Yea we really need some numbers of engines that have the two ring set ups. I dont know if there is a way to tell if it has a single or a double ring engine other than tear it apart. if it is old enough i imagine you can bet its a single ring engine. I am not sure at which point they introduced the double ring.


Ok so I had a chance to work on this again today. I got some very interesting information today.

Heres what I started with. I fabricated a way to find tdc. Basically what I did was take a spark plug and knock out the ceramic. I them bored it out to fit the stub on the end of my cheap but yet works very well harbor frieght dial indicator. I drilled and tapped some holes to put set screws in to hold it all together. It is then screwed into the plug hole on the cylinder head. I then fabricated a degree wheel and pointer. I had a buddy of mine cad it up and i hand drew the numbers. I glued it to a piece of plywood and then sanded it to shape. I then applied a few coats of polyurathane to help protect it.

Ok so you turn the flywheel till the dial indicator stops. note this number. then keep turning. the flywheel will turn a few degrees till the needle starts to move again. when the needle moves again note this number. if you move the flywheel to halfway between these two numbers and then set the degree wheel to TDC 0 degrees then this will be the exact TDC. now you can check port timming.





Ok so once my tdc was established here is what i found for port timming

Exhaust opens at 110 deg and closes at 250 deg for a total of 140 deg exhaust port timming

Intake opens at 115 deg and closes at 245 deg for a total of 130 deg of intake timming.

Ok so after finding my port timming I then marked on the bearing housing and flywheel the TDC and 10, 20. 30 deg marks before and after TDC



So when performing my tests today i also got to see what the timming of the stock ignition is. this si where it gets kind of interesting as the stock ignition is a little more complex than I had thought. I did also confirm that the flywheel and the coil is a macthed set from manufactrere and there is no interghanging them if the crank has different keyway location. When I used the new coil with the old flywheel it was so far advanced I could not read it. If I had to guess I would have to say it was around 50 deg BTC.

When running the engine and using my timming light i found that it had about 20 degrees advance in it at a low rpm. I was increasing the rpm to see if it had a advance curve in it and at one point in the rpm range it changed to 29 deg BTDC. If you throttled it up at a certian point it would shift from 20 to 29 degree advance and back again as throttle was reduced. It was a very pronunced change when it happens. kind of like flipping a switch to a different setting and not like a curve at all. So again I now know what the timming of the ignition is and i now know these stock coils have a little more in them for electronics than i had first thought. I dont think it would do me any good to change the crank and coil setup to the new one to see what it is. I am betting it will be 20-29 degrees or something very close. I know the newer crank is timming retarded on the keyway but so is the coil electronically as I have now proven.

Ok so with all this information I now went to test #7. this is a three part test of the reed vavle.

First test is to use the stock valve with the engine set up just like test 6 to get a baseline rpm for the day.

the first rpm baseline is 7050. 120 rpm less than the last time I tested but it gives us a baseline for today.

The next part of this test is to modify the reed valve by narrowing it by the attatching end. I read about doing this I think on one of crazy herbs sites. its the one in the middle and the one on the left is stock.



Ok when all put together and runn here is what I got

RPM 7410 for a net gain of 360 RPM !!!!!!!

Wow I have got to say I was sure supprised at this improvement. still 240 RPM better than the testing of the other day.

Ok so now i was thinking it would be nice to try cutting a reed out of a thinner shim stock. the stock valve is .006 and while looking at my feeler gauges a .003 valve would really work good in my opinion. I looked for some shim stock and all I could find was a grainger and they sell it in such a quantity that it is not cost affective to me. I need a small bit and they have it in rolls. i think the smallest is 6 inches by 50 inches. its about 14 bucks which is not to bad but i hate to spend that much for a small test. If anyone knows where I can get a small quantity for cheap please let me know.

I was looking at a roll of thin rubber i had in the shop and got to thinking if it would work as a reed valve. I cut one out and tested it to gas. I dont think it is gass proof but it should work long enough for a test. It is the one on the right in the picture. Ok so i installed it in the engine and tried it out. when i tried to start it it would run just a little bit then stop. i could never get it to run. I had figured ok its just to soft and would not work and was about to give up for the day. I decided to go ahead and pull it apart so it would not disentegrate into the engine from the gass and this is what I found.



What I didnt realize is with the rubber when tightening down the reed stopper the end would ip out farthur that with the metal reed valve. What had happened here is the crank hit the reed stopper and turned the whole thing sideways wiping out the locator pins. I put it all back together and used some small screwws to replace the pins and keep it all in place. I then reset the reed stopper and then reassembed the whole thing and ran it.

Rubber reed RPM 7410.

Ok so now the RPM did not improve on this test. I have two thoughts on this. Either i have reached the volumetric efficency end of this set up with the rubber and modified metal valve or the ignition has a rpm limmiter as i had read somewhere else on another post. This is very possible as the RPM was the same. I will have to get my new ignition installed to be able to know this. Again it may bee that the modified reed is as good as it get with the port sizes or the ports just cant possible flow anymore.

With both of the modified reed valves the idle was much improved and could be run very low very reliably. again i think the lesser resriction to the valve allows a higher gas velocity with the larger carb size. at any rate idle is gratly improved with this modification.

I guess the next place to go from here is to rework the intake manifold and bell shape the port on the reed valve end and maybee try to enlarge the intake port some and see if i get even more rpm increase. If I dont i guess then i need my new ignition to see if i can get more and then i will know there is a rpm limiter built into the stock ignition.