solex idle lacks "stamina"

i have a 2003 solex, and for the most part, it has run like a dream until recently. now what happens is that it runs fine while driving it, and will idle fine for a while (30 seconds maybe?) and then dies out. this is a problem at some of the longer lights in town. it starts back up right away but takes a second to get to the point where it can accelerate normally.

do you think it could be that the mixture is off on the fresh tank of gas i just mixed up? that's the only thing i have changed... i have even driven it in hotter and more humid times than these and it was fine.

this problem coincides with me taking it up and down hills for the first time. i don't know if it's related, but this engine sure doesn't like hills.

thanks for any ideas.

Re: solex idle lacks "stamina"

if by a change in mixture you mean the fuel:oil mixture, yes .. that could affect idle.

At idle the air:fuel mix is rich, about 8:1. If the idle situation were already borderline, this rich mix in combination with a richer (more oil) fuel:oil mix could foul the plug. Other influences could be spark plug heat range and plug gap. A cold plug and small gap would be more prone to foul and kill the spark.

Higher humidity and hotter air temps also tend to richen the air:fuel mix. (Water vapor displaces air. Less air per volume of air richens the mix.. Hotter air is less dense and richens the mix for the same reason.. less air per volume..)

So, if you've got a carb with an air mixture screw, try leaning the idle air mixture a bit .. elsewise, if you've added more oil to the fuel mix recently, cut back to where it was.. or try a combination of both.

Adjust oil according to specs or to synthetic oil-mfg recommendations. (Those who've got an oil-pump that can only deliver one set fuel:oil ratio should use only the oil type recommended in the owner's manual.) For conventional oils, no tail-pipe oil drips and little or no smoke is pretty safe.

If a top speed plug chop (use a brand new plug) shows definate sooty residue (unburned fuel residue) on the plug, try a hotter plug. Set the gap to factory specs or a little wider if there's a lot of miles on the engine..

But if the bike's been modified with a different carb or main jet or other changes then all bets are off.. you gotta get down and tune it more carefully.. the general tendancy is to jet too rich where both low RPM performance and peak power suffers.

Re: solex idle lacks "stamina"

thanks for the input. i didn't purposely change the mixture, but who knows. maybe it was slightly off because last time i mixed the gas right in the tank on the moped, and this time i mixed it in a gallon portable tank. i'll try diluting it.

the carb has no idle screw and there are no modifications done to the bike.

i always check the pipe for drips and there are none.

i'll try a plug chop (always hated that term) if things don't improve.

i thought maybe my engine was complaining about the new terrain i have been making it conquer. perhaps it only wants to be revved at stop lights just like those harleys.

Re: solex idle lacks "stamina"

Never mix the oil and gas in the fuel tank. A glob of oil could block the filter, carb passageways or fuel pipes. Always mix it in a separate container. BrianSolex

Re: solex idle lacks "stamina"

ok.. It's possible that the more difficult terrain heats the engine more than usual. Hot weather adds to this heat. And long periods of idle with no air flow over the engine heats it more .. and it all adds up.

Perhaps idle adjustment was set under milder conditions.. if idle is adjusted on a cool engine it likely won't idle when hot. Try getting the thing as hot as practical before setting idle speed (and idle mixture?).

i really know nothing about the Solex .. i guess it has a "Solex" carb. Depending on the carb it may be possible to adjust more than idle speed to prevent it from dying.

Re: solex idle lacks "stamina"

If I had to make a guess, I'd say that, as the thread suggests, it's heat related.

Running any 2-cycle up or down a hill is going to heat things up. Up the hill, the increased load builds heat. Down the hill, the tendency to keep the throttle closed limits lubrication, which also builds heat.

The solex uses a combination of free-air and forced-air cooling. When you come to a stop, the free-air part decreases quite a bit.. no more wind moving through those little fins. Heat stored in the top-end is free to migrate throughout the engine, and to things like the carb, fuel pump and (metal) lines.

Are solex prone to vapor lock in high-heat? They use a fuel pump, so I'm sure it's possible. Just one bubble in that line between the pump and carb, and you will stall.

Re: solex idle lacks "stamina"

thanks for the advice. funny thing is that velocruz actually gives directions on mixing gas in the tank. i'll be sure to cut that out.

Re: solex idle lacks "stamina"

also, what sort of plugs do you use? mine came with one made by "flash power." can you even find that in america?

Re: solex idle lacks "stamina"

Nate,

Please let me know where they are giving those directions so that I can take care of it. Thanks.

