Friday, May 29, 2015

Cracked the egg

I forgot how much real estate these things take up. Was like gravel in there.

Thursday, May 28, 2015

Saturday, May 23, 2015

It begins... pre-unit rebuild

The weekend I've been looking forward to and also dreading is here. Max and Lori are in Socal and I have 3 1/2 complete days alone. I'm completely wiring the 750 Hondamatic and tearing down the pre-unit. Maybe I can go see Mad Max or something, too. Anyway, I spent all yesterday getting the motor out and assessing the damage. Yup, there's a hole in the piston. I used my new super awesome magneto timing light and it told me my timing was perfect. After examining the head gasket, it looks like it was blown around the center bolt... and I'm not suprised. I was never able to get that bolt to seat right. I did what I should have done in the first place and chased all the barrel threads and the head bolts. That made a world of difference and am kicking myself I didn't do it. So why did I hole the piston? Head gasket leak? The other theory is the rings never set right, I'd always been blowing smoke. The barrles looked good just glazed. Going to try to split the cases today.

Thursday, May 21, 2015

I won a big prize, one might even say a Trophy

Lori and Max went away for the weekend to visit family and then I turned around and traded my durn 'ol XS650 for a 1964 TR6. An original, complete but disassembled, should run Trophy 650. I am quite pleased. Actually we both are quite pleased. It was a good trade.

Tuesday, May 12, 2015

Monday, May 11, 2015

Master Mechanic Journal: CB750 Edition

To prove my mechanical aptitude, I decided to try to alleviate the low idle "chunk" sound on the lower left of the motor. In my eyes, it was 1 of 4 possibilities: cam chain, clutch, starter clutch, or carb sync was needed. I'd already tackled the cam chain and pulling in the clutch didn't eliminate the sound, so I figured it one of the other two. Since the bike is kick only, I decided to just rip out anything to do with the starter. I pulled the starter out and plugged the hole in the case. Then I pulled the rotor off and removed the starter clutch barrels. And while I was there, I removed the big starter gear off the crank and put everything back together. I was so proud of myself.

Well now I had a leak at the cover. And then I discovered that the starter gear's bushing actually covers a hole in the crank the oils the gear. And now that hole had open access to spray oil everywhere, thus reducing my oil pressure! So I got to rip back in a put the gear back, and replace the cover's gasket. And I still have a leak.

Well that didn't fix the chunking sound, so I ponied up and bought a MotionPro carb sync. I calibrated the tool and spent 2 days trying to get the damn thing to sync. My readings were all over the place! I'd blip the throttle and 3+4 would jump up, then come back down, and 1+2 would be higher. So frustrating. I went through everything: checked for air leaks, tightened the clamps, slacked the throttle cable as much as I could. Nothing helped.

I was getting ready to sell all my bikes and become a peanut farmer. I started going through all the bolts on the carbs and discovered that the 3 bolts and 1 nut on the connecting shaft for the carb lifters were loose! They either worked themselves loose or I forgot to tighten them 2 years ago... oops. That also explains the horribly wonky idle I've always had. Basically the lifters could move a little on the shaft and that would severely affect idle and sync. Once I tightened those up it became much easier to sync.

After all this, the low speed chunk is still there. I'm starting to think it might be inside the gear cluster/final drive sprocket area.

Finally, I had that horrible wobble of death on grated roads to figure out. I've gone through everything and added a fork brace, so it has to be the square profile front tire. I recently got that Duro and decided to put it on and try. You can see how much rounder the profile is.