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Discussion Starter #1
Ok, first post for this thread. Here we go.
Got the bike Spring 2017. Didn't run when I got it, figured out some electrical issues, cleaned the carbs, tried a new battery, replaced some fuses, and thanks to the folks here, got it idling roughly. The whole plan for getting this bike was to do a custom build and learn more about these machines. So knowing it had some life was sufficient for the time.


Fast fast forward to now and the start of the rebuild. As it stands now:
Engine is off the frame and the tear down has started. Opened the valve cover and.. hmm something looks odd... oh that valve spring doesn't have an adjustment bolt or lock nut.. oh and neither does that one. Thankfully I found those hiding right behind the springs with no signs of damage. Keep removing parts, start the cylinder head bolt pattern and #8 doesn't seem to want to move. Hmmm, maybe a touch more pressure *snap*. Remove the cylinder head and there is about 1" of the bolt sticking up from the threads... it's still there, soaking in penetrating oil.

One of the valves was stuck down and scored the top of the piston. Cylinders are spotless and piston rings have good movement, but will go for a hone.



Gunk on the clutch springs.


81 CB400t tank I'm thinking about using.

More pictures to come.

The plan: full tear down and rebuild. Trying to balance being on a budget and replacing what needs replaced. I want this to be my everyday bike (at least in the summer here in the PNW) and for long rides. Probably stock airbox/carbs, maybe 2-1 exhaust, LED lights, smaller battery, a rewire would be nice but we will see. I'd like to keep it stock for reliability, but upgrade where it's beneficial/affordable.

I'll be scouring the forum for help and asking questions here too I'm sure.
Any suggestions for tearing down/rebuilding would be appreciated. I've done some motor work before, but this will be my most in-depth thus far. I have the FSM and Clymer handy and the knowledge here.

I want to be thorough since I have the motor off the bike and mostly opened up.
Any suggestions of parts that have a better modern replacement? ie. charging components, etc.

Thanks in advance! I'm looking forward to learning from the folks here and contributing where I can.
 

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Welcome. I used to live in Seattle. Great bike scene. Good luck with your project.
If you haven't already, check out Backfire. It's a bike night in Ballard.
 

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To use that tank look at your older frames where the tank mount pucks are, notice on the SC frame there's a thru hole in the same location. Large bolt to hold pucks and the front mount is set.
I'll advise you to get the tank boiled out and pressure tested. These have the same problem the SC tanks do in that the rear lower corners are below the petcock so they become water traps. They rust thru in this area. If there's holes they can be brazed closed and a tank liner/sealer used.
You don't want a smaller battery if you're planning on everyday and trips. I'll recommend the MotoBatt MB12U as a good AGM battery. I'll also suggest upgrading the voltage regulator to the MOSFET type.
In working on the snapped off head bolt, get a piece of sheet metal from the hardware store. Drill a 10mm hole in it and fit it over the broken bolt, tape in place. That will protect the gasket surface. Be patient with trying removal, go slow. I'd soak it for a few days like you're doing hitting it with a hammer periodically to jar the threads. In the mean time continue to strip the engine down completely. Drilling the stud is the absolute last resort to removal. Once the upper case is stripped down and de-oiled/greased stick it in the oven or barbecue to heat it up to 200-300 degrees. Now, with a large pipe wrench try to unscrew it (this is where the sheet metal is really important). Vise grip, channel locks, etc are all useless for this.
 

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Discussion Starter #4
Welcome. I used to live in Seattle. Great bike scene. Good luck with your project.
If you haven't already, check out Backfire. It's a bike night in Ballard.
Thanks! I actually grew up in Asheville, I'd love to take a nice scenic ride back someday!

Thanks LDR for the advice. I keep soaking and tapping that bolt a couple times a day. As I get down that far I'll give the oven trick a try.

The tank does have different mounting pucks, given that it passes a pressure test and is road worthy, I was thinking of either pulling the mount off the 81 cb400 frame the tank came from, or fabbing up something.
I'll check out that battery, reliability is a key factor in all of this. I would like to get away from the heavy lead/acid batteries for many reasons...
I found a MOSFET style from rmstator.com for $129, does that sound right?
 

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Discussion Starter #5
Ok, here are a few more pics what not.




Thank you LDR for the quick guide on making the locknut socket to remove the clutch!





Got all the plates removed and found this... sharpie marker for scale. The plates and friction pads are all within tolerance as, everything looks pretty dang clean and good... except this scratch.






I have some new friction pads, the plates are within tolerance. New springs on the way too. Got all the parts cleaned up and ready to be put back together. Think there is a need for concern on the scratch on the pressure plate?

Next up, oil pump and gear shift linkage.

I have the oil seal kit and gasket kit. Any other items i should add to the shelf while still in tear down mode?
I'm looking at starter rebuild kits too. Trying to locate a m20x1.5 bolt to help get the flywheel off, then I'll be able to assess what the stator looks like.
 
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Discussion Starter #6
Which one of these is not like the others.... and of course it is #13 from the diagrams and I can't seem to find them anywhere. I have an 81 CB400T that I may be able to tear into and see if I can snag a bolt from there.



Stuck valves scored the piston. It's not very deep. I'm checking for any other damage but the piston rings look good, cylinder walls look good. But I'll go for a hone, and new piston rings. I'll keep reading the forum for suggestions on boring and going for a larger piston... think it's needed? Any benefit to that V just a hone?



And here is the damage to the valves...



Can I replace the valves on just one cylinder or should I replace them in both cylinders?

I have the cases cracked and almost ready for cleaning and maybe some paint. Trying to check the tolerances of everything and seeing what needs replaced. So far, things are looking good. Although I think I may need a new set of vernier calipers for accuracy.
Almost ready to try LDR's oven suggestion for getting the snapped cylinder head bolt out.

Slow and steady. Trying to get parts ordered soon so I'm not waiting too long once I start putting things back together.
 

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I only see 4 usable head bolts in the picture, the ones w/o corrosion. Honda is supplying all except for #10 in this fiche Western Honda Powersports- Honda Dealers 50 years In AZ Motorcycles ATVs Sales Parts Service & Repair and www.cmsnl.com has that one available. https://www.cmsnl.com/cm400t-1981-b-canada_model48573/90081-mc0-000-bolt_90081413000/#.WnehNainE2w
I'd go ahead and replace all of the valves since it's apart and the valve seat will have to be cut to match the new ones anyway. That way you have a known good head. Here's a suppliers for valves: Motorcycle Restorations
59161 Nelson Avenue Yucca Valley, CA 92284
+1 626 429 4464
Take the cylinder and pistons into a machine shop and get them measured, You may be in spec and just need to hone.
 
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