to be running better.

Does it sound like there's crap in the tank that the carb cleaner is demolishing? Someone I talked to also recommended an inline fuel filter for that case. Thoughts? Thanks for all the help diagnosing this problem!

 

Your carbs need to be CLEANED, spotless. And you can do it for a hell of a lot less than $400 by doing it yourself.

Check/adjust valve clearances
Clean carbs
set fuel levels
sync carbs
install an inline filter
change oil and filter
new plugs
running sync

All of these things need to be done in order. Don't skip a step or you will be right back to square one.

Take it from someone who had never taken a carb apart before, if you read everything, take your time, and do everything we suggest, you will have the bike running better than new.

 

Did this "full safety check" involve REMOVING the rear wheel to LOOK at the brake shoes? Because if it didn't, it wasn't a "full check" at all.

Flooding carbs ARE an "urgent issue" you could damage the motor if the oil is being diluted with gasoline.

Your symptoms are those of a bike in dire need of carb service/valve adjustment/carb adjustment.

You're not going to "fix" it running carb cleaner through it; what you may do is hurt the motor in the process.

 

In reference to what the "mechanic" said:

Na, gas flooding in from your carbs, drenching your plugs and screwing up the main source of lubrication/cooling the bike has-truly it's not urgent. WHAT!

Does anyone need anymore evidence that there are some crappy bike mechanics out there.

zhalbert, we weren't trying to scare you, or at least not into taking your bike to the money munchers who often just don't know what they are doing. We were trying to motivate you to take your safety seriously and your bike under your care. Which you can do-really you can handle it. You just need to go step by step and ask questions as you need to. You will not be thought less of or criticized for trying and asking.

The list tskaz gave you is correct and in order, I would do the oil change now. Honestly you can do it all yourself, learn a lot about motors and bikes, have fun doing it (although you will likely want to curse occasionally); and even having to buy tools and parts you will spend less than you would at a shop-which often ends up doing it wrong anyway.

Your sooty plugs are from too much fuel (incomplete combustion) and the engine's behavior indicates carb problems such as air/fuel mixture is wrong, fuel level is wrong (in your float bowls), and your carbs need to be synched. Yes you need an in-line filter, but you should not ride until the list tskaz gave you has been completed.

At this point make sure no more fuel can flow to and past your carbs (remove tank or make sure petcock doesn't flow while set to "on"-which is normal operation), change your oil/filter with motorcycle oil to start-then search on here (and get manual) for how to complete the list. You can do it.

 

The FIRST thing you should do is buy yourself a Workshop Manual.
The BEST one is Yamaha's Factory Manual, ... specific to your bike.
Then, ... Haynes; and all the rest.

The Factory Book also has the Owner Manual.

If you suspect the Petc0ck or and the Carb Floats are leaking; install a Fuel Shut-Off Valve right after the Petc0ck.

Briggs & Stratton Gas Shut-off Valve.
10-Bucks
"Paint" some of the Red Plastic Valve and the Hose Clamps with Black Fingernail Polish and the Valve virtually disappears in the shadow of the tank.

Shuts OFF the flow of Gas.
No flooding.
No fouling.
No smell.
No needing to change the Oil and Filter.

<< == Briggs Valve = =>> << == Installed & Painted = = >>

 

It did involve removing the tire--I requested it specifically.

Thanks so much for the advice, I will remove and clean the carbs when I have a chance. My main challenge is finding a place to dismantle my bike, as my studio apartment is in a complex which prohibits working on vehicles.

I'll keep you all posted.

 

You'll need to develop some sort of an ONGOING maintenance situation; getting this one issue fixed is not the only thing you're going to need to do. Bikes these old do require a certain amount of regular maintenance, most of which is not practical to pay to have done. You don't adjust the valves once, you do it every 5000 miles. You don't service the carbs once, they need to be cleaned, verified and adjusted every 5000 miles as well. Oil and filter changed every 2500 miles.

You need to beg, borrow, barter or rent a corner of a garage somewhere.

 

Back in the Mid-80's, when I was living in an apartment outside Boston; I traded "Handyman Duty" for half a two-car garage.
A widowed lady, living in a big place, traded me garage space for doing some handyman work and taking care of removing the snow after a winter storm,

She paid me for parts and labor to get a 10-Horse Sno-Blower repaired and running. I charged her neighbors 15-bucks a driveway all winter long.

