Hello everybody,
Last weekend I decided it was time to bring back to life an engine I had bought a long time ago; a Homelite 30cc (has a big carb and homemade muffler, but everything else is stock, as far as I know). I shelved it for several reasons, without even giving it a run. So I put fresh fuel on the tank, installed a cone (so I could ease the start by using my drill instead of a stick) and gave it a try.



The tank was at almost at the same level of the carb, and the tubes lines were direct. The fuel could get to the carb without restrictions. I had opened the carb and it looked like new. To make sure the ignition was OK, I unscrewed the plug (almost new) and made it spark outside of the engine. With the stick it required a strong hit to make a nice spark, but with the drill it worked very clearly. Deep Purple’s “Space Truckin’” (made in Japan version, obviously) was roaring from the speakers on the other side of the workshop. The clouds gathered to create a rain storm, and the wind whistled while dancing with the leaves. The situation seemed just ideal to make an engine fire up.
Yet, after many random explosions, the best I could get was a few seconds of noise at a about 10-15% top rpm with the starter an butterfly closed, after priming it and giving it a good spin. High and Low needles started at 1-1.5 turns, but I changed that to see if it improved anything (it didn’t). Definitely, something was wrong, but I had other stuff to do so I decided to work later on it.
After thinking of it, I believe I found the main reasons why it didn’t work properly.
First, and I’m almost ashamed to say this, after looking at several pics of similar carbs, I believe I reversed the pulse and fuel connections; I connected the tank (blue line) to the pressure port and plugged the fuel intake (green cross). I wasn’t sure which was the right port, so I looked carefully and saw that priming the engine trough the current port (blue line) would make the carb pour the fuel through the small holes on the venturi. I guess I was wrong… I just hope I didn’t break or bend anything (should I check the needle valve lever height in the carb, perhaps?).



Second, I don’t see any pressure lines going to the carb, so it can pump the fuel to the engine. Perhaps such connection is done through the carb spacer, I don’t recall if my engine worked that way (I’ll check when I get to my workshop).
There’s a hole indeed, I don’t know for which reason (perhaps to make staring easier?), in the middle of the block. I plan to close it with a headless screw and some glue to fill the gaps, unless I hear of a better idea.



My theory is that the engine ran shortly on the primed fuel, as it wasn’t able to get enough (if any) fuel to keep running - because of the possible lack of pumping and wrong fuel piping. But even then, shouldn’t a primed engine start effortlessly?
Just to make sure I’m pointing in the right direction,
[ul][*] I have to reverse the piping connections.[*] I should use a high temp rated epoxy to install the nipple, and plug the hole.[*] If there’s no pulse port throught the carb spacer, I’ll have to drill a hole in the crankcase, epoxy a nipple to it and connect that to the carb (as you see in the pic). By the way, is there a preferred place to make that hole?
[/ul]




I would like to try a few things on this engine, as it’s my first gasser, but I must make sure it works flawlessly first, so any help will be welcome. [&:]
Have fun!

close the blue line. It is for the carb priming bulb.
the green cross is the fuel suction line that goes to the tank (with felt clunk inside the tank)
Do not connect anything else to this line.
The tank also needs one fill line, plugged when not in use
and one vent line, always open.

Thanks pe reivers!
I forgot to mention the tank had two lines; the one with the weighted end headed straight to the carb (well, I had a gas filter in between), and the other was plugged (used only for refilling). Now I realise that, without the vent line, if I had ran the engine for a long time it would struggle to suck fuel beyond a certain point. [:@]

Instead of making a 3rd hole, can I just unplug the 2nd line and refill throught it when I need it? Also, is there an "elegant" way to make the vent line, so that fuel won't spill when you do certain maneuvers?

Install a T fitting in the carb fuel line. Fill there, plug for flight, leave vent open.
Simple answer for vent line is to wrap the vent line one loop around the fuel tank then out. OR make a loop in the line that goes above the tank.

Terry,
a T-line in the carb fuel line is a constant source of trouble. It is all too easy to introduce lint or other debris 9from your wiping cloth etc) into the carb screen.

Hi again!
I couldn't work on the engine, but I've been able to solve a couple of things. [&:]
The engine DOES have a working pulse hole. Right under the intake port there's a hole, which is routed through the carb spacer and then goes into the carb (small hole between throttle arm and intake nipple, the other one near "mexico" is closed).



I found how to tap the hole in this link. The hole is 4.22mm wide; I'm a bit worried that there might not be enough thickness to make the same 10-32 tap (~5mm), but if it worked for them, it should work here too. Regarding the set screw, they're chromed and have a small chamfer at the end. Is it a good idea to grind the end straight, or it's just unnecesary work (or even worse, making it easier for the coating to come off)?



As for the carb spacer, if I got it right, it must match exactly the shape of the intake port and the diameter of the carb (mine is around ~15.88mm on the engine side, and has a 12.7mm venturi), isn't it?
Would be of any help to smooth the path along the spacer?



Again, I'm sorry if I'm making dumb questions or being too picky, I've never "played" with engines at this level and I'm not familiar with things. [:'(]
See you!

Success! [&:] After some efforts and sweating, it started and ran for a few minutes. I'm glad I was wearing my headphones, it is incredibly LOUD! [X(]
It needs a full needle adjustment (it only worked with 50% throttle or more and reacted very slowly to input), but I was able to create a blue smog cloud in the workshop.
I hope to have more time next weekend to do the basic stuff (plug the hole & enlarge the spacer) and measure rpm after each change (my device was unable to "see" the prop).
Thanks guys!