Re: solex idle lacks "stamina"

Nate,

I use an NGK BP6HS on my 3800s. You can use as hot as a B4HS. Many people use a B5HS. The Flash Power is not worth looking for. Here are some other good ones for Solex:

Bosch W 175 T1 (aka W8AC)

Champion L86

Autolite AE32

Denso W16FS, W16FS-U

AC 44L

gap is 0.5 mm or 0.020 "

Make sure the spark plug cable has not been melted,damaged or become brittle from touching the cylinder.

Re: solex idle lacks "stamina"

There are no adjustments on the Solex carburetor. The most interesting thing about the Solex carb is that there is no float bowl. Any unused fuel at the carb gets sent back to the fuel tank. Cleanliness is very important. The orifices are tiny and the smallest piece of dirt or whatever can clog the passageways. Sometimes the jet gets a little restricted/clogged and needs to be removed and blown through to clear it. Never use a piece of wire to clean the jet as you can scrape the inside the smallest amount and change it's characteristics.

Re: solex idle lacks "stamina"

Solexes are not hill-climbers. On steep hills, it's necessary to pedal to help the motor out.

It's important to make sure that the metal fuel pipe from the pump to the carb isn't touching the engine crankcase cover.

Check the filters in the carb and fuel tank to be sure they're not restricted. A restriction in the fuel pipes will also cause it to stall. They can be removed and cleaned with compressed air. I've already mentioned cleaning the fuel jet the same way.

Problems with the spark plug and/or wire will cause a stall also.

Re: solex idle lacks "stamina"

very interesting carb system... my fuel injected Lincoln does the same thing :)

It seems like every moped has some bits of creative engineering here and there ..

Re: solex idle lacks "stamina"

Yes, every moped has it's good points and bad points I guess.

Re: solex idle lacks "stamina"

http://velocruz.com/owner_setup.htm

under "hints to happy solexing:"

"3) The proper oil/fuel mixture is 2-3%. (This means a 40 to 1 ratio -- which is approximately 3 1/2 oz. of 2-cycle oil per gallon of gasoline.) Still confused? Think of approximately 1/3 "kitchen measuring cup" of oil per gallon of regular gasoline. (Or consider filling a container the size of a film canister with oil and mixing it with one tank of gasoline.)"

Re: solex idle lacks "stamina"

what is the best way to get to the filter in the tank?

Re: solex idle lacks "stamina"

Brian,

You mentioned that you use a BP6HS in your 3800, but the other plugs you talk about are not equivalents to a 'BP' style - they are all straight 'B' style equivalents.

The 'P' refers to a protruded tip.. which can strike the piston in the wrong application.

Can you clear this up?

Re: solex idle lacks "stamina"

Yikes! I'll get right on that.

Re: solex idle lacks "stamina"

Thanks. Yes I'm aware that it's a projected tip. There is no clearance problem. I thought Nate asked which plug do I use. My personal preference at the moment is for the BP style plug in my '70s 3800s. But, I recommend using an NGK B5HS or one of the equivalents that I listed, for his 3800, while I'm still experimenting with the BP style plugs. I apologize for any confusion that I caused and hope this clears it up.

Re: solex idle lacks "stamina"

Nate,

To get at the filter in the tank physically, you must remove the tank. Siphon the fuel out of the tank or with a friend tip the bike over and empty the tank. Loosen, but don't remove, the bolt holding the tank near the carb. Remove the other two bolts and disconnect the fuel pipe. With the tank removed and the fuel pipe removed from the tank, insert a wood screw into the opening where the fuel pipe was, turn it a little to hook the filter and pull it out.

You can see the filter when the tank is empty or nearly empty by removing the cap and shining a flashlight inside. It is a little white plastic piece about an inch long.

Re: solex idle lacks "stamina"

Brian - you also mentioned a carb filter. Where is that?

And while we're on Solex carburation, how do you adjust the idle? My idle is far too high, yet the throttle arm is bottomed out. Adjusting the cable wouldn't help, is there an idle adjustment screw I should be looking for?

Zeke

Re: solex idle lacks "stamina"

Zeke,

To access the carb filter on the 4600, remove the air cleaner assembly. You'll see (or should see) a clear/white piece of tube sticking up about 1/2" on the tank side of the carb. Pull that up and out of the carb and you should see that it's a filter about 2 1/2 " long. If you see any particles in the screen part you can try to blow it out with compressed air. It's best just to replace it. I've used carburetor cleaner spray to clean them.

