Crud in engine cooling passages?

[DSA]

Hi all,

I am replacing the water pump on my '76 (and will carefully avoid going into a rant about what a giant PITA this job is). I'm looking at the front cover, and taking a peek into the coolant passage reveals the build up of some dark-color gunk.
Here's a pair of photos, though it's a little hard to tell:

IMG_1992.JPG (90.92 KiB) Viewed 325 times

IMG_1991.JPG (97.57 KiB) Viewed 325 times

This in itself doesn't really strike me as an issue; the cooling passage doesn't appear to be meaningfully constricted. But it does make me wonder if this is happening somewhere else, maybe in a narrower area? I plan to take the radiator to a shop and get it boiled out, but what can I do for the engine block? I've read online that you can run some chemicals through that will flush it...but I don't know if that will play well with the o-rings in these bikes.

Is this even a legit concern?

Thanks in advance!

[Fred Camper]

Perhaps try compressed air if you can close the outlet down with a plate with a 1/8 inch hole or something similar.

[Sagebrush]

I used over the counter cooling system flushes on my 1100s when I had them. No issues resulted. So long ago I don't remember brand names but I bought them at auto parts stores.

[Sidecar Bob]

Before you even think about a rant keep in mind how long the old pump lasted and how much harder it would have been if the pump was located just about anywhere else on the engine.

[DSA]

Thanks for the good suggestions - air and flushing with chemicals it is.

Bob: You're right, but I refuse to admit it right now . I spent all of yesterday evening trying to pry out the oil seal; it was stuck in there like nothing I've ever seen. Came out as shrapnel...and with some nicking to the pump body where it sits. I really hope the new one seals. I suppose if it doesn't, I can replace the oil pump housing. The pain there will not be to the wallet; they on ebay for ~$20. But I see 3 more big JIS bolts need to be removed for that

[Sidecar Bob]

JIS screws inside the engine generally come out fairly easily, being just held in by the original application of torque.
It is corrosion due to water infiltration that makes the ones on the outside of the engine difficult (one more reason I'll never own a pressure washer).

[DSA]

Everything's back together - it seems like nothing is leaking. Water leaked out of the weep hole lightly and briefly, but then stopped (seals seating?) On the downside, the bike will not shift properly; only neutral, 1st and second area available. I've read enough to know that this is probably the front cover gasket being too thin. I bought a KP gasket kit, for reference. Just ordered a NOS OEM one off ebay and waiting for it to show up.

[redglbx]

DSA, this is one of those times that I can’t recommend using JIS screwdrivers strongly enough ! It just makes dealing with and not stripping the heads out on the screws, my buddy (thanks Ed !) and several here kept preaching to me about how much better they worked vs standard Phillips head. Being a skeptic I thought “yeah right” and then I got one !

Can’t recommend them strongly enough!

[Sidecar Bob]

Not so much better but different. No Japanese manufacturer ever used Philips screws for anything. What they use is something called Japan Industrial Standard (JIS) screws. Phillips and JIS are both "cross point" but with significant differences.

Philips screw heads & drivers were designed for mass production on assembly lines with power screwdrivers. The head recesses and driver tips are tapered so that the driver will "cam out" before enough torque can be applied to break the head off with those power screw drivers.

The Japanese figured out that it is much better for the recess and the tip to engage positively and use power screw drivers with clutches that stop turning the bit before the head breaks off.

Using Philips drivers in JIS screws almost always results in damage to the screw head (using JIS drivers in Phillips screws can damage the driver so don't do that either).

In 1967 they changed the thread pitch of JIS screws and added a dimple (punch mark) between 2 arms of the cross so if you see that dimple you know it isn't a Phillips screw. I can't remember when but they have stopped supporting the JIS screw head standard some yeas ago so the divers are no longer always marked as such.

If you have the option I'd recommend replacing the M6 JIS head screws with the M6 with 8mm hex head type used on the GL1100. Not only can you use a wrench to turn them but the heads don't have recesses that will fill up with dirt.

[DSA]

Oh I've been using JIS screwdrivers - I purchased a set the day after I got the bike. Those front cover bolts were still beastly hard to remove.
I bought a set of socket heads from Robin, that is what I put the front cover back on with.