So you bought a CM400 / CB400T, now what...(50+ Build Links!)
- Thread starter Frankenfe
- Start date
Frankenfe
Coast to Coast
Re: So you bought a CM400 / CB400T, now what...(49+ Build Links!)
jorgo, nice contribution to the thread, I love the seat on your bike. probably the best way to handle the frame line / seat issue with these frames. Your right the CB200T & 250T Frame has the same design as the bigger CB / CM 400 450, Thus the same challenges. In looking back now, the route you took may have been the better suited one.
Plus I do have a growing interest in building a Brat/Bobber style bike.....
jorgo, nice contribution to the thread, I love the seat on your bike. probably the best way to handle the frame line / seat issue with these frames. Your right the CB200T & 250T Frame has the same design as the bigger CB / CM 400 450, Thus the same challenges. In looking back now, the route you took may have been the better suited one.
Plus I do have a growing interest in building a Brat/Bobber style bike.....
Re: So you bought a CM400 / CB400T, now what...(49+ Build Links!)
Thanks Frankenfe,
Its my first bike and been a fun build. I copied the seat design from some of the bratty 750s on bikeexif a while back and it seems to suit the frame shape fairly well. Just sat the front of the tank down a little to try and get a horizontal line matching the seat line. Has some firestones now and just have to paint the caliper and maybe the peg brackets black and its done. Will add a few more pics.
Thanks Frankenfe,
Its my first bike and been a fun build. I copied the seat design from some of the bratty 750s on bikeexif a while back and it seems to suit the frame shape fairly well. Just sat the front of the tank down a little to try and get a horizontal line matching the seat line. Has some firestones now and just have to paint the caliper and maybe the peg brackets black and its done. Will add a few more pics.
Attachments
Re: So you bought a CM400 / CB400T, now what...(49+ Build Links!)
hello
I watch this forum for a long time and I finally decided to enroll
I too have a 400 CM I change, here's a photo and a link for more details
http://www.cafe-racer.info/phpBB2/viewtopic.php?f=13&t=6844
Excuse my English but it is a translation because I'm French
here there is a very fine achievement and jaurais several issues especially in the carburetors
I have a 400 engine CBT I would like to change slightly to put on my bike
jos
hello
I watch this forum for a long time and I finally decided to enroll
I too have a 400 CM I change, here's a photo and a link for more details
http://www.cafe-racer.info/phpBB2/viewtopic.php?f=13&t=6844
Excuse my English but it is a translation because I'm French
here there is a very fine achievement and jaurais several issues especially in the carburetors
I have a 400 engine CBT I would like to change slightly to put on my bike
jos
Frankenfe
Coast to Coast
Re: So you bought a CM400 / CB400T, now what...(49+ Build Links!)
Jorgo, I can't speak for Non USA Models, but It looks to me your model is more closely modeled after the US CB400T model. The CB has the longer triangular cast aluminum piece on each side for Swing Arm / Peg than the CM. (Look at jos01's bike just above notice the smaller triangualr Piece. The reason I bring this up is there are minor frame differences between the CM & CB Frame. This traingular pice for one, As I recall the battery Box is also mounted differently, has adifferent Air Box and thus mount tabs different, and if I am correct the (I call it Peanut Tank) tank on yours is used oonly on the Bigger CB models not the CM. The CM had a longer "Tear Drop" tank and the rrear mont point is about 2" further back in the frame, You may want to check into this before paying for a Later CM Tank.
Jorgo, I can't speak for Non USA Models, but It looks to me your model is more closely modeled after the US CB400T model. The CB has the longer triangular cast aluminum piece on each side for Swing Arm / Peg than the CM. (Look at jos01's bike just above notice the smaller triangualr Piece. The reason I bring this up is there are minor frame differences between the CM & CB Frame. This traingular pice for one, As I recall the battery Box is also mounted differently, has adifferent Air Box and thus mount tabs different, and if I am correct the (I call it Peanut Tank) tank on yours is used oonly on the Bigger CB models not the CM. The CM had a longer "Tear Drop" tank and the rrear mont point is about 2" further back in the frame, You may want to check into this before paying for a Later CM Tank.
callmesb
It's a jungle man...gotta swing.
Re: So you bought a CM400 / CB400T, now what...(49+ Build Links!)
