Topic: A rebuild is looming; which one? CB650 or CB550? VIDEO ADDED

[Scott S]

 I recently swapped an '82 CB650 engine and carbs into my '72 CB500. Love the relative ease of the swap. The power is amazing. I'm not crazy about the side covers not fitting as well as they should around the carbs. Other than that, no complaints......until.....

 I adjusted the valves/chain on the engine stand and, after about 500-600 miles, did them again. I still have a fair amount of valve train and/or cam chain noise. But that's not the biggest issue.

 A few weeks ago, I noticed that I parked the bike with the petcock in the ON position. Oops...better check the oil and make sure no gas crept by.
 Instead of finding a high oil level, I noticed a LOW oil level. Added nearly a quart if oil (  ) and away we went.

 About 20 miles into our ride, my GF asked what was smoking underneath the bike. Pulled over and checked, only to find the breather tube was blowing a lot of smoke. The bike is an early build CB500 and the breather vents to the atmosphere. No biggie, I thought....I have a little blow by. That explains the oil around the frame and swing arm. Never a lot, and not enough to cause concern. What did cause some concern was a low, knocking noise from the bottom of the engine. Never noticed it before. Doesn't happen when cold.
 Checked the oil today (less than 50 miles since I added that quart) and it's nearly a quart low again! WTF!?!?
 I also noticed that I don't hear the knocking noise now, just  the valve train or cam chain noise. Why would ADDING oil to the proper level cause it to knock?
 And I've NEVER noticed the bike to smoke from the exhaust, never leaks a drop, etc. Can I SERIOUSLY blow by a quart of oil in 50 miles and not notice it anywhere else?!

 So......CB650 rebuild stuff isn't all that available. I thought for half a minute about a 550/650 hybrid but, nah, not quite at my skill set right now.
 A 592cc rebuild on the 550, using a 650 cam, is looking pretty attractive right now. It won't have the power of the stock CB650, probably, but I feel like I could accomplish  this much quicker and easier.

 Thoughts?

 

[Scott S]

 I guess one thing that would help me decide is a diagnosis on the CB650 issues. The bike runs STRONG, doesn't smoke from the exhaust ever, plugs look great, muffler is oil/soot free, etc.
 What does losing THAT much oil from the breather tube point to?

 Machine work will be about the same if I need overbore pistons. Finding them for the 650 can be a challenge.

[kghost]

A lot of blow-by from the engine may have vented the top qt. out the breather.......

[Scott S]

 But why does it show up as low on the dip stick? It's showing almost a quart low now. I even looked at pics of the CB650 dip stick on ebay to make sure no one had swapped mine out!

[iron_worker]

Ha I was just going to suggest you make sure you have the right dipstick. Over filling will definitely cause oil to be blown out.

Are all your crankcase breathers hooked up correctly /not plugged so you're not building up positive crank case pressure somehow?

IW

[Scott S]

 The bike is a '72 CB500 and the breather hose from the engine is vented to the atmosphere.

 I re-read the response from kghost and I see what he's saying now, but wouldn't blow by come out of the exhaust, too? Or is this an indication of a problem with the valves or guides?

 Also, when I checked the oil earlier today, it was after a short ride, with the bike on the centerstand. Just checked it again and it's not as low as I thought. Maybe down some, but not nearly a quart like I thought.

 So.....if I checked it wrong before and overfilled, that would certainly explain the blow by out of the breather, sure....
 But why would that cause a knocking noise (that I don't seem to hear now that the level is back closer to normal)?

 And what about cam chain or valves ticking after an adjustment?

 Maybe I just need to do a leak down test and may get by with valve stem seals and lapping the valves?

[Scott S]

 I'm about to head out the door for work, but I'll see if I can get a video this weekend of the tapping/clicking on the top-end. Heck, it may be normal, for all I know...

[davesee]

i find checking the oil to be tricky on the 650. the manual says to stand it on the centre stand, warm the bike to operating temp, then stop the engine and let it sit for five minutes...then you take your measurement. you can get a lot of variance if you don't do it this way. be aware that you can top up the oil a bit and take a reading with the dipstick right away and it will seem full as the oil running into the case gets on the dipstick. give it about a minute after top up to measure with the dipstick.

