Hello All,
Newbie here looking for some insight. I was practically given a Big Daddy 260 last year. I took it home cleaned out gas tank, installed new plug and fuel filter along with a new fuel pump. this thing suprised me how well it ran with the exception of the reverse limiter is too sensitive. I realized one day that there was water in the oil and I was low on coolant. Thinking it was a head gasket I parked it and ordered a complete gasket set. My son and I pulled it apart taking care to bring it to top dead center and zip tieing the cam gear and kept slight tension on it while removing the head and cylinder, removed all the old gaskets until spotless (son hated that part) reinstalled cylinder and head, torqued to spec and finished with remaining components. As I had hoped it started and idled beautifully until.... I hit the accelerator and it feels like it is misfiring until the rpm gets to (my estimation) 1300 rpm then it feels like it catches up and runs like a striped ape. I have adjusted the timing from point to point of just missing the valves but to no avail.

I thought possibly that in the process of reinstalling the cylinder we may have spun the rings to where they matched rather than opposing. I pulled the head back off and inspected it, found there was a broken primary intake spring, and the rings were fine. I ordered a set of valves and springs with another head gasket set (fortunately all cheap purchases) installed valves and springs, cylinder and head, bolted everything back on and guess what....Same doggon thing, no change.

I tend to compare the performance issue to a carburated engine that has a bad accelerator pump or a bad vacuum advance. So I pulled carb off cleaned it and checked accelerator pump and it was fine, reinstalled and yep you guessed it....no change.

I am no stranger to combustion engines as I run an auto repair shop but do not have alot of experience in the small engine repair albiet it is a 4 stroke. Any Suggestions??

Thanks in advance

 

Checked for vacuum leaks?

 

Yes many times. While running I sprayed with carb spray around carb and coupler. No change in idle.

 

Running rich on idle. You may have to retune your carb. Use the idle/air screw to bring up the rpm to a fast idle. Then use your mixture screw and turn it out until the idle does not increase anymore. Then turn the screw back in until the idle does not drop any more. Turn it back out till the idle does not increase again then back off 1/2 - 1/4 turn. If your count is not close then start over. Then you can turn your idle back to normal.
Only their thing I can think of is your coil is not putting out a hot enough spark until the rpm climb up.

My little 110 does the same if I let it sit and idle to long it will load up and bog out until I get rpm up. To lazy to adjust