New guy with a lawnboy

You will have a very hard time getting this thing started,it is my guess around 100cc or more.I did an approximate calculation of how much continuous force it would take at the pedals and came up with something like 150 lbs plus to overcome the compression of the engine, and that was assuming a 6" roller .It would require a down force of at least 80 lbs on the roller to keep it from slipping.Does not look practical to me.With that 6 roller size you would be doing 33mph at 3000rpm.
 
I dont have a recoil. I dont plan on getting one. I got it to turn over. Just need a new carb.
 
Original is a bowl carb. I have a diaphragm tilly, but its old and needs a rebuild kit. I might as well buy a new one.
 
id stick with a bowl type carb for this type of application, diaphram carbs can be a pain in the junk when it comes to varying throttle positions.

you should look into the dellorto replicas (if you have a round manifold to slide it onto) or if you really want to stick with the diaphram the walbro 603.
 
I made a mistake in my calculation (crank dimension is 1/2 of stroke not equal to it!)That changes things somewhat. I takes 100lbs + at the crank to turn the thing and about 50lbs+ roller pressure to keep it from slipping.That is with a 6" roller,more with a smaller one!.You need a compression release,to get going (not feasible on 2 strokes).I should mention also that I assumed a 2:1 ratio between front & rear sprocket,if this was reduced to 1:1, the requirements would be cut in half (or the roller size reduced to 3" from 6)
 
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You need a compression release,to get going (not feasible on 2 strokes).

why isnt it feasable on a 2 stroke? man i have CM cutoff saws at work that have compression relases to start them. i fix them 8/10 times they get rented out because people rip the recoils off them trying to start it without em. and they are only 60cc!
 
You are quite right, a compression release not infeasible in principle on a 2 stroke,that's true,but is rarely seen on lawnmower engines as far as I know.How is it implemented, a spring-loaded valve in the head?.It would appear smart to enlighten your customers about this very nice feature!,IMO.
 
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lol well tell em... they never listen haha

all it is is a little sealed plunger in the side of the cylinder! pretty cool!
 
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