Bike started, ran for a bit, now doesn't want to start

[badeaslava]

Hello everyone,

I have a 81 GS650E. I've cleaned out my carbs recently, i dipped them in pinesol for a day or so, they weren't too dirty to begin with. I got new O-rings and replaced all the original ones. I also blew through the small passages with my carb cleaner can to ensure they are clean and functionable. Ensured that the float normal position is within spec. After installing the carbs on the bike, i sprayed some starting fluid in the carbs to get it going and started it up. The bike ran for a good 2 or so min, i even connected the air intake manifold and got idling rpms to be around 800 (btw what is the normal idle speed?) I turned it off and restarted just to check and it started right back up no prob. Then it died and I can't get it started anymore. I sprayed more starting fluid in the carbs, the gas line from the petcock is full with fluid, so I'm guessing it has gas, but i have no definite way to check whether there's gas in the bowls.

I don't know the history of the bike, since this is the first time i got it started after i bought it over a year ago. The gas is the original one, maybe i should add some Sta-bil just to make sure it's still flammable, but the bike ran for a couple of minutes just fine so I don't think it's the gas.

i also took of the sparkplugs to find that they are badly oiled, and these are new I installed them myself. So my guess is that the cylinder rings are leaking oil, i suppose that's a project for the winter time - rebuild the pistons. I wiped them off with a rag and put reinstalled them with the hope that maybe the spark wasn't getting through, but i still couldn't get the bike to start. Any ideas what else it could be and any troubleshooting. What could have changed while the bike was running to cause it to not start again? My next step was to test compression to see whether the rings do indeed need replacing. is there any way to test whether the carbs have been sufficiently cleaned, but then again it ran fine for a bit.

Sorry about the long post, i just thought to give you as much info as possible. Thank you for any help and/or advice!

 

[chuck hahn]

How much gas is in it? Fuel below around 3/4 of a gallon will not feed the carbs fuel. Try using the nPRIme setting and let it set for about a minute, choke and start while on PRIme. if it starts then switch down to the ON spot.

If it still wont hit, be sure to put it back to ON. These petcocks can leak
fuel into the crankcase if left on PRI and let setting for a while.

 

[chuck hahn]

Old gas into freshly cleaned carbs!!! GOOD GOD!! Rinse the tank out WELL with some fresh gas..just dump some in and close the lid and shake the heck out of it and dump it into a bucket...Now youll see what just got sucked into your fresh carb rebuild.

Rinse it a few times too!! sad to say this, but you may be in for another carb job to get the jets clean again.

Look for a poster named Nessism and click on the link at the bottom of his signature page and follow his tutorial to the letter.

 

[badeaslava]

Thanks Chuck, the more i think about it the more i realize you're right. It def wasn't a good decision to use old gas, but i suppose I'm getting really good at rebuilding the carbs now ) i'll do it again and get new gas. Any ideas how to clean the tank properly, maybe some sort of cleaning solution? i don't have rust in it, just sludge from at least what i can see in the refuel hole.

As for the oily spark-plugs, do you think a compression test and a rebuild is in order?

Thanks

 

[Steve]

I've cleaned out my carbs recently, i dipped them in pinesol for a day or so, they weren't too dirty to begin with.

That may have gotten the dirt off the outside and left a nice clean smell, but personally, I don't think that Pine-Sol is the proper cleaner for the carbs.
And, ... dirt on the outside of the carbs does not matter. What matters is the crud inside the carb, that you can not see.

I got new O-rings and replaced all the original ones.

Did you get the kit from cycleorings.com? If so, good. If not, you likely did not get all the o-rings that you need.

I also blew through the small passages with my carb cleaner can to ensure they are clean and functionable.

Seeing spray come through a hole only tells you that it's not plugged. It does not assure you that it is CLEAN and operating properly.

Ensured that the float normal position is within spec.

22.4mm? Measured from the STEP on the float, not the top?

After installing the carbs on the bike, i sprayed some starting fluid in the carbs to get it going and started it up.

One of the WORST things you can do to your bike. Please ditch the starting fluid.

... i even connected the air intake manifold and got idling rpms to be around 800 (btw what is the normal idle speed?)

The "air manifold" should be installed. The bike will start and idle without it, but will not do much more than that.