I was like a "Driving Miss Daisey" situation.
Her son staked me cash for gas and expenses just to have somebody looking-after his mother.

 

Greetings all.

Sorry for the delay--was away over the holidays and am just now getting back into it.

So, step #1 - check valve clearances. I've run into probably a dumb problem. I got to the point where I removed the cylinder head cover, but the shop manual says to check the valve clearance with the cam lobe 180 from the cam follower (Question 1 - how do I rotate the crankshaft?). I got ahold of a set of feeler gauges, but I don't see where I'm supposed to be checking--is it in between the cam and the shim? The manual has a set of mystifying illustrations that didn't help much.

I've checked out some youtube videos, but they're on different motorcycles and I can't translate it to my bike (650 seca). Is there a good guide somewhere with slightly more in depth instructions on checking valve clearances?

Thanks.

 

Since you asked so nicely


bigfitz52's valve adjustment write up with pics

 

Thank you!!! Just what I was looking for. (I guess my forum search skills suck worse than I thought they did.....)

 

I've got a question about checking the clearances with the feeler gauges, something I couldn't figure out from bigfitz's post. When I have the cam lobes turned 90 degrees from their respective shim, even the smallest feeler gauge doesn't go very far between the two. Should I be able to pass it all the way through, or am I doing something wrong?

Second, when getting the ignition cover off, the gasket broke on one side. It's still intact though. Is it essential I replace that? (seems like I should, I'm just asking in case its not).

 

should go all the way with a slight drag
really you should but some gasket in a tube will work if it's all there with no gaps

 

The lobes should be sticking STRAIGHT UP in relation to their respective shim's surface. If that's how you have them positioned and you cannot get the smallest feeler gauge through, then you have a seriously tight valve; they can become "dead" tight. Are they all like that?

That gasket isn't super critical; it's to keep crud out, not seal anything in (like most gaskets.) It would be a good idea to replace it at some point but it's not an area of great concern. Put a small dab of gasket sealer at the point it broke, or just refit it carefully as is.

 

Fitz - yes, all the valves are like that. I'll do my best to describe what I did--I basically turned the crank CCW until the big end of the cam lobe was perpendicular to the shim (if the shim was level, it would look like an egg standing straight up, big end down). I tried getting the .010 feeler gauge between the lobe and the shim, even bent the gauge so it was flat against the shim, and I can't get int in more than an eighth of an inch. All of the valves are like that too.

In other news, getting frustrated with the valves, I decided to start into the carbs. I finally got them off (took a couple hours... had to push the hoses into the airbox to get the bank out). I'm just starting to do a thorough clean, following the church of clean guide. Will probably be right back here with some more questions soon.

Thanks a lot for the help, guys. I'd be up shit creek without it

 

You definitely don't want to run that mill until you get the shims swapped if they are that tight.

 

Okay - I have an update.

For posterity, here's a really dumb mistake I made. I decided to check the valve clearances with my set of feeler gauges, write down the clearances, and only THEN check the manual to see if they're within spec. What I realized after much frustration was that my set of feeler gauges (someone just gave me a spare set that was laying around) are much too big to check the valves. The smallest gauge is almost twice as big as the maximum clearance for my bike, so I need to get a new set. Embarrassing, but hopefully that'll help some newbie in the future. New set is on its way.

So I took the carbs off and cleaned them. Aside from some minor hiccups, everything looks good. Everything was really clean, and is even cleaner now. I know I was supposed to wait to install the fuel line filter, but I decided to do it now while I had my carbs off since I'm worried there is junk in the tank. I also drained the tank as best as I could (the reserve still has a bit of gas sloshing around), and was surprised how clean the gas looked. I put some fresh stuff in anyways.

Next I put it all back together and tried to get it running. It took forever to get started, but I finally did. It ran fine for a few minutes, then lugged and died (the same problem I originally had). Someone recommended I try starting with the fuel cap open, so I did (with the petcock on prime). Magic! It started right up and had no lugging sound at all. I could rev the engine just fine, and ran it at idle for about 10 minutes. I even rode around the parking lot in 1st gear while it ran like a champ.

