1979 CM400A Winter Rebuild [COMPLETE]

Maraakate said:
Not a big deal. I have time this weekend and will revise the pictures. How do you apply it?

Honestly I've had it apart enough it's really not that scary like it was before.
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I use a finger tip to literally smear it, you can see the surface thru portions of the smear. You're only looking at a couple thou thickness to get a good seal.
 
Removed, for the next round just the bottom case or both cases with a smear of my finger? Thanks for stopping me before it became a problem. That's why I'm posting this stuff as I go.

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I thought it was a bit much myself, but it was hard to be sure just how thick you laid it on until I saw some of the ooze after you tightened the bolts.

One side only for Hondabond. And I use my finger too.
 
Now done correctly by smearing it with my finger and minimizing excess.

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EDIT: UPDATED ORIGINAL POST ABOUT THIS.
 
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OK, after it's all bolted up here's how you reassemble the torque converter side. (Will break up into two posts because of picture limit).

For the oil pump and primary gear slide the washer over crankshaft.
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Slide the primary gear over it, with the washers. You may have to move the gear on the oil pump and the primary outer gear (for torque converter) to get it to align.
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To install the oil pump chain hang the chain over the smaller sprocket that goes on the primary gear. Attach the bottom of the chain to the oil pump and put it together. There's a dowel pin and you may have to move the washer a little while putting the gear on.
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Take the gear shifter shaft and with it more oriented pointing to the left (facing you) start inserting it.
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Push down on the top to clear the "pizza cutter" and be mindful of the alignment on the bottom with the large spring and pin that sticks out.
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Watch out for that last bit, it may be a big tough because of the seal on the left side. You'll know it's not there yet because it won't clear the spring retainer on the pin at the bottom.
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Take the inhibitor arm and slide it over the torque converter shaft.
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Put the thrust washer over the inhibitor arm on the torque converter shaft and then attach the spring. Orientation matters.
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Put the tiny collar into the transmission countershaft.
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Seated.
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Put the larger collar over the shaft.
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Seated.
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Place the idler gear (with needle bearing) over the shaft. Don't lose the alignment washer.
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Put the double coil ring in place on the shaft. Beware, the inhibitor arm may have a tendency to "pop" out while you do this. The torque converter presses up against that washer on it's shaft with the inhibitor arm and keeps everything in place once all these gears are meshed up.
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Seated.
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Put the thrush washer on the kickstarter spindle.
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Put the kickstarter pinion gear on... and that's it for now!
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Please remember to anyone following at some point me and you will have to torque the primary gear bolt on the crankshaft! You'll also want to adjust the counter balancer chain tension one last time. THEN we can put the torque converter on! I don't think any of this should be done until the cylinder and head are on, yes?
 
Smear technique worked better for you, still a tad heavy witnessed by the squeeze out along the mating surfaces but by in large, good. (y)
I would wait for at least the cylinder to be in place if not the entire top end before moving to the sides.
 
Right, I just figured I'd get the basics on and actually torque the 17mm bolts for both side of the crank after the top end is assembled. At this point it's top end, then torque converter. I'll get bored later and end up putting the chain on and the collector.
 
Small set back, and I should have known better. Oh well.

I had everything back together, sans the top end of course. Torque converter reinstalled, crankshaft bolts torqued to spec, stator, the 3.5 qts required for rebuild. Kicked over slowly about 20 times while holding the cam chain up to circulate some oil/prime it. Verified shifting. Routed all wires and cables correctly.

Starter was not connected. I turned the key on to test the gear indicator lights since reattaching the gear switch and wanted to test oil pressure lamp. Starter wire was hanging then slightly touched the solenoid and starter bumped for about a second. Cam chain knotted, similar to when you lay a chainsaw chain down and it always likes to do that. First there was the swearing, of course. Second, I calmed down, un-knotted the chain and rotated slowly. No damage to anything else, but one of the links in the chain seemed to absorb all that pressure and there is a tight spot in the chain. Time for a new chain, which I immediately ordered after calming down and will have to inspect the bottom for any metal debris. I don't think that happened. I drained the oil and removed everything. Oil looked good. I just need to drop the engine again.

