I just bought this vehicle for off road use only.  the drivetrain is all stock with the 1.3 motor and 5-speed.  The guy I bought it off of included some new parts and told me it might need a tune-up.  At first, it starts up and idles fine.  Then at some point, it  starts idling rough and will sometimes stall.  I have taken it for a drive a few times, and it seems to be really gutless IMO (I know its no race car, but it should be a little better than this).  Sometimes it will stall at stop signs.  I wasn't able to reach 50 mph on the level road.  It just doesn't have the guts.  I have been reading these forums and taking multiple steps to eliminat the common issues. 

Here's what I have done so far:

I checked the spak plugs, wires, distributor cap, and rotor.  No problems found, but replaced them with new since they were included.  It is getting good spark. I used a lite-up wire tester.

I bought a compression tester.  Checked each cylinder (1 by1) with throttle plate zip tied open. Each cylinder got to about 150 psi after a few cranks.  After 5 seconds it leveled off at 170-180psi. 

I bought a fuel / vacuum gauge and checked the fuel pressure at the carburetor.  It was steady at 3 psi.  The one forum I read said that that was good.  I checked the fuel filter.  The seller said that he replaced it recently and I can see that it is not visually dirty. 

I checked the original O2 sensor using 2 different methods.  I plugged one end of my multimeter into the O2 sensor and after it was warmed up and running.  read 0.00 mA and steady. the one online guide I read said it should fluctuate between 0-900 mA.  I then switched it to read voltage and it read steady at 0.00 V.  the manual I have said it should fluctuate between 0-0.80 V.  I replaced the O2 sensor (also included with the purchase).  Post replacement all multimeter readings are the same as before.  So I don't think the O2 sensor was bad. 

Early on I did spray carb cleaner all over the throat of the carb while holding the carb at partial throttle.  After I read about the vent tube, I checked mine and all looked good.  I sprayed into it and pulled it out and sprayed directly in the hole.  I reinserted the vent tube.  Took for a drive after all these improvements and still no noticeable change in performance. 

At this point, I am thinkin it is a carb issue (which kinda scares me) or a timing issue.  Any other suggestions?

I am looking for a quck fix, as I would like to take it wheeling this weekend.  I don't have a timing light, but I plan to borrow one tonight.  I have never used one before, but I am sure I will figure it out.  Any pointers would be appreciated. 

I read a lot about these carburetors (supposed to be one of the most fuel efficient and complicated carbs around) and I am not sure if I have the time to invest fixing the carb, if it is a complicated fix.  As I mentioned, I do have a vacuum gauge that I could use to diagnose vacuum leaks.  But I am not sure what vacuum pressure to expect on the ~10,000 vacuum lines coming out of the carb.  If there is a step by step guide for troubleshooting the carb, please point me to it, because I wasn't able to find one online. 

Sorry this got a bit wordy, but I know you guys like to know all the details. So there is what I have... Please help! I live in South Central Pennsylvania, and would be open to someone coming to take a look at it if you live nearby.  I will also be looking into selling it after this weekend wheeling adventure.

I forgot to mention the body and roll cage is all custom (irrelevant to my questions).  See the picture I attached.  As I stated earlier the drivetrain is all stock samurai besides a cone style cool air intake filter.

Check the catalytic converter. Go to  muffler shop. When they are plugging up they start fine but get worse as they warm up.

Check the catalytic converter. Go to  muffler shop. When they are plugging up they start fine but get worse as they warm up.

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Check the catalytic converter. Go to  muffler shop. When they are plugging up they start fine but get worse as they warm up.

Thanks for the advice about the catalytic converter. 

Closest muffler shop is about 30 minutes away and this isn't road legal.  Can I just do a test similar to what's shown in this video?

How to check your vehicle's catalytic converter.

(Skip to about the halfway point; the guy is pretty annoying)

I seem to remember him or someone else stating that upstream of the cat, the pressure should be between 0-2.5 psi.  Plugged cat could get around 15 psi or so. Do those numbers hold true for the Samurai? 

I thought of using the O2 sensor hole, but I did not enjoy replacing the O2 sensor last time and I don't think my Vaccuum gauge came with an adapter for an O2 sensor hole.  I will likely pursue just drilling the hole on the frontside of the cat and taking a pressure reading that way as shown in the video. 

If it is in fact the cat being plugged, I am thinking I will just hollow it out.  Anybody have any bad experience with that, besides it not being technically road legal?
 

I contacted the guy I bought it off of and he said that the cat was just replaced with a brand new one, so I am hesitant to invest any time checking into the cat.  I might check it anyways if I can find a plug to install after I drill a hole in the exhaust. 

He also suggested Sea Foam.  I had never heard of the product, but apparrently a lot of people including some on this forum have had good results:
http://www.zukiworld.com/forum/general-suzuki-forum/seafoam-anybody-use/

Any thoughts on using Sea Foam and where I should put it (just in the tank, or as some suggest in the brake booster vacuum line???)? I am not sure I am clear about where I would find that vacuum line, but I do have the service manual that I will check.  Also I am wondering if I should take off my cat to do the Sea Foam additive. Is there a good chance that using this will mess up my new cat if I release gunk from the carburetor?

