alec.korver
Been Around the Block
Okay so I have been working on my cb200 engine for quite some time and it is still giving me headaches.
So far I bored it over by .25 and installed new pistons and rings. It was also honed. I installed new valves and lapped them in. I did the kerosene test on them and they do not leak. New gaskets all on the top end, and the surfaces for the gaskets were all refinished.
The problem I am having is low compression. I checked my compression and it is 120psi in each cylinder wet/cold, engine removed from bike with no carbs.
So I tried to isolate the problem. I did a leak down test at TDC and I don't have any leaks to speak of anywhere. The valves all seal correctly, there is no hissing into the crankcase, and their is no air escaping at the gasket.
I have tested my compression tester on my other engine "cb175" and that engine reads about 135/140psi per cylinder. *it has not had a rebuild*
At this point it was seeming as if it was not generating the compression to begin with. I retested it, this time I squirted oil into the cylinders, and I had a HUGE compression increase. I had about 210psi per cylinder... Probably too much oil....
The rings are offset by the recommended angles, and the pistons and ring clearances from the cylinders are all within spec.
Lastly I put some clay/pladough and checked my clearances between my pistons/valve/compression chamber, there seems to be more than ample clearance between everything. Probably close to .5mm - 1mm
Anyways, I am unsure as to how to proceed. I am running stuck and am determining if my next best option is just to mill down the block/head in order to reduce the clearance and increase my compression. Any help/insight would be appreciated
*note: the rings do not seem visibly stuck at all*
*The compression before the rebuild was also poor*
*I have replaced my new rings with another set of new rings and there was still no change*
*tappet clearances and timing were all adjusted to spec*
*The timing is for sure spot on*
So far I bored it over by .25 and installed new pistons and rings. It was also honed. I installed new valves and lapped them in. I did the kerosene test on them and they do not leak. New gaskets all on the top end, and the surfaces for the gaskets were all refinished.
The problem I am having is low compression. I checked my compression and it is 120psi in each cylinder wet/cold, engine removed from bike with no carbs.
So I tried to isolate the problem. I did a leak down test at TDC and I don't have any leaks to speak of anywhere. The valves all seal correctly, there is no hissing into the crankcase, and their is no air escaping at the gasket.
I have tested my compression tester on my other engine "cb175" and that engine reads about 135/140psi per cylinder. *it has not had a rebuild*
At this point it was seeming as if it was not generating the compression to begin with. I retested it, this time I squirted oil into the cylinders, and I had a HUGE compression increase. I had about 210psi per cylinder... Probably too much oil....
The rings are offset by the recommended angles, and the pistons and ring clearances from the cylinders are all within spec.
Lastly I put some clay/pladough and checked my clearances between my pistons/valve/compression chamber, there seems to be more than ample clearance between everything. Probably close to .5mm - 1mm
Anyways, I am unsure as to how to proceed. I am running stuck and am determining if my next best option is just to mill down the block/head in order to reduce the clearance and increase my compression. Any help/insight would be appreciated
*note: the rings do not seem visibly stuck at all*
*The compression before the rebuild was also poor*
*I have replaced my new rings with another set of new rings and there was still no change*
*tappet clearances and timing were all adjusted to spec*
*The timing is for sure spot on*