Normal idle speed is 1100 +/-100 RPM.

I sprayed more starting fluid in the carbs, ...

There you go with that bad idea again. Please stop it.

..., the gas line from the petcock is full with fluid, so I'm guessing it has gas, but i have no definite way to check whether there's gas in the bowls.

You can loosen a drain plug from the bottom of the bowl, but that will only tell you that there is gas in the bowls, too. What you REALLY would like to know is whether gas is getting from the bowls, up, through the jets, into the engine. Until you CLEAN the carbs (with the proper stuff), that won't happen.

I don't know the history of the bike, since this is the first time i got it started after i bought it over a year ago. The gas is the original one, maybe i should add some Sta-bil just to make sure it's still flammable, but the bike ran for a couple of minutes just fine so I don't think it's the gas.

Sta-Bil does not make stale gas any more combustible.

Since you don't know the history, it's best to start with a clean slate and do ALL the required maintenance, even if the previous owner assured you that it was done. We all know that (almost all) previous owners are pathological liars and will tell you anything to sell the bike.

i also took of the sparkplugs to find that they are badly oiled, and these are new I installed them myself. So my guess is that the cylinder rings are leaking oil, i suppose that's a project for the winter time - rebuild the pistons.

If you installed them new, ran the bike for two minutes and they are oiled up like that, how long did it take for the smoke screen to thin out? Did anyone call the fire department, thinking your place was on fire?

I wiped them off with a rag and put reinstalled them with the hope that maybe the spark wasn't getting through, but i still couldn't get the bike to start.

This leads me to ask "just where is the oil?" If it's on the ceramic insulator around the center electrode, there is no way you are going to "wipe it off with a rag".

What could have changed while the bike was running to cause it to not start again?

There are a LOT of things that need to be checked before starting a bike that you don't know anything about, and you have basically not checked any of them, so we are all guessing here.

My next step was to test compression to see whether the rings do indeed need replacing.

Not a bad step, but be aware that compression figures will be a bit lower on a cold engine that has not been run for a year (or more).
It might give you an idea of general condition, but I would not base a "rebuild or not" decision on a cold compression check.

is there any way to test whether the carbs have been sufficiently cleaned, but then again it ran fine for a bit.

The best way to ensure the carbs are cleaned is to clean them properly with the proper chemicals. Look on BassCliff's site for the CV Carb Cleaning Guide by Nessism, or you can look for any of Nessism's posts and click the link in his signature.

Sorry about the long post, i just thought to give you as much info as possible. Thank you for any help and/or advice!

Not sure why people think these are telegrams with a 25-word limit.

There is actually a 5000-word limit per post, feel free to use whatever is necessary to describe your symptoms and what you have done. Your description so far is wonderful.

And, you should also know that cleaning carbs is just one part of getting the bike running properly. You should also check valve clearances and verify the integrity of the electrical system.

Did you get a MegaWelcome from BassCliff? LOTS of information there.

.

 

[chuck hahn]

If you have new orings and are careful removing them you just reuse them. I dont think a full on tear down will be needed, but i would reflood the passages with carb spray and air and repoke and rinse the pilot jets and the needle jets. Maybe remove the adjustment screws and rinse thru them as well. Goal is to rinse any sf that sludge that could have gotten sucked thru.

As for tank rinsing, On old tanks I just dump some laquer thinner in and let it sit and swish it around every once in a while till the crap is dissolved.

DONT DONT DONT ever pour the thinner out the filler neck unless you lobe bubbled up paint!! Drain it out the petcock hole and be carefull not to splash it around in the process.

 

[badeaslava]

Thank you very much Steve and Chuck for your help. I cleaned the carbs again yesterday, didn't dip them this time but did blow through the jets and passages to make sure they're clean. I did follow Nissim's instructions to clean them the first time so that should be ok. I also cleaned the tank with mineral spirits with some nuts and bolts in it and I'm glad i did, it was indeed rather sludgy, i'm hoping this was the culprit of the problem. I'm going to put some good gas in it today (i was thinking higher octane midgrade, you think that's reasonable?) and try to start it up again.

Regarding the smoke screen, there was indeed one and I was getting worried that the neighbors would complain at one point. It wasn't black like I would expect from burned oil, it was sort-of bluish in color, can't tell for sure though. So my guess is that indeed it's burning oil, which means more work for me...