On the 4600 V2 and V3 there is no idle screw. There should be a spring holding the throttle barrel about halfway closed at idle. (Take off the air cleaner assembly. Look down the throat of the carb and move the lever to see the opening and closing of the barrel.) The spring goes from the lever to the casting for the cable. You may have to adjust the position that the throttle cable is locked up at on the pulley. Roll the throttle handle forward and adjust the cable on the pulley until you have the correct idle, 1500 if you're using a tach, by ear/feel otherwise.

BrianSolex

Re: solex idle lacks "stamina"

That's just it - I can't move the throttle handle any more to lower the idle. It won't go any further. There is another bolt through the the handle that it bottoms out on.

I'll try and post a picture tonight. (After I check the carb filter for ancient solidified premix. =)

Thanks again for all your help.

Zeke

Re: solex idle lacks "stamina"

Zeke,

I don't know of any bolt that goes through the throttle handle. Does it look like something original or something that somebody added?

If you have the throttle handle rolled all the way forward and the throttle barrel is not half way closed, you have to loosen the cable lock on the pulley and reposition the lever/pulley to a position where the barrel is half closed when the throttle handle is rolled all the way forward. When you roll the throttle handle back, the throttle barrel should open all the way. If you don't have the necessary travle in the throttle handle, I've got to think there is a problem with the handle somewhere.

BrianSolex

Re: solex idle lacks "stamina"

here is an update on my end...

i thought there were no oil drips from the exhaust, but after it sat for a few days, i noticed some. i added some seafoam to my 1 gallon tank, as the bottle recommends, and things are running fine. i rev the engine a bit at stops, and it hasn't stalled for a while.

i have also discovered that an old leather camera bag of mine fits on the luggage rack perfectly and serves as an excellent saddle bag of sorts.

i read that you had a good time at the nyc solex/citroen rally. congrats! it sounds like we may have another solex convert from that rally as well!

Re: solex idle lacks "stamina"

Nate, That's good news that your Solex is running well.

Post a photo of your bike with the side bag, I'd like to see it.

We had a great time at the event on Sunday. Maybe you can make it next year. Glen kept an open mind and had a great first time Solex experience. I posted photos on the general discussion forum on this site.

Re: solex idle lacks "stamina"

I realise that I've sort of hijacked his thread at this point, since Nate's "Flying Bicycle" is up and running again, but I'm still confused regarding the idle position for the throttle arm.

On my 4600, a spring holds the throttle arm at its lower limit - won't go no further. When I roll the throttle handle on the handlebars, it pulls on the throttle arm (against the spring) which increases the RPMs. "At rest" the spring pulls things back to the lower limit. This is where I would expect some sort of idle adjustment device to come into play, but there doesn't seem to be any.

I'm missing something somewhere...

Zeke

PS - I did clean some crap out of the carb filter - thanks for the heads up there.

Re: solex idle lacks "stamina"

Zeke,

Hold on now. Are you saying that the spring is on the bottom side of the lever? Look at this picture and see where the spring is hooked up. Is this how yours is hooked up? This is the hook up for the 4600 V2 and V3. The spring should go through a hole in the lever on the carb, not on the hook on the bottom of the lever. Also, the cable should be coming up to the carb pulley from the bottom, not down to it from the top. Again, check the picture and let me know how yours is hooked up. BrianSolex

1121894809_4600_throttle_adj.jpg

Re: solex idle lacks "stamina"

Brian -

I have it hooked up as illustrated. The extra bolt I was referring to is located between the throttle arm mounting/pivot bolt and the lower hook above the arrow (that I'm not supposed to use).

I've made an attempt to attach an image.

Zeke

1121913028_4600_throttle.jpg

Re: solex idle lacks "stamina"

Oh, that's the bolt you're referring to. That is supposed to be there. It limits how far the arm can travel on the 4600 V2 and V3. When the lever is lifted all the way up and that screw is hitting the little post on the carb casting, that is the idle position. Your throttle handle grip should be rolled all the way forward at this point and then lock the cable to the pulley. Looking down the throat of the carb, the barrel should be half closed. When you roll the throttle hand grip back, the lever on the carb should move down and the barrel should open. If, by the time you roll the hand grip all the way back, the barrel doesn't open completely, you have to try locking the cable on the pulley at a different position, so that when you roll it all the way forward, the barrel closes halfway and when you roll it all the way back, the barrel opens completely.

When you're having this high idle problem, is the motor still on the tire? Or is it when you have the motor lifted off the tire?

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