(Not really) The slowest project ever - CM400T

Re: Slowest project ever - CM400T - HELP! Carb tuning! :(

Thanks for the replies guys.

I'm trying to get the float needles to seal, there doesn't seem to be anything there, I'm tempted to just hold it by hand and see if it seals with carb cleaner instead of gas put in the carb.

You are right about the exhaust collector. It's big, ugly, heavy, but it does keep the bike quiet. It actually is fairly quiet, so I'll keep it for now. I don't really want to fabricate a new exhaust, not until I come up with a design I'm completely in love with.
 
Re: Slowest project ever - CM400T - HELP! Carb tuning! :(

I do like what you've fabbed up. I just couldn't believe the actual weight of that thing once I removed it and held it. The space it created underneath gave the bike a better look before my mufflers were put on. What you've done would preserve that space, if clamped or welded directly onto the header pipe. ^_^ Keep up the great work.
 
Re: Slowest project ever - CM400T - HELP! Carb tuning! :(

Alchemist said:
YAY to videos:

[youtube=425,350]RamYSf3afTA[/youtube]
Click to expand...

I wouldn't touch the timing. But looking at the exhaust setup you have there and the pods, I would say you need to rejet the carbs. If your running your carbs on stock jets and no baffles then you have a change in back pressure as well as air flow in through the pods, which will mess up how it runs. Try a size up in the main jets and see if it improves. Nice job btw, thanks for the vid. I will be working on my CM400 this winter so I am taking notes. I like your solution to the difficult seat/frame issue with this model. -MBS
 
Re: Slowest project ever - CM400T - Video of backfiring p6

Backfiring could be cause by excessive unburned fuel in the exhaust that is reigniting, you said it was running rich so that is what lead me to suggest the rejet. Thought I should explain that in case no one knows what the hell I am talking about. Still I could be wrong. -MBS
 
Re: Slowest project ever - CM400T - HELP! Carb tuning! :(

MBS said:
I wouldn't touch the timing. But looking at the exhaust setup you have there and the pods, I would say you need to rejet the carbs. If your running your carbs on stock jets and no baffles then you have a change in back pressure as well as air flow in through the pods, which will mess up how it runs. Try a size up in the main jets and see if it improves. Nice job btw, thanks for the vid. I will be working on my CM400 this winter so I am taking notes. I like your solution to the difficult seat/frame issue with this model. -MBS
Click to expand...

wouldnt a size up make it run richer? Sorry if thats a dumb question, but Im a noob with carbs..
 
Re: Slowest project ever - CM400T - it's ALIVE (w/ video)


Hiya , like the minimalist thing going on. I wonder could you tell me where you got the electronic tacho from as my friend was looking for one for her special. x
 
Re: Slowest project ever - CM400T - Video of backfiring p6

+1 on what MBS said. If it's like my 750 then you do need to go one size up on the main jets and even drop the needle c-clip down a notch to richen the mixture.

I may be wrong but it didn't sound like a backfire so much as a miss. Have you checked your points (clean and gap) and maybe a new condenser might be in order too.

Scott
 
Re: Slowest project ever - CM400T - Video of backfiring p6

Yeah you maybe right, I am pretty sure you have to up in size though, it worked on my bike. Again, I could be totally wrong, but you have nothing to loose. I bet there is a shop out there that would just give you a bunch of different size jets to try out. They usually have tons of used jets lying around the shop. Since you have a modified exhaust and air intake on your bike it will not work correctly to spec, and there is no spec for what you have made, so its trial and error. Welcome to the world of having a custom bike....ain't it fun? Seriously, though I think your issue is with the carbs, I would start there and then move on to the ignition and electrics. Are both pipes getting hot? If its anything electrical its likely to be something simple, like a spark jump. Run it in the garage or in the dark and look for spark jump from the wires and spark caps or coil if possible, that would throw of the timing and a new wire is like .50 cents. Hope it helps. -MBS
 
Re: Slowest project ever - CM400T - Video of backfiring p6

It's not going to be a points or condenser issue. These bikes have a CDI ignition.
 
Re: Slowest project ever - CM400T - it's ALIVE (w/ video)

miss alliekat said:
Hiya , like the minimalist thing going on. I wonder could you tell me where you got the electronic tacho from as my friend was looking for one for her special. x
Click to expand...

It's an acewell speedo. I got it from:
http://www.electrosport.com/speedometers/

I checked my spark plugs again. My right cylinder plug is clean - spark is strong. Left cylinder is black (was black last time i checked too, i just didn't clean it) - spark is strong. So that means my left side is running rich for whatever reason, or maybe it got flooded a few times and ran rich at those times.

Anyway, I have Tony coming here tomorrow - from the HELP forums, so I'm hoping he'll be able to make my bike happy and in the process I'll learn something new. I have to admit, carbs still scare me because it's such a trial and error science...
 
