PNO_in_Cali
New Member
Hello all!!
Long time lurker but first time poster. Decided to try a final attempt and ask for your help before going to the mechanic ($$$!)
I picked up this CB200 in Massachusetts for $200, title-less and rusty. Brought it along to CA in the back of my car a few years ago and took apart the top-end to have the cylinders re-borred. Rebuilt the motor outside in the back yard under a tarp following the Haynes manual using no torque wrenches or any serious micro-measuring tools and got the thing idling nice at a steady 1200RPM in about an afternoon. No problems. Rode it around the west-side of LA for a year. Until the old coil crapped out.
Now that I live above my own garage workshop, I figured i could take a few months to redo the electrical system. So I got one of the solid-state batteries, a new coil, and while I was at it, changed the aesthetics of the bike, which I am really happy with. While I was at it, I had the motor out to repaint the frame and so I decided to have the valves lapped. Now that I have the right tools, I measured the valve-stem to guide clearances and everything checked out within spec (although borderline). Added new valve seals. The newer pistons and rings that I installed the previous year all checked out, the cylinder is smooth and still has the score marks from the honing. Nice. I assembled the motor and checked compression with my crappy compression measuring tool. When it was running it registered 100psi on both sides. Now I had 90psi. Weird. Realized that the new headgasket (with copper spray coating applied) was upside down(textured side was down and not up). So I flipped it, and using my new torque wrench, went to 20lbs-ft instead of the recommended 16lbs-ft of torque on the column-compression nuts on the head-cover. Compression reading using the crappy meter is now 120PSI. Thumb is blown off the hole every cycle.
Now I have a shiny smooth frame, shiny polished motor, new seat cover, dropped handlebars, chopped rear fender, new LED-taillight.. Can't wait to get it out again! set the carbs to the recommended specs in the Haynes. Here is where the trouble starts!
Thanks to the new coil and improved compression, the bike will start up right on the first kick. No choke. The idle will die once the motor warms up. You can take it around the block and as far and fast as you want if the throttle is open, but as soon as you start slowing down you can tell that it wants to die and it always does. In addition, smoke is pouring out one of the exhausts. Filled my garage up with it quick leaving me light headed. It is gray/whiteish. not black. Plugs are filthy black. The air-mixture screw seems to do very little. Air boxes off also result in no improvement. It will idle normally if I have the idle-screws set in pretty deep. Probably around the 1 turn out mark or deeper. I believe that this state is being driven by the main jet, not the pilot. The jets are clean and I check them often.
More observations: With the idle screws turned in deep, turning off the petcock while the bike is running will result in a sharp increase in rev'ing as the gas in the bowls is consumed and is dropping. If I turn the idle screws out at this point, then I can get it to idle nicely once more. but then turning the petcock back on results in the engine cutting out. I've started trying to limit the amount of gas that flows into the carbs in order to maintain a lower gas level by adjusting the float level, but I haven't really characterized this very well. From what I can tell, the smoke level has improved dramatically if I do this, but I still can't get around the block without the motor cutting out at lower RPMs. As long as the petcock is not on, I can run the bike on one cylinder at a time and do those adjustments, but turning the petcock back on makes all those adjustments somehow irrelevant once more.
Theories: 1. The added compression that I created is pulling too much gas out of the stock pilot jet. I need a smaller jet. These are hard to find for these old carbs. 2. oil is flowing past the valves on the smoky side of the bike.
Solutions: 1. Release the compression on the head a little bit. 2. Try new aftermarket carbs that will let me try different jet sizes. 3. get new valves and valveguides and springs from Kibblewhite (I believe their 175 valves will fit a CB200, no?). 4. I've also thought about switching the idle jets from one carb to the other to see if the smokyness switches to the other side.
Now I open the discussion to you all. What do you think?
Thanks for reading!!!
Long time lurker but first time poster. Decided to try a final attempt and ask for your help before going to the mechanic ($$$!)
I picked up this CB200 in Massachusetts for $200, title-less and rusty. Brought it along to CA in the back of my car a few years ago and took apart the top-end to have the cylinders re-borred. Rebuilt the motor outside in the back yard under a tarp following the Haynes manual using no torque wrenches or any serious micro-measuring tools and got the thing idling nice at a steady 1200RPM in about an afternoon. No problems. Rode it around the west-side of LA for a year. Until the old coil crapped out.
Now that I live above my own garage workshop, I figured i could take a few months to redo the electrical system. So I got one of the solid-state batteries, a new coil, and while I was at it, changed the aesthetics of the bike, which I am really happy with. While I was at it, I had the motor out to repaint the frame and so I decided to have the valves lapped. Now that I have the right tools, I measured the valve-stem to guide clearances and everything checked out within spec (although borderline). Added new valve seals. The newer pistons and rings that I installed the previous year all checked out, the cylinder is smooth and still has the score marks from the honing. Nice. I assembled the motor and checked compression with my crappy compression measuring tool. When it was running it registered 100psi on both sides. Now I had 90psi. Weird. Realized that the new headgasket (with copper spray coating applied) was upside down(textured side was down and not up). So I flipped it, and using my new torque wrench, went to 20lbs-ft instead of the recommended 16lbs-ft of torque on the column-compression nuts on the head-cover. Compression reading using the crappy meter is now 120PSI. Thumb is blown off the hole every cycle.
Now I have a shiny smooth frame, shiny polished motor, new seat cover, dropped handlebars, chopped rear fender, new LED-taillight.. Can't wait to get it out again! set the carbs to the recommended specs in the Haynes. Here is where the trouble starts!
Thanks to the new coil and improved compression, the bike will start up right on the first kick. No choke. The idle will die once the motor warms up. You can take it around the block and as far and fast as you want if the throttle is open, but as soon as you start slowing down you can tell that it wants to die and it always does. In addition, smoke is pouring out one of the exhausts. Filled my garage up with it quick leaving me light headed. It is gray/whiteish. not black. Plugs are filthy black. The air-mixture screw seems to do very little. Air boxes off also result in no improvement. It will idle normally if I have the idle-screws set in pretty deep. Probably around the 1 turn out mark or deeper. I believe that this state is being driven by the main jet, not the pilot. The jets are clean and I check them often.
More observations: With the idle screws turned in deep, turning off the petcock while the bike is running will result in a sharp increase in rev'ing as the gas in the bowls is consumed and is dropping. If I turn the idle screws out at this point, then I can get it to idle nicely once more. but then turning the petcock back on results in the engine cutting out. I've started trying to limit the amount of gas that flows into the carbs in order to maintain a lower gas level by adjusting the float level, but I haven't really characterized this very well. From what I can tell, the smoke level has improved dramatically if I do this, but I still can't get around the block without the motor cutting out at lower RPMs. As long as the petcock is not on, I can run the bike on one cylinder at a time and do those adjustments, but turning the petcock back on makes all those adjustments somehow irrelevant once more.
Theories: 1. The added compression that I created is pulling too much gas out of the stock pilot jet. I need a smaller jet. These are hard to find for these old carbs. 2. oil is flowing past the valves on the smoky side of the bike.
Solutions: 1. Release the compression on the head a little bit. 2. Try new aftermarket carbs that will let me try different jet sizes. 3. get new valves and valveguides and springs from Kibblewhite (I believe their 175 valves will fit a CB200, no?). 4. I've also thought about switching the idle jets from one carb to the other to see if the smokyness switches to the other side.
Now I open the discussion to you all. What do you think?
Thanks for reading!!!
