Topic: Jessezm's CB400F cafe

[jessezm]

Ran home for lunch and the new coil came in the mail (the problem was not with the ignition--it was an internal short in the new coil, apparently).  Threw it on, static timed the bike, tucked in all the wiring, put on the fuel tank and connected the lines, said a prayer, and fired her up....   She runs!@!!11!!!!    Oh boy does she run!   I have to say, this day has been a looooong time coming, and she sounds mean as hell!  I'm so excited I want to ride her back to work, but alas, I think I will follow break in procedures (not that there's any agreement on that....).   Stay tuned for more tuning...

[Syscrush]

Your lunch break was a whole hell of a lot better than mine!

[jessezm]

But the rest of the day sitting at my desk sure is gonna suck!

[jessezm]

Well, just got back from my first 10-mile ride.  The bike really rides great!  I can't believe how light and agile it feels, too--just hugs the road and corners really tight.  What I really can't believe is that I just took it apart, did all this work to it, then put it all back together (including rewiring the whole thing), and it just started right up with a quick push of the starter!  Totally had me floored for some reason.  I guess the 10-months of careful study and tinkering has paid off...

Anyhow, I did a quick timing adjustment to get it spot on (literally took 20 seconds of idle time), and turned in the air screws a quarter-turn to see if that fixes the bit of off-throttle popping I'm getting.  Plugs look ok--#4 was clean as a whistle, if maybe a bit lean.  #1 looked just right, and #2 and #3 look to be a bit rich.  I figure once I get her broken in and synchronize the carbs, I'll be able to get it dialed in better with some plug chops.   But for now, it's break-in time!  think I'll go for a nice ride tonight.

One thing that's really going to be hard is trying to keep the rev's around 5k during break in.  The problem is that the bike really wants to start making real power in the 6k-7k range, so it's hard to feel like I'm keeping the pressure up enough to seat the rings during break in keeping her at 5k or under.  I've already gone up a bit higher, and the engine felt pretty happy there.  I find myself dropping gears and engine breaking before long inclines and then laying on the throttle up the hills through the gears.   Think I'll post in the regular forum for advice on this one...

[leogriss]

Congrats!!!
I bet you got a lot of attentions when you went for a ride!
So I guess the bigbore kit you bought from ebay did pretty good job making your engine happy huh?
Now I have no hesistation to purchase one for myself.
Please post a video for us if you have time!
I would love to hear your monsterrr!

[Owned]

What main jet size and needle position are you starting with?

[jessezm]

Wow, just got back from another thrilling ride!   Yeah, so far, I am very impressed with the big-bore kit from ebay.  I had the piston domes ceramic coated and the skirts coated with dry-film lubricant.  The motor makes a ton of heat in this 90+ degree weather, so I'm glad I had that done...

I still cant get over the sound of this bike, though--it's got a smooth, throaty roar that makes the engine sound and feel twice as big.  I couldn't help myself, and just went down an exit on the highway, and in 5th gear, doing about 72mph, at 6000 rpms, the power was just starting to kick in, and I still had another gear to go!  I'm gonna have to take it a little easy, because it's too tempting to just roll on the throttle and let her really go.  damn what a ride!

I'm still trying to figure out who of my friends has a digital recorder i can use so i can get the sound of this thing posted here.  stay tuned...

[jessezm]

What main jet size and needle position are you starting with?

My mains are 90
Pilots I dropped to 38
needle is one position rich from center
Air screws are 1.75 turns out

She feels a bit rich from take off, and if I keep the revs way low she wants to stall.  I may be able to come down one size in mains to 85, and turn the air screw back out to two turns, and maybe go with a #40 pilot jet.  I'm going to have to do some plug chops to really see what's going on, though.  Man, I wish I knew someone with a runway I could borrow...


***EDIT  Corrected main jet sizes, that's 90, not 190!!!

[myhondas]

get out your video camera and do a quick video of the bike with a startup....understand that you won't be able to fully rev it, but it will help in your documentation. I do like the looks of the headers.

[RickB]

I couldn't help myself, and just went down an exit on the highway, and in 5th gear, doing about 72mph, at 6000 rpms, the power was just starting to kick in, and I still had another gear to go!  I'm gonna have to take it a little easy, because it's too tempting to just roll on the throttle and let her really go.  damn what a ride!

Mate that was so good to read. I can't wait for this with my 400. So stoked for you buddy.

[Syscrush]

One thing that's really going to be hard is trying to keep the rev's around 5k during break in.  The problem is that the bike really wants to start making real power in the 6k-7k range, so it's hard to feel like I'm keeping the pressure up enough to seat the rings during break in keeping her at 5k or under.  I've already gone up a bit higher, and the engine felt pretty happy there.  I find myself dropping gears and engine breaking before long inclines and then laying on the throttle up the hills through the gears.   Think I'll post in the regular forum for advice on this one...

Decide for yourself if this makes enough sense to trust your motor to it.

[jessezm]

One thing that's really going to be hard is trying to keep the rev's around 5k during break in.  The problem is that the bike really wants to start making real power in the 6k-7k range, so it's hard to feel like I'm keeping the pressure up enough to seat the rings during break in keeping her at 5k or under.  I've already gone up a bit higher, and the engine felt pretty happy there.  I find myself dropping gears and engine breaking before long inclines and then laying on the throttle up the hills through the gears.   Think I'll post in the regular forum for advice on this one...

Decide for yourself if this makes enough sense to trust your motor to it.

