Jump to content
Sign in to follow this  

Need some advice on an old 2 stroke (plug wet)

Recommended Posts

Need some advice. Got my 2t project up and running. 67 Suzuki 80cc. Rode it for a few minutes the other day with some premix, then today got the oil injection hooked up. Dumped the premix in the tank and added some regular. When I was making sure my oil line (this bike just has one) was flowing, I was an idiot and loosened the banjo bolt at the engine side while it was running, and it died. After that the kickstarter wouldn't turn at first, but then seemed to free up. Maybe this did something bad?

Now, I can kick it over and it will run, but only for a minute or two, and only when I give it some throttle. After that it won't turn over. I pull the plug and it's wet. Swap in my extra plug and it fires up, but again, only lasts a minute or so before dying. I can repeat this after drying and cleaning the plugs.

Two thinks worth noting:

1: it looks like I have a small leak at the base of the cylinder. I put a new gasket on when I put it back together, but who knows. I'll need to deal with that, but I'm not sure if it is causing this problem.

2: I also found a tiny little crack on my exhaust pipe back where the bracket mounts. When it is running, I can see a tiny bit of seepage that burns off on the pipe.

I'm running a Mikuni VM18 round slide carb on this bike with an oiled UNI filter, and I've left it alone as far as jetting goes. No idea which direction to go as far as changing settings on it.

Thanks folks!

Share this post


Link to post
Share on other sites

Don't assume your oil injection is working. It may have to be bled or may not work at all. Sounds like the piston is getting hot and siezing. Drain the gas, put premix gas in and spray some wd-40 or fogging oil in the piston for lubrication. I would run the premix until you see a ton of smoke and are sure the injection pump works.

You probably didn't hurt the piston. As for the wet plug, the floats may be stuck open, or the pilot air screw channel may be plugged. I would clean the carb if you haven't already.

Share this post


Link to post
Share on other sites
Don't assume your oil injection is working. It may have to be bled or may not work at all. Sounds like the piston is getting hot and siezing. Drain the gas, put premix gas in and spray some wd-40 or fogging oil in the piston for lubrication. I would run the premix until you see a ton of smoke and are sure the injection pump works.

You probably didn't hurt the piston. As for the wet plug, the floats may be stuck open, or the pilot air screw channel may be plugged. I would clean the carb if you haven't already.

Well, my oil line is clear, and I can see the fluid moving through the line all the way to the hole in the block. No leaks or anything either. There are the occasional small bubbles, but it seems to be within the specs of what the manual says.

I was actually running both the premix and injection for a quick ride around the block, and then I drained the premix. One thing I noticed was some slight smoke coming out of the plug hole when I pull the plug. Guess I can switch back to premix to at least see if it is the pump not working.

As for the carb.....it's brand spanking new. Still think it would be a culprit?

Thanks for the help.

Share this post


Link to post
Share on other sites

Did the new carb come with the same jets, and did you set the air screw to the same place? Usually it should be 1 1/2 to 2 turns out from all the way in.

I remember a few people with the old oil injection bikes where the injection pump failed or they didn't trust it. They just ran premix all the time. It may take some running time to prime. Most oil pumps won't push air.

Share this post


Link to post
Share on other sites

When you loosen the banjo bolt the engine will suck air in and cause the motor to run lean. Also, any leak at the cylinder base gasket would allow air/fuel mix to shoot out before the transfers open and air to leak in during the intake cycle. The same holds true for the exhaust leak if it close to the port. I run a very small amount of premix (100:1?) and monitor the injector oil reservoir in my old 2-strokes to be sure they are pumping oil.

Also, if you put in a new ring did you gap it? Many times they are too tight and the ends need to be opened up.

Once every thing is right, then worry about jetting and stay on the rich side.

Share this post


Link to post
Share on other sites
Did the new carb come with the same jets, and did you set the air screw to the same place? Usually it should be 1 1/2 to 2 turns out from all the way in.

I remember a few people with the old oil injection bikes where the injection pump failed or they didn't trust it. They just ran premix all the time. It may take some running time to prime. Most oil pumps won't push air.

The carb was not functional when I bought the bike, so I have no idea what the jetting was on it. Air screw is set at 1 3/4 out. The engine was running fine for the hour or so I was playing on it after I got it fired the first time. This stuff didn't happen till after I tried switching to the oil injection.

I was going to just run premix, but the general consensus was that it was a major risk on this engine.

