Author Topic: Broken valve adjuster, again  (Read 2381 times)

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Offline laminaytrap

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Broken valve adjuster, again
« on: April 02, 2015, 07:21:34 AM »
Hey!

It's been a while since I've been on here but I just pulled out my bike for the season and I heard a ticking...

I've heard this noise before so I pulled the cam cover and voila! Another broken adjuster.

This is my second on on the same rocker in two seasons, I've adjusted the valve 3-4 times an the past 3 years and yet I've only ever lost this one.

Obviously I will be replacing it, any thoughts on cause? Could that valve be sticky and catching a ride up on the piston?
Of course I had to extract the screw from the oil passage :S

Thanks,

Jon

Offline 70CB750

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Re: Broken valve adjuster, again
« Reply #1 on: April 02, 2015, 07:23:44 AM »
When the adjuster broke for the first time, you replaced it with new one and that one broke now?

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Offline laminaytrap

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Re: Broken valve adjuster, again
« Reply #2 on: April 02, 2015, 08:25:34 AM »
Yeah,

It is possible that it came loose, but knowing that I was replacing a broken one I imagine it would have been done up tight(er). New OEM part, I bought two at the time, but now I have misplaced it.

Jon

Offline laminaytrap

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Re: Broken valve adjuster, again
« Reply #3 on: April 02, 2015, 08:27:21 AM »
Also if anyone has thoughts on where that oil is coming from I'm listening... On the front left in the fins.

Jon

Offline evanphi

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Re: Broken valve adjuster, again
« Reply #4 on: April 02, 2015, 08:37:00 AM »
Also if anyone has thoughts on where that oil is coming from I'm listening... On the front left in the fins.

Jon

Probably the pucks under the cam towers. Are the spark plug areas oily too?
--Evan

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K5 Crankcase/Frame, K4 Head and Cylinders, K1 Carbs (42;120;1 Turn)

She's a mix-matched (former) basket case, but she's mine.

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Offline 70CB750

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Re: Broken valve adjuster, again
« Reply #5 on: April 02, 2015, 08:45:26 AM »
Yeah,

It is possible that it came loose, but knowing that I was replacing a broken one I imagine it would have been done up tight(er). New OEM part, I bought two at the time, but now I have misplaced it.

Jon

I hear you, replacing broken adjuster, there is a little chance you would leave the new one loose.

Looks like something is wrong there, hopefully some head expert will chime in here, if not, I would try to reach  to MRieck:

http://forums.sohc4.net/index.php?action=profile;u=49

Prokop
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I love it when parts come together.

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Offline Don R

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Re: Broken valve adjuster, again
« Reply #6 on: April 02, 2015, 09:44:59 AM »
Check the end of the valve and the adjuster pad for a wear pattern, maybe that will give a clue. When the new one is on, roll the engine through a rotation and try to see if there is a problem with the contact area. Could the rocker be bent? Does the adjuster have the same amount of thread showing as the others when it is set properly?
 I bought a bike that had an 812 kit with bad valve/piston interference, the valves had worn clearance grooves into the piston tops and yet it still ran. They seem to be pretty robust, it did have one valve carboned up so bad it was hung open.
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Offline Don R

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Re: Broken valve adjuster, again
« Reply #7 on: April 02, 2015, 09:47:34 AM »
 You might spot check the lash after it's running again, just to be sure nothing is moving. Do the surrounding rockers maintain their lash setting?
No matter how many times you paint over a shadow, it's still there.
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Offline laminaytrap

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Re: Broken valve adjuster, again
« Reply #8 on: April 02, 2015, 11:56:02 AM »
Probably the pucks under the cam towers. Are the spark plug areas oily too?

Hope not, they were replaced when everything went back together a year or two ago :(

If MRieck notices he can chime in, I haven't seen anyone else with this problem, meaning it is likely rare and/or I screwed it up/there is damage on the valve/rocker from it breaking last time.

Check the end of the valve and the adjuster pad for a wear pattern

Unfortunately it seems that in both cases the adjuster breaks/annihilates the pad, thus forensics are hard to do. It is consistent with it becoming loose. Maybe some blue Locktite next time?

That being said the valve stem looks perfect, and no noticeable misalignment of the rocker side to side. It could be bent up, but also the cam looks mint.

The only weird thing about my head is that I am not running the rocker shaft bolts, only the alignment bolt. I am pretty sure this is not an issue.

As for the oil it may not be coming from there but more towards the centre and running to the outer fins when parked, then cooking there on the next ride. Motor was last washed >5000 miles ago :/ I'll do it soon, I promise.

Will update when I have the new part in hand, dealer isn't taking orders over the phone and I don't have time today, looks like tuesday.

This is really the last thing I thought I'd be doing today, first nice day of the season.

Jon

Offline laminaytrap

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Re: Broken valve adjuster, again
« Reply #9 on: April 02, 2015, 11:59:41 AM »
You might spot check the lash after it's running again, just to be sure nothing is moving. Do the surrounding rockers maintain their lash setting?

Yes the other rockers appear to be fine, not funny business there.

Jon

Offline evanphi

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Re: Broken valve adjuster, again
« Reply #10 on: April 02, 2015, 05:55:02 PM »
Probably the pucks under the cam towers. Are the spark plug areas oily too?