I got very lucky, it could have been much worse. A nice thing is that I will be able to re-use o-rings, seals and gaskets because everything was greased before assembly and it's never been fired.

What I've learned is, don't try to save some time on assembly later if it involves electronics. I think putting the rest on, like the stator and torque converter was an OK thing to do that would cause no harm. But no point in attaching that battery because of what happened. I was embarrassed to admit this in the thread last night, but I'm OK with admitting it now. Not a huge deal, I'm sure you guys have made even dumber mistakes in the shop. We all fall short. Chain will be here in a few days and I'll get it back together and keep all updated when machined parts are here.
 
It's easy to get ahead of yourself sometimes, particularly when you're at a point where there's nothing to do until the parts for the next step are ready. I've had to disassemble an engine partially before because I was thinking too far ahead and forgot a part, and it's frustrating in the moment for sure. It took me years to understand what my parents meant when they said I should walk away from it and think a bit, but of course they were right because with age comes the learning process from those experiences. Good that it was only the chain that was damaged, and really the lesson here is to not have the battery connected until the engine is complete.
 
I guess a nice bonus out of all of this is now I am very intimately familiar with complete R&I of the engine. Which honestly is not very scary to me anymore.
 
I still have the old info in my computer .Questions just ask. I think you are doing a fine job on this rebuild and dont think you will have any problems. Biggest pain in the butt for me was reinstalling the balance chain slippers.

Looking great.

Bill H
 
So far everything seems good, besides that blunder.

My trick for doing the slipper is partially setting it up before placing the crank holder. As you raise things up I finger tight the shorter bolt/front bolt (facing the balancer adjuster) to pull it up. Then after it's lined up I add the oil strainer and that bolt completes it.

Letting that rear balancer naturally rest with very little tension as per the confusing image in the book does work and prevents the annoying thing of being a tooth or two off after assembly.
 
For the curious... you CAN remove the starter without requiring removal of the oil cooler if you're worried about finding the gasket for it.

Remove the oil pressure sensor cover. Remove the wire for the oil pressure sensor that is held in with a 7mm bolt. Remove the sensor itself. I had to use a pair of needle nose vice grips to get mine out. Was kind of stuck to break it free. Probably from years of dirt and heat/cool cycles. Remove the two 10mm bolts for the starter. With a new o-ring it will be kind of annoying to get it out, but just wedge a flathead or plastic tool and CAREFULLY pry. It will come loose, then you have to rotate the starter forward for the bottom to clear the oil cooler.

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A little story on myself. First one of these I built I put the balancers in 180 degrees out. All back together and on the center stand. Rev up the rpm some and when I let off the throttle the bike hopped backwards on the center stand. Tom said I should make a vid of it and post it on U Tube. It was funny. Not funny was taking it back apart to repair it.

Bill H
 
Sorry to hear about the mishap but you're learning a great deal. One rule that was beaten into all apprentices was disconnect the battery before doing any engine work, literally beaten in some cases.
You know you're getting good at engine removal when you can have it out and partially disassembled in an hour.
 
Yeah the balancer system seems to be the most annoying part on the 400/450 twins. Would have been better to have access to the chain from a cover. But with the oil pump and primary gear there's not a lot of room. Lack of oil pan is unfortunate as well. This means you have to drop the bottom end to get access to that strainer.

I wouldn't quite say I'm at an hour, maybe 90 minutes.

I'm very fortunate that it wasn't catastrophic. Could have damaged or bent the rods.
 
Maraakate said:
Yeah the balancer system seems to be the most annoying part on the 400/450 twins. Would have been better to have access to the chain from a cover. But with the oil pump and primary gear there's not a lot of room. Lack of oil pan is unfortunate as well. This means you have to drop the bottom end to get access to that strainer.

