cylinder head bolt threaded insert depth

Does anyone have any experience with threaded inserts in this situation and what depth did you install them to? can anyone foresee any issues having the insert threaded in just below the mating surface for the head/jug? my master mechanic friend didn't seem to think it was a big deal, but, i wanted to use the OE bolts so i installed the insert at a depth the same as the other threads. however, that bolt is stretching and there are some other issues so this is just what was crossing my mind, any help would be great thanks.


so.. i don't have the engineering data but i'm sure there is some reason the threads start so far down into the jug, however.. maybe not. All i can think/figure is that the farther up the point of attachment is, the higher levels of heat the threads would be subjected to as it gets closer to the actual point of ignition and i'm sure the metal 'moves' a little bit more in that area as well. Also, having the threads further down it would end up pulling on a greater amount of material vs if the threads started immediately at the top of the jug.  Now, with a threaded insert i'm not sure if that really matters.

If it's a helicoil type, I would stack them to get the same length as original threads.  Also, they are available in different lengths.

its an ezlok type, stainless. I'm not necessarily concerned with the strength of the threads, its much stronger than the aluminium, what i'm concerned with is the depth that the insert is inserted into the jug. That being said, two inserts would cut down on a lot of the vibration, so, i had considered that element. i'm not entirely sure if it matters or not and its a little bit of a trick to get the depth right relative to the bolt length and where the threads are on the bolt relative to the depth of the insert.  Also.. i've never had luck inserting two heli-coils and then getting the threads to line up correctly... so, i was hoping i could find someone who had actually done something similar and how far they the insert was into the jug

It sounds like you're wanting to try to install your insert in such a way as to make up for the bolts pulled /stretched threads. Can you not buy a new bolt to eliminate that concern?

yeah, after some digging i was able to find a bolt in close to the same size and hardened(10.9), also with a non-reduced shank so i could have a machine shop thread the rest of the bolt for me making this less of an exact science and allow to use more than one insert. 


Well, its just a variety of different things, also, finding that same size bolt wasn't possible locally, had to be ordered so i was just looking for other options for things i could pick up locally. after thinking about it, i'm sure i'd be fine as long as the insert wasn't literally even with the mating surface. a centimeter or so below i'd probably be ok. Often when these bolts start stretching they just keep stretching, it doesn't take much at all to fail a head gasket..(literally, any stretch, less than a millimeter) so, i'm in the process of getting the head off right now and i'm going to see what exactly is going on or if the insert itself is moving or whats happening.. (and in the process fighting this silly mechanism for releasing the cam chain tensioner and i don't know why honda didn't use a bolt instead of a pin for the locking mechanism on the valve lifter/decompressor mechanism).

reason for aftermarket bolt is because OE bolts have a reduced shank and cannot have additional threads cut/added, therefore aftermarket bolt was ideal because of that situation. a bolt is a bolt as long as it meets the hardness requirements for a given application. i'm sure it exists somewhere, but, for all intents and purposes its impossible to find a bolt in these specifications with full length threads. why so many threads? because i was considering using two inserts for additional insurance and needed the additional thread length/amount.


alignment with the insert was perfect, right in the middle of the threads. this is the 3rd gasket.. first one bolt rattled loose, retorqued but gasket was still failing. installed anti-vibration washer(nord lock) and loctite bolt stayed in place but bolt ended up stretching... and i think the gasket was just poor quality anyways on the second attempt.. i'm using a cometic on this recent/3rd because its what the P.O. was using at it seemed to seal fine.. (and yeah, checked for flatness, no issues). 