Hi, guys...love this thread. It's keeping me sane during my build. Not (exactly) sure where I'm headed, but here is where it started:
And here is where it stands:
I need to put some spoke rims on, clean up the front end, figure out what the hell I'm going to do with those goofy stamped fins attached to the hoop portion of the frame. Anyway...it's come a long way, but I have even farther to go. Hoping to have her on the road shortly and keep chugging from there.
Hi, guys...love this thread. It's keeping me sane during my build. Not (exactly) sure where I'm headed, but here is where it started:
And here is where it stands:
I need to put some spoke rims on, clean up the front end, figure out what the hell I'm going to do with those goofy stamped fins attached to the hoop portion of the frame. Anyway...it's come a long way, but I have even farther to go. Hoping to have her on the road shortly and keep chugging from there.
Re: So you bought a CM400 / CB400T, now what...(49+ Build Links!)
I figured I'd give y'all an update on my project. It's dead. Winter killed it haha
Alas, I did find a MUCH better bike that I've been working on, hurrah for Kijiji! I bought a '79 CB400 Hawk II, with only two previous riders and 10,500 KM on the odometer, I got one hell of a steal. Easily the newest vintage bike around. It's not in perfect condition, but in better than any I've seen locally. The seller (3rd owner technically) never rode it, just bought it off the second owner/rider last fall because he'd rather practically give it away then store it again (his since 2004). I noticed right away it had a 2-1 MAC exhaust, which is a $300+ value, which I kept very hum-drum quiet about. In all, I talked him down $120 because he had no UVIP yet and since we couldn't start it I had no idea what it would need to run right.
Sorry, I don't have pics yet guys. The seats gone to a local leather worker for re-upholstering ($150 local, vs $300 in town, we should support our local businesses), and the tanks off because I was cleaning the carbs today. They're reassembled and back on now, and I've installed my new battery, but when I went to turn the key and start her up, we get no dash lights or anything. We (neighbour and I, he's been riding for 30+ years) tested some of the circuit starting at the battery but haven't got past the ignition yet. He feels it's likely a faulty ignition switch, so I've got to disassemble my cluster tomorrow to get it out and check it for faults. If it's dead, then I have a good one on my other (now dead) project bike that I can rob. Does any one here have any experience testing the ignition circuits of these 400 twins? Any advice would be nice.
I figured I'd give y'all an update on my project. It's dead. Winter killed it haha
Alas, I did find a MUCH better bike that I've been working on, hurrah for Kijiji! I bought a '79 CB400 Hawk II, with only two previous riders and 10,500 KM on the odometer, I got one hell of a steal. Easily the newest vintage bike around. It's not in perfect condition, but in better than any I've seen locally. The seller (3rd owner technically) never rode it, just bought it off the second owner/rider last fall because he'd rather practically give it away then store it again (his since 2004). I noticed right away it had a 2-1 MAC exhaust, which is a $300+ value, which I kept very hum-drum quiet about. In all, I talked him down $120 because he had no UVIP yet and since we couldn't start it I had no idea what it would need to run right.
Sorry, I don't have pics yet guys. The seats gone to a local leather worker for re-upholstering ($150 local, vs $300 in town, we should support our local businesses), and the tanks off because I was cleaning the carbs today. They're reassembled and back on now, and I've installed my new battery, but when I went to turn the key and start her up, we get no dash lights or anything. We (neighbour and I, he's been riding for 30+ years) tested some of the circuit starting at the battery but haven't got past the ignition yet. He feels it's likely a faulty ignition switch, so I've got to disassemble my cluster tomorrow to get it out and check it for faults. If it's dead, then I have a good one on my other (now dead) project bike that I can rob. Does any one here have any experience testing the ignition circuits of these 400 twins? Any advice would be nice.
MBS
Live, breath, sleep HONDA!
Re: So you bought a CM400 / CB400T, now what...(49+ Build Links!)
I found on my 79 cm400T that one of the soldered contacts on the underside of the ignition came loose due to age and vibration. Caused me to have no lights and other issues. Couldn't re-solder the factory contacts, so I used liquid steal to hold the contact in place then sealed all the contacts with another coat of liquid steel. Never going to move or lose a connection there again. Try it if you find the connection failed on one of the wires. Cheaper than a replacement ignition switch and hardly visible. -MBS
I found on my 79 cm400T that one of the soldered contacts on the underside of the ignition came loose due to age and vibration. Caused me to have no lights and other issues. Couldn't re-solder the factory contacts, so I used liquid steal to hold the contact in place then sealed all the contacts with another coat of liquid steel. Never going to move or lose a connection there again. Try it if you find the connection failed on one of the wires. Cheaper than a replacement ignition switch and hardly visible. -MBS
Re: So you bought a CM400 / CB400T, now what...(49+ Build Links!)
