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Discussion Starter · #1 · (Edited)
Stripped the threads this bolt goes into:
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Appears to go where circled. EDIT: Picture is from a different engine and is used to illustrate the location of the bolt:
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Any opinions as to how this might affect performance? I'm hoping that it will not since it is not a head bolt proper the way I see it but the bolt does go through the head. I'm thinking it may or may not leak oil. I can snug the bolt up but any more than that the bolt will continue to turn without reaching the proper torque. It's a spare engine of unknown condition but it turns over and the plugs looked good when I removed them.
 

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Your best solution is to repair the threads in the block with a thread repair insert.
 

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Yep I agree with the others. Use a Helicoil insert to repair to stripped thread.
 
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Typical boo boo on these bikes, some newbie reads to torque head bolts to X pounds and does the four big one to the correct and then wonders why the two smaller bolts stripped. This is a good time to learn to use a helicoil if you don't already know. I'm sure You Tube has plenty of features on this.
 
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'84 CX650E that is evolving into a GL500
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Or reads the torque spec from the chart and thinks a 6mm bolt with a 10mm head is a 10mm bolt.

Before I did anything else I would see how deep the hole is and if there are more threads that the original bolt doesn't reach (you might get away with a slightly longer bolt).
 

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Since the block is out of the frame, you should fix it correct with a Heli-Coil. With that said, it won't leak if you just assemble it, with the proper copper-coated gasket. 😉
 
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Discussion Starter · #9 · (Edited)
Frankly, looking at that engine I'd say you have bigger concerns. :sneaky:
That kind of gets to the purpose of my question. I found the engine loose in a junk yard. I can't see repairing the threads, new gaskets, etc when I don't know if the engine is otherwise OK. Since the original engine is out of my GL650 I'd like to drop this one into my GL650 frame to test it, but I don't want to do so without that bolt properly secured if doing so will risk causing damage. In my mind I'm like "Is the cylinder going to blow?" Like that. As for how it got stripped I got to go pretty far back, like 7-8 years. I'm not even sure that the bolt was in the engine when I got it. The only thing I definitely recall is saying to myself that this will be a perfect time to test that used clicks on torque wrench I bought off of ebay and also that I was pretty stoked about doing so since it was the first time I'd ever used that style wrench. :rolleyes: That being said, I came across some notes that indicate the bolt (all four of the similar bolts, actually) were not present. That triggered a memory of noticing a bucket of parts lying next to the engine when I bought it, parts that went with it, and that those parts may have included the thermostat housing, coolant tubes etc., parts that I think are bracketed to the engine using those bolts. Last night I said to myself "Wait a second! That bolt hole could have already been stripped!" Well, whatever, it's stripped now.
 

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1978 CX500 "The Grub", 1983 GL650I "Nimbus"
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At most, you might have a minor oil leak with that bolt missing. The big bolts around the cylinder do the real work.
Verify the length of the bolt you tried. If only engaging a couple threads, the torque wrench could easily strip them.
 
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Discussion Starter · #11 ·
At most, you might have a minor oil leak with that bolt missing. The big bolts around the cylinder do the real work.
Verify the length of the bolt you tried. if only engaging a couple threads, the torque wrench could easily strip them.
Great, thanks.
 

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I've seen these bolts loose in motors where the heads have been retorqued and these bolts missed with large oil leaks.

From what I've seen you may have anything from no leak to a motor that covers itself in oil just from a few short rides. Compression won't be effected though.

I'd be fixing it if it were mine.

The front two of these bolts hold the thermo housing and the rear two hold the airdam.
 

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I should have said, I wouldn't run it that way for any length of time. It should be OK for testing.
 
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Fixing it after testing the engine will mean using a fresh headgasket and other small stuff. That'll cost you a lot more than a helicoil now .....
 
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Installing a helicoil is easy. If you haven't done one before this would be a good time to learn.

I'd recommend buying a kit; The big multi size kits are expensive but kits with a few helicoils of the size you need plus a drill bit and a tap aren't so unless you have a big shop that does a lot of mechanical repairs.... Well let's just say I've only bought 2 sizes so far.
You will also need a drill, a tap handle (if you don't have a metric tap & die set you should consider getting one if only for cleaning dirt out of threads). and a tool for installing the inserts into the holes (I always keep a few "worn out" Phillips screwdrivers for making needed tools from so I made my own).

You just use the bit from the kit to drill the stripped hole out to the required size (if you don't fight it the bit will follow the hole straight & true), run the tap into the hole to cut the threads (1/4-1/2 turn in to cut then 1/8 turn back to clear the chips is good practice), screw the insert in until it is just below flush with the face and tap the end of the tool to break the tab off, then screw the bolt in.
 

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You forgot cleaning out all the swarf before installing the insert.
Also, be sure to mask all the openings into the lower parts if the engine. You need to keep all that loose metal out.
 
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Discussion Starter · #19 ·
Before I did anything else I would see how deep the hole is and if there are more threads that the original bolt doesn't reach (you might get away with a slightly longer bolt).
This seems to have worked. I bumped up the bolt length from 55mm to 60mm and it torqued to 13 ft-lbs with the thermostat bracket in place. 13 ft-lbs is the low-end standard torque value for 8mm bolts listed in the FSM (13-18 ft-lbs). I am reluctant to use aftermarket head gaskets on a 650 engine, positive reviews of Joe Hovel's gaskets notwithstanding (I have two). Just don't want to go there unless absolutely necessary. Thanks for all the input.
 

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