180jota

Is it possible to convert four strokes from glow to gas? Does the conversion involve more than machining the head for a spark plug, and adding an ignition unit and trigger? Are some engines more suited for this conversion than others? Newbie.

Big_Bird

My Feedback: (1)

Welcome to RCU.

Yes some of the 4 stroke engines can be converted to gas. CH Electronics has the stuff needed. Since gas engines run hotter than glow engines you may have a problem keeping the engine cool. You need to get more specific on the engine to get a better answer. Usually the larger engines are easier to convert such as 1.2 cu-in and up.

Ken

http://www.ch-ignitions.com/

w8ye

My Feedback: (16)

The head does not have to be machined for a spark plug. C-H has 1/4-32 spark plugs.

With gasoline. the needle valve is so sensitive, its difficult to set.

You have to run a lot more oil with the gas than you do when using a Homelite or Poulan because there are no needle bearings in the rod.

The neatest thing I've seen is a glow four stroke converted to ignition, but continue to run glow fuel in it. It gives you an engine that will just tick tick over at idle.

Enjoy,

Jim

180jota

I'd like to run a Laser 200 V Twin on gas. I guess what I'm most curious about is whether or not the engine would have to be modified mechanically in addition to the ignition changes. For example, is the compression ratio of an engine designed for glow also suitable for gas? Any changes to the combustion chamber? What about seals? Can I use the same carburetor? With or without modification?

oslim

Re Laser 200 V twin: Comments from Big Bird & W8ye will apply. Guessing you will need two ignition modules & two Hall-Effect sensors & twice the ignition battery capacity to fire two plugs per cycle. You may want to ask CH-Ignitions whether you would need two separate batteries to supply two modules firing on the same engine.

tkg

My Feedback: (1)

It would cost something in the neighborhood of $500 to convert to gas.
1. 2ea CH ingiions @$170 ea
2. Custom needle valve and needle valve body, finer threads and longer taper
3. Custom throttle barrel, you need a barrel groove that is sorta like expo. Leaner in the mid range
4. An oiling system for the lower end, remember that these engines are lubed by blowby fron the cylinder. The only oil in the bottom end carried by the blowby. You will burn about %50 less fuel using gas sooo the lower end gets less oil. And you now need an oiling system.

180jota

Thanks, all. The ignition stuff I'm not worried about. Carb work sounds do-able, but sketchy. How do ya know exactly how much modification is required in order to effect the change from a 7 or 8:1 A/F ratio to 13 or 14:1? Oiling-wise I can cobble something together, although I'd be happier with a needle bearing big end on the con rod. What about compression? Are glow engines built with a different compression ratio than gas?

tkg

My Feedback: (1)

Compression is not a problem, you will have controlled spark timing so you can control detonation. The longer taper and the finer threads
are to make the needle less sensitive. Most twin needle glow carbs can be set lean enough at idle and full throttle, but the groove in the throttle is a straight line. So you need to make a barrel with a curved groove in it so that barrel turns it does not open the main fuel inlet as far in the middle and this will make it lean enough. Both the high and low would be stock placemnt on the groove. Its a matter of cut and paste. Last one I did took about 7 tries to get it right.
Have the crank pin checked for hardness, its needs to be 60 rockwell to run needles on, most pins for bushed engines are in the 30 range