I wouldn't quite say I'm at an hour, maybe 90 minutes.

I'm very fortunate that it wasn't catastrophic. Could have damaged or bent the rods.
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Yes you are very fortunate there.(y)
 
Back on the bench. Sorry did not flat rate time it 😂. Bottom of the case was good, no debris. No metal shavings or any scary stuff going on. Easy to remove the Hondabond this time because it's only been a couple of days and was not excessive so wiped it all off with thinner in about 20 minutes.

I believe the chain comes tomorrow since DSS had one at their Hanover warehouse which is a stones throw from me.
 
Maraakate said:
Back on the bench. Sorry did not flat rate time it 😂. Bottom of the case was good, no debris. No metal shavings or any scary stuff going on. Easy to remove the Hondabond this time because it's only been a couple of days and was not excessive so wiped it all off with thinner in about 20 minutes.

I believe the chain comes tomorrow since DSS had one at their Hanover warehouse which is a stones throw from me.
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Whew! All good news then. (y)
 
old timer said:
A little story on myself. First one of these I built I put the balancers in 180 degrees out. All back together and on the center stand. Rev up the rpm some and when I let off the throttle the bike hopped backwards on the center stand. Tom said I should make a vid of it and post it on U Tube. It was funny. Not funny was taking it back apart to repair it.

Bill H
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Got the new chain, and was getting ready to install and I noticed I did the exact same thing! Since fixed, bolted it back together and in the frame. Good thing I have to go back in there! I'll update the original post about that.

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Found out something interesting, the superseded base gasket seems to be a mirror image for the oil jets. The original is not. I decided to go with the original out of one of my NOS OEM kits.

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Starting to look like something again... I thought more about the superseded base gasket. I noticed those cut angles. I guess it would work either way so they simplified it.

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Looks like, so far, the collector box fits correctly. Some small bit of wrestling to line the two bolts up, but not that bad.
 
This project is still on-going. Machine work is almost finished so I believe in the next few weeks I can start reassembly. In a related note, someone has brought me a 79 CM400A to fix for them. They purchased the repro header pipes from DSS and they fit just fine into the collector with no issues. They look quite nice, so I'll likely purchase these in the future.
 
Machine work is officially done. Will be sending off the funds shortly.

Question for Jim, I believe for these engines the pistons are both at TDC at the same time due to the design of the engine being 360 degree crank? Rather, it's a matter of the mark on the camshaft during assembly and then setting the valves based on the lobes? I am aware that the best thing to do is remove the rocker adjustment screws to prevent trashing the valves during this delicate operation.
 
Maraakate said:
Machine work is officially done. Will be sending off the funds shortly.

Question for Jim, I believe for these engines the pistons are both at TDC at the same time due to the design of the engine being 360 degree crank? Rather, it's a matter of the mark on the camshaft during assembly and then setting the valves based on the lobes? I am aware that the best thing to do is remove the rocker adjustment screws to prevent trashing the valves during this delicate operation.
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Yes, it's a 360* crank so both pistons are TDC at the same moment.
The cam will align with the gear in one of 2 positions, doesn't matter which. There's a keyway on the left end that will face up or down with the crank set at TDC. The 2 hash marks on the gear should be aligned with the top of the head.
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Check sent to the machinist, should be receiving the parts in about 2 weeks.

For the curious, total cost of this rebuild, including the shipping ended up being about $3200.
 
Maraakate said:
Starting to look like something again... I thought more about the superseded base gasket. I noticed those cut angles. I guess it would work either way so they simplified it.

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Looks like, so far, the collector box fits correctly. Some small bit of wrestling to line the two bolts up, but not that bad.
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Did you purchase that collector box NOS ?
 
bilbikek411 said:
A quality Repro to match the specs of the original ?
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Fits fine, but one side for the heat shield has the screw slightly askew however barely makes it. The inside has some tubes, but I don't think curves are the same. It doesn't have actual paint, but some kind of powder-like coating used to protect it similar to cheap aftermarket body panels. This means you must remove it and prep it and paint with VHT exhaust paint. See previous page or two in this thread for the process and comparisons.