side note..  this bike is mostly a nightmare. in my years as a mechanic and of all the vehicles i've owned i've never had a vehicle give me more trouble and be more time consuming for what should be pretty simple and straight-forward.. i'm just venting/ranting but every time i take something apart to make a repair something else fails or a thousand threads strip out.. had this 1/2 tooth timing issue, which was a mystery, seemed to work itself out somehow and as putting it back together for some reason it just lined up properly all of a sudden..(and no, only 5k on bike, but even then timing chain is not worn out) but now there is this really awesome top end noise but i'm not really entirely sure what it is.. could just be that the valves are tight because this valve cover gasket must have been thinner or something.. (or it could be the cam detonating as the large 12mm bolt in the center of the valve cover decided to strip upon reassembly..). also this really weird metallic sound like something is tapping the gas tank every time the crank rotates(turning it over via the kickstarter)... this i also have no idea of its origin.. as this is a new sound to me(and makes no sense).. however, i guess its possible that its related to that larger center bolt on the valve cover only having like 6ft-lbs on it..


but, its 1am.. i have to work in 6hrs, guess i'll be creeping it to work in the am..(good thing A to B is only 5 miles and country roads..)



um, i guess it is possible that the noise i am experiencing are the valves contacting the piston.. but.. there is literally zero resistance as far as that goes.. so i dunno, which is also why it is so weird.. i thought that maybe by magic the timing chain jumped between attaching the cam gear and putting the valve cover back on.. as it was immediate upon first turning it over but it runs great..

Edited by Timmoto

What bike and year?  Why not just ebay another cylinder?  

92 xr250l and yeah i know i, thats not looking like such a bad option.. I can't get the valve cover to seal to save my life, it leaks next to no matter what i do, needs new copper compression washers on pretty much every pin for the rockers too.. At the least it would be really nice to work out of a spare, if i can find something cheap i might think about doing that. That being said, this new head gasket seems to be sealing up fine, funny how easily it starts now with a nice seal around the combustion area.. go figure... but, the valves are in really good shape and the seats are really good to. I stopped by my friends auto shop to pick the guys' brains there and i'm thinking that really weird hollow sound is just the valves ticking, but it just sounds weird in 'slow motion'. I'm about to adjust them(although.. this new gasket has already failed.. i'm thinking about leaving the valves alone for the time being and applying a little ultra black rtv and let it set overnight and that'll give me a little more room back with the valve clearance and help its seal). except that same shop, they have this nice compact drill i'd be able to fit in and put a heli-coil in that center bolt on the valve cover. that center bolt on the valve cover is a M8 x 1.50 ?? i think. its not fine thread so thats just my guess, have to find that out and get a kit together, hopefully before the weekend. anyone know for certain what size that bolt is?

I think it's M8 x 1.25.  I had to helicoil that one too.


I had the same problem with a 250L.  Your bike was overheated in a major way at some point.  I'll bet your stator is dark roasted brown, too. 


I got a cylinder from a 2000 XR250 and slipped my freshly bored cylinder into it.  You simply heat it up in the oven and the old one drops out.  Then put your cylinder in the freezer and new block in the oven.  I made a wood fixture to clamp it in until it cooled.  


I also bought new oem bolts.  The waisted bolts are part of the engineered design not just a random bolt. 


After three blown head gaskets, problem solved.  I have ridden a couple thousand miles with it now.  I also installed an oil cooler which made a dramatic difference in how long the oil lasts. 

thanks, thats really good info. I'll see if this current head gasket holds up, if it fails then i'll start looking around for replacement parts and follow a similar path that you figure out. thanks again for that info, really good to know

Hi guys. May I ask for some Info? Could you suggest what is the thickness of the original head cover steel gasket of xr400r. I bought an aftermarket gasket kit and the gasket is 0.5mm thick which is approximately 0.02in.

You must use the steel shim gasket from Honda and NO sealant.  Too thin a gasket clamps the cam bearings and damages the head and rocker cover.

valve cover? thickness will vary, you'll have to adjust the valves pretty much guaranteed after changing the valve cover gasket.. sort of a design quirk of these engines. i can measure an old gasket i have tomorrow.



also, so far so good on this issue. made sure to cake the threads in lock tight, nord lock washer, everything seems to be staying in place, i'm happy.

Adjusting the valves is not a problem. I have doubts that the gasket I have now is thicker than normal. There are marks on the ball bearing outer races indicating that those have been rotating in the journals. Valves are loud regardless of how many times I have adjusted them, even with gaps smaller than necessary. I think that the cam together with the ball bearings may be rocking up and down due to thicker cam cover gasket.

