Holy compression!
- Thread starter Wags
- Start date
- Status
Wags
Active Member
- Local time
- 7:10 AM
- Joined
- Aug 26, 2016
- Messages
- 196
Here's the other thing. The arrow reed valve and all the material I had to remove from my tranfers to get them to match, not to mention the Boost port material that was removed had to be made up in the crank case. I stuffed around the bearings to make up for that loss. Besides the ability to pump more fuel into the combustion chamber, I wonder how much extra compresion comes from that modification? I am not good at trig and most of the formulas I read about that could give me an idea, had to many variables.
Here's a silly question...how do i know if I have detonation? Besides looking at the edges of the piston. Are there identifying sounds? My spark plug is the perfect light chocolate color.
Here's a silly question...how do i know if I have detonation? Besides looking at the edges of the piston. Are there identifying sounds? My spark plug is the perfect light chocolate color.
D
Deleted member 12676
Guest
I once had detonation at 155psi and slightly lean jetting. It happened when carrying around a pal of mine on my 100cc street Suzuki. I didn't hear anything so if there's anything to hear it's very slight. Left a crater in the middle of the piston. So I retarded the ignition and richened the jetting. Eventually I reduced the compression to 135psi because the engine was getting too hot.
Stuffing the crank a little still isn't going to make up for all the space that the arrow adds (since its set back from the cylinder).
Wags, what exactly did you do to the crank to true it? What exactly did you do to the conrod?
Isn't it wonderful to have a smooth ride? No one believes me when I tell them. They have to experience it to believe it.
There are even people on this forum that fight against any efforts to balance the engine because some professor on a video said it was impossible to completely balance a 2 stroke (which is true). But it is possible to balance it till all you feel is a slight tingling and you can see what's in your mirror.
Stuffing the crank a little still isn't going to make up for all the space that the arrow adds (since its set back from the cylinder).
Wags, what exactly did you do to the crank to true it? What exactly did you do to the conrod?
Isn't it wonderful to have a smooth ride? No one believes me when I tell them. They have to experience it to believe it.
There are even people on this forum that fight against any efforts to balance the engine because some professor on a video said it was impossible to completely balance a 2 stroke (which is true). But it is possible to balance it till all you feel is a slight tingling and you can see what's in your mirror.
Wags
Active Member
- Local time
- 7:10 AM
- Joined
- Aug 26, 2016
- Messages
- 196
I took the crank to my local motorcycle and snowmobile mom and pop shop where I know the owner. I asked if he could ballence the crank and he explained exactly how expensive a balancing machine is and it's not something he has to do. But he told me he could make sure the crank shaft was true. He took his time and it is now perfect. as for the conecting rod I took my dremel and smoothed all the flash and rough spots only around the upper rod and around the outside of where the wrist pin goes through making sure not to compromise the structure. It was hard to measure the actual weight removed but after pivoting the upper on my digital scale through the hole process I removed about 1.73 grams. That number is in reference to nothing. Just a number I started with in case I need to do it again or remove more. Dumb luck.
D
Deleted member 12676
Guest
nice work. looks better than mine. 
Steve Best
Well-Known Member
First of all, Maxima Castor927 is not a synthetic. Exact opposite. It is castor bean oil.
Excellent stuff. I am using it right now on my motorized 48cc bike.
I find the more you use of it, the better it works, due to the sealing effect I'd guess. I'm using 24:1.
Messy black drippings but very little smoke and goes like hell. Better than the Motul 800 synthetic 40:1.
Cylinder walls are holding perfect. Subjectively less wear evident than the synthetic. Great for sloppy tolerance motors.
Wags, if you don't believe in the value of squish bands, just keep adding headgaskets to lower the compression pressure. My testing (and I am a die-hard Jennings follower) has shown that squish is needed to keep detonation at bay in these engines, so I like to keep 0.5mm to 1.5mm squish and about 20%-50% area in the head. Chamber shape, squish slope and other things enter into it too. No simple answer. Try adding another or a thicker headgasket and see where it takes you. Otherwise machine the cylinder head chamber bowl out larger.
Another approach is to raise the cylinder with more base gaskets (and lower the head if need be). Raising the exhaust port will lower the compression pressure somewhat and move the powerband to a higher rpm.
If you like the way the engine works now, open up the chamber bowl.
Compression favours low rpm power only (especially on a piped 2 stroke) and throws heat into the piston like crazy. It is hard on chrome, wristpin and big end bearings.
Excellent stuff. I am using it right now on my motorized 48cc bike.
I find the more you use of it, the better it works, due to the sealing effect I'd guess. I'm using 24:1.
Messy black drippings but very little smoke and goes like hell. Better than the Motul 800 synthetic 40:1.
Cylinder walls are holding perfect. Subjectively less wear evident than the synthetic. Great for sloppy tolerance motors.
Wags, if you don't believe in the value of squish bands, just keep adding headgaskets to lower the compression pressure. My testing (and I am a die-hard Jennings follower) has shown that squish is needed to keep detonation at bay in these engines, so I like to keep 0.5mm to 1.5mm squish and about 20%-50% area in the head. Chamber shape, squish slope and other things enter into it too. No simple answer. Try adding another or a thicker headgasket and see where it takes you. Otherwise machine the cylinder head chamber bowl out larger.
Another approach is to raise the cylinder with more base gaskets (and lower the head if need be). Raising the exhaust port will lower the compression pressure somewhat and move the powerband to a higher rpm.
If you like the way the engine works now, open up the chamber bowl.
Compression favours low rpm power only (especially on a piped 2 stroke) and throws heat into the piston like crazy. It is hard on chrome, wristpin and big end bearings.
Last edited:
Wags
Active Member
- Local time
- 7:10 AM
- Joined
- Aug 26, 2016
- Messages
- 196
I have excellent power right now and I'm thinking some it has to be so to the squish band. I'm going to try the next size up copper head gasket I have and see where that takes me. Oh, and I didn't even look at the castor bottle for the word synthetic. That's just what I was told when it was sold to me for high revving engines. Good to know before I looked like an even further jackass.
- Status