Incidentally, why is starting fluid so bad? it was suggested to me by multiple motorcycle enthusiasts.

Thanks again!

 

[tom203]

Just use 87 octane. Starting fluid is a bigshock to intake system- about all it can tell you is you have some kind of compression and spark at about right time. OK if you spend winter in far north.

I like Pine-sol but I doubt it's adequate for gummed up carbs - tiny passages in these carbs make it hard for a cleaner to reach. If bike has sat idle for a while, rings might not be free and it could smoke till rings loosen up.

 

[Steve]

Incidentally, why is starting fluid so bad? it was suggested to me by multiple motorcycle enthusiasts.

Actually, when properly used, it's not that bad. The problem is that it is WAY too easy to not use it properly.

I have not used any for so long, I have forgotten what the label says, but I seem to remember something about a "1-second burst of spray". That will work for a much larger engine. Our smaller engines would require much less.

And, ... (most of us) being men, we usually subscribe to the basic drag racers' philosophy: "If some is good, more is better and too much is enough."

However, with the rather EXPLOSIVE qualities of ether (the main ingredient in starting fluid), you can easily blow the engine apart.

.

 

[badeaslava]

Ok, here's an update:

I put in new gas today, and started my bike up again. I had the throttle idle screw too high immediately so it was idling high but i unscrewed it and it seemed to work ok. Now i get this issue: when i run the bike with the choke off when i rev the engine the rpms hang high and then slowly go down if even. When the choke is on the rpms go decrease quickly after i let go of the throttle, in a way that you'd expect it to work properly. So i thought that i was running too lean of a mixture (since choke on richens the mixture) so i unscrewed the fuel pilot screws until 4 turns and it seemed to make it better but still the rpms were hanging. Sometimes with the choke off i was revving it up and the engine was effectively stalling (rpms falling) which to me indicates the inability of the fuel supply to cope with airflow.

Also the fact that choke is on doesn't affect the idling rpms of the engine, correct? Since the idling rpms are controlled by the amount of air and thus the butterfly, which the choke doesn't affect. Please correct me if i'm wrong.

What it could also be is that the airbox is a real PITA to put back and seal properly so I attached it but I'm sure it's not vacuum tight. Maybe the mixture is becoming too lean due to some leaking air between the airbox and carbs? But then again the flow of air should be restricted by the butterfly downstream, so it shouldn't technically affect the mixture.

Any guesses and suggestions to what i could do next will be highly helpful I'll try to seal that airbox tomorrow to the carbs, but it's a huge pain. First thing i'll do on the bike during the rebuild is replace it with pods (and rejet). I also haven't balanced the carbs yet, could that be also part of the issue?

Thanks again to everyone! This is an awesomely helpful community.

 

[chuck hahn]

Did you replace the orings in the intake manifolds? Where were the mixture screws set at when you initially started the bike? You have CV carbs so all you have is the one screw at the back of the carbs on top.Initial setting would be around 2 1/2 out. To richen the circuit you go out and to lean you go in.Its fallin because now at 4 your way over rich and it cant burn the fuel. Go back to the 2 1/2 out and make 1/8 turn adjustments from there. It doesnt take very much screw movement to make a massive change.

 

[badeaslava]

No i did not replace the orings in the intake manifold boots, i took them out and inspected them, they had no tears and were in general relatively soft, so i decided not to change them.

As to the quality of the mixture. I thought that hanging rpms is a sign of a too lean mixture? I did start with the screws turned 2 1/2 out from the bottomed position and this is when it was dropping rpms when twisting the throttle, now that i've unscrewed the pilot screws it seems to be revving up properly but hanging with rpms high after i release it. Also the fact that it seems to run well with choke full on made me think that the mixture was overly lean when running otherwise (choke off).

I suppose next thing is replace those intake boot orings...they sell them at the dealer?

 

[chuck hahn]

Broke the seals on the old orings and now they arent sealing most likely then. Massive air leaks such as this will make it lean way out. Get some either and start the bike and let it idle. Spray it on each manifold and see if the RPMs rise as its getting sucked in thru the gaps.

 

[Steve]

As to the quality of the mixture. I thought that hanging rpms is a sign of a too lean mixture? I did start with the screws turned 2 1/2 out from the bottomed position and this is when it was dropping rpms when twisting the throttle, ...