Edited by messat

valve cover? thickness will vary, you'll have to adjust the valves pretty much guaranteed after changing the valve cover gasket.. sort of a design quirk of these engines. 




This has been discussed here and for those who missed it . . . .   It's more than a valve cover.  It's a rocker box with the top half of the cam journals  integrated into it.  You cannot use a paper gasket here because paper compresses.  If the gasket is too thin, it will clamp the cam bearing and bind the cam.  If it's too thick, the cam will jump up and down.  It must be steel and .010" thickness.  The Honda gasket has a very thin black coating to help it seal and it's reuseable unless some idiot used sealant and glued it to the cover.  Sealant also has thickness and will also cause the cam to jump up and down.  


If your rocker box cover was overheated and warped due to having the wrong gasket then it's junk.  Throw it away and get a replacement.  If the head is badly warped, it may be junk too.


Also, you don't need locktite on the head or cover bolts.  Using locktite on a steel bolt into aluminum threads is asking for problems.  The only place I use locktite on the top end is on the exhaust flange studs and nuts.  I use blue, never red. i swear i'm half zombie lately.. i don't even know why i posted that. thanks BajaRambler, all good info to be posted around.



on a side note, and take this with a grain of salt. i came across someone who most likely had some issue with their head, but they were using ultra black on either side of a thin gasket(can't get much thinner than 30Ga), and then ultra grey around the cam bearing race... um, apparently with success. This is also on a pretty clapped out XR, middle journal was all walked out in the cam/head, that aluminium bit, said it didn't create any problems either. um.. ultra grey is fairly hard, so i guess i can see this working, but, all the same, it would still move around some.. anyhow, tis the reason for the forewarning, i wouldn't really recommend this route, but, i guess its an option before buying all new top end parts..



Also, if one was so inclined, an option would be to make a gasket out of a .010 sheet of copper. Copper is relative to a liquid in that is doesn't compress, it displaces. Under a very high load it will however compress, but, thats not an issues here. However, the displacing factor is an advantage because it will migrate into crevices/imperfections.  Just something to consider in place of an OE gasket, copper is easy to work and will hold its thickness very well under compression.  


--edit p2 

also, when i measured my gasket, it was .012, which i would image the .002 is from the sealing material.. however, that is a vvveerrryy small increment, but, worth noting. i'm not sure its possible, maybe super conservative RTV layer could be used to mimic this .002 thickness.. However, it would have to be tested honestly(aka, taken back off and measured after curing)

Edited by Timmoto



It sounds like you're on the right track.  


I struggled with this on an XR250.  The paper gasket from the previous owner measured .007" and it was clamping down on the cam bearings restricting rotation of the cam.  I made another paper gasket .004" and sandwiched them together.  Then the cam turned freely.  At that point, I called around and found out the oem gasket was steel and .010".  That's when I ordered the expensive oem gasket.  Luckily, the PO never got the bike running due to cam chain off one tooth and pilot jet clogged solid.


I like the copper gasket idea.  It would transfer heat between the head and cover very well. 

yeah, the copper idea is fairly cost effective also, $10 for a 1'x1' square 30ga piece(.010).  A friend of mine suggested that if there were issues sealing and the RTV route were to be followed. the whole thing could be assembled and use plastigauge on the outer cam bearing race, take it back apart and check the clearance, then depending a shim could be made. I thought that was pretty clever, a little involved, but clever.  I have a sheet of copper ordered, I've been using aftermarket metal gaskets. they have the right thickness, but, the sealing material they are using is low quality. The copper should seal a little better, at least over the cheap steal aftermarkets.   Thanks for the info BajaRamber, good stuff.

Edited by Timmoto

I forgot to mention that I used plastigage to check clearances.


I like making parts, too, but wouldn't it be easier to just buy the oem gasket?  They are reusable.


Tip: Position the cam lobes down when removing/replacing the rocker cover.


Are you sure 30 gauge copper is .010".  Different materials such as steel vs. stainless of the same gauge come are different thicknesses.

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