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1969 CB450 top end rebuild

1K views 3 replies 3 participants last post by  circling the drain 
#1 ·
Hello forum members, Bob here from Massillon,Oh. I recently did a top end job for a friend on his 1969 CB450, had it bored.025 over and a valve job done at a local machine shop. I did not disassemble the head, I took it complete to the machine shop. This machine shop has done work for me before with no complaints. I got the parts back and installed the top end on the engine, got the timing marks on the cam shafts lined up and the LT mark on the generator in line with the index mark on the stator. I then got the cam chain fished thru the head and installed a new link and pressed back together. It was finally together and ready to start, I hit the button and to my surprise it didn’t start. My surprise was a strange clicking noise instead coming from I believe the head, and it didn’t seem to have any compression. I pulled the plugs and my guess was spot on, no compression! I have no clue what has happened or what has gone wrong. I have done top ends on other bikes with great success so it’s not my first rodeo. I didn’t take the head apart as it looked to complicated for me so the machine shop did it with the shop manual I left with them. Any ideas what may be happening with this top end job gone wrong ?
 
#3 ·
Hello Mike, thanks for your reply, I didn’t order parts for this engine, I was just a wrench on it. Do you think there is a chance on the valve train being put together wrong ? I did notice after I put the cylinder on the pistons just came to the top of the jugs minus the dome, so I figured the pistons were the correct ones. The owner of the bike his family owned a Harley Davidson dealership that the lovely Harley Davidson would not renew their franchise cause they only had 1 dealership so they got shut down ! Anyway I figured he bought the correct pistons. The noise I hear sounds like a valve slamming shut, I heard this noise when I was putting all in time. I am lost what it could be, I did turn engine over with a wrench on the bench before installing into frame, seemed to turn over fine, no issues there ! Totally lost, thanks for any help.
 
#4 ·
The 450 head and cams are not difficult to properly time when reassembling the engine, but the cams can have ghost marks on them that look somewhat like the actual timing marks sometimes and it can be misleading. If the cam timing is off, either on one cam or both, it's highly likely there are bent valves as already mentioned. Regardless the noise, the top end needs to come apart to check the valves. Can't speak to the pistons since no pictures of them were posted. For the next reassembly, you should download the factory service manual
 
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