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Discussion Starter · #1 ·
I rebuilt a CB350 motor and sold the bike to a friend of mine.

He was out riding yesterday and broke down. I went out to see if I could help and found the camshaft to be seized. The engine was still turning over, so the timing chain either broke or the camshaft sprocket bolts loosened up causing sprocket to spin freely on the cam (while causing some damage to valve casing)... maybe could be another issue?

I was very careful when putting the cam sprocket bolts on as I had already made that mistake before. I ordered two sets of bolts from ebay and used the better looking bolts to hold the cam sprocket to the cam while applying the red loc-tite and being very careful the shouldered bolt went into the correct insert.

He is a new rider who broke down on a 55 mph stretch, good spot to gun it but I'm not sure how hard he was pushing it. It broke down after he turned off that road.

I would be shocked if those camshaft bolts loosened up, but it's certainly a possibility.

The timing chain was an endless timing chain too, I did the full bottom/top rebuild.

Oil level was good and making it to the top end alright.

Has anyone broke a new timing chain before?
 

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Discussion Starter · #2 ·
Brand new endless chain was purchased from Sirius Consolidated. I also made sure to clean the grease the manufacturer puts on.
 

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By your description, it's a strange event. If the cam was seized, the engine shouldn't turn... if you red loctited the bolts, they shouldn't have come out, and it's pretty unlikely that the new, endless cam chain broke as well. If it turns over, the first thing you should do is take off a valve cover on each cylinder and rotate the engine to see if valves on both sides open. You're sure it had oil flow to the top end, as well as it was full of oil when he was riding it?
 

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Discussion Starter · #4 ·
The valves do not move when the crankshaft is turned.

There was a minor oil leak from one of the valve covers, cover was little loose. And oil level was good on dipstick.

Yeah, I'm stumped.
 

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Man, sorry to hear that news.

Hopefully you find the issue and post it, maybe with pictures.

I'm building one myself and am interested what happened.

Once again, sorry I can't help.

Maybe the chain broke could still rotate bottom end, as long as it isn't jammed in the casing. Bolts shearing off on the cam sprocket maybe.
 

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Discussion Starter · #7 ·
butlite - yeah the situation really sucks. I think he was just 20-30 miles into his first ride on it.
 

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Were the bolts you purchased from ebay New or Used?

There was a thread on the life expency of those bolts put up on the site maybe (2) years ago.
A guy did an expirement on how many times they could be torqued down before the failed.

If you had a new endless chain there is a very good chance the bolts sheard off if they were used.

The cam would not move from the weight/pressure of the valve springs on the rockers/cam lobes.
If you got REAL Lucky the cam stopped with all 4 valves closed.

Remove the Stator Cover then Pull the Spark Plugs and turn over the crank with a 14 mm wrench.
You should be able to look into the cylinder and see the top of the piston.
If there was an open valve I suspect you will see damage to the top of one piston.

If you don't see any damage you might have gotten lucky but Murphy's Law says not likely.
 

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Discussion Starter · #12 ·
The bolts were used. I thought I had read that most people were reusing them with good results torquing them down with red loctite. I was looking to purchase new but couldn't find the correct bolts anywhere.
 

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Discussion Starter · #13 ·
Do you know where I can buy new bolts? I'm going to order some so I have them on hand just in case.
 

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Brand new endless chain was purchased from Sirius Consolidated. I also made sure to clean the grease the manufacturer puts on.
Never heard of removing nor have I removed any product that came on a timing chain. Where did you find that information?

I hope you didn't clean it using something like brake cleaner .....

Also those bolts may have backed out if you didn't prep both the bolts and internal threads properly. Oil and other contaminates reduces the effectiveness of thread lockers considerably.

The other thing to consider may be blockage of an oil passage from some sealant or debris. I have found a lot of gasket material in oil passages in these engines.
 

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Discussion Starter · #15 ·
I followed the saturday's wrench rebuild series when assembling and they mention that the cam chains sometimes come coated in a preservative that needs to be cleaned off. I just wiped it down, as they did 5 minutes into this video:
.

I cleaned the bolts with mineral spirits. I was very cautious when putting those bolts back in since I have had them back out on me before. I'm guessing they were just weak as yendor suggests.
 

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There are other possibilities. There are orifices that control oil flow to the head. The orifices are small and can be blocked easily. If you used silicone type sealant, it also is prone to blocking oil flow. Low oil flow can cause the cam to seize to the head, causing the chain and or sprocket bolts to break.

Could also been an oil pump failure. If you are tearing the motor down, oil pump and orifices would be important to check.

Sent from my SM-T830 using Tapatalk
 

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Discussion Starter · #17 ·
I used threebond sealer. I'll check the oil pump and see if anything looks off there.
 

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I followed the saturday's wrench rebuild series when assembling and they mention that the cam chains sometimes come coated in a preservative that needs to be cleaned off. I just wiped it down, as they did 5 minutes into this video:
.

I cleaned the bolts with mineral spirits. I was very cautious when putting those bolts back in since I have had them back out on me before. I'm guessing they were just weak as yendor suggests.
Well I will file that under Internet Lore ..... any preservative is oil based and unless there is specific instructions from the chain manufacturer then it is fine to install out of the package. Soaking the chain makes for a messy install in my opinion. I just lube them up after install.

Mineral spirits have oils in them and are very slow to evaporate, correct cleaner for thread lockers is acetone, you can buy Loctite cleaner but the msds shows it is just a high percentage of acetone.

Did you torque the cam bolts taking into account the use of a lubricant, Loctite in this case?
 

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Discussion Starter · #19 ·
No. I am reading about that now though and see that it's unnecessary. But, I just did a quick search.
 

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Discussion Starter · #20 ·
What is the correct torque spec with the red loctite on these bolts? I've seen 7 ft.lbs to 15 lbs. I think I was at 8 ft.lbs. Maybe not enough torque.
 
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