CM400T Build / Questions

LongDistanceRider said:
Full advance is 43* +/-2* at 4500-5300 per the FSM. Lazy advance may have you at 6K before full advance takes place
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There’s an obvious full throttle lag exactly at 4,500, I think I mentioned this before. I assume if it’s happening at the correct rpm then the timing is correct? I’ve only been in 5th once so I haven’t been able to thoroughly test it honestly. Once the bike is fully warmed up this spot seems to midigate.
 
Most people don't know how these bikes are supposed to ride and are surprised when things fall into place. You should verify the timing before you tear your hair out and assume other problems. If you're serious about keeping the bike long term then, in my opinion, spending the $40 for this timing tool will go a long way with diagnostics in the far future. Things do go bad, even with good care and storage and you do have to sort of become your own mechanic to a certain extent with these vintage bikes.

I will say, do not waste time on very cheap timing lights. Reviews tend to conflict on Amazon with their accuracy and viewability. The Innova is the same tool they sell at Autozone, etc. but half the price. It's a good one, I've used it a lot.
 
Maraakate said:
Most people don't know how these bikes are supposed to ride and are surprised when things fall into place. You should verify the timing before you tear your hair out and assume other problems. If you're serious about keeping the bike long term then, in my opinion, spending the $40 for this timing tool will go a long way with diagnostics in the far future. Things do go bad, even with good care and storage and you do have to sort of become your own mechanic to a certain extent with these vintage bikes.

I will say, do not waste time on very cheap timing lights. Reviews tend to conflict on Amazon with their accuracy and viewability. The Innova is the same tool they sell at Autozone, etc. but half the price. It's a good one, I've used it a lot.
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Sounds good, adding to the shop list for December haha.
 
Anyone have any leads to valve cover gaskets and the grommets for the bolts? I also need to do my clutch plates and springs. I’d like to get stuff that isn’t an arm and a leg but isn’t horrible quality. Not sure where to look.
 
AustonG said:
Anyone have any leads to valve cover gaskets and the grommets for the bolts? I also need to do my clutch plates and springs. I’d like to get stuff that isn’t an arm and a leg but isn’t horrible quality. Not sure where to look.
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Did you take a look at the link about identifying and locating parts in your Welcome Package that I posted in my reply to your introduction? A lot of helpful suggestions in it.
 
The cover grommets are a Honda only item, might as well get the gasket from them at the same time.
HINT: when the VC bolts stop turning don't tighten more. Unless you like removing broken bolts
 
Before I jump to just buying frictions plates and springs I want to ask thoughts on the weirdness of my clutch.

So, when I adjust for the leaver on the crank case it’s at about 95*, not the whatever 120* it should be. Anything past 95* there’s just nothing at all. Micro-adjusting from the handle leads to 2 things…

1. The clutch is fully engaged when the lever is released, but coasting with the clutch lever pulled (clutched disengaged) results in a rather loud revolving sound from the transmission (I assume it’s still grabbing slightly) but it doesn’t bog the motor at all.

2. Reducing “slack” in the handle removes the noise when clutch is disengaged but there’s no play at all in the handle like there should be (worries me the clutch might not be engaging fully).

I have a hard time believing it’s worn plates when the bike only has 6,000 miles, unless the previous owner just really didn’t know how to drive. Could this be springs that aren’t strong enough? Stuck plate? Damaged clutch leaver?

I haven’t pulled anything apart yet, just wanting to gather some thoughts before tearing into it. Maybe you all know something I don’t.
 
Don't know about degrees. I use the hour clock with 12 o'clock being the lever pointed perpendicular to the case.
The cable adjusters need to be backed off before the following
The case lever adjustment should be set so there's 1-2mm of free play. Use a 17mm open end wrench to move the lever. The usual spot the adjustment ends up at is @11 o'clock.
Once the free play is set the bar lever adjuster is used to position the freeplay there which also set the engagement point. 3/8"-3/4" freeplay is spec.
 
I know what you mean on the degrees, Imagine a straight line with the bike front to back, the lever is going to be pointing somewhere between 90-120 degrees off that line. My CM400 which has a much snappier clutch feel, is a little over the 110 mark with all the slack taken out, but my CB400 is closer to the 95 degrees you mentioned. the CB has a much softer squishy clutch but no noise and does not slip at high RPM, I also am curious how close to 90degrees can you get before we should consider changing the clutch. If you can't get it adjusted where the noise goes away then you may have to do some dis-assembly.