Yes, a hanging idle is the sign of a lean mixture. Just because you have the screws turned out does not mean that fuel is getting through, though. Since you have not cleaned the carbs, you are assuming that gas is getting through. You really need to stop guessing and tear the carbs down for a full cleaning and refurbishment.

Also the fact that it seems to run well with choke full on made me think that the mixture was overly lean when running otherwise (choke off).

The "choke" opens up a different set of passages for both air and fuel. The rest of the carb can be plugged SOLID and it will run on "choke".

I suppose next thing is replace those intake boot orings...they sell them at the dealer?

Yes, they are available at the dealer, but he will probably have to order them.

Since you should really clean the carbs, too, you will need a full set of o-rings for them, too. You can get all the o-rings you need, along with new stainless bolts to hold the intake boots, from fellow GSR member Robert Barr by visiting his website: Cycleorings.com. Do not bother with "carb rebuild kits", either. The o-ring kit is all you will need, and it costs less than one of the four "rebuild kits" you would need.

.

 

[badeaslava]

So i did clean the carbs - 2 times now: the first time soaking them in Pinesol (arguably not the best decision) then i did replace all the orings (from robert barr), and second time when i sprayed carb cleaner through all the passages after running it on old gas.

I also sprayed some ether around the intake manifolds to see whether there were any leaks due to old orings and i saw no response of rpms to it whatsoever leading me to the conclusion that this is not an issue and the sealing orings to the block need not be replaced. The conclusion from all of that is that indeed the fuel supply is somehow reduced to the airflow.

the other day i looked into how exactly these CV carbs work and it turns out that the fuel supply between 1/8 and 3/4 open throttle is controlled for the most part by the needle jet and jet needle so i think i need to look into making sure all those passages are clean. Also it seems to me (correct me if I'm wrong please) that the level of fuel in the float bowls would also have an effect of how lean the mixture would be (ie the less the fuel level the leaner the mixture). And although i did adjust the floats in the carbs to be ~22.4mm from the housing (without the gasket) mechanically, i'm not too confident about that measurement, because the fuel inlet spring is very finicky and I think it compressed a bit while i was measuring it. Any advice on doing that more properly ???

So my next plan of action is to do the fuel level measurement in the bowl by attaching a clear tube from the bowl drain holes and seeing how far that raises. the manual for 650e says it's supposed to be 5+-1mm from the the main carb body (that's not much leeway on that number, what happens when the bike leans into a corner, does the fuel mixture change then as well??)

I'm really stubborn to do the soaking of the carbs again in the "right" stuff, since it seems unnecessary but I'll swallow my pride if the above mentioned plan doesn't make the bike run better.

Thanks to everyone for comments, please do post if my reasoning doesn't make sense or with any advice. I'll keep you updated on the progress.

 

[TopTechRacing]

May I suggest carb cleaner for the leak test. Ether is really way too dangerous for a vacuum leak test.

 

[Gorminrider]

funky float gauge....

 

[Steve]

So i did clean the carbs - 2 times now: the first time soaking them in Pinesol (arguably not the best decision) then i did replace all the orings (from robert barr), and second time when i sprayed carb cleaner through all the passages after running it on old gas.

You still need to clean them properly.

I also sprayed some ether around the intake manifolds to see whether there were any leaks due to old orings and i saw no response of rpms to it whatsoever leading me to the conclusion that this is not an issue and the sealing orings to the block need not be replaced.

Spraying anything around the joints is not necessarily the definitive test. It might seal fine at cooler temps, like when you are testing, but have problems at full operating temperature. Or it could be the other way around.

You said you replaced "all the o-rings", but now you mention spraying stuff around the intake boots to check them. If you did not replace the intake boot o-rings, you did not replace "all" of them. If you had replaced the intake boot o-rings, this test would not be necessary.

the other day i looked into how exactly these CV carbs work and it turns out that the fuel supply between 1/8 and 3/4 open throttle is controlled for the most part by the needle jet and jet needle so i think i need to look into making sure all those passages are clean.

It has been said (a time or three) that a full, proper dipping (soaking) in carb cleaner dip overnight tends to do that.

