As regards to the Bowman ring deal, I have yet to see an engine that didn't respond with more power when equipped with one of his rings. As you mentioned, ring seal is dependant on many factors. Frank's rings seem to seal better under a variety of conditions (and piston positions apparently.) A good leak down test at TDC doesn't necessarily mean that the ring is sealing well for the entire power stroke as your tests have already shown. Once again, just speaking from actual experience, a Frank Bowman ring is just about guaranteed to add some power, especially to a used engine, given that the bore is good enough to seal any ring at all.
I am sure this is true to some point but if you dont have a leakdown test before and after you will never know for sure. there is a gain in power indicator but its still nice to have hard core numbers.
If you read through the posts again where i did my leakdown tests you will see where i rotated the prop under pressure and could see the condition of the seal all the way through the stroke. remeber i was saying on my first cylinder that the best spot was at TDC but far worse everywhere else?
As far as th adapter that i used if you look at it in the pictures it is an adapter off of a compression testor i had on hand already. it just so happened the quick change end already fit a air chuck i got at harbor frieght.
I was prepared to make an adapter by welding an air chuck fitting to a spark plug after knocking all the ceramic out.
I looked in the plug hole and found that the cylinder has two transfer ports per side. So, from all the experimenting, this cylinder should respond to exhaust port modification. Am I correct on this assumption? Also, from what has been determined. lowering the cylinder by going to a thinner gasket should help some. I found the original gasket to be around .030" thick. I cut a new gasket that is around .015" thick. This should give a slight performance increase, correct?. I have already went to a 11.1mm carb on mine. Another thing that seems to help is a more free flowing muffler. I used the stock muffler with some of the guts removed. I put a single 1/2" id outlet which may not be enough to get the most performance. Has anyone used a Wackerengines muffler on their conversion? If so, what are your thoughts on this muffler? Did anybody modify the stock muffler? If so, what did you do and how did you do it?
If anyone is interested, a guy on Ebay has numerous parts for the Ryobi including a complete gasket kit for the engine. The price isn't too bad especially if you can make a good offer. I got a complete kit from him a while back for around $12 shipped. This is what I used as a pattern to cut a new and thinner base gasket.
What kind of adapter was used in the plug hole for the leak down test and where can it be found?
Thanks
I have not had any power gains on this mod but i havent worked on this cylinder set up so far. others on here have and i do belive them. you are correct on the gasket. again be very carfull you dont get piston to head interferance as some engines do some dont .
there is a procedure somewhere to put some solder in the cylinder and smash it with the piston to see how thick this area is. be sure to do this over the wrist pin or the reading wont be right.
On the muffler aftermarket or modified stock the key seems to be as much flow as possible. it is very possible to modify a stock on as it has been done here with much sucsess. the aftermarket ones are lighter and look neater though but a modified stock one will work just as good.
as far as gaskets i just buy then at the local engine shop they are pretty cheap really and i dont think i pay that much for the three gaskets i use carb, backplate and exhaust dosent add up to five bucks where i get them.
I think it is fair to say that you dont need to spend alot of money to make a good running ryobi. there really isnt any aftermarket parts for sale that i have seen that produce anymore power than a good well put together stock setup with a modified muffler and a larger carb. sure an electronic ignition is nice as it stats better and idles better and is lighter but a stock one gives just as good performance.
I cant remeber Av8tor what cylinder are you using as I rember you had gains in the exshaust mod to?