Topic: CB550 Top End Rebuild

[CJK]

Piston to Valve clearance completed using the clay method.

Without any HG, the Intake clearance was 0.100” across the board and the Exhaust was 0.065”.

I would assume a standard thickness MLS HG (0.040”) would be appropriate. 

[CJK]

Well the MLS head gasket and adjustable cam sprocket arrived from DynoMan so was finally able to begin final re-assembly. I used assembly lube in the cylinders, installed HG and torqued down the cylinders to 15 lbs.

Then I installed CB650 Cam + CB550 Adjustable cam sprocket, + more assembly lube on the journals, and cam lobes. Set 1-4 to TDC, and secured the sprocket to the cam with the notch parallel to head surface.

All was going well, all the screws were going in, then it was time to begin torquing them down the 0.8-1.2 kg/m (I set torque wrench to 7 ft lbs). I started evenly and in the center, similar to process for torquing down cylinder head nuts.

I made it to the second bolt of the center 4 under the breather cover and the bolt sheared off in the head. I wasn’t at 7 ft lbs, yet so really I just got unlucky with an old bolt. My fault for re-using old hardware. The bolt is 10mm head, 5.25mm shaft diameter.

My question is...now what? Any recommendations?

I’m currently sipping Japanese whiskey, and walked away from it for the night because I’m pretty upset and hoping I didn’t ruin the head Mike modified for me.




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[flatlander]

just take that cover off again and see what you got. depending on how it broke off, there are different methods to get it out. if you're lucky you can just grab it with some pliers and turn it out. if it's too far down you could use a small sharp chisel, gently tapping it to turn the bolt out. post a pic of it here and people will give you more advice how to remove it without causing damage.
anyway, the head is not ruined. the bolt just needs to get out.

[dave500]

ive said it before and ill say it again never torque any 6mm bolts down.

[calj737]

ive said it before and ill say it again never torque any 6mm bolts down.

Nothing wrong with torquing 6mm bolts, just crappy hardware. The "torque value" is so low for a 6mm that "firm and hand tight" is plenty, absent of a torque wrench.

[CJK]

Thanks Flatlander, Dave and Cal. I’ll pull the valve cover off after work today to take a look.


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[CJK]

I took the valve cover off to look at the bolt.

Thankfully, it doesn’t look too bad. It did shear off above the hole so I have something to with.

I’ll be ordering 4 new bolts (M6x1x32.5mm) to replace all of the center bolts. I have stainless steel bolts for all the other valve and breather cover hardware. The center (4) weren’t included in the kit.

I may be able to grab it with vice grips. If not, I might be able to grind a small notch in it, and unscrew it with a flat head.

Any other ideas I’m missing?




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[bryanj]

Hopefully not bottomed and will turn out easy. Pretty blue pucks, not seen those before.

[CJK]

Hopefully not bottomed and will turn out easy. Pretty blue pucks, not seen those before.

I hope so, too. I’ll take a crack at it Saturday morning.

I was expecting black ones, but they fit and feel nice. I got them from 4into1, which is local to me.


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[calj737]

Tack a nut to it. Turn it out with a wrench. The heat from the weld will loosen it fully.

[dave500]

ive said it before and ill say it again never torque any 6mm bolts down.

Nothing wrong with torquing 6mm bolts, just crappy hardware. The "torque value" is so low for a 6mm that "firm and hand tight" is plenty, absent of a torque wrench.

torqueing 6mm not only risks snapping bolts but moreso stripping the soft alloy thread they go into,just nip them down they aint wheel nuts.

[calj737]

ive said it before and ill say it again never torque any 6mm bolts down.

Nothing wrong with torquing 6mm bolts, just crappy hardware. The "torque value" is so low for a 6mm that "firm and hand tight" is plenty, absent of a torque wrench.

torqueing 6mm not only risks snapping bolts but moreso stripping the soft alloy thread they go into,just nip them down they aint wheel nuts.

A proper condition 6mm bolt torqued correctly and accurately won't snap. The metal is designed for that specification. The alloy threads, they too need to be in good condition to hold a 6mm bolt, torqued by wrench or by hand.

Yes, I don't use a torque wrench on these bolts because the application doesn't require it. But I do and have do so elsewhere where it does matter. A quality torque wrench and quality hardware are required. 

[addictedtocafe]

I think a dremel notch in the center and an impact screwdriver might be your best bet.

I don't like torquing m6 bolts either - and I have had lots of failures of original hardware. All new bolts in that size for me, these days. In fact, if it isn't a specialty fastener (IE washered nut, or special non-standard sizes), I replace all hardware.  FWIW

[CJK]

Thanks, all. I’ll be removing the cam and head tomorrow so that I can work on this. I think I’ll try Cal’s idea of tacking the nut first because worse case there’s no damage. If that doesn’t work, I can still grind a notch into the bolt and unscrew.

I think the lesson learned from me is that 1) Use new hardware as cheap insurance and 2) While you *could* torque these bolts down to 5 ft lbs as Honda recommends, hand tight is sufficient and much less risk of destroying the soft aluminum threads or shearing small bolts.


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[CJK]

Good news: after removing the cam, I was able to grab the threads with needle nose pliers and unscrew the bolt.

