Author Topic: HELP! cam tensioner bolt, busted in case  (Read 759 times)

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Offline Sailormade

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HELP! cam tensioner bolt, busted in case
« on: June 26, 2010, 02:03:56 PM »
Guys, Ive got my 350f engine out on a stand. "The plan" as they often start, was a mostly cosmetic retouch.  long story short, my cam tensioner bolt is broken off in the case. :'(    Then my easy out busted off in the pilot  :'( :'(   My question:
1. Do i need to split the case to change it out? My thought is the only way to get it out will be from the inside.
2. If yes,  what else should i do while I'm there? Are there any wizbang things to make life on the 350 even more fun?

This is number 2 of my 350f's, I've had it for a few years and never did anything with it. 12000 mi are on the engine, everything else looks really good with the exception of the head seeping oil. I was going to do the top end gaskets in an attempt to fix those, but if it's coming apart......    

Who makes the best gasket set?

Thanks for all the tips i've already mined from you guys! Hope someone has an easy fix for this.

Don
« Last Edit: June 26, 2010, 02:06:56 PM by Sailormade »
1973 CB350F Candy Bacchus Olive
1973 CB350 / 400F Flake Matador Red
2009 Triumph Bonneville SE

Offline rangelov

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Re: HELP! cam tensioner bolt, busted in case
« Reply #1 on: June 26, 2010, 02:48:55 PM »
I hate to be the bearer of bad news.

If you snapped off an easy out in a stuck bolt inside the engine, you will need to completely disassemble the engine.  To remove the bolt and easy out will require an EDM (electro discharge machining).  The easy out is much too hard to drill out.  You might be able to crack it into pieces.  But, not likely and not without buggering the case.  You need to find a shop with a good reputation for removing easy out from aluminum motorcycle cases.  If done correctly your threads should be no worse than they are now.

In my experience, I had to Heli-coil the hole afterwards.

Unfortunately, there are no good shortcuts, especially with an easy out wedging things tight in there.  Don't take shortcuts, you'll probably cause even more damage.

You should try penetrating oil.  There are plenty of good suggestions on the forum.  That might help loosen the bolt.  You will still need to EDM the easy out. But once the the easy out is out the bolt may not be stuck.  Or most likely you will need remove them both using an EDM.

When reinstalling the bolt use Loc-Tite. The should hold the bolt from backing out and seal out corrosion.  If bolt is installed dry, inside an engine, the threads can stay dry, react with the aluminum and seize over time.  Anti-seize will work, but you'll always be worrrying about the bolt backing out with catatrophic results.  It happened to me on a stock, unopened engine.
« Last Edit: June 26, 2010, 02:59:37 PM by rangelov »
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CB750K4, Boss maroon metallic, 836cc, RC Engrg 4 into 1, Forks by Frank, air assisted front forks,  JC Whitney 16" rear.

Offline Sailormade

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Re: HELP! cam tensioner bolt, busted in case
« Reply #2 on: June 27, 2010, 07:37:10 AM »
Thanks a lot!  That's what I figured. This should be a fun, at least I'll know the real deal for the rest of the engine...  For the record, the last shop i had the bike at apparently broke it off, and put it in place with some JB weld. So, any one in San Diego, I can tell you where NOT to take your bike.

Don
1973 CB350F Candy Bacchus Olive
1973 CB350 / 400F Flake Matador Red
2009 Triumph Bonneville SE

Offline rangelov

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Re: HELP! cam tensioner bolt, busted in case
« Reply #3 on: June 27, 2010, 08:40:11 AM »
There is one more option.  You could use Dremel tool with an 1/8"  carbide bur. 

That's what I used to remove broken fender bolts from my fork sliders.  They wouldn't budge when drilled out.  So I removed all the material possible then picked out the thread and bits.  They were softer than an easy out, not much.  You have to be really careful to not remove the threads from the aluminum.  But getting out the bits was a real pain.  I did bugger the threads a little.  The thread is still fairly good shape and holds a load.

Problem is bits are expensive and break easily.  Use higher speed.  It less likely to chatter an could be easier to control.

It is worth a shot.  You use a helicoil.  I'm not sure how much material is in there.

On my KZ900, the cam chain tensioner bolt fell out and I think that I had to helicoil that case hole, not sure since it was about 1980.

On my Z-1, the main cap bolts were seized and snapped.  That what I had EDMed about 1985.

http://forums.sohc4.net/index.php?topic=76835
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CB750K4, Boss maroon metallic, 836cc, RC Engrg 4 into 1, Forks by Frank, air assisted front forks,  JC Whitney 16" rear.