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Discussion Starter #1 (Edited)
I bought this 1981 CM400C about a month and half ago as a project. This is my first motorcycle that I've ever owned. Overall it appears to be in pretty good shape. The carburetors weren't on it when I bought it so I don't even know if it runs yet. My goal is to get it running and restore it to pretty close to original. Short term I want to get it running and ridable and then this winter rebuild the engine. I'm working through the items in the "Basic Checklist for the New to You Old Bike" post. I figured I would share my progress for anyone interested. I started with rebuilding the carburetors since they were already off the bike. I've completely cleaned and rebuilt the carburetors with new gaskets, jets, o-rings, etc and they are ready to go back on the bike. I've done some polishing on the top covers and I think they are looking pretty good.

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I've done some other work already as well and I'll be sharing my progress as time permits.


Thanks for looking.


Jay
 

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Discussion Starter #3
I did some polishing on the left side cover tonight. A lot of work though and still a long ways to go. This was a couple hours of work with a buffer wheel attach to my drill press and black buffing compound. I need to get me a benchtop buffer. No sanding beforehand. I found HerrDeacon's polishing process in his CB400T Hawk project log a little bit ago. I like the results on his stuff. I'm going to try his method instead.

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Same situation I got myself into last summer. You're gonna wanna check the compression..I thought I got mine all put together and ready to ride, then bam..no power at all. Had to get my head worked on and new valves, rings, and all that good stuff. Amazingly fun bike though. Thanks for sharing and literally everything you will need to know is available on this forum; it's a great bunch of guys. Good luck with your new project!
 

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Paid $400 for the exact same model about two years ago. same color and everything. I had to install a new carb due to the throttle-cable arm having been broken, rebuild the one working carb. the bike had sat for over a year but (proud moment) I got it running within 24 hours of bringing it home. AAAAAAaannnnnd then ran into my first major problem. It seemed the exiter coil on the stator was bad and the rotor was rusted all the way around. I replaced the rotor and got a used stator online, but the stator I bought had its own issues. I still cant get the bike to act right in high RPMs. It runs underpowered with sudden bursts of voltage. So I think it is a better stator but the exiter coil is still not 100%. Hoping I won't have to pony up for a new CDI. I hope everything goes well for you. It looks like your patience level with the restoration is paying off. Thanks for posting.
 

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Discussion Starter #6 (Edited)
Yeah, this site is great. It's a wealth of knowledge and I'm learning a ton just from searching and reading other peoples posts.

I am concerned about the compression as well. I'll definitely be checking that once I get it running. I've done several other things already, including adjusting the valves, installed new spark plugs, adjusted the balancer chain, lubed all the cables and I've cleaned up the sprockets and chain and relubed the chain among other small items. I drained the oil a couple of weeks ago and discovered that the after marker oil cooler the PO installed was routed all wrong as mentioned in another post about the oil cooler. I've since gotten a new oil drain bolt to replace the one the PO drilled out and plugged up the fitting in the oil filter cover. I'll probably replace that cover eventually. The oil was pretty black when I drained it.

I haven't refilled it with oil yet. I just ordered replacement gaskets for the side covers and the oil filter cover a few days ago. Maybe this weekend I'll get the right cover back on. I don't know though, I didn't see working on the bike anywhere on my wife's honey-do list.

I learned how to bench sync the carbs from the Rebuilding VB Carbs post and I bought a sync gauge. So the carbs are sitting on the workbench ready to go back on the bike.

I'm not in a hurry to get it running. My 16 year old son on the other hand, that's a different story.
 

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Once oil is back in you can run the compression test. It'll be a tad low on a cold engine but you'll get a good idea of what you're working with.
areich2690
You might start a topic in the SOHC section on the problem
 

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Discussion Starter #8 (Edited)
My new side cover gaskets aren't in yet, but I did get an opportunity to clean up the old gasket material off the covers. I still have a few spots of old gasket material left on the crankcase surfaces, but I'll get those cleaned up before I put the covers back on with the new gaskets.

