michael whiteman
Well-Known Member
- Local time
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- Joined
- Mar 2, 2021
- Messages
- 899
I did this thinking the 22lb springs rated to 7000rpm was just a little too much for my need. There are two YouTube videos showing 18lb springs in a 79cc engine so I followed along. I know to check for coil bind but got distracted and forgot before final assembly. Anytime you change the valve springs you want to check this before you torque the head in case you might need to remove them.
These 18lb springs are taller and the wire diameter is much larger causing them to bind or what's refered to as "coil stack". With my stock cam at full lift there is NO space between the coils. This is NOT a good thing. It will bend your pushrods and put extreme pressure on your camshaft lobes shortening their life expectancy. I ran my engine this way for 10 miles and detected a different sound never heard before. After that I removed the cover and discovered this issue. All because I neglected to check for coil stack in the beginning.
It's really hard to get truthful answers about performance mods for the little 79cc engine. It seems all this information and the performance parts are directed toward the 212cc engine, and don't believe evrything on YouTube. The guy on DirtGear TV actually had the 18lb springs on his bench with the Honda p/n 1475-883-000 showing. That's what I ordered. He led everyone to believe it's cool, but I know for sure he did not check his springs for binding. I worked in a machine shop and built race car heads so shame on me, but how about the the want-to-be hot rodder that doesn't even know what to look for. This misleading incomplete information is criminal in my opinion.
After two days of research and many phone calls this is what I have found.
Eric from Grey Goat Garage representing OMB Warehouse told me this: We do not offer any springs known to fit the 79cc head.
The good news? The stock springs will get you to 5500 rpms...which is about the same time the stock rod starves for oil and wants to weld itself to the crank!
The Tech Dept. at AGK Racing said this: The 22lb springs have less coils than the 18lb springs and they are shorter. The 22lb springs are closer in length to the stock springs. We always use the 22lb springs in our 79cc builds. They do everything we want them to. They don't coil bind and they don't float the valves at less than 7000 rpm. We've built some 79cc engines with 26lb springs but those were all-out builds. You have to use a welded cam with 26lb springs. We ran our 79cc builds over 8000 rpm with these springs. 18lb springs work in a mild 200cc build, but they are not a good choice for the 79cc engine.
So now my choice is the 22lb springs or add some shims to the stock springs and get them up to 6000rpm. I'll let you know soon.
These 18lb springs are taller and the wire diameter is much larger causing them to bind or what's refered to as "coil stack". With my stock cam at full lift there is NO space between the coils. This is NOT a good thing. It will bend your pushrods and put extreme pressure on your camshaft lobes shortening their life expectancy. I ran my engine this way for 10 miles and detected a different sound never heard before. After that I removed the cover and discovered this issue. All because I neglected to check for coil stack in the beginning.
It's really hard to get truthful answers about performance mods for the little 79cc engine. It seems all this information and the performance parts are directed toward the 212cc engine, and don't believe evrything on YouTube. The guy on DirtGear TV actually had the 18lb springs on his bench with the Honda p/n 1475-883-000 showing. That's what I ordered. He led everyone to believe it's cool, but I know for sure he did not check his springs for binding. I worked in a machine shop and built race car heads so shame on me, but how about the the want-to-be hot rodder that doesn't even know what to look for. This misleading incomplete information is criminal in my opinion.
After two days of research and many phone calls this is what I have found.
Eric from Grey Goat Garage representing OMB Warehouse told me this: We do not offer any springs known to fit the 79cc head.
The good news? The stock springs will get you to 5500 rpms...which is about the same time the stock rod starves for oil and wants to weld itself to the crank!
The Tech Dept. at AGK Racing said this: The 22lb springs have less coils than the 18lb springs and they are shorter. The 22lb springs are closer in length to the stock springs. We always use the 22lb springs in our 79cc builds. They do everything we want them to. They don't coil bind and they don't float the valves at less than 7000 rpm. We've built some 79cc engines with 26lb springs but those were all-out builds. You have to use a welded cam with 26lb springs. We ran our 79cc builds over 8000 rpm with these springs. 18lb springs work in a mild 200cc build, but they are not a good choice for the 79cc engine.
So now my choice is the 22lb springs or add some shims to the stock springs and get them up to 6000rpm. I'll let you know soon.
