Tag: Motorcycle

Tonight I hooked up the Harbor Freight ultrasonic cleaner (that is now property of the class) which everyone seems to own and use to clean carburetors. For a solution I used about 55/45 SimpleGreen to water because the carbs were just filthy.
For each I ran a cycle of 8 minutes, 4 times with the air intake valve side down. The basket was crammed full of the rest of the carb and parts. In retrospect, someone pointed out to me that will make the clean a little less effective and instead I should hang the carb itself by a clothing hanger directly above the ultrasonic emitter. Good point. The heater heats up quickly and although there is an over-heating cutoff built in, it will get hot enough to boil before that happens to pay attention here. This took most of the evening; I will get the other side that was sitting out of the water later.
After their final bath, I rinsed all of the big parts in solvent because the gunk just didn’t want to let go. The cleaning solution was completely filthy; light would not penetrate it. The next step is to clean everything with carb cleaner. The problem is that there is a layer of gunk that just does not want to let go of the surface, so I’ll come back with brushes and q-tips and a guitar string next week.
The pictures show how much a carb fits into the cleaner, along with how many parts you can cram in there but probably should not. At the end of the night, I try to keep my work-space in decent order.
Continue reading “CB750F: Day 11”

Back to class again. This time it is only twice a week but for 4.5 hours. The majority of the evening was spent taking the rack of carbs apart. Not much to screw up here, but I always find a way. Most of the screws were stuck and/or stripped out, so Brian helped me with the last one using just a pliers. Arriving late to class, that is all I got done.
Most of these photos are for my reference later. In particular the spring locations are important.
For directions I’m using the Honda service manual, Mike Nixon’s guide, MacGregor Carb Cleaning Services guide, and Randakk’s rebuild kit.
Continue reading “CB750F: Day 10”

Tonight was preparation for break. Hooked up the adapter cable to the battery for the trickle charger and learned about what it means to ground a circuit (fireworks in face) along with a trick of wrapping the screwdriver in a layer of electric tape to insulate it.
It was real hassle getting the bolts into the nut on the battery posts, so I stuck some paper tape underneath to jack it up and pulled it out once it was gripped.
Finding a carb kit is still a work in progress, I suspect that I will buy individual jets.
Debating buying an ultrasonic cleaner; though it is certainly easier than building one. One interesting item I found though was a drop-in transducer, which could turn any container into an ultrasonic cleaner!
The cheapo nitrile gloves aren’t cutting it, they break too much, got a recommendation for the Microflex MidKnight Nitrile gloves instead.
Brandon shared his carb gaskets with me, they look like they will fit (thanks!). I might break apart that rack so I can replace/clean all of the diaphragms.
The rest of the night I just cleaned off the bike; she is in rough shape and deserves to be clean.
Continue reading “CB750F: Day 09”

Tonight was mostly Q&A along with cleaning; I won’t be able to rebuild the carbs before class ends tomorrow.
May I leave the trickle charger on? Yes. Does the kickstand or center stand need new rubber? No and maybe. Ratio of water to simple green for the ultrasonic carb clean? 2/1. May I leave parts here over break? Yes. Do I need to replace the gas in the tank? No, it is already OK. Should I get a new air cleaner? Yes. Does carb cleaner damage the seals? Yes, that is why we took them out. How do I measure the petcock line? Inner diameter. Are digital torque wrenches any good? Maybe, but they are generally fragile.
Took the exhaust, muffler, and chain guard home. It took a while but I cleaned most of the 3cm of gunk accumulated in the chain guard off.
Continue reading “CB750F: Day 08”

Today I was well enough to even think of working on the bike, at all. Got back to researching a carb rebuild kit. It has been interesting searching for one, Pat helped me find one that probably works and then I searched for more and got these results:
denniskirk.com: no
knfilters.com: no
outwestmotorcycles.com: no
randakks.com: no
vintagecb750.com: Probably part # 48-1963
mrcycle.com: no
ebay.com: no, or rather found the kit fro Kaizen without jets
dimecitycycles.com: yes
partsnmore.com:no
mrcycles.com: individual parts
bikebandit.com: individual parts but no microfiche!
cheapcycleparts.com: individual parts
In summary, there are not a lot of kits.
Only one, and two if you count vintagecb750 with a big “maybe” since it doesn’t specifically support the model I need. They do have one model specific kit, but it doesn’t have new jets, and that is the plan. I will go with dimecitycycles.
It has been interesting learning about how well this model is supported. My original idea was to go with a Honda CB750 because there is such good support for it out there. From what I am seeing, this model was not as prevalent as the touring style bike, so there isn’t as-good support. Also choosing first year of the model was a mistake. With persistence and patience though it should go fine.
Although I did purchase the original service manual along with the Haynes, resources like mrcycles.com that have the microfiche for the OEM parts online are extremely helpful for managing the replacement of parts.
The paint store had Simple Green for sale, so I bought some. I figured since the bike is mostly stripped down I can clean off the gunk that has accrued everywhere, and that it is less inexpensive in time and money to completely disassemble the bike and refinish it.
Addendum: 01/18/13
power-barn.com doesn’t have kits, either.
jetsrus.com, no.