Re: Slowest project ever - CM400T - Video of backfiring p6

These carbs are almost exactly the same as the ones in my CB400T. Before you go playing with jets, you really need to get the carbs apart, clean everything really well, and get a new gasket set for each. Missing the little o-rings at the air screws can throw their adjustment off. You should have no problem any of this from a dealer or online. At the very least, get new float valves. If they're not sealing right, your fuel level will be too high and you'll run rich. You may need new air-cut-off valves too, if you're backfiring under deceleration. Then check the rubber o-rings between the head and the rubber manifolds that attach to the carbs for air leaks. You need to spray some aerosol around the carbs while it's running to see if the idle speed changes. Synchronizing the carbs is huge too.

Once that's done, you can start playing with the jets. The clymer says 72 primary, 118 secondary. The air screws should be 2 turns out. The needles are not adjustable in these carbs.

Mike
 
Re: Slowest project ever - CM400T - Video of backfiring p6

woodardhsd said:
These carbs are almost exactly the same as the ones in my CB400T. Before you go playing with jets, you really need to get the carbs apart, clean everything really well, and get a new gasket set for each. Missing the little o-rings at the air screws can throw their adjustment off. You should have no problem any of this from a dealer or online. At the very least, get new float valves. If they're not sealing right, your fuel level will be too high and you'll run rich. You may need new air-cut-off valves too, if you're backfiring under deceleration. Then check the rubber o-rings between the head and the rubber manifolds that attach to the carbs for air leaks. You need to spray some aerosol around the carbs while it's running to see if the idle speed changes. Synchronizing the carbs is huge too.

Once that's done, you can start playing with the jets. The clymer says 72 primary, 118 secondary. The air screws should be 2 turns out. The needles are not adjustable in these carbs.

Mike
Click to expand...

I second what Mike is saying here. I assumed these things were done when suggesting the jet change. But if not, Mike is definitely right in doing these things first..its a part of servicing carbs on any bike properly. Air leaks and worn valves can be the cause of many problems.
 
Re: Slowest project ever - CM400T - Video of backfiring p6

+2 on Miek and MBS. I did what they suggested then ended up with 74 primarys and 128 mains with modded exhaust and pods. Now runs awsome, smooth revs right to redline without any misses or backfires. plugs look good from idle to steady 8k. Messed with a few jet sizes to get these. Found I didn't need to change the air screws much if any from the settings Mike Suggested. To check the running condition is a bit time consuming but worth it. I warmed up the bike, then let it idle. Shut off, checked plugs. IF good, then went for a ride at a steady 3K, hit the kill switch/grab clucth to stop motor, pull over side of road and pull plugs, if ok, move on to 5K, 6K , 7K 8K. Just need to run it for 2-3 minutes and check. Anytime you get lean or rich you need to change something. Either juets or float needle or pilots depending on rich or lean. If ound my bike runs spot on to slightly rich (better than lean) never fouling plugs with stock settings, clean carbs and the new jets. Good luck, it is a bit of a process but once done your bike should run well. Pods and free flow exhaust add some noticable pick up to the bike.

Cheers
 
Re: Slowest project ever - CM400T - Video of backfiring p6

Just curious if you guys think the change to a K&N filter would cause much difference, i.e. the need for re-jetting? (That's what I am running in the stock air box)
 
Re: Slowest project ever - CM400T - Video of backfiring p6

In the stock air box it shouldn't need a rejet, unless you open up your exhaust. Stock exhaust with the K&N would be fine. If you removed the rusty heavy belly box crossover, it might need a re-jet to the main jet.
 
Re: Slowest project ever - CM400T - Video of backfiring p6

Hey guys, so I had Tony come out today to take a look at my bike.

There were a few issues with it:
1. Valve clearances had to be adjusted
2. One of the secondary jets holes were plugged
3. I hooked up the overflow hoses wrong
4. Need an inline fuel filter

umm... dont' remember. Anyway, great guy. Really knows what he's doing, he quickly pin pointed the problems (I was in a rush) and got everything done. The bike is now ride-able, but it'll have to be re-jetted at a later date.

I'm very happy!
 
Re: Slowest project ever - CM400T - Video of backfiring p6

Those are some simple/quick fixes too!

I'm glad you got the best going. I hope I can get mine up and running once it's together!
 
Re: Slowest project ever - CM400T - Video of backfiring p6

Good to hear you got it sorted. Be careful riding if you are lean, I had a lean condition on my 400 I didn't know about....now I have a 450 in there, Learned the hard way lean is bad. Lost a piston in the right cylinder and it toasted the motor. Jets are super cheap, like $2.00 ea so for $4.00 you can up your jets and correct your mix. It is far cheaper than a new motor.

Cheers,

Maritime.
 
Re: Slowest project ever - CM400T - Video of backfiring p6

Wow Maritime, that's a sad story. I didn't realize running lean could cost a piston. Just out of curiosity, what exactly happens to the motor to kill a piston with a lean mixture?
 
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