You can put half the can in the gas tank ond half in the Carb. I just poure dit in a ltlle at a time while it was running just careful not to stall it. I would still check the Cat first before I started on the Carb and eliminate it. You just weld over the hole. Check the fuel level on the Carb in the sight glass on the front of it. If the Carb is dirty and plugged up, it may start to starve off after the choke opens up.will cause it to stutter and lose power.  Let it warm up and look down the Carb into the primary throat. When you  open the throttle and rev the engine with it running, you should see gas spurting into the Carb. It would be helpful if you could find another Sammy to look at so you could see what it is supposed to look loke.  It may need a rebuild but I would eliminate the Cat first.

I checked the cat.  I drilled a hole upstream (in front of the cat).  Took a pressure reading.  It never gets above 1 psi, which makes sense, because it is a brand new cat.  The gauge is brand new and works good.  I can get the gauge to around 2 psi with the pressure from my lungs.  (Cat eliminated)

I did the whole can into the tank as directed.  I also had the aeresol spray can which I sprayed all over the carb with the throttle zip tied at about 2500 rpm.  I had a piece of carboard behind the tail pipe and didn't see any gunk on the cardboard.  I took it for a drive and it exhibited all the same symptoms, stuttering and sometimes backfiring.  When I try to pull a hill in 2nd gear.  Pedal to the floor, this thing should be letting me get into 3rd gear (paved road not that steep of a hill).  It just starts stuttering and almost forces me to downshift to 1st.  When I say stuttering, it sounds nasty like its missing, but will have short bursts of power for like a half of a second. 

Not sure about that carb fuel sight glass. I haven't seen it, but I will look for it and check the manual as well.  Also, when you say the primary throat do you mean the one on the right without the throttle plate on it (or choke plate, not sure what its called)?

I have looked in it while revving the motor and it doesn't seem to be getting any fuel down the bigger throat on the right.  That seems like it may be the problem, any ideas of a quick fix for it.  I don't have too much time to mess with it, but I do have a vacuum tube tester and a whole roll of new vac hoses.  Just not sure where to start and whether I should do these tests with the engine running or not.  Any idea which vac line would be suspect

The primary is the one on the left with the choke plate. The fuel comes out of the small tube in the round cone shaped thing in the center. I have bent the end of a Carb cleaner tube and shot cleaner in the end of it and cleaned out a clog.

So I looked at the manual and found the fuel sight glass.  I couldn't see any level in it, but it was dark and the carb is a bit dirty.  The glass did look like it had a yellowish tint to it, so I guess that could mean it has fuel level in it. 

The primary throat (the one on the left with the choke plate) does have fuel coming out during idle and when I hit the throttle.  However it is not a steady stream.  I have sprayed carb cleaner on it as well as the sea foam spray.  I will try using the nozzle like you said to spray directly into the nozzle. 

I spent about an hour and a half messing with vacuum tubes.  I don't think the roll I bought would quite replace all the lines, so I was trying to pick and choose.  I did find 2 vac lines rippednear the bottom front of the carb (I think they were actually tied into the intake manifold.  I changed them out with new, but after another test drive still no improvement.

The good news is I think I have eliminated every possible cause except the carb (and possibly the computer that controls it, but I don't know much about that). 

I am losing heart on this project and don't have the time or money to dump into this anymore.  I may tinker with it a little more tonight and tomorrow, but come Friday evening I will just be running it as-is (gutless). 

Anybody interested in buying a nice Samurai dune buggy.

I have sprayed carb cleaner and sea foam into each orifice of the carburetor. 

I replaced a few vacuum lines and disconnected and shortened a few of them due to the ends being worn out.  I also Sprayed Sea Foam spray and carb cleaner into each vacuum line while running.  After about 1.5 hours of tinkering with the vac lines, I took for a drive - no improvement.  I decided to just run it as is.  While running the first 10 minute offroad driving I did, I lost a bunch of power, and it was sputtering like never before.  I couldn't quite make it to the campsite since it was so gutless trying to climb the steep hill. 

I almost gave up on it, but then someone convinced me to take it to do some serious offroading.  Everything went great in compraison to other experiences.  It seemed to have more power and didn't die out on me going up hills.  I am wondering if the carb issues just worked themselves out after running it hard after the carb cleaning.  I wouldn't say it is running flawlessly.  I think there are still some issues in the carb, but they only cause a momentary studder rather than a total loss of power.  Maybe it helped that it was a pretty cold day (around 32 deg F) while offroading.  Maybe the motor never had a chance to get to the temperature that the carb was causing issues. 

Anyways, my 4-wheeling with this vehicle will not likely resume for close to a year from now.  I would really rather find something with 4 doors that i could haul more people in.  So if anybody is interested in buying this dune buggy Samurai, see the picture at the top of the post.  The frame is very clean, and there is nothing on the body (fiberglass) or roll cage (aluminum) to rust.  I am asking $1100.  Could be made road legal by just adding mirrors.  Turn signals and lights all work great and it does have a cover (ragtop).  I can send videos of me offroading in it. 
Feel free to email chemicalgutter|removethispart|@yahoo.com