Need to order a new fuel line, it is pretty neat because although it is now totally inflexible, it had still worked correctly. There is probably a painful metaphor hiding in there.
Took the jets out and put them in order. The idle jet has “98” written on it, the one on top (T). Before taking the idle jets out turned them to all the way in and wrote that down so I install the new ones at the correct setting. There is oxidation in the float bowls, I’m going to buy an ultrasonic cleaner and use true green on them, and put the whole rack in the dip tank next week. Used a socket for the topmost jet. The pin holding the 4th carb float didn’t want to come up but was coerced eventually.

Sprayed carb cleaner in each of the jets and on the parts a little bit. Pat found the kit I need on http://vintagecb750.com/, the key was to select “Series 2”!
The right-hand grip is all rotten, pulled the tape off.

Need to order parts and an ultrasonic cleaner, too.

Tonight I pulled the carburetor rack out. Visually it appears that they won’t come out. Just starting at it you see that it has to be lifted up from the air box side, but when you try it, it barely moves. Left the two choke and one throttle cable hooked up, and tried to stand over the bike and it was still not enough. The start of it is just lifting it up to give it some space.

Finally I just focused all of my pulling on the right side and then it popped right out of the manifold side. In the future, I would slide the metal retainer on the air-box side shrouds all the way back, I think that they were holding the carbs in, and made it difficult to get out. Also when I did pop them out, the retaining clips were sort of mangled out of shape, but not damaaged though, I just bent them back into shape.

Then I pulled out the left side.

In the process, the rings on the air box side got kind of twisted out of shape so I squeezed the back right. That left the row of carbs just sitting in there. It didn’t want to slid out because the throttle cable was blocking it from coming out, so I removed that. It didn’t resist, I should check if that is a problem. I couldn’t figure out how to disconnected the choke and my teacher, Pat, showed me there is a slot where the wire-and-ball sit inside of to secure to the assembly.

Although I had vacuumed the area, after pulling out the carbs a ton of carbon looking junk appeared all over the bench, the engine block, and even sitting on the edge of the manifold gaskets.

Next time I would loosen the rings on the air box side almost all the way, I think that would have helped.
This can not have been good for the running of the engine. I vaccumed all of that up and put the battery back in and took the compression measurements again.
Just kept turning it over and over watching the pressure go up, and the teacher and entire room stopped and stared at me, I learned my lesson, just test it out 4 and 6 cranks. Basically just watch the PSI needle pop-up and that is one crank. The measurements were PSI at 4x: 100, 92, 75, 100 and 6x: 110, 110, 100, 125. Pat said ok, cylinder 3 is less. Why? I said bad rings, or valves are not sealed. Pat what else, and why? I forgot the head gasket seal, and that running lean will cause overheating that will seize the cylinder. The spark plug said it was lean, I think because it was not worn out and blackish like the other ones. Pat said to put a half cap of oil in the cylinder and test it again, this time 100 and 125, perfect! The rings are bad. We will leave it for now and once we get it running check how good the rings are operating.
Took the top, the slides, and the float bowls off tonight and left it for tomorrow. Ther was years of crud stuck on the outside of the carbs so I scrubbed in off in the solvent station. Most of the screws holding the covers and float bowls on were stripped so Pat showed me what is an impact-driver and how to use it. Awesome. Laid everything out to make it easier to know when something disappears!

Took the exhaust and muffler off, muffler first. There was a bolt missing from the thing that attaches them. There was one missing stem and one stem that came out from the parts that hold on the muffler. Teacher said that I can go to U-Spray to media-blast it and paint the exhaust, it is in decent enough shape. Maybe this is a POR-15 candidate.

That bolt that was misaligned in the frame, I used a jack to lift up the frame. It was specifically for stuff like this, I was surprised to see that you can turn it and lift it just with your hand.

Teacher brought the compression tester adapter, it was 114 and 110 on 1 and 2 but in the process the battery wore out. 4 turnovers wasn’t enough to test it, so Teacher said turn it over until the gauge doesn’t go up any further. I set up the battery charger and 12V on medium for 40 minutes, I will test the other two tonight.
Followed the direction in the service manual to get the carbs out. Set up a drain pain under the carb drain hoses, loosened the air cleaner bands, loosened the airbox top bolt, and slid the air cleaner back. Loosened the manifold bands, drained fuel out of the carbs, and disconnected the drain cables. Still figuring out how to get the shrouds off the carbs on the manifold side, they are solid and stuck on there. I will finish tomorrow.

Once we look at the carbs we will look at what parts to order.