Thanks MBS! Turns out that when we removed it, two wires were completely corroded off, despite a hack job of a repair job by one of the previous owners. We managed to rob the ignition switch + harness plug from my 81 cm400e parts bike, after much fussing and cursing at the mess of wires in the headlamp bracket. Problem solved right?
Wrong
Now I can't find the key to my parts bike, so I have a new switch but no key to match With no luck finding it yet, anyone know if a locksmith can make a key without having one to copy?
Thanks MBS! Turns out that when we removed it, two wires were completely corroded off, despite a hack job of a repair job by one of the previous owners. We managed to rob the ignition switch + harness plug from my 81 cm400e parts bike, after much fussing and cursing at the mess of wires in the headlamp bracket. Problem solved right?
Wrong
Now I can't find the key to my parts bike, so I have a new switch but no key to match With no luck finding it yet, anyone know if a locksmith can make a key without having one to copy?Re: So you bought a CM400 / CB400T, now what...(49+ Build Links!)
Another update guys! It's been a busy weekend, but we actually got the bike to turn over and start up! Hurrah! Here's how...
First we had to take the dash cover off and pulled the ignition switch off it's mount to check the bottom. Like I said, 2 of 6 wires were toast so I pulled a replacement switch from my parts bike, FINALLY found the key, and actually got dash lights!
Afterwards it turned over but wouldn't start. So we removed the spark plugs to find they're almost brand new just kinda dirty and oily. After spraying them with carb cleaner solution and air drying them with compressed air, we put them back on and got it to start and run! It ran really lean and dirty for several reasons, mostly cause it's not tuned right, hasn't been started since last year, and had excess oil to burn off that previous owner put in. We ran it for 5 minutes at a high throttle before calling it a day.
This weak I'll be tuning it and taking it to go get safetied and plated. Yay!
Another update guys! It's been a busy weekend, but we actually got the bike to turn over and start up! Hurrah! Here's how...
First we had to take the dash cover off and pulled the ignition switch off it's mount to check the bottom. Like I said, 2 of 6 wires were toast so I pulled a replacement switch from my parts bike, FINALLY found the key, and actually got dash lights!
Afterwards it turned over but wouldn't start. So we removed the spark plugs to find they're almost brand new just kinda dirty and oily. After spraying them with carb cleaner solution and air drying them with compressed air, we put them back on and got it to start and run! It ran really lean and dirty for several reasons, mostly cause it's not tuned right, hasn't been started since last year, and had excess oil to burn off that previous owner put in. We ran it for 5 minutes at a high throttle before calling it a day.
This weak I'll be tuning it and taking it to go get safetied and plated. Yay!
tsbigdog
Been Around the Block
Re: So you bought a CM400 / CB400T, now what...(49+ Build Links!)
Could someone do me a favor and post a picture of how their center stand spring is attached to either the swingarm or frame? I have an E model that I added a center stand to and I can't seem to find any info out there on how it's attached. I've checked the Clymers. I even looked at exploded parts diagrams I found online. It's such a stupid thing, but if I can't figure it out I'll have to remove it. It came with a large "C" shaped bracket also. Thanks in advance.
Could someone do me a favor and post a picture of how their center stand spring is attached to either the swingarm or frame? I have an E model that I added a center stand to and I can't seem to find any info out there on how it's attached. I've checked the Clymers. I even looked at exploded parts diagrams I found online. It's such a stupid thing, but if I can't figure it out I'll have to remove it. It came with a large "C" shaped bracket also. Thanks in advance.
Re: So you bought a CM400 / CB400T, now what...(49+ Build Links!)
Has anyone here have problems with running on only one cylinder? Mine keeps doing this to me. I start it cold, choke up, and it catches but then runs only on one cylinder (left side) until i blast the throttle long enough to open up the other. Then when I take it down off choke, it sometimes goes back to idling on one cylinder after running choked on two. Also, the right side spark plug kept fouling more than the left (did a swap test and still fouled). I thought if gas is getting to the point of ignition, but the plug keeps getting fouled by gas, then it's simply not sparking. Which means either (a) poor or no spark, or (b) a fuel mixture that's too lean.I bought new plugs, but it's still running on one cylinder after a cold start. I should also note I have a MAC 2-1 exhaust on the bike from previous owner, could I possibly need to re-jet/tune my carbs to accommodate for that. Anyone have any experience with running 2-1 exhausts?
