Skyliner70cc
Active Member
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- Joined
- Nov 17, 2007
- Messages
- 1,338
I have built many motorized bikes over the past 5 years. I currently have 3 personal builds that ride in my spare time.
I'm amazed by the differences in the engines and their unique personalities. Currently, I have an engine that is just not developing the same amount of power as my other two. Simply put, its a dog but I do ride it a lot because it also happens to be my smoothest running engine and is comfortable, but not fast, on long rides. Luckily, I have a SBP shifter kit that helps a little in trying to extract the most power out of this engine.
Here's what i've done to date:
1. No airleaks in carb, head, head base gasket, or engine cse. I've ruled these out already.
2. Engine broken in as my others and has at least 300 miles This engine has less power than my others before they were broken in. Engine just recently got a new head and new rings. 100 miles on "re-ringed" engine and it runs the same way..weak. The base gasket under the head was partially blocking the ports but replacing it and ensureing it was correctly trimmed did not help much.
3. Added a high compression slant head. Unlike other two engines, no noticeable increase in power although compression is noticeably higher because pedal start is much more difficult.
4. I've done the replacement carb and gasket thing several times. I've got 6 spare carbs from other engines and have tried 3 of them. They all run the same.
5. Tried new CDI, different plugs, swapped magnetos, done about everything under the sun with no improvement. Swapped 4 different mufflers. The one muffler that actually seemed improve things was one with baffle removed. Maybe its the louder sound that makes it feel stronger
My next step is to add a tuned pipe and see if that helps. This bike is a good ride and with the decreased power, it will be reserved for street use and I'll use the other two for trail rides where I really need the torque to climb hills.
Anybody else had an engine like this? Maybe this one is sleeper and is taking much longer for rings to seat. I usually see an incredible amount of power different at the 100 mile mark. Maybe this one will come around at 500 miles but not sure if I'll ever get there. I ride mostly on trails cuz cagers scare me.
I'm amazed by the differences in the engines and their unique personalities. Currently, I have an engine that is just not developing the same amount of power as my other two. Simply put, its a dog but I do ride it a lot because it also happens to be my smoothest running engine and is comfortable, but not fast, on long rides. Luckily, I have a SBP shifter kit that helps a little in trying to extract the most power out of this engine.
Here's what i've done to date:
1. No airleaks in carb, head, head base gasket, or engine cse. I've ruled these out already.
2. Engine broken in as my others and has at least 300 miles This engine has less power than my others before they were broken in. Engine just recently got a new head and new rings. 100 miles on "re-ringed" engine and it runs the same way..weak. The base gasket under the head was partially blocking the ports but replacing it and ensureing it was correctly trimmed did not help much.
3. Added a high compression slant head. Unlike other two engines, no noticeable increase in power although compression is noticeably higher because pedal start is much more difficult.
4. I've done the replacement carb and gasket thing several times. I've got 6 spare carbs from other engines and have tried 3 of them. They all run the same.
5. Tried new CDI, different plugs, swapped magnetos, done about everything under the sun with no improvement. Swapped 4 different mufflers. The one muffler that actually seemed improve things was one with baffle removed. Maybe its the louder sound that makes it feel stronger
My next step is to add a tuned pipe and see if that helps. This bike is a good ride and with the decreased power, it will be reserved for street use and I'll use the other two for trail rides where I really need the torque to climb hills.
Anybody else had an engine like this? Maybe this one is sleeper and is taking much longer for rings to seat. I usually see an incredible amount of power different at the 100 mile mark. Maybe this one will come around at 500 miles but not sure if I'll ever get there. I ride mostly on trails cuz cagers scare me.