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When I was adjusting the valve clearance, I cleaned up the valve cover as well. I found some old RTV sealant in the gasket groove and along the edge of the valve cover. I got it all cleaned out and replaced that gasket as well since it was cracking. It's now back on the bike.

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I probably won't get an opportunity to work on the bike this weekend since it's Mother's Day weekend.


Happy Mother's Day to all the mother's out there!!
 

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Sweet progress!! Good luck mate!
 

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Found ya!...niiiice polishing there, subbing this build to see how you get on m8!
 

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Discussion Starter #13 (Edited)
I haven't done too much in the last few days. I came down with a case of bronchitis and the doc told me not to do any sanding for a week or so because it would irritate my lungs even more. So no work on my covers this week. The antibiotics have kicked in and I felt well enough to do some work the last couple evenings. So I started working on the front brakes and master cylinder. I pulled the master cylinder all the way apart and I had ordered a rebuild kit for it two or three weeks ago. It was pretty nasty inside and under the bowl. A lot of junk in there. I didn't get any before pictures of it though. I got it rebuilt along with a o-ring for the bowl. I'll probably replace the bowl eventually. I replaced the diaphragm as well because it has a rip in it.

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I pulled the front caliper as well. The pistons were froze up in it. I got them out, but scratched them up in the process. One of the dust seals is pretty torn up and then other one isn't a whole lot better.

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I'll have to order some new seals and might have to order some new pistons as well.
 

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Discussion Starter #14
Unfortunately I have had no time to work on my bike. I've had a completely unrelated little side project I just completed though. We're having a Pinewood Derby March of Dimes fundraiser up at work tomorrow. So me being interested in things of this sort and a little competitive, I had to build myself a car and enter it in the race. Hopefully it will do well. I know, I know, this has absolutely nothing to do with Honda Twins.

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Discussion Starter #15
I finally had a chance to work on the bike last night. My new pistons and seals recently came in along with a couple replacement boots for the caliper. I got it all rebuilt last night and got everything back together and the caliper pins and bolts greased. I then tried to bleed the brakes. I can't get the master cylinder to build pressure. I tried the technique of removing the banjo bolt at the master cylinder and placing my thumb on the whole, working the lever till fluid started escaping by thumb instead of air, tried the reverse bleed process using a syringe to push the fluid up to the master cylinder from the caliper. No luck. I have the caliper off and raised up above the master cylinder. I'm finding it hard to do the bleed process by myself of opening the bleed valve, pulling the lever, closing the bleed valve and then releasing the lever. Hopefully I can get my son to help me out tonight. I'm thinking I may pickup a vacuum pump this weekend as well depending on how things go this evening.
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Discussion Starter #16
I still haven't gotten the front brakes working. I spent some time last night working on the side covers again. Finished round 1 of the sanding with the 220 grit paper. Next up will be 400 grit wet sanding. My teenage daughter came out and asked me if she could help me sand some. I was quite surprised, but very happy. I thought she would only stick around for 10 minutes or so. She helped sand for about 45 min. Maybe her phone was dead.;)
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Discussion Starter #17
It's been a long time since I posted or got a chance to work on my bike. I have made some progress. I finally got the front brake bled and working well. Turns out a resembled the master cylinder wrong and had the plunger gasket seal in backwards. Also during this process it got punctured by the spring. After much frustration I took the master cylinder apart and that's when I discovered my error. Luckily the old plunger gasket seal was still in real good shape and I got it all back together and working.



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Discussion Starter #19
With the front brake finally done and solid, I started working on the next task, rebuilding the forks. Both are leaking, one worse then the other. I got them off and taken apart without any problems.


I ordered new oil seals, dust seals, guide bushings and piston rings as well as some o-rings for the connector air hose and the fork covers.


I started reassembling the forks tonight. I wasn't paying attention and installed the guide bushing in the slider before putting the fork tube in. Any idea how to get this bushing out?



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A slide puller or internal jaw puller. Just have to be slow and easy working all the way around it to pull it.
While the front end is apart this would be an excellent time to clean and grease the steering stem bearings.
 
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