Some combination of prime + cap open, and the bike runs great. If I switch back to fuel on or close the cap, it lugs and dies after a couple minutes. Because I wasn't very scientific about it, it could be one or both of those variables. It was getting dark though so I had to leave it there for today.

A note about the gas tank: the guy I bought it from said when he got ahold of the bike, the tank was completely rusted so he put a "new" one on (it has lots of surface rust on the outside--inside looks clean as far as I can tell). I think he said it was also from the same model, but I could be misremembering. It's a Yamaha tank anyways. He said he deliberately broke the lock on the cap so that it could be opened with a flat metal piece, since he always loses the gas cap key. It kinda looked like he mangled the key hole with a flathead.

Anyways, when I was draining the tank, I noticed that if I shook it up, there was a hiss coming from the cap. I opened it and noticed a lot of crap around the opening. I ended up taking the whole locking assembly apart and cleaning it really well. I'm not sure if there was supposed to be some kind of paper gasket that just disintegrated, or if there was 3 decades of mud, but I got LOTS of gunk out of the cap. I put it back together, shook the tank, and still noticed a hiss though it was much smaller than before. Granted I didn't do an A+ cleaning job, but it was at least a B+. The rubber part that does the bulk of the sealing has tiny cracks all over it, but it's still pretty pliable.

Think it's an issue with the vent or the petcock?

 

If your cap was that full of junk then it's likely in your petcock too. It has a prefilter and overall it only likes gasoline, it takes very little non gas matter to funk up the works of the PC.

Do you have a clear fuel line? If not go to the local auto parts store and grab one of those. You will be able to see your fuel going to your carbs and know if you have flow, it only takes a tiny bit to idle but when you throttle up it will draw more from the float bowls and if your taking it out faster than it's going in you will go lean and it will die.

You shouldn't need your cap open at all to flow fuel, or want it open either (non fuel stuff entering the picture again). The tank doesn't seal up that tight under new conditions, but considering your PO story who knows what's going on with that tank-I wonder if he just 'borrowed' it and that's why the lock is busted.

Get the rebuild kit and give your petcock new life, and rebuild your cap's rubber parts while you have the tank emptied. You will want to be sure the tank is CLEAN or your flow will get junked up again.

 

Thanks for the advice. I did as you suggested and picked up a PC rebuild kit. I took it apart and cleaned it extremely thoroughly and replaced old parts. When I put it back together though, I'm still having issues getting it to continue running.

When I switch to prime, it runs great. When I switch to fuel though, it lags and dies in a minute or so. I've switched it back to prime just before it died too, and it comes right back to life.

I don't know fully how the vacuum system works, but when I was rebuilding the PC, I noticed the vacuum port had "something" in it. I could suck on it with good airflow, but if I blew into it, something would stop the airflow. I couldn't get the brass nipple off to peer inside, but I ran carb cleaner through it from both ends and a sewing needle, and it seemed as clean as I could get it without taking it apart further. Could this be related to my symptoms at all?

 

make sure you have everything oriented correctly...if you do'nt, the petcock lever is basically upside don and things won't work right. Double check that and let us know...........

dave f

 

I believe it is. I took copious notes / sketches when I was rebuilding it, and double checked fitz's guide. The passage on the vacuum port is pointing down and to the rear, as it should be. The lever works the same as it did before--I can't think of what else to check?

 

Unfortunately, YES.

That "something" in the vacuum port is the "anti-backup" valve; it's nothing more than a simple bakelite disc but it's VERY IMPORTANT. It's covered in my article; go back and read it carefully. See picture #7 and its caption.

If you managed to kill it in some manner (so that you can both blow and suck through it) then the petcock will not work properly. It is supposed to make it so you can only suck on it, not blow through it.

If it now flows air freely in both directions, it's why the petcock isn't working properly. Ya done murdered it. Sorry.

 

I'm not reading that to mean he killed it. Sounds like it's still working right as he DIDN"T take apart. I don't read that to mean that he stuck the needle all the way through, either, but that's my interpretation.

I'm wondering two things right now:

1. the pulse line - do know for sure that:
the vacuum line is clean and clear
that the nipple on the intake boot is clean and clear do you know for sure that the line isn't crimped somewhere
that the line is actually connected from the petcock to the intake boot

2. the petcock itself - are you doubly sure that:
the tower isn't on backward
that the diaphragm is not ruptured

Check those and let us know......

