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

[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.

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[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

[Steve]

Any suggestions?

Just the standard fourth-down strategy: drop back 5 yards and PUNT.


We have been offering suggestion after suggestion, yet we don't see them followed, why should we offer more?

From your latest post, my responses in blue:

Originally Posted by 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.
But have you stripped them down, dipped them overnight and replaced all the o-rings? I see in your first post that you replaced o-rings, but did you get the kit from cycleorings.com and replace ALL of them?

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).
Yes, you are understanding somewhat correctly.

I am running without the airbox, WHY???

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??
NO. The ONLY time there is any airflow through those passages is when you are using the "choke". Any other time, there is NO air going through there.

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.
I have heard of some creative stuff before, but this one takes the cake.

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.
It really does not matter how "restricted" the intake is, as long as you jet for any difference. The carbs were jetted at the factory for a good, overall compromise in running ability and performance. If you install ga header, you change the air flow capacity, so need to add more fuel to the additional air. If you install pods, you again increase air flow capacity, so you need to add more fuel. If you remove the pods and go with NOTHING, guess what, you need to re-jet. Did we know before this that you were running without any kind of filter?

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

I don't remember if you had changed the intake boot o-rings. That is another good possibility for an air leak. Air leaks cause a hanging idle.

As much as I enjoy offering suggestions, I do like a little feedback that says "ok, I tried that, but it didn't work" or "ok, I did that, now have another problem". I am all out of suggestions at this point until I see a post that says "HEY, I did all that and it works now!!!".

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[tom203]

Since you enjoy learning about CV style carbs ,have a look at this

http://will.mylanders.com/mc/notes/read.pl?file=3

Like has been stated, your carbs need deluxe cleaning and all o-rings replaced . You need the airbox and filter box to run decently above about 3000 rpm- starting and idling is no problem without them. A hanging idle with throttle plates closed (resting on idle stop screw) usually means airleak between carb and engine - old dried out boots will resist sealing well.

[badeaslava]

Hello everyone, I apologize for being somewhat unorthodox in posting exactly what i have done and have not done in a systematic manner, but i do actually try to follow all the advice and suggestions posted here. Thank you for taking the time to troubleshoot my bike with me, i really do appreciate it!

To follow up here's a list of everything I have done so far to my carbs:

*disassembled them and dipped them in Pinesol for a day

*blew through all the passages with carb cleaner (multiple, multiple times) the spray came out uniformly with high power through all the passages that I knew of, which suggests they are free of blockages.

*adjusted the floats using the mechanical caliper measurement and clear tube attached to the draining orifice methods. I adjusted them within spec.

*replaced all orings from cycleorings.com. I did NOT replace the intake boot orings, but I just ordered those and will replace them when they arrive, i'll update you on the results of new orings.

*while the bike was running i sprayed around the intake boots with ether to see whether the rpms respond (ie there is a leak there) and did not see any effect whatsoever

*all these tests i was running without the airbox installed tightly, simply because I just can't get it fitted over the carb throats, especially the 2 inner ones. I can't get my hands in that space to force the airbox boots onto the carbs. Is there any technique anyone knows to do that? i think mine might be badly deformed too.

Steve, you are correct about the vacuum passage not having any flow of air, i misunderstood that principle when i was looking through the manual. but for some reason i felt suction force when i blocked them with my thumbs, but it could have been imagining things that i wanted to see

I have another question if i may: when the gas runs out on my bike the engine revs up by itself without touching the throttle. It makes somewhat sense because the mixture becomes leaner and leaner as the gas drains from the bowls but the throttle plates are always closed. Is this normal, or is it my bike's issue probably associated with a vacuum leak?

It doesn't make sense to me in general why a lean mixture causes hanging rpms. It runs hotter, is worse for sparkplugs, pistons, but when the throttle plates are closed the airflow is restricted to the combustion chamber, so what keeps the rpms high? there's not much air-fuel to combust still.

Thanks again for all your help, I'll install those intake boot orings and try to install the airbox and post updates soon!

[UK-GT]

*all these tests i was running without the airbox installed tightly, simply because I just can't get it fitted over the carb throats, especially the 2 inner ones. I can't get my hands in that space to force the airbox boots onto the carbs. Is there any technique anyone knows to do that? i think mine might be badly deformed too.

Regarding re-fitting the carbs, they are a pain in the neck!! I had to remove the Air filter box (you will need to move the rear brake reservoir, remove the battery to undo the reg/rec & etc). Then you can get your hand in the back of the air intake chamber and push the two middle intake rubbers onto the carb and do the screws up.