If you put the bike in gear, pull the clutch and roll it by pushing it around do you still hear the noise?
 
esmith250624 said:
I know what you mean on the degrees, Imagine a straight line with the bike front to back, the lever is going to be pointing somewhere between 90-120 degrees off that line. My CM400 which has a much snappier clutch feel, is a little over the 110 mark with all the slack taken out, but my CB400 is closer to the 95 degrees you mentioned. the CB has a much softer squishy clutch but no noise and does not slip at high RPM, I also am curious how close to 90degrees can you get before we should consider changing the clutch. If you can't get it adjusted where the noise goes away then you may have to do some dis-assembly.

If you put the bike in gear, pull the clutch and roll it by pushing it around do you still hear the noise?
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At 90 degrees you lose all the leverage of the clutch arm and the bar lever gets really stiff.
 
Okay I finally got to where I can look at the clutch. Have the cable slacked so that the lever is free to move. The lever has virtually 0 friction (I can move it with my had), up until 11:56~ish where it abruptly stops and a wrench must be used to turn it further. This to me indicates that the clutch is not disengaged internally all the way out, so possibly springs? Or the plates are worn that far?
 
my CB4000 is in the same spot, still working but as LDR says probably getting close to needing replacement. that extra slop up to the poin shown in the picture is the same for me, normal, just getting close to worn out.
 
What are the odds I could re-use the metal discs / plates and just replace the clutch pads? I’m not sure how this would go considering it’s a wet clutch. I’ve only done car clutches.
 
Alrighty, so I replaced the plates and springs, had my dad help me do it. Did everything according to the Clymer service manual, the outer plate is in the right spot, etc. However the clutch is still pretty stiff (I think it’s the cable but I’m unsure). More importantly, the clutch seems to “drag” when pulled in. Like if you roll the bike in 1st with the clutch pulled in you can feel it hit the gear and kinda slowly work free. I have all the levers adjusted properly to my knowledge, it just seems there’s not enough “swing” to disengage the clutch. Is there something internally I could’ve missed or could be broken?
 
Unlike an automotive clutch a multiplate wet clutch never fully disengages. It disengages enough to slip, the oil creates a drag friction also while also reducing friction wear. Cold oil will exacerbate the engaged feeling.
 
LongDistanceRider said:
Unlike an automotive clutch a multiplate wet clutch never fully disengages. It disengages enough to slip, the oil creates a drag friction also while also reducing friction wear. Cold oil will exacerbate the engaged feeling.
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Okay good to know, I was totally overthinking then. Thank you for the response. I’m leaking a bit of oil out of the valve cover gasket, I just replaced it. So I’ll have to figure that one out.
 
AustonG said:
I’m leaking a bit of oil out of the valve cover gasket, I just replaced it. So I’ll have to figure that one out.
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When you change a valve cover gasket on these engines, you should always change the bolt seals as well because new ones provide more pressure to help the valve cover gasket to seal its best.
 
And remember those bolts have a shoulder and won't continue to get tighter beyond a certain point. Over-tightening them usually results in breaking off the bolt.
 
IMG_8656.jpegIMG_8657.jpeg

Replaced the buckhorn bars with some CB bars and put some risers under them. I need to replace the bushings under the bar supports because one side is worn more than the other causing them to be titled. May opt for just making some steel inserts.
 
Hey everyone! Been awhile since I’ve posted. I’m currently in the painstaking process of painting my bike.

Is there a guide on how to remove the headlight bucket for the cm400t? Wiring is my worst enemy and I don’t want to mess it up. Removing it seems like a huge PITA.

Thanks for your help!
 
Service manual is your friend, but you will have to disconnect everything in there and remove the turn signal stalks and it will come out. Take pictures as you remove it as everything is in there in a specific way.
 
Maraakate said:
Service manual is your friend, but you will have to disconnect everything in there and remove the turn signal stalks and it will come out. Take pictures as you remove it as everything is in there in a specific way.
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Ahhhh I hate to b*tch but that does not sounds like fun.

I’ve already spent a good 16 hours prepping my gas tank and it’s still not ready…
 
AustonG said:
Ahhhh I hate to b*tch but that does not sounds like fun.