Also it seems to me (correct me if I'm wrong please) that the level of fuel in the float bowls would also have an effect of how lean the mixture would be (ie the less the fuel level the leaner the mixture).

You are correct. Not only does it have an effect on the needle circuit, it affects ALL the circuits, but not necessarily by the same amount. That is why it is best to set for the proper level and make any jetting changes based on that.

So my next plan of action is to do the fuel level measurement in the bowl by attaching a clear tube from the bowl drain holes and seeing how far that raises. the manual for 650e says it's supposed to be 5+-1mm from the the main carb body (that's not much leeway on that number, ...

"Not much leeway"? Did you notice that it happens to be the same tolerance for the float level? 22.4mm +/-1.0mm.

..., what happens when the bike leans into a corner, does the fuel mixture change then as well??

Believe it or not, ... NO. Not only does the fuel mixture not change, the level does not change, nor does it slosh to one side of the float bowl. Because the bike leans to counterbalance in the turns, the apparent "down" direction changes from perpendicular to the earth to a line that runs through the center of gravity through the tire contact patch. Actually, it's been there all along, but when you are riding in a straight line, it also happens to be perpendicular to the earth.

I'm really stubborn to do the soaking of the carbs again in the "right" stuff, since it seems unnecessary but I'll swallow my pride if the above mentioned plan doesn't make the bike run better.

That's OK, you would not be the first to do so. Do you really think that we are all sitting here, conferring amongst ourselves, just trying to string you along, trying to see how long it will take? It has been said that you should learn from the mistakes of others, because you will not live long enough to do them all yourself. Trust me, many of us have been exactly where you are, adamantly saying, "but it couldn't be ...". That is why we have our standard replies of "clean the carbs", "adjust the valves" and "re-wire the stator and R/R ground". It's not just because those keys are stuck on the keyboard, it's because that is what it takes.

Too bad your carbs are not all that easy to get in and out. To me, that would be that much more incentive to do it right, do it ONCE.

That is a pretty good tip.

One caution, though. I think it's the VM carbs, or at least some of them, that have slots down the sides of the drain screw threads so you can drain the bowls without totally removing the screws. That hose will not block the gas from flowing out those slots.

.

 

[badeaslava]

I've lathed a little aluminum bolt and fitted an oring on it to serve as the adapter between the float bowls and a vinyl tube, it works well, but i haven't been able to get ahold of a level to make sure the carbs are level when i do the test. The fluid in the vinyl tube does drastically react to slight angling of the carbs (rightfully so).

Steve, the leaning into turns keeping the fluid level approx constant makes sense due to centripetal acceleration, but how about when you're riding up or down a hill? I suppose this is why the float bowls are round in shape and they are positioned right in line with the main jet cylinder. But it seems that the gas in the bowls would be all over the place for those offroad dirt bikes. I suppose it's not as important for 2 strokes maybe?

It's awesome to be able to learn from the mistakes of others, but I'll give this one a shot before I do so, besides I'm learning a lot about how mikunis work which is very interesting out of its own I'm in generally fascinated with the idea of learning from every experience life throws at me, good or bad.

Thanks for all the suggestions, i'll keep updating...

 

[badeaslava]

I have a quick update: i've checked the gas levels in the bowls, it's within speck, i cleaned the carbs one more time blowing through the passages.

Reinstalled everything ... same thing, nothing changed, the revs hang at 4k. I've then turned my attention to the rectangular orifices on the top of the intake boots, they lead to the top diaphragm and cause the floating cylinders to go up and down based on airflow such as to keep the velocity in the venturi approx constant (hence the CV, constant velocity, if i understand correctly). I am running without the airbox, which caused me to think that there may be too much airflow through those top passages causing too much pressure on the diaphragm and raising the CV bowls thus keeping the RPMs high ??? does that make sense?? At any rate i tried plugging them up with some rags to reduce the flow and the rpms seemed to behave a bit better, not ideal but better. So now i;m thinking that the restricted airflow of the airbox is primary in the proper operation of these carbs but for the life of me i cannot get it installed. I guess the rubber boots are old and not flexible anymore, i tried greasing them with a bit oil but no matter how much i yanked and pulled i couldnt' get them to slide over the carbs. Is there any trick to that?

my battery is dead again so i can't test it anymore, but i"ll reconvene later. Any suggestions?

Thanks