However, I think it will sound the same and perform the same. We will find out soon.
 
Here is the posts with relevant info:

1979 CM400A Winter Rebuild

Yeah, but the thing is the book doesn't mention it, not even in the addendums. So it seems to be a sneaky change at some point. Well I was wrong. It's actually the 1980 year. And it was in the book. I just missed it. The reason I went back and looked was because I pulled the bolts from the...
www.vintagehondatwins.com www.vintagehondatwins.com

1979 CM400A Winter Rebuild

Yeah, but the thing is the book doesn't mention it, not even in the addendums. So it seems to be a sneaky change at some point. Well I was wrong. It's actually the 1980 year. And it was in the book. I just missed it. The reason I went back and looked was because I pulled the bolts from the...
www.vintagehondatwins.com www.vintagehondatwins.com
 
Looking at the other posts helped.
I'm glad you were able to purchase a new(repro)power chamber;I hope it will give the same midrange power to your bike as the original had.
I have seen/spoken with many owners of 400/450 even CX500 models that have entirely removed the power chamber and run separate exhaust pipes,which I think takes away 'mid-range grunt' performance from the bikes.
 
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bilbikek411 said:
Looking at the other posts helped.
I'm glad you were able to purchase a new(repro)power chamber;I hope it will give the same midrange power to your bike as the original had.
I have seen/spoken with many owners of 400/450 even CX500 models that have entirely removed the power chamber and run separate exhaust pipes,which I think takes away performance from the bikes.
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That's a myth. I worked on a cm400a that had sportster pipes welded and ran exactly the same as my stock cm400a
 
Maraakate said:
That's a myth. I worked on a cm400a that had sportster pipes welded and ran exactly the same as my stock cm400a
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LDR explained the purpose of the power chamber once, long ago in land far away, I'm not sure I really get it, but it's a Honda thing that does kind of seem to be like vestigial organ. That's why I call it the exhaust gizzard.
 
Maybe other pipes, but the sportster pipes did nothing except change the exhaust note obviously. I personally did some runs from a stop up a large, steep hill near me on both bikes. They both reached the same speeds at the same points more or less. I didn't have it certified obviously, but if there was a difference we're talking margin of error difference only detectable on specialized equipment i.e. a dyno.
 
I believe it had something to do with the pulses generated as the engine fires. These are not high performance engines whether the CX series or CM series.

If you love the bike then enjoy the ride. ;)

Good detailed work there Frank. Is it still wearing one of those mufflers?
 
No the mufflers are still good. I still have yours on the left side and is holding up nicely. Thanks for the pipe and the really great price on it. A perfect "pre-owned" pipe for someone like me who rides often and is not making it a show piece.
 
I've never ridden an auto with a torque convertor, might be an interesting experience. I sense the low/mid range like coming out of a corner that I had to slow a bit more than I thought but just use throttle to pick back up.
 
Maraakate said:
Maybe other pipes, but the sportster pipes did nothing except change the exhaust note obviously. I personally did some runs from a stop up a large, steep hill near me on both bikes. They both reached the same speeds at the same points more or less. I didn't have it certified obviously, but if there was a difference we're talking margin of error difference only detectable on specialized equipment i.e. a dyno.
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In reply to myself, it's worth mentioning I have not noticed any difference in performance with a later-era VB carb that has a fuel accelerator diaphragm versus the 78 and 79 (maybe 80?) years. Again, same test, same bikes. The only difference between them besides the diaphragm is that I did the "trick" of changing the main from 65 to a 68. May also be necessary if you defeat the fuel acclerator diaphragm but I have no idea and have never tried to do so. Could be an interesting project for someone.\

EDIT: This doesn't mean that larger, high performance bikes may not require it. I don't know, but for the 400 Twins it seems like it doesn't do much for performance.
 
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