Small Engine help

[Foster]

25cc BVM200VS Poulan Blower Help

So, I spent the evening tearing the motor on this hunk of junk down to piston in one hand and cylinder in the other. I checked everything that I could think of. I was out using it and it died. Thought that it was just out of fuel. Refilled with 40:1 and tried to keep going. It never started again. At fist I thought maybe carb. Sprayed that out. No start. I thought maybe it ate it's piston ring. I never checked compression because I didn't know what it should have been but I opened it up and the cylinder is beautiful. Smooth and no scoring, ring is intact. I thought maybe the spark plug isn't sparking so pulled it, set it on cylinder top and gave it a yank. Spark looks ok. I am at the end of my diagnostic knowledge and I am ready to run out and buy a new blower tonight at home depot. I like fixing small engines but I need to get these leaves up and don't have another night to blow. Anyone have any genius ideas? I looked at some other things but I am a novice tinkerer and could easily have missed something obvious. Feel free to point out stupid things I may have missed here. I thought about getting a new plug and giving that a try but I feel like it might be a waste of money. Thanks in advance guys!

[Bob Morgan]

I have an old chain saw that just won't stop running, however I have had to replace the itty bitty fuel lines twice because they would get hard, crack, and suck air. If you can squirt a little fuel directly into the carb and get it to fire, it might be good to look at the lines.
Just a thought.

[safiri]

Next time, pull on the cord slowly to feel for compression before you tear it down. Can also remove the spark plug, put your thumb over the hole, and pull.

Three things to check, in order of ease for a single cylinder, on all engines:
1. compression. doesn't typically fail quickly.
2. spark. plug can foul slowly, magneto and computer will often fail quickly. Think KTM 105.
3. fuel and air.

If no compression on a small two stroke, then it is probably cheaper to buy a new whatever.

If no spark, inspect spark plug wire. You may be able to remove the plug cap, cut down the wire by 1cm, and replace the cap as sometimes the wire will corrode/degrade up near the cap. Read of this on dirt bikes as well, BTW. Check the on/off switch and the wire(s) running to/from. Make sure the short out wire isn't melted or frayed and shorting.

When you pull the plug, note if it is wet with gas. A short spray of starting fluid (not great on a two stroke, so don't do it a lot) into the plug hole or carb (remove air filter first) and see if you get any firing. If you do you know you have spark and compression and no fuel.

The fuel lines do get brittle. You know when your soda straw has a crack in it and you are trying to slurp up your Dr. Pepper? Yeah, doesn't work. If the lines are translucent, watch to see if fuel is moving through them when you pump the bulb. One pulls fuel from the tank, the other returns excess to the tank. The line out from the tank will have 5 - 15 cm of line in the tank with a weighted filter on the end of it. This allows the fuel to be drawn no matter how you are holding the device. Remove cap and fuel and look in to see it. (Don't use a match for light! )

The small two stroke carbs in chain saws and blowers that I have torn apart have a diaphragm that pumps the gas using engine vacuum. I have had a couple that junk (varnish??) got into the chamber and plugged/blocked/kept needle from seating a passage or two. Thus carb couldn't pump fuel. Remove carefully so as to not tear, inspect diaphragm for tears, clean. Carb cleaner, not brake clean. IIRC, this is on the bottom of the carb. Follow the fuel lines.

All said, go out and buy a new blower. Set the old one aside for a rain day. Then try to fix it. Chances are the new one will fail in the foreseeable future.

For parts I have used this site: http://www.psep.biz/
They ship quickly, have had good prices, etc. The site is kind of clunky. In fact they have a sister site http://www.psep2.biz/pages/OemParts but the Shopping Carts don't combine. In that case I copy both carts into an email and send it with instruction to call for CC info or just call so as to get the $8 / order shipping and not pay twice.

Hope this helps.

[Foster]

Thanks guys.

Bought a new blower and finished yard work.

Then went back to "fixing" the old one. New spark plug did nothing. Starting fluid doesn't do anything. I am thinking I may have terrible compression or an ignition problem. I have a compression tester so I will check that out this week. I stink at electrical so I am hoping it is compression. I will check it out and get back. Thanks for the great info. Even if it doesn't solve my problem I am learning heaps taking this thing apart over and over

I am pretty sure I have a good spark though so I am betting compression. When I ground the spark plug on the top of the cylinder I get a spark when I pull the cord. If compression checks out ok I am going to be lost so hopefully that is the issue. I also thing maybe I actually need to further disassemble the carb to confirm everything is clear but the spark plug is wet so I think I have fuel delivery.

To be honest this is an exercise in 2-stroke education more than fixing the stupid blower. I need more shop time and I figure this is a good chance to get some.