After that, I reinstalled the cam, then used non-hardening gasket material to seal the pucks in place (following along in Hondaman’s book. I cleaned it all up and put the valve cover back on and hand tightened all the bolts

Tappet adjusted to spec and the engine is back together. I noticed my timing mark (T - F) for 1-4 is slightly off TDC (5-10 degrees).

I set the cam timing based on piston 1-4 TDC, not the timing plate as I noticed it was off at that point. From what I remember, I can bend springs to adjust the timing plate to the proper location.

Exhaust headers (MotoGPwerks courtesy of Cal) with SS spigots were installed.

Next step is to finish cleaning carburetors to be spotless, then put them back on. With the JMR Stage 2.5 head work, CB650 cam, the MotoGPWerks exhaust, port matched intake runners and TinTop Anti-pod filter, I think this engine should breathe nicely.

Living at sea level, I think I’ll start jetting at 1 size up from Stock specs. My beginning thoughts are #40 Slow Jet, Lift needle +1 notch, #105 Main.

Any other thoughts/recommendations?


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[calj737]

Carb settings should be VERY close as you describe them.

[CJK]

Carb settings should be VERY close as you describe them.

Awesome! Thanks for confirming my thoughts.

I’ve learned from reading the many threads, where the person overestimates how much fuel is actually needed. The classic case of thinking more fuel = more power.


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[calj737]

There is a possibility that less fuel may be needed actually. You've raised compression and volume, so, the same amount of fuel may net out to be equal to your prior ratio.

Start with a clean IDLE chop.

[RAFster122s]

Any updates to share Chris?

[CJK]

Any updates to share Chris?

I wish, I had to come down to 29 Palms for two weeks for military work so that hindered me.

Everything is back together.
Carbs are bench-synced. 
Static timing is set.


So next step is to gas up the carbs and get it running, then carb tuning and dynamic timing.

I do have an adjustable cam sprocket that I wanted to advance the timing in the future, but I wanted to get it running nicely before I do that so I have a reference point. I still need to get a degree wheel to do that.


I ended up putting 100# mains in the carbs. I realized I didn’t have 105# so I’ll order those.

I anticipate having it running by the weekend of 22-23 June. Bummer because I wanted to be riding around, but it’s been a long term project anyway so I’d rather not rush an imaginary timeline.



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[RAFster122s]

Thanks for your service Chris. Which branch of the military are you in, Army or Marines?

Like Calj said, you may be OK with stock jetting. Worth a try and it will only cost a few sets of plugs, to do plug chops, to find out. You will need several sets anyway to be certain it is properly jetted even if it does need the 105s. Or a spark plug cleaner to blast them clean.

Good luck wrapping things up on the bike so she is running.
David

[CJK]

Thanks for your service Chris. Which branch of the military are you in, Army or Marines?

Like Calj said, you may be OK with stock jetting. Worth a try and it will only cost a few sets of plugs, to do plug chops, to find out. You will need several sets anyway to be certain it is properly jetted even if it does need the 105s. Or a spark plug cleaner to blast them clean.

Good luck wrapping things up on the bike so she is running.
David

Hey David, I’m in the Marines on the Reserve side, happy to do this as a side hustle but grateful to not be on active duty. I did a deployment, it was bittersweet.

Anyway, I just returned back home late yesterday. Today, I put some gas in the carbs, kicked it over a few times then used the electric start to get it running. It started! It was a great feeling to hear it firing on all 4 cylinders. I let it idle for a couple min, then shut it down due to time.

However, I’m concerned with noise coming from the valve cover. It’s a clicking noise that corresponds with RPMs so I’m quite positive it’s either Camshaft, Rockets, Valves, or Tappets.

I checked the valve tappets, and confirmed they are set at 0.05mm Intake and 0.08mm Exhaust. I checked the tappet covers, which show no signs of contact with the tappets.

I didn’t use a stethoscope, but I felt the valve cover while the engine was running. To my touch, it felt like rockers are contacts the top of the valve cover.

I did have concerns when fitting the valve covers about how it was fitting at TDC.

I took a video so you can hear audibly how loud it is.

Video:
https://share.icloud.com/photos/0OjwvxCxb6XDdWzw-UutvGHHw#San_Jose,_CA

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[RAFster122s]

If you do not have a 77 or 78 cam cover it could be noisy due to eccentric wear of the rocker shafts in the cover. They cause cam and tappet wear and is a design flaw they fixed on the later covers by pinning the rocker shafts. I could not open the zip file on my tablet so I could not listen to your video at the moment.
The valves on the bike do tend to be noisier on these bikes or is it noisier than normal.

[CJK]

Apologies, I wasn’t sure if that’d work, but here’s the video hosted on YouTube

So the new head is from a 77-78, I believe as the rocker shafts are the newer style that are not pinned.



I found a post where TinTop talked about these valve covers wearing down, which causes similar noises I’m describing. However, I don’t see an elongated (oval-shaped) rocker channel  (No gap visible in picture) so I don’t think it’s that.


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[flatlander]

according to this picture that you posted, you'd have one of the newer style covers:



this has 8 bolts under the breather cover. the old style has only 4. the additional bolts keep the rocker shafts in position.

to be honest, i don't hear anything too unusual in your video. might be the video sound or might just be me. but with the 650 cam and right clearances, there would be no risk of rockers contacting the cover.
just checking: are you sure you set the tappet clearances at the right points? the description in the honda manual confuses many people.