I’ve already spent a good 16 hours prepping my gas tank and it’s still not ready…
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Many people think bikes are easy to work on compared to a car because things are smaller. It's simply not true.
 
Was able to get my tank and side covers painted over spring break. This was my first ever time doing professional level automotive painting. Despite my inexperience I am happy with the way it came out. Excited to see it on the bike after proper cure time.

I did get some mild orange peeling on the clear, which I should be able to sand / polish out in the next week.

Went with a high metallic tuxedo black, hard to see on camera, but it’s beautiful in the sun. The tank LDR sold me turned out incredible.

Next I’d like to powder coat the fenders and rims, which might make some purest cringe, but yolo.

IMG_9234.jpeg
IMG_9238.jpeg
 
Out of curiousity…

Does anyone know if seat latches of an E model (79-81) are the same as the seat latches on a T model (79-81)? My bike is a T, but I have an E tank. I want to get a new lower profile seat for looks, but I wanna make sure it doesn’t ram into the tank like current seat. Wanna insure the latches still line up.

Thanks!
 
AustonG said:
Out of curiousity…

Does anyone know if seat latches of an E model (79-81) are the same as the seat latches on a T model (79-81)? My bike is a T, but I have an E tank. I want to get a new lower profile seat for looks, but I wanna make sure it doesn’t ram into the tank like current seat. Wanna insure the latches still line up.

Thanks!
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One way to check things like this is to look at the parts fiches at places like CMSNL, Partzilla and NOS Parts Now. Find the part numbers for both latches and if the middle 3 digit number is the same, then the same part was used on both bikes.

www.cmsnl.com

LEVER,R.SEAT LOCK for Honda - order at CMSNL

✓ Get the LEVER,R.SEAT LOCK ✓ Manufacturer Part Number: 77221-447-000 ✓ Quality part
www.cmsnl.com www.cmsnl.com

www.cmsnl.com

LEVER,R.SEAT LOCK for Honda - order at CMSNL

✓ Get the LEVER,R.SEAT LOCK ✓ Manufacturer Part Number: 77221-447-000 ✓ Quality part
www.cmsnl.com www.cmsnl.com

It would seem so.
 
ancientdad said:
One way to check things like this is to look at the parts fiches at places like CMSNL, Partzilla and NOS Parts Now. Find the part numbers for both latches and if the middle 3 digit number is the same, then the same part was used on both bikes.

www.cmsnl.com

LEVER,R.SEAT LOCK for Honda - order at CMSNL

✓ Get the LEVER,R.SEAT LOCK ✓ Manufacturer Part Number: 77221-447-000 ✓ Quality part
www.cmsnl.com www.cmsnl.com

www.cmsnl.com

LEVER,R.SEAT LOCK for Honda - order at CMSNL

✓ Get the LEVER,R.SEAT LOCK ✓ Manufacturer Part Number: 77221-447-000 ✓ Quality part
www.cmsnl.com www.cmsnl.com

It would seem so.
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Interesting, thank you!
 
The Latches are the same I believe, but the distance between the latches is what you need to verify. I have T models, but the distance between the CB and the CM are different, I would guess that all the CM's for that year range are the same, but to verify someone with and E model frame can measure the distance between the latch mounting holes.

Do you have a gap where the seat meets the tank? Is that what you are trying to solve?
 
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esmith250624 said:
The Latches are the same I believe, but the distance between the latches is what you need to verify. I have T models, but the distance between the CB and the CM are different, I would guess that all the CM's for that year range are the same, but to verify someone with and E model frame can measure the distance between the latch mounting holes.

Do you have a gap where the seat meets the tank? Is that what you are trying to solve?
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The opposite, the T model seat is too long and had to be bent up “over” the E tank. This causes rubbing and the sort.
 
I have found this seat on eBay for around $180 (may try to source one cheaper). It’s supposed to be a direct mount. I like looks, a nice blend between “cafe” and the stock seat. A bit more streamlined.

IMG_9243.jpeg

www.ebay.com

1979-1981 Honda CM400 A C T 1981-1983 CM450 A C E Motorcycle Seat Black | L2626 | Front | 3 Months | Vietnam

CM450 A C E 1981-1983. CM400 A C T 1979-1981. Custom-handmade motorcycle seat for the following Honda model It's powder coated throughout with black paint for weatherproof. Fits directly on the bike.
www.ebay.com
 
I have noticed, and maybe some of you can help me. This might be wordy so get ready.