It would appear as though we're not getting enough fuel to the right side carb, because we injected some up the run-off tube from the bottom of the bowl and it started up and ran on two cylinders from cold. So then we thought it might be a problem with the fuel tube that goes from left to right carb, but that appears to be clear and operates the float bowls correctly. Nothings jammed as far as we could tell.
Did a compression test as well. The left read at 165 psi, and the right read at 160 psi. Both cylinders seem to have the right compression (book says 170-199, but my research indicates 150-165 is more realistic for honda's 400cc twin cylinders).
As far as I can tell, the CDI unit is the only common possible denominator that pops up in all the trouble shooting problem areas (mis-fires when idles, misfires when running, poor acceleration, etc) but my neighboor (expert rider and ex-aviation mechanic) doesn't think that has anything do with the problem.
I'm truly stumped, I don't know what could be causing this to happen.
Has anyone here have problems with running on only one cylinder? Mine keeps doing this to me. I start it cold, choke up, and it catches but then runs only on one cylinder (left side) until i blast the throttle long enough to open up the other. Then when I take it down off choke, it sometimes goes back to idling on one cylinder after running choked on two. Also, the right side spark plug kept fouling more than the left (did a swap test and still fouled). I thought if gas is getting to the point of ignition, but the plug keeps getting fouled by gas, then it's simply not sparking. Which means either (a) poor or no spark, or (b) a fuel mixture that's too lean.I bought new plugs, but it's still running on one cylinder after a cold start. I should also note I have a MAC 2-1 exhaust on the bike from previous owner, could I possibly need to re-jet/tune my carbs to accommodate for that. Anyone have any experience with running 2-1 exhausts?
It would appear as though we're not getting enough fuel to the right side carb, because we injected some up the run-off tube from the bottom of the bowl and it started up and ran on two cylinders from cold. So then we thought it might be a problem with the fuel tube that goes from left to right carb, but that appears to be clear and operates the float bowls correctly. Nothings jammed as far as we could tell.
Did a compression test as well. The left read at 165 psi, and the right read at 160 psi. Both cylinders seem to have the right compression (book says 170-199, but my research indicates 150-165 is more realistic for honda's 400cc twin cylinders).
As far as I can tell, the CDI unit is the only common possible denominator that pops up in all the trouble shooting problem areas (mis-fires when idles, misfires when running, poor acceleration, etc) but my neighboor (expert rider and ex-aviation mechanic) doesn't think that has anything do with the problem.
I'm truly stumped, I don't know what could be causing this to happen.
furyphoto
I shoud probably be working right now
Re: So you bought a CM400 / CB400T, now what...(49+ Build Links!)
I'm not a master motorcycle mechanic by any means, but process of elimination is the way to go. An engine needs compression, spark, and fuel to run. You have compression, so I would start with:
Eliminate spark as an issue.
Gap Plugs
Spark Test (take plug out touch against cylinder head and check for strong spark)
If you are having spark issues then it is an electronic problem, or a short somewhere on the plug lead.
Check spark plug leads for worn or bare spots that could cause a short to the frame or cylinder head (I had this happen to me on a boat outboard once, temporarily fixed with a good wrap of electrical tape on the bare spot, but get new leads!)
You can swap the leads on the cylinders to see if the problem switches over to the other side.
Use a multi meter to check plug leads for breaks in the wire
or just replace them if they are old and worn.
Still have spark problems? then look at your CDI
If you have strong spark, it's probably a fuel issue:
check for vacuum leaks
clean carbs
sync carbs
check valves for correct operation and clearance (you should do this anyway)
As for your exhaust, there is always a good chance that a previous owner did not know to re-jet the carbs after an exhaust change. I'm not sure what is required for the MAC 2-1 but there is a good chance it needs to be done. It is unlikely that would cause your one cylinder problem though. But if you are seeing hesitation throughout the throttle range after everything else is looked after, then re-jetting/carb adjustment would probably help. 400 twins are apparently famous for being tough to re-jet and run smoothly after air-filter/exhaust changes.
I am sure other more experienced mechanics can chime in to cover what I have left out.
Andrew
I'm not a master motorcycle mechanic by any means, but process of elimination is the way to go. An engine needs compression, spark, and fuel to run. You have compression, so I would start with:
Eliminate spark as an issue.
