Buff CB
New Member
After doing a full rebuild on my 78 CB750F my worst fears are becoming reality. I can't get her to start for anything. Here are the bullet points to help describe what I've done so far.
-Full engine tear down. I've taken everything apart down to the crankcase separated.
-Rebuilt engine using pictures taken during tear down and a Clymer manual
-Took great care to position camshaft in correct timing with points and pistons.
-Carbs were taken off and cleaned by my father who only cleaned two. Those two were in great condition so he didn't touch the other two.
-Stock headers replaced but installed baffle for a shorter exhaust.
That's the build part here are the symptoms
-No burp or cough of any kind just constant cranking using the starter
-Backfires loudly when timing is retarded but nothing when "right on" or advanced.
-There are no pods or filters over the carbs right now but always starting with full choke.
-Double and triple checked that I'm getting spark at TDC when on the compression stoke on piston #1.
-All four plugs spark strongly.
-Have used starting fluid only to get more backfiring
-The engine does get flooded if I go at it too long so I know it's getting gas. It's new gas too.
-I've checked the timing with timing light while starting and it's bang on.
-I've checked the valve clearances all over and they are up to spec.
-I've checked the points clearance and they are also up to spec.
My dad is a hobby mechanic and he and I are both stumped profusely. The one thing I haven't checked yet is the compression due to me not having the right size plug to test it. I will have one next week and will test that as well.
Thanks for any info or insight anyone might have. I've watched this entire riding season go by and it's killing me.
-Full engine tear down. I've taken everything apart down to the crankcase separated.
-Rebuilt engine using pictures taken during tear down and a Clymer manual
-Took great care to position camshaft in correct timing with points and pistons.
-Carbs were taken off and cleaned by my father who only cleaned two. Those two were in great condition so he didn't touch the other two.
-Stock headers replaced but installed baffle for a shorter exhaust.
That's the build part here are the symptoms
-No burp or cough of any kind just constant cranking using the starter
-Backfires loudly when timing is retarded but nothing when "right on" or advanced.
-There are no pods or filters over the carbs right now but always starting with full choke.
-Double and triple checked that I'm getting spark at TDC when on the compression stoke on piston #1.
-All four plugs spark strongly.
-Have used starting fluid only to get more backfiring
-The engine does get flooded if I go at it too long so I know it's getting gas. It's new gas too.
-I've checked the timing with timing light while starting and it's bang on.
-I've checked the valve clearances all over and they are up to spec.
-I've checked the points clearance and they are also up to spec.
My dad is a hobby mechanic and he and I are both stumped profusely. The one thing I haven't checked yet is the compression due to me not having the right size plug to test it. I will have one next week and will test that as well.
Thanks for any info or insight anyone might have. I've watched this entire riding season go by and it's killing me.