When I bought the bike the clutch felt off, like, it engaged and disengaged fine. It honestly didn’t seem like it was slipping either, but the swing of the arm took forever before engagement (as mentioned previously). This resulted in the bike feeling sluggish. Like I was fighting getting it to moving. It also felt like it “lurched” a bit in low rpms, ESPECIALLY gears 1-2 at 15-25mph.

I replaced the clutch, the lever still took forever to reach any form of resistance (disengaging). I realized the distance between the pusher (idk what it’s called) and the bearing on the spring plate was rather far. I remedied this by making a washer to fit between this gap. This eliminated the lever swing problem. However, the clutch still feels the same. It lurches slightly in low rpms, and it feels like the bike is still kinda underpowered. Gears 1 and 2 feel abnormally slow. 3-5 feel fine. 55mph at 4,800 rpm in 5th.

This has lead me to some theories:
1. The clutch isn’t fully engaging and is slipping very slightly in low rpms (which to me wouldn’t make sense because it drives fine in higher rpms and gears 3-5)
2. There’s a throttle cable issue and it’s engaging harshly, causing it to “lurch” when trying to cruise in low rpms.
3. Transmission issues, which would be beyond my basic knowledge.

I’m not sure what to do, the bike is fun in higher gears at high speeds, cruising and the like. It’s traffic or low speed driving that feel weird. It feels lurchy and sluggish. This isn’t a motor issue I don’t think, it’s synced, carbs function great, revs well, etc. Also, the clutch is loud, like not in a bad sounding way, it’s just loud.

Any help would be great, I know it’s hard to steer me in the right direction when you can’t physically drive it. I hope my explanation helps.
 
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AustonG said:
I have noticed, and maybe some of you can help me. This might be wordy so get ready.

When I bought the bike the clutch felt off, like, it engaged and disengaged fine. It honestly didn’t seem like it was slipping either, but the swing of the arm took forever before engagement (as mentioned previously). This resulted in the bike feeling sluggish. Like I was fighting getting it to moving. It also felt like it “lurched” a bit in low rpms, ESPECIALLY gears 1-2 at 15-25mph.

I replaced the clutch, the lever still took forever to swing. Realized the distance between the pusher (idk what it’s called) and the bearing on the spring plate was rather far. I remedied this by making a washer to fit between this gap. This eliminated the lever swing problem. However, the clutch still feels the same. It lurches slightly in low rpms, and it feels like the bike is still kinda underpowered. Gears 1 and 2 feel abnormally slow. 3-5 feel fine. 55mph at 4,800 rpm in 5th.

This has lead me to some theories:
1. The clutch isn’t fully engaging and is slipping very slightly in low rpms (which to me wouldn’t make sense because it drives fine in higher rpms and gears 3-5)
2. There’s a throttle cable issue and it’s engaging harshly, causing it to “lurch” when trying to cruise in low rpms.
3. Transmission issues, which would be beyond my basic knowledge.

I’m not sure what to do, the bike is fun in higher gears at high speeds, cruising and the like. It’s traffic or low speed driving that feel weird. It feels lurchy and sluggish. This isn’t a motor issue I don’t think, it’s synced, carbs function great, revs well, etc. Also, the clutch is loud, like not in a bad sounding way, it’s just loud.

Any help would be great, I know it’s hard to steer me in the right direction when you can’t physically drive it. I hope my explanation helps.
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To clarify, this could very well be a mixture of very torquey (short) gearing and my noobness to driving motorcycles (this is my first bike).

Additionally, I drove my friends 1980 (Same year as my bike) CB400, and didn’t notice this problem. Which could be an old clutch that doesn’t engage as harshly, or transmission / sprocket ratio difference. Idk anything about the CB’s
 
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Also, I would like to give 2 example scenarios to help understand.

1. Imagine cruising at 15 mph in first gear, I’m not sure what rpm this translates to but let’s say 4,000. You roll off the throttle and feel the engine braking, normal. Without touching the clutch, you roll back on the throttle and the bike lurches forward harshly and then accelerates. This seems weird to me.

2. 1st gear stretches up to like 20 in 5-6K rpm if I remember correctly. This seems normal, but I feel like I have to give it pretty heavy gas to keep up with normally accelerating traffic. Are these bikes just kinda slow? I know they are old, but damn haha.
 
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