DaveF

 

If the little bakelite disc was damaged by the knitting needle so that it now allows airflow in both directions, the pulse from the intake manifold will "bang" the diaphragm back and forth, rather than holding the valve open as intended (and as necessary for proper operation.)

The petcock will not operate correctly if it's allowing airflow through the vacuum port in both directions.

So I guess the first question would be: "does the vacuum port now allow airflow in both directions?"

If the answer is "yes" then my above comments apply.

 

Yup, we're both saying the same thing from different angles of attack.
Davef

 

Aw, crap :/

For the record, after my over zealous cleaning job, there was no change in the way the fuel flowed, so it seems like the underlying problem may still be there.

So what's my solution, do I need an entirely new PC, or is it possible to fix this?

 

can you take the petcock apart (once again) and this time lay all the parts out for us to see what you have , or take closeup pics of each step? If we can get our eyes on it, we might see something........

Dave F

 

DOES the vacuum port allow airflow in both directions? That may be your issue.

 

I'll be happy to do that, thanks for taking a look. Leaving for a short vacation tomorrow morning so I won't have a chance to take my petcock apart again before I leave.

However, one question; I want to make sure I'm reading you correctly. I read your guide again, and I don't think I've run afoul of anything there.
1. "...and make sure it's free in there. You can hear it rattle about" -- I can.
2. "...and test by blowing in the port." While I CAN blow in the port, I can't do it continuously. I blow in for a couple seconds before I feel the disc cutting off the airflow. When I reverse the direction, it allows continuous airflow.

Does that answer your question?

 

Yep. And it tells us that it's at least part of the problem. If it doesn't stop airflow immediately, it's not working correctly. The "pulse" from the manifold is quite rapid, so the little check valve has to be able to work quickly to prevent the airflow from going both directions.

Use a 6-point socket and unscrew the vacuum nipple from the diaphragm plate, and inspect the little bakelite disc. If it's clean and intact, then it's fine and you'll need to clean and possibly polish the chamber that it sits in.

 

I attached a few photos of my petcock with the vacuum port taken apart. The little disc looks completely fine to my eye... there is an indentation where the nipple touches it, but it looks clean and whole otherwise. I tried attaching a few photos, not sure if they turned out very well.

So after cleaning the disc with carb cleaner and a cuetip, I also sprayed carb cleaner into the body of the vacuum port and swirled a cuetip in where the disc sits until it came out clean. Then I put just those 3 parts back together (the vacuum port, the nipple and the disc), and tried blowing on the nipple. The airflow is significantly less restricted now, so I'm going to give it another shot.

 

Good news! I think the petcock flow issue is now fixed. The extreme clean on the vacuum port seemed to do the trick. It runs fine on 'fuel' now, so I was finally able to take it to a shop just down the street to get the sheared drain plug out and change the oil (which smelled like gas). Once that's done, I'm pretty confident it'll run smoothly enough to do fuel levels, sync, etc.

Thanks for the all the help, I'll be sure to post an update soon.

 

So the petcock will hopefully stop letting fuel through when it's not running. Awesome. I hope you got fixed good this time

Next thing to address is the sticky float/needle or more than just one, that is allowing the gas to run through the carbs into the cylinders. If the needles were sealing completely, gas wouldn't get through even if the bike was left on PRI.

Dave F

 

Well the question is--maybe I already fixed the float needle issue..? As a way of trying to solve the original problem I already cleaned the carbs. After putting them back on the bike, I couldn't get it running for longer than a minute or two due to the petcock problem. Now that the petcock's fixed and I got a new oil / filter change, I will really be able to test my carb cleaning job.

What's the best way to do this? I was going to ride for an hour, then smell for gas in the oil again. Do I need to go for a longer period of time? Shorter?

 

You need to wet-set your float levels; in the process of doing this you will discover any fuel shutoff issues, as that's what's being adjusted.

As for testing the petcock, leave it in the ON position and disconnect the fuel line. Except for the initial dribble, it should stay drip-free.

When you do the float levels, you will have verified their function and the petcock can be tested as above. Then just ride the bike, and keep an eye on the oil level. A sudden rise indicates a problem.