Share this post


Link to post
Share on other sites
When you loosen the banjo bolt the engine will suck air in and cause the motor to run lean. Also, any leak at the cylinder base gasket would allow air/fuel mix to shoot out before the transfers open and air to leak in during the intake cycle. The same holds true for the exhaust leak if it close to the port.

That makes total sense. The exhaust leak is way back on the muffler section, but I get your point. Today I pulled the cylinder off and added some Hondabond to the gasket to see if that will fix that leak. It was in a specific spot, so I'm hoping that will be enough to fix it. If not.....maybe I need to double up on the gasket?

I run a very small amount of premix (100:1?) and monitor the injector oil reservoir in my old 2-strokes to be sure they are pumping oil.

That sounds like a great idea.

Also, if you put in a new ring did you gap it? Many times they are too tight and the ends need to be opened up.

Once every thing is right, then worry about jetting and stay on the rich side.

I didn't (the manual didn't mention it) but once they were on there, they seemed to fit fine. The piston appears to move through the cylinder just fine too.

Tomorrow I plan on taking a second look at my oil lines and see if I can't bleed them a bit better. The line from the oil tank is good to go.....solid blue oil ll the way through, but the line from the pump to the block has the occasional small bubble running through it.

Thanks for all the advice. I'll report back tomorrow.

Share this post


Link to post
Share on other sites
how much compression does it have?

Haven't measured it, but it feels good according to the ol' thumb over the plug hole test. :thumbsup: I'll try and test it once I make sure my leak is fixed.

Share this post


Link to post
Share on other sites

Okay, compression was a hair above spec.

I did get her to run again though. After fixing the leak at the cylinder, and switching back to premix, I still couldn't get her to fire up. Took the carb off and had a look. Everything looked great. Put it back on and was messing with the idle adjusting screw, and realized that the air adjusting screw was turned all the way in. oops...not sure how that happened, but once I backed it out a turn or two, it started right up. I left the idle screw at 1 3/4 out from closed, and adjusted the air screw till it is idling at a good speed.

Now, it seems that when I give it any throttle above say a third or half, it bogs and dies. If I pull the plug it's wet, and there is also some black oily stuff coming out of the tailpipe. Is this the point where I need to start rejetting? Am I too rich?

I have the oil injection hooked back up and it seems to be working okay, but I have left the premix in the tank for now. Any advice on what I should do there? Finish the tank? Drain it and and run something like 100 to 1 like was suggested?

Thanks again guys......I appreciate the patience and help.

Share this post


Link to post
Share on other sites

I would finish the tank, maybe dilute it with some regular gas. It won't hurt anything until it is consumed.

It sounds like you are definitely too rich, probably on the main jet. I would take the top off of the carb and take the needle out of the slide. Take the little clip off (in a safe location in case you drop it) and put it back in a slot or two higher on the needle. Reassemble and test run. This will lower the needle and give you less gas at medium throttle settings. If this does not do enough, you can take the main jet to a bike shop and get one a size smaller. They are around $5 for the common ones.

Share this post


Link to post
Share on other sites
I would finish the tank, maybe dilute it with some regular gas. It won't hurt anything until it is consumed.

It sounds like you are definitely too rich, probably on the main jet. I would take the top off of the carb and take the needle out of the slide. Take the little clip off (in a safe location in case you drop it) and put it back in a slot or two higher on the needle. Reassemble and test run. This will lower the needle and give you less gas at medium throttle settings. If this does not do enough, you can take the main jet to a bike shop and get one a size smaller. They are around $5 for the common ones.

I should be paying you, GSA. :thumbsup: I moved the clip up to the top notch on the needle, and whadda ya know.....it runs.....and well. Of course, I can only get it to second gear on my backyard sidewalk, but I can rev it sky high in neutral and zero bogging. Hopefully I can do some test riding tomorrow after my appt at the dmv to try and get this thing titled/registered.

One note.....I still have some black liquid coming out of the end of the pipe. What kind of indication could that be?

Share this post


Link to post
Share on other sites

Some "spooge" is normal on a 2T, especially if its running rich. It should slow down to almost nothing as you close in on the proper jetting. It is just oil residue.

Happy to help. It took me awhile to figure these carbs out.

Share this post


Link to post
Share on other sites

Create an account or sign in to comment

You need to be a member in order to leave a comment

Reply with:

Sign in to follow this  

×