Hope not, they were replaced when everything went back together a year or two ago :(

Jon

Were they sealed with a non hardening gasket sealer? Correct thickness (ideal is 30 or 40 thou more than the recess)?
--Evan

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Offline scottly

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Re: Broken valve adjuster, again
« Reply #11 on: April 02, 2015, 06:44:29 PM »
The most common cause of broken valve adjusters on 750s is excursions deep into the red zone on the tach, such as when the trans pops out of gear at 8000 RPM WFO. :(
Don't fix it if it ain't broke!
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Offline laminaytrap

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Re: Broken valve adjuster, again
« Reply #12 on: April 03, 2015, 01:06:25 PM »
No I didn't use gasket sealer, must have missed that part in the assembly manual... Guess I need a hot cam now.

I don't usually rev over 9000, but I do occasionally get up in the revs. Could it be from a missed shift? Sometimes the trans refuses second when I am already hard on the throttle. Not usually looking at the revs, as I have not an indicator of those. Maybe next week.

The funny thing is I don't remember it being broken (noisy) when I rode at Christmas...

Oh well time will tell.

Thanks all,

Jon


Offline evanphi

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Re: Broken valve adjuster, again
« Reply #13 on: April 03, 2015, 07:38:15 PM »
No I didn't use gasket sealer, must have missed that part in the assembly manual...

It's not in the official manual. ;) Buy HondaMan's book. It is outlined there.

Also, here: http://forums.sohc4.net/index.php?topic=107040.0
--Evan

1975 CB750K "Rhonda"
Delkevic Stainless 4-1 Header, Cone Engineering 18" Quiet Core Reverse Cone, K&N Filter in Drilled Airbox
K5 Crankcase/Frame, K4 Head and Cylinders, K1 Carbs (42;120;1 Turn)

She's a mix-matched (former) basket case, but she's mine.

CB750 Shop Manual (all years), searchable text PDF
Calculating the correct input circumference for digital speedometers connected to the original speedometer drive

Offline scottly

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Re: Broken valve adjuster, again
« Reply #14 on: April 03, 2015, 09:34:51 PM »

I don't usually rev over 9000, but I do occasionally get up in the revs. Could it be from a missed shift? Sometimes the trans refuses second when I am already hard on the throttle
Yes, a missed shift at full throttle might allow the engine to exceed 10,000 RPM, the same as popping out of gear. My adjuster didn't break during the high RPM excursion, but sometime after. It's possible that the high revs loosened the lock-nut, and the end of the adjuster screw contacted the adjuster cap, which snapped it off.
You might want to look at the bottom side of the adjuster cap, to see if you see any marks.
Don't fix it if it ain't broke!
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Offline laminaytrap

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Re: Broken valve adjuster, again
« Reply #15 on: April 06, 2015, 04:12:31 PM »
No signs on the bottom of the caps, they are the tall finned ones so maybe they have more clearance than the short style.

Since I am still waiting for parts I decided to do some touchups



Hopefully it will not look too crazy installed. Really want to go with a polished valve cover in the future, but it is too much work for now.

Jon

Offline Don R

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Re: Broken valve adjuster, again
« Reply #16 on: April 06, 2015, 08:20:06 PM »
 It sounds like you did your due diligence. Must have just came loose. My K0 has a chromed cover that refuses to seal. I sanded it with a piece of 400 grit on a slab of glass. There are areas that are not level, I got a cycleX laminated rubber on metal gasket. Haven't tried it yet.
 On my big block chevy I installed T&D shaft rockers which look like big cb750 honda ones. They say to blue the end of the valve and check the pattern after a full rotation, it should be centered on the stem, if it's too high or low the geometry is off. The T&D's have shims to go under the stands to correct it where we don't.  This might not apply since we can't adjust the shaft but it might provide some insight.
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Offline PeWe

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Re: Broken valve adjuster, again
« Reply #17 on: April 07, 2015, 02:57:03 AM »
I missed a gear back in the days, the lock nut came loose completely direct.  I heard the ticking and checked. I was lucky to find the nut thru the hole resting on the head just beside when the adjuster cap was removed. Took it out and adjusted the valve lash, locked with same nut. I think I tight the nuts harder since then.
This was when I had the OEM tool kit under the seat

About revs....at my last test drive a few days ago I noticed that my latest cam does not mind the green area after the dangerous red zone. 9300---> Twisted the throttle on 2:nd gear, passed my friends car and slammed in the 3:rd gear after 9000... had to release very quick when the bike became a little bit too happy with a wheelie still climbing... :o The road had a bump that helped the front wheel to get airborn a little bit too much.
« Last Edit: April 07, 2015, 03:03:38 AM by PeWe »
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Offline laminaytrap

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Re: Broken valve adjuster, again
« Reply #18 on: April 07, 2015, 05:11:54 PM »
Maybe I need to loose some weight, getting the wheel up has never been that easy, less so now (see pic.). I am more likely to spin then lift. I'll rebuild the clutch and see though.

I think the valve cover turned out nice, still need to clean a bunch of stuff up, but it's all working.

Rode 20 miles today, no I'll effects.