Yeah, I've been trying to research the best methods to use, and actually, that is exactly what I've been doing, with hard throttle pulls through the gears, then engine braking for deceleration, then rinse and repeat.  I guess I'm combining that with other info I've read here that you should keep the revs between 3k-5k for the first, 200 miles or so, then move to 3k-7k.   The technique you linked to is mum on rpms I think.   I definitely don't feel comfortable taking her to redline yet, but that's 10.5K.   7k-8k would feel really good, and I think I could follow the method in the link a lot more closely by opening it up just a bit more to get those hard throttle runs (I'm only at about 1/2 throttle at 5k I'm guessing...)

Any advice is welcomed!

[jessezm]

I couldn't help myself, and just went down an exit on the highway, and in 5th gear, doing about 72mph, at 6000 rpms, the power was just starting to kick in, and I still had another gear to go!  I'm gonna have to take it a little easy, because it's too tempting to just roll on the throttle and let her really go.  damn what a ride!

Mate that was so good to read. I can't wait for this with my 400. So stoked for you buddy.

Your moment is coming my friend!  Make sure to bench sync those carbs, set your static timing, and check for spark before you fire her up, but my bet is that your bike will take its first breath as effortlessly as mine did.  Didn't even want any choke!

[Syscrush]

The technique you linked to is mum on rpms I think.   I definitely don't feel comfortable taking her to redline yet, but that's 10.5K.   7k-8k would feel really good, and I think I could follow the method in the link a lot more closely by opening it up just a bit more to get those hard throttle runs (I'm only at about 1/2 throttle at 5k I'm guessing...)

Actually, it's pretty explicit:

On a Dyno:
Warm the engine up
completely !!

Then, using 4th gear:

Do Three 1/2 Throttle dyno runs from
40% - 60% of your engine's max rpm
Let it Cool Down For About 15 Minutes

Do Three 3/4 Throttle dyno runs from
40% - 80% of your engine's max rpm
Let it Cool Down For About 15 Minutes

Do Three Full Throttle dyno runs from
30% - 100% of your engine's max rpm
Let it Cool Down For About 15 Minutes
Go For It !!

I don't understand anything about why load or RPM should be limited after the first few minutes of running.  Once you are confident that the fuelling is good enough, and the lubrication and cooling systems are working, I don't see any reason why you shouldn't be running through the rev range at wider throttle openings.

The motoman procedure makes a lot of sense to me, but this is your motor and your decision.

[jessezm]

Yeah after I posted I went back and read that same portion (I was looking at the "on the street" procedure, not the "on the dyno" one)...  That's sort of the conclusion I'm at.  The only thing I really worry about is running the bike too hot--it's still in the 90's here and I can really feel the heat coming off the motor after a good haul.  I think I'll stick to running it in the evenings after it cools.

[Syscrush]

That article was written about modern 600-1000cc sportbikes, which is why the article acts like it's a big deal to run to redline in 2nd gear on public roads.

For a CB400 that's not such a problem.   You should be able to do a WOT run to redline in 2nd and maybe 3rd without getting too illegal, I would guess.

[jessezm]

Hey, that's 466cc to you, buddy!   

[going4speed]

RPM and load on a cold motor has to do with tolerances in the motor.

Tolerances on a hot engine are much smaller than a cold engine.

Thing about the rod heating up and in turn the associated shrink in inside diameter of the rod journal.  The same goes for the crank.  As it warms up it grows in size and the shrink of the rod ID and the increase in the crank journal OD causes the tolerances to be much smaller.  This in turn allows for a better oil film at the interface.  The engine is actually running on a thin film of oil and the control of this oil film is critical.  With a cold engine the tolerances are larger allowing parts to move around possibly gall each other...I could continue...

Short story..heat up your engine before you beat on it. 

The technique you linked to is mum on rpms I think.   I definitely don't feel comfortable taking her to redline yet, but that's 10.5K.   7k-8k would feel really good, and I think I could follow the method in the link a lot more closely by opening it up just a bit more to get those hard throttle runs (I'm only at about 1/2 throttle at 5k I'm guessing...)

Actually, it's pretty explicit:

On a Dyno:
Warm the engine up
completely !!

Then, using 4th gear:

Do Three 1/2 Throttle dyno runs from
40% - 60% of your engine's max rpm
Let it Cool Down For About 15 Minutes

Do Three 3/4 Throttle dyno runs from
40% - 80% of your engine's max rpm
Let it Cool Down For About 15 Minutes

Do Three Full Throttle dyno runs from
30% - 100% of your engine's max rpm
Let it Cool Down For About 15 Minutes
Go For It !!

I don't understand anything about why load or RPM should be limited after the first few minutes of running.  Once you are confident that the fuelling is good enough, and the lubrication and cooling systems are working, I don't see any reason why you shouldn't be running through the rev range at wider throttle openings.

The motoman procedure makes a lot of sense to me, but this is your motor and your decision.

[Syscrush]

Thing about the rod heating up and in turn the associated shrink in inside diameter of the rod journal.

Incorrect.  Thermal expansion is like magnifying a picture - outside dimensions grow, and so do inside dimensions.  So the ID of the rod journal will increase as the rod heats up, not decrease.

[going4speed]

Is it Friday yet?

The rod will grow but what happens to the overall diameter of the rod with bearing?

If the bearing is constrained within the rod and has a coefficient of thermal expansion similar would the bearing then have a smaller diameter?

I guess the whole thing would likely grow at the same rate?

Thing about the rod heating up and in turn the associated shrink in inside diameter of the rod journal.

Incorrect.  Thermal expansion is