The XL cylinder head:  (translated from Marc 2003)

(the XL- illness)


Which XL driver doesn´t know it, what has begun with a light film of oil, often ends in the total mess. Machine and also driver cannot save themselves from hot oil. 

A typical problem at almost all XL 500 models is the thick area between valve- and cylinder head. By thermal problems it comes to leaks at the outlet side. The valve head cannot be tightened and also not evenly be attracted correctly, favored by weak, torn or faulty threads. 

For the solution (yes, there is a !!!!) I did some measures:              

At first i have removed the upper engine mount. Attention!! HONDA warns of this step from an official side. Frame break and change of the road performance can be the consequence. Within the former 13 years I have driven some tracks, have not spared my XL in any vacation and joined in some Enduromeetings. Also after the most exact examination of the frame I haven't been able to discover a weak point.  

Further I have renewed all threads in the cylinder head. Where it was possible I employed M8 Heli-Ceul thread instead of M6 threads. Where the place didn't suffice I built in M6 thread inserts. I have put carrier bolts into all renewed threads instead of screws. To ensure the right length I extra manufactured them. An exact analysis of the rocker box cover is necessary here. This must be altered correspondingly. It is partly possible to leave the upper thread of the carrier bolt with M8. For this the corresponding drillings gets on-drilled.


I also have got tips of other XL 500 drivers:


Tuesday February 13th, 2001:

I can say to you how I have solved the problem with the cylinder head. Because the preholder of my XL didn´t have much knowledge about an XL (so i suggest) he has turned off all carrier bolts. What to do in this case. To solve this problem a fitter turned new carrier bolts: At the bottom, into the cylinder  8 mm, at the top (cylinder head) 6 mm. Therefor it is necessary to calibrate exactly the depth of the threads in the cylinder. Leave the threads by 1-2 mm shorter, so one can screw the bolts quite in and therefore prevents a turning off the course of thread. Don´t use Helicoil but drill the cylinder and drill a thread into it (very carefully). Because of the bolts, which are (at the top) 6 mm one can put on and screw on the cylinder habitually (without drilling). As sealing I take a sealing which is used by Mitsubishi. But be careful, there are two different sealing of Mitsubishi, one is only the mass and one has metal dust. This one with the metal dust is the better one. My XL is completely dry. With kind regards Günter.



Harald Grossheim wrote:

To the enoiose topic cylinder head and its lid:

The sealing miracle is called ELASTOSIL (Company Wacker Chemie)

a transparent silicone, against which all other so-called thick masses (e.g.

“Dirko” etc. are bad, and even the "XOel" shuts up) Combined

with intact, at the best bushed threads in the cylinder head, the cylinder head

leak problem is solved for all times (to drive with or without motor suspension becomes

a matter of taste). I would not recommend Helicoil for a final thread repair. It is not made for repeated screw in and screw out . For small money there are Thread busches which you can use without special tools.



Friday, July 7th, 2000 23:26

Hello Volker,

I have just read the page about the cylinder head, simple and good designed engine but the execution is partly lousy.

Honda offers a replacement kit (cylinder head with valves). All carrier bolts and threads are amplified and what is even better the thick area is approx. 30% taller. Prize 2 years ago approx. DM 850.

A real option, especial when you consider that a new normal cylinder head costs approximately the same amount without valves.

You have to ask your dealer whether the Kit is still deliverable.

Bye Uwe     



Sun look 2000 00:38:56, 20

Hello Volker

i just read about the mess making cylinder heads. I built

helicoils in three XLs and don´t agree, that this is not for eternity.

All machines are thick for three or four years. A stupid preholder had built in

Screws into the cylinder head and cut corresponding threads (6.25 mm.) I asked Böllhof (manufacturer of helicoil) whether this is still recoverable with helicoil. The answer was yes, the nuclear hole drilling may be 6.3 mm too.

Thick mass is “Elring”, not hardening, on silicone base.





Andreas Harz, Georg-Fröba Str.9, 64347 Griesheim

It has become sort of “religion war”, what XL-drivers tell one another about the leak problem of the XL.

My advice: the upper engine mount doesn't have to be removed as long as you take the drilling of the hold disks to flight with the frame mounts. Furthermore a flat head as well as lid is important eminently. When these points are adhered you put some “Dirko” (as thin as wafer) on the cylinder head and its lid which must be as clean as possible and puts everything together. Ready. Till now, I never had a oil mist at the engine!