Faster in reverse?

[tew45]

I did not get a new cylinder but So far all specifications listed call for compression of 80 and 85 even when new. I thought it may have something to do with the loop ports but the piston still goes up and down no matter which way it is running. There might be a difference of engine speed between forward and reverse for some reason I have no way of measuring cranking speed. I also thought there might be a difference in volume of fuel mixture that is pulled in by crank case pressure from F to R. Does the other two cycle carts have the same type of difference in compression?

[mb523]

My 2-stroke ezgo had different compression readings from F to R when my rings were cracked and the jug was worn. It was a huge difference though.

With a new piston, jug, and rings, forward seems to be the same as reverse. When broken in, I think I had 130 in both F and R. I will check for ya and let ya know.

It is possible that, being the old cylinder, the rings aren't sealing in F as well as they are in R due to some wear. Seems minimal though.

[tew45]

I have been working with the Harley cart the last two week ends and have noticed another symptom of faster in reverse. It must be the configuration of the two cycle engine for it seems ( with the spark plug removed ) the engine turns faster using the starter in reverse than in forward and in the start mode I don't know if the charging circuit is a factor or not but I an inclined to believe the charging circuit is not a factor during starting. I will check the circuit diagram to see if there is a factor during starting. Again I believe that I still do not know exactly it runs faster in reverse!!!!!!!!!

[rod1bmf]

Okay I have been following this thread. And I have the same problem. I have two of these units Harley-Davidson 3-wheel. From my experience I believe it charges as forward and reverse that is why there is so many wires coming off of the backward forward lever switch. I have replaced the carburetor I have replaced the piston and jug I have replaced the seals the gas does not have any ethanol in it and still runs much faster in reverse then forward did anybody come up with a solid answer for this yet

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[tew45]

I think we found that the engine will turn faster in reverse due to the piston offset causing less friction. That is the only difference found other than the fuel loop scavenge port. The engine will start running faster in reverse but only for a limited speed. All this assuming the timing and compression is in good order

[sho305]

Could have to do with how the rod moves in the crank case, it can affect what the air charge in there does possibly how it goes into the transfer ports.

When I had a G1 yamaha I did advance the timing, it did retard reverse and slow it down, but faster in forward. Still timing has nothing to do with cranking compression.

[tew45]

Probably not. the only difference is piston pin offset! Compression should be the same after run time on new rings or top end.