Topic: CB750 K0-1, the motorcycle that ate my brain!

[HondaMan]

The pistons I wanted to use had broken middle rings and there were segments riding in the grooves. I'm assuming since the cylinders appear good and the segments are pretty smooth whoever put these pistons onto the sandcast bottom end broke them and it ran like that.

Was it the middle iron ring?

[Don R]

The pistons I wanted to use had broken middle rings and there were segments riding in the grooves. I'm assuming since the cylinders appear good and the segments are pretty smooth whoever put these pistons onto the sandcast bottom end broke them and it ran like that.

Was it the middle iron ring?

Yes they both were, I honed the cylinder, and it cleaned up fine. I got a set of rings on the way. I'm getting excited to see it with the motor back in and the set of long awaited Italian 4-4 pipes on it.
  I'm trying to never say the B word. 

 Who needs a 1971 K0?

[BenelliSEI]

Parallel lives?

[Don R]

  We do have a lot of common interests and find similar projects interesting.

  My former fab shop partner/welder is coming by in the next couple weeks after moving 4 hours away. He's buying out my half of the Hossfeld bender and may weld the stainless-steel exhaust on my firebird. He wants to build some race cars again and needs to raise a roll cage on his stepsons Jr Dragster.
  The bottom line is, I need to leave these Hondas alone and get busy re-fitting my exhaust, it rubs the rear of the driveshaft when the axle is hanging from the coil-overs.

[Don R]

 I did spend some time on the car exhaust but had bike stuff out and want it put away so I worked on the cylinder and head. I did dig out the original head and began to clean it up. I flushed the cam towers and was surprised at the goop that came out.

[BenelliSEI]

Done….. I hear you; tough choices! I know once the race season starts, I spend a lot less time on the bikes. Nice choices to have to make. Keep smiling!

[Don R]

 Agreed, I have a checklist of tests and changes our racecar needs, it was acting like it has an intake vacuum leak, I'll pull the efi and pressure test the top end. since it got the replacement CFE heads it's never really been consistent. It needs new O2 sensors in the efi and data recorder, since it burns leaded fuel, they don't last.  I got a genuine Holley one and an Ebay Bosch replacement to compare readings. The ebay one is likely a cunningly cloned china part.  I plan to put the gas carburetor back on it, or swap the efi to canned E85 fuel. 
 

[BenelliSEI]

Good luck for the coming season. Our first race is the last weekend of April. I need to pull the front shocks (and remote reservoirs) and get them out to the rebuilder. The LF was leaking at the end of the season and they are overdue.

[Don R]

   Our racing association has a new schedule suited better to our location. We race at 3 of the 4 closest tracks to where we live and all of them are 1/4 mile. Most of our racers are from Chicago and Kenosha, the tracks are farther from them than from us. Byron, Cordova and Tri-States in Iowa.
  Now we'll see how excited about it my driver is, asking her about what races she wants to go to is like asking my wife where she wants to go for dinner.

[BenelliSEI]

   Our racing association has a new schedule suited better to our location. We race at 3 of the 4 closest tracks to where we live and all of them are 1/4 mile. Most of our racers are from Chicago and Kenosha, the tracks are farther from them than from us. Byron, Cordova and Tri-States in Iowa.
  Now we'll see how excited about it my driver is, asking her about what races she wants to go to is like asking my wife where she wants to go for dinner.

Now that made me chuckle! We have a four weekend series, each over a month apart. Every weekend is two full days of 8 hour enduros. On two of the weekends, we have an optional four hour race on the Friday afternoon, after practice. We plan on starting all of them!

[Don R]

 I'm waiting on standard piston rings from Canada. I've used them before and was pleased with the result.

 Edit, the rings arrived. I'd have ordered two sets but ebay said they only had one. It took a while, I guess getting parts over the border isn't as easy as it once was. At least I beat the tarriffs.

