Surging and Bogging Down

[I<3Dirt]

I've been searching a lot here in the past 3 days, and found a lot of good information but found that my problem could be a couple of things, and I want to try to narrow it down a bit.
The bike is a 1984 Suzuki PE175, rebuilt the engine about a year ago and ran great until a little while ago.
I'd had some problems with it stalling after it heated up, but those seemed to go away on their own. But after a trip last weekend it stalled and wouldn't start.

So I replaced the plug, filter, and cleaned the carb.

A few days after replacing those parts it started up right away and ran good for the few minutes that I rode it around the backyard. I didn't get to fully warm it up,due to the fact that it's fairly loud and the neighbors don't like it.But I figured because it was running fine during that time that it was fixed. I brought it back out a couple minutes later because I wanted to fully warm it up.( the neighbors don't like us anyway because of our quad and dune buggy being run a lot )
Well, it started on the second kick again and ran decent for a few seconds but as soon as I gave a little throttle it bogged down and the idle stared to surge a bit. I got on it and a couple seconds after putting it in first gear it starting surging so badly that it finally died. I can start it up easily but it just does the same thing. Sometimes it won't surge it will just bog down under a load.

The couple things that I found it could be is either jetting, float adjustment or the air mixture screw.
As far as the jetting, how can a completely mechanically stock bike need a leaner jet if nothing has been changed on it?
Float adjustment, can it just randomly come out of whack like that? I don't have a manual and can't find a free one online, so I don't know what the stock height should be, is there a general height that will at least make the bike run?

Thanks
Brandon

 

[just_a_rider]

Sounds like it's starving for gas, (running lean) run your air screw in a half turn or so and see if that helps, you can also raise your needle jet a notch or 2. If you find that it runs better like this you'll need to go bigger with the jetting. Float settings to low will not allow the bowl to fill enough to keep it fed when giving it more throttle. A float setting to high will cause it to run rich.

 

[BSWIFT]

On a bike of that age, you should look at the intake boot. If there are cracks, you probably have an air leak. As the engine warms up, the rubber expands opening up the cracks. You may also have a left side cranks seal out.

 

[I<3Dirt]

Update:

I messed around with the bike a little this morning. It fired right up again, second kick and idled great and didnt bog or surge until i put it in gear, where it then bogged down and died. Started back up, and for about two seconds, it'll run perfect and then it bogs down under throttle.

I checked for cracks around the boot and didn't find any. So I started adjusting the air screw. I have it 4.5 turns out (i know, way too much) and if I keep it at WOT in neutral, it stays running but barely, it surges up and down. One thing I did notice is during the surging I looked down and on my airbox theres a short plastic vent hose molded to it, and there was a greyish-white, foamy liquid coming out... what is it?
The air screw is leading me to think that it's running too rich. Am I right?
If so, I would need to change the jetting, but why would I need to change it if the bike is still stock? There hasn't been any drastic weather changes, so I don't see how it would've changed.

 

[I<3Dirt]

Well I think I've fixed it. I took the carb out one last time. Cleaned it out, and made sure the float was set correctly. I put it back in making sure to tighten down the boots around each side of the carb to ensure that no air leaks were going to appear. It started up after a few kicks and seems to run great now, lots of tourque and idles decent again. I haven't had a chance to let it warm up fully yet, and probably won't be able to until next weekend, but it seems to run fine now anyway.

Thanks for the help.

 

[BSWIFT]

:cool:

 

[kx125412]

My bike did that from being excessively rich. It would idle really well but as soon as it was under load, bwahhhhhh. I leaned out the needle a couple clips and it fixed her right up. Still rich but that'll be fixed in the spring.

 

[atcomx98]

Also try cleaning out the fuel filter and fuel line.

 

[I<3Dirt]

Bringing this back up...

After riding it for about 20-30 minutes today with no problems, it abruptly started sputtering and lost all power. It does it under a load, or in neutral. It sputters, and bogs down under any throttle, it doesn't completely stall unless I let off the throttle, but sounds horrible. I also noticed that gas was leaking out of the Carb. vent lines. Thats caused by the float being too low right?...or too high?
As for the sputtering/bogging, I think I may have mixed it too rich, so I'm going to drain all the fuel tomorrow and mix it to the proper ratio, will that possibly hep?

 

[2strokerfun]

Sounds like float needle is sticking and flooding your bike. The answer to you float question would be "too high", but, technically, if the float is set correctly, it really can't go "too high" because the needle still stops the float, but if stuck open, the needle won't stop the gas from coming in the bowl anyway. Common problem on older bikes. Try a new needle and seat.

 

[bro]

Does your bike have a metal gas tank?

If so, check it for rust.
If there is crap in your tank, your bike will run fine after cleaning the carb until another little piece of junk gets in there. It could cause the float needle to not close completely too and flood the carb.

 

[I<3Dirt]

Does your bike have a metal gas tank?

If so, check it for rust.
If there is crap in your tank, your bike will run fine after cleaning the carb until another little piece of junk gets in there. It could cause the float needle to not close completely too and flood the carb.

No it's a plastic tank, and I'm going to drain the fuel today and check for debris in it. Probably take the carb. off too, and give it another cleaning and check the float height/needle.
Thanks for for replies.

 

[Morvo]

It does sound like a float problem in the carb, check for holes/splits in the float while you are adjusting the height of it. You mentioned before about greyish liquid coming out from somewhere, have you drained your oil recently to see what colour it is? If it's a milky greyish colour then chances are your head gasket has popped so it's leaking water into the engine. Do you have white smoke out of your exhaust by any chance?

 

[rmc_olderthandirt]

I am going to chime in and echo the "needle valve" suggestion.

I have seen plenty of cases where the needle valve gets mucked up and it can cause all sorts of problems.

Like any valve, the "needle" and the "seat" need to be in good shape in order for the valve to completely shut off the gas flow. When a valve gets old, it tends to leak.

I have also seen cases where some gunk has gummed up the valve, causing it to stick. If it sticks open, gas flows everywhere. If it sticks closed, you run out of gas. If it sticks halfway, it can drive you nuts! Every bump you hit could make it stick in a different spot.

If you have gas flowing out the vent lines then you have a float / valve problem. I would just bite the bullet and buy a new needle valve and put that issue to rest.

Rod