[OriginalOwner]

Ok, here's an update:

,,,the engine the rpms hang high and then slowly go down if even. ...Also the fact that choke is on doesn't affect the idling rpms of the engine

*all these tests i was running without the airbox installed tightly, simply because I just can't get it fitted over the carb throats, especially the 2 inner ones. I can't get my hands in that space to force the airbox boots onto the carbs. Is there any technique anyone knows to do that? i think mine might be badly deformed too.

Wait. Am I missing something here?

How do you figure the high and hanging idle is not a result of your airbox not being properly connected?



But either way, I'd enjoy hearing a few tips, tricks or techniques concerning the wrestling carbs back into place.

[Gorminrider]

A heat-gun on old boots really helps. It temporarily softens the rubber.
Whatever, apply heat-that-doesn't-burn...Even a rag wrung out fresh from boiling water wrapped 'round might help a bit.

But I have trouble believing the airbox is the trouble just because it leaks. I like Tom203's opinion above. "You need the airbox and filter box to run decently above about 3000 rpm- starting and idling is no problem without them. A hanging idle with throttle plates closed (resting on idle stop screw) usually means airleak between carb and engine - old dried out boots will resist sealing well." The airbox can't really affect airflow(except to shelter the carb air intake and keep dirt out) until the engine is demanding lots of air whereat, it's intake size and filter restriction can be compared to the carbs. BUT air is compressible too yadayada

.... 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.

You'd better doublecheck. If you have CV carbs like mine(BS34S),as Steve said,No airflow into those oval ports at to diaphragm unless the diaphragm is ripped or not seated properly. They just compare air pressures and smooth the throttles response versus lifting the slide with a cable. And maybe the slides are sticking. This might give a hanging idle. Or maybe you forgot the springs.

[OriginalOwner]

I just re-installed my carbs after a rebuild and I had the nearly the exact same symptoms as badeaslava. I suspected an air leak.

After looking closer, I found I never tightened the hose clamp for the boot on carb no. 3 on the airbox side. The boot was on, the clamp just wasn't tight.

Once I tightened it, the high and hanging idle went away.

[badeaslava]

Hello everyone,

After a few weeks of busy at work I finally found some time to work on the suzuki. I replaced the intake boot orings with new ones from Cycleorings.com in hope that they would get rid of the hanging idle...and they did not. I also managed to reinstall the airbox. I found a relatively easy way to do that instead of removing the battery holder etc etc. I just took out the filter, stuck a blunt object inside the airbox, such as a socket extension or a screwdriver with a blunt/covered tip and pushed on the inside of airbox boot covers until they slid onto the carb throats. First i tightened the outer ones, cabs 1 and 4 and then i tightened the inner ones, it helps since you can push the outer ones from outside with your hands. At any rate, after going through all the hassle of doing that.... i still have the hanging idle. I don't know what else to do but i'm giving up on it for now, since I'm going to do work on the bike through the winter and firstly rejet with a dynojet kit and put air pod filters on it. Could the hanging idle be cause by a bad balancing of the carbs (i never vacuum balanced them)?

However, i have a different issue now that i really need help with. Before, despite the hanging idle, at least the bike started and ran somewhat, mostly on choke, but still it ran. Now that the temps in new england started to go down (about 40-50) i can't even get the bike to start. Moreover i started to get this weird issue with the starter motor. when i press the start button, the solenoid actuates and provides 12V at the starter ( i checked that with a multimeter) but the starter doesn't crank at all. The battery is full. Sometimes it cranks the engine but it still doesn't start. It's intermittent this starter problem. To get around it I usually shift into 5th and rotate the rear wheel by hand "backwards" which turns the starter motor i assume, then i try to start and it cranks but still does not fire. Then it dies again and I gotta turn the wheel backward once more to get it to crank.

Has anyone seen anything like this, where do i start to troubleshoot? take out starter motor and test it? It resembles to me a seized engine, but then why does it work sometimes but not others?

thank you for your help. If it's not one issue it's another with these old bikes

[hjfisk]

Have you checked your oil level? With all your carb problems has your crank case filled with gas? This could stem back to your other problems , a bad fuel petcock?

[badeaslava]

Good call hjfisk, i was suspecting that it could be fuel in the oil. I did drain the oil today and smelled gas in it, from what i could tell it wasn't much but it's hard to know for sure, i don't remember how much oil i put in exactly. My guess is that it's one of the float bowls jamming from closing properly, or do you think it could be worn fuel inlet needle?

Do you think i should also replace the oil filter or this one will hold. My task here is to ride the bike about 3 miles to the garage where I'll store it for the winter and probably do a whole bunch more work on the engine, at that point i'll change the filter and take a look a the carbs (for the 5th time or so) to see whether it's leaking.