[Don R]

 I was looking at tank sets from Yamiya and saw the Brighton prototype gold with a  white over black stripe set. I once considered making a prototype clone and annoyed Vic by mentioning it on his prototype thread. If Yamiya thinks it's OK, who am I to argue? 

 The Brighton bike has the regular appearing gold sidecover emblem and a CL77 taillight with a painted bracket. I'd love to find an emblem similar to the one on Vic's bike. I already have gold emblems bought for it. It wouldn't hurt my feelings to paint flat silver over the Busso heat shields but there's no sense making it ugly for the sake of clone accuracy.

[Don R]

 I got a smoking deal on a new old stock Vesrah full gasket set, ordered a pair of seal kits and for the GS1100, I got a phone charger adapter that clamps to the handlebars, has two phone charger ports and a digital volt meter.

[Don R]

  Today I checked the end gaps and wound the rings onto the pistons. My gasket set didn't ship, the payment fell off of my checking account for paypal also. I guess I'll message the seller since it's the 4th day.
 Edit: the set did finally ship. I bought 3 things paypal put 2 things on my checking and one on my credit card.

[Don R]

 I looked at the gold/white stripe Brighton clone tank set at Yamiya, a repro seat and a 67 cb350 taillight. I'm thinking about $3K can make my prototype clone. Sidecover emblems are up in the air but I think it had sandcast type gold shields on gold paint. I'd need a knob type oil cap too. The cylinder fins can be squared up a bit.
 I'm wondering how original the prototype was when it sold, it has aluminum top shocks and no coil covers in the pictures I see.
 A perfect place fora Vietnam handmade double cut front fender.

[Don R]

 I got two pistons on the rods before I ran out of gas today. One pin clip shot away like it was going into orbit, but later I found it in the rag that's over the crankcase holes.

[Don R]

 Aww, man I rolled an oil ring. It turns out there's a spot in the piston that the oil rings and expander won't all fit without pooching out. I turned off the lights and came back in. Fortunately, I have a spare.

[RAFster122s]

Don, sorry to hear about the troubles you are having. It ain't because of inexperience! Hang in there and you will overcome...
David

[Don R]

 Once again, I am wrong. I fiddled with the oil rings for a while and got the thin rings and expander to sit right. No clue what was happening. I cooked out since it got to 50* F  and didn't try the cylinder again.

[Don R]

 I tried to put on the cylinder again, no go. I measured the expander all the way around, no difference found. I broke off a small piece of a file and went all the way around the groove looking for a burr. Tried multiple times, the bottom oil ring does not want to tuck in. I've gotten the other cylinder 4 times straight.
 I went around the taper of the cylinder with a flap wheel and smoother the transition from taper to hone marks. Assembly lube, oil, Lucas red grease, no improvement.

[BenelliSEI]

Don….. I had this issue with S/C Project too. Gave it a light hone and tried to install a fresh set of std. rings  to the original pistons. All the rings gapped perfectly in the bores and the piston clearances were spot on. HOWEVER, no matter how much I fiddled the oil control rings they would not fit correctly. In the end, I subbed in the originals and moved ahead.

[Don R]

 I'd buy one-piece oil rings if I could find them.

[HondaMan]

Try the M/C brand rings (eBay). I use them pretty often.

[Don R]

 I drug it out of my brother's back yard, my first bike in years. Then along came many other easier bikes, false starts, repairs, welding, acquiring what I took from it, wrecking my
 GMC Dually when I took the gnarly engine case to the car wash in winter, but it keeps gnawing away at my time money and ultimately, my brain. 
 I just watched a video about the kookie original T bucket TV car, called "the car that ate my brain" and this project came to mind.

[Don R]

I decided to try putting the cylinder on it again, this time I removed the expander and oil rings, no matter what I did the thin rings would not seat properly on the expander and fit into a groove.  I removed an expander from an F2 set and used it with two good thin rings and it finally surrendered.
 The M/C that ate my brain. After a beer break, I'm going back out to put on the head. I'd love to slip this engine into the frame and free up some space so when the snow melts, I can abandon my storage unit.