[Scott S]

 Here's a video I took this morning. Bike starts right up, warms up quickly and runs well. Goes down the road nicely. The bike is fully warmed up in this video.
 I was hoping to capture the valve/cam chain noise up top, but the lower end noise came through louder in the video. While it's definitely noticeable in real life, the vid makes it sound a little worse than it is. In real life, you can still here the valve train.

 You can see that the bike doesn't smoke or leak anywhere. I didn't notice it smoking from the vent tube anymore. I think I may have overfilled it that day. But what's with the noise?
 Diagnosis?

CB500/650 engine noise

[Scott S]

 I guess if you listen closely you can hear the mechanical whir of the valve train, too. Sound normal?

[iron_worker]

I don't know if I'd classify that as a knock. It sounds more like the bike is "chugging" and causing the chain to whip and/or the clutch to rattle. Have you sync'ed your carbs lately?

IW

[Scott S]

 Yes. Carbs were synched with a vacuum gauge.

[bwaller]

It sounds like it's dieseling a bit to me too as if the butterflies aren't perfectly synched.

Yours is pretty good but I have difficulty with sound of these vid clips. 

[Scott S]

Yes. Carbs were synched with a vacuum gauge.

 I take that back (too many bikes). ... I think I only bench synched these carbs. However, I don't hear this noise when the bike is cold. I don't think....
 You guys have me second guessing myself now.

[Greggo]

That bike is sweet Scott.  What was the breather setup for that 650 motor? 

[iron_worker]

A carb sync is much easier to do than an engine rebuild so I would start there. lol 

IW

[Scott S]

That bike is sweet Scott.  What was the breather setup for that 650 motor? 

 I'm not sure. I assume it was routed to the air box somehow.

 The '71 CB500 just had a hose vented to the atmosphere and that's how it is now.

[Scott S]

A carb sync is much easier to do than an engine rebuild so I would start there. lol 

IW

 Damn skippy! I already have the seat and tank off to access the carbs. I was going to synch them tonight, but since I'm in this far, I'll let it cool down and double check my valve and cam chain adjustments, even though it was just done less than 100 miles ago. I'd kick myself later for not checking them.

[Scott S]

 Looks like you guys may be right. I hope so, anyway...

 Here's a vid from a few minutes ago, followed by one showing the bad synch. Now....how the heck do I access the 8mm lock nut once I get it synched?! Looks like Honda had a special tool for that.

CB500/CB650 engine swap noise, video #2

P8130029

[Scott S]

 And can someone go over the cam chain adjustment? I followed my manual, but I want to know if there's a better way.
 This is from the HondaCB650 forum:

"A loose cam chain can make a lot of noise. Remove the center valve cover and check your cam chain tension with a screwdriver directly at the sprocket. Turn the engine at the crankshaft with a 24mm socket.
The tensioner may require several efforts until you have reasonable tension. If your tension varies considerably with position, replace the cam chain before it tears off."

[Scott S]

 Dude....could Honda have made the synch screws any harder to get to on these carbs?!

 I can access #1 and #3. I might just have to live with #2. If I can get #1 and #4 a little closer to #2, then I think that will help.

[Tews19]

I wish I had some insight Scott. I am curious about the oil checking procedure... I understand the engine is a direct bolt on but with different geometry with the frame would the placement of the engine be at a different angle possibly from a 650 frame to yours/

[Mo]

Sorry, I don't have anything to add. Just wanted to say damn Scott, a 650 engine in a 500. An ultimate sleeper 

Sorry to interrupt, but did you post about your conversion somewhere? Sounds like something worth considering down the line.

[Scott S]

 Take a look here:
http://forums.sohc4.net/index.php?topic=67907.0

 The engine swap starts on page 4.

 The oil level thing....yeah, that might have been my goof up. I put the bike on the center stand and let it sit there for a minute or two before checking the oil. Apparently, you need to let it sit there for about 10 minutes on the CB650. I think I just overfilled it and it blew it out of the breather hose. It's back to the normal level now and not smoking from the breather any more. DOH!

[Scott S]

 Well, you can't check the cam chain tension at the sprocket on a CB650.



 I adjusted the valves again, adjusted the cam chain per my manual, and synched the carbs.



 Yes, I know that #3 is still off just a little. You simply can NOT access the adjustment screw with the carbs on the bike. Period. I'm just glad it was that close.
 The dieseling and knocking is gone, but I still hear some valve train noise. Maybe it's just normal. Video to come.