1964 Honda Dream CA78 Rebuild-storation

sarals · Post by **sarals** » Wed Feb 05, 2014 4:54 pm

Bob, 48 has a SOLID point. Graham, Ed and I initially thought the knock pins were the reason I had head gasket leakage with my engine. I'm not sure, now, that that was the true reason. As you know, the ONLY place there is oil flowing under pressure through the barrel/head is through the front corner studs, which sit in oil passages. There is no oil flowing under pressure anywhere through the rear of that cylinder. The O rings around the knock pins and the head gasket seal the oil passages. In my case, the O rings were seemingly working, but the gasket was not. Why? It was a Rocky gasket that came from an old gasket kit that I bought ages ago. I don't think it was a thick enough gasket. Ed sent me a new head gasket from one of his vendors. He explained that it was slightly thicker than the Rocky iteration I had on the engine. He also sent me shorter knock pins. Now, the second time (the third time was the charm) I took the head off the engine to chase that leak I used knock pins that I had cut down to the same length as the ones he sent me. It still leaked! So, I'm almost certain the head gasket was the issue. I did use his knock pins, along with new copper washers under the cap nuts on the head.

BTW, I torqued the cap nuts to 21 ft/lbs (except for the front corners, which are at 18 ft/lbs).

G-Man · Post by **G-Man** » Wed Feb 05, 2014 5:08 pm

sarals wrote:Bob, 48 has a SOLID point. Graham, Ed and I initially thought the knock pins were the reason I had head gasket leakage with my engine. I'm not sure, now, that that was the true reason. As you know, the ONLY place there is oil flowing under pressure through the barrel/head is through the front corner studs, which sit in oil passages. There is no oil flowing under pressure anywhere through the rear of that cylinder. The O rings around the knock pins and the head gasket seal the oil passages. In my case, the O rings were seemingly working, but the gasket was not. Why? It was a Rocky gasket that came from an old gasket kit that I bought ages ago. I don't think it was a thick enough gasket. Ed sent me a new head gasket from one of his vendors. He explained that it was slightly thicker than the Rocky iteration I had on the engine. He also sent me shorter knock pins. Now, the second time (the third time was the charm) I took the head off the engine to chase that leak I used knock pins that I had cut down to the same length as the ones he sent me. It still leaked! So, I'm almost certain the head gasket was the issue. I did use his knock pins, along with new copper washers under the cap nuts on the head.

BTW, I torqued the cap nuts to 21 ft/lbs (except for the front corners, which are at 18 ft/lbs).

The voice of experience......

They say that experience is the thing you get just after you needed it most......

G

Bob750 · Post by **Bob750** » Wed Feb 05, 2014 5:43 pm

LM- Thanks for your input. Your valve job is the secret weapon in this Dream!

Graham- It looks like I'll be taking you up on your offer. Thank you! I really appreciate it! I'll PM you with my info.

48- Thank you for the compliment and the advice! I think you may be onto something. I'm quite sure it's not the knock pins, which are the same ones I removed, cleaned and reused. It's not the sleeves, which were zero-zero with the face of the cylinders, which itself was in very smooth, excellent condition. The O-rings were new. The only unknown here is the gasket. I'm putting considerable trust in the fact that the engine didn't leak a drop for the 200 miles we rode it before I had to address the transmission problems, so I'm pretty sure about the studs and nuts not bottoming. Graham's offered me a screen and cap nut, so my case bottom leaks will be solved. Also, I'm quite sure the throttle cable is routed correctly: from the handlebar through the top clamp side hole, through the first frame hole on right side (with clutch cable), down the frame, and it makes a smooth arc to the carb. The thing is, with all the adjustment taken up in the middle (barrel nuts all closed together) the jacket is still too long (or the cable itself is too short.) It wasn't bound anywhere and there is slack in the jacket, but when it's hooked up it's not right at the slide.

Sara- Thanks for your take on this. So let me be clear, no matter what you did, the only thing that stopped the leak was the thicker gasket on the third try? If so, I think I'll try your torque values to see if it could be that simple. And since I can do that by partially dropping the front of the engine and leaving the lower bolts attached, I'll try that before dismantling the head. But I'll be ready to tackle that if new torque doesn't do it.

Thanks again, everyone! I'm gonna get on that cable and see if I can make it work.

48lesco · Post by **48lesco** » Wed Feb 05, 2014 8:41 pm

Bob - Unless there's an early/late difference, I've only ever seen the internal throttle cables routed behind the headlight bucket, around the steering neck, and into the frame on the LEFT side with the harness or one hole behind it. I attached some measurements of an OEM cable for you to compare yours to. I have a few more OEM head gaskets than I really need too...
-48

Bob750 · Post by **Bob750** » Wed Feb 05, 2014 9:47 pm

Thanks, 48.

I haven't taken the cable out yet, but when I do tomorrow, your photos will be a great help.

* If it's the same length as your OEM, I'll install it through the LEFT side and see if that makes the difference.
* If it's not a standard length, I'll debate whether to a) ask Retrobikes whatsupwidat? and try for an exchange, b) try to modify mine, or c) order OEM from Nick or wherever else I can find one.

In fiddling with it on the bike today, I can see nowhere to make up the ~1 to 1.5 cm I seem to need to make it work right, and have some adjustability.

As for the head gasket, I'm going to re-torque to a higher value and see if that eliminates the seep. If not I'll pay you a fair price for shipping me one of your OEM head gaskets and dig into it.

I did run it through the gears today, though, and the transmission works very smoothly with the good parts you sold me! :-)

Cheers!

sarals · Post by **sarals** » Thu Feb 06, 2014 9:37 am

Bob, I am 95% sure it was the head gasket causing the leak on my engine, yes.

Hopefully your leak can be tamed by a retorque!

I'm pleased to hear your gearbox is working nicely! I had to fiddle with that on my bike. The index roller was sticking and the shift drum wouldn't rotate. One thing after the other!

sarals · Post by **sarals** » Thu Feb 06, 2014 9:37 am

Graham - the Voice of Bad Experience! ;)