Gap Plugs
Spark Test (take plug out touch against cylinder head and check for strong spark)
If you are having spark issues then it is an electronic problem, or a short somewhere on the plug lead.
Check spark plug leads for worn or bare spots that could cause a short to the frame or cylinder head (I had this happen to me on a boat outboard once, temporarily fixed with a good wrap of electrical tape on the bare spot, but get new leads!)
You can swap the leads on the cylinders to see if the problem switches over to the other side.
Use a multi meter to check plug leads for breaks in the wire
or just replace them if they are old and worn.
Still have spark problems? then look at your CDI
If you have strong spark, it's probably a fuel issue:
check for vacuum leaks
clean carbs
sync carbs
check valves for correct operation and clearance (you should do this anyway)
As for your exhaust, there is always a good chance that a previous owner did not know to re-jet the carbs after an exhaust change. I'm not sure what is required for the MAC 2-1 but there is a good chance it needs to be done. It is unlikely that would cause your one cylinder problem though. But if you are seeing hesitation throughout the throttle range after everything else is looked after, then re-jetting/carb adjustment would probably help. 400 twins are apparently famous for being tough to re-jet and run smoothly after air-filter/exhaust changes.
I am sure other more experienced mechanics can chime in to cover what I have left out.
Andrew
MBS
Live, breath, sleep HONDA!
Re: So you bought a CM400 / CB400T, now what...(49+ Build Links!)
Andrew's advise seems pretty spot on. The only bit of advice I would add is be sure to ground the plug to a frame mounted bolt or bracket when checking for spark. The CM400 and similar Honda models have many rubber mounted components that insulate from vibration and thus serve as a poor ground. Checking spark against a rubber mounted component, like the valve cover, would give a false diagnosis of weak or no spark. So just be sure to try different ground points for the plug. Good luck. -MBS
furyphoto said:
Andrew's advise seems pretty spot on. The only bit of advice I would add is be sure to ground the plug to a frame mounted bolt or bracket when checking for spark. The CM400 and similar Honda models have many rubber mounted components that insulate from vibration and thus serve as a poor ground. Checking spark against a rubber mounted component, like the valve cover, would give a false diagnosis of weak or no spark. So just be sure to try different ground points for the plug. Good luck. -MBS
Re: So you bought a CM400 / CB400T, now what...(49+ Build Links!)
We did spark tests on both sets of new and old spark plugs. Spark is good and consistent.. it's likely an air or fuel supply problem. I dug through my clymers manual today at work and came up with the following short list of possible causes to the following symptoms; Engine Idles Erratically, Engine Misses at Idle, Engine misses at high speeds, engine lacks acceleration. While each symptom had a list of its own possible causes, I've cross-referenced the most common probabilities. Here's what I've come up with...
-Carbs incorrectly adjusted (too lean or too rich)
-Improper carb main jet selection
-Clogged jets in carbs
-Carb float height incorrect (proper height is 14.9 mm)
-obstructed fuel line, shut off valve, or fuel filter
-choke valve stuck
-improper valve timing
-leaking head gasket or vacuum leak
-dirty or clogged air filter element
-weak cdi pulse generator
-weak ignition coil/ cable insulation deteriorated (causing a short)
-fouled or improperly gapped spark plugs (going to check gapping as u guys suggest)
If anyone can help me narrow down that list with their own expertise / experience that would be greatly appreciated. I'm back at it tomorrow and will update once I make progress
We did spark tests on both sets of new and old spark plugs. Spark is good and consistent.. it's likely an air or fuel supply problem. I dug through my clymers manual today at work and came up with the following short list of possible causes to the following symptoms; Engine Idles Erratically, Engine Misses at Idle, Engine misses at high speeds, engine lacks acceleration. While each symptom had a list of its own possible causes, I've cross-referenced the most common probabilities. Here's what I've come up with...
-Carbs incorrectly adjusted (too lean or too rich)
-Improper carb main jet selection
-Clogged jets in carbs
-Carb float height incorrect (proper height is 14.9 mm)
-obstructed fuel line, shut off valve, or fuel filter
-choke valve stuck
-improper valve timing
-leaking head gasket or vacuum leak
-dirty or clogged air filter element
-weak cdi pulse generator
-weak ignition coil/ cable insulation deteriorated (causing a short)
-fouled or improperly gapped spark plugs (going to check gapping as u guys suggest)
If anyone can help me narrow down that list with their own expertise / experience that would be greatly appreciated. I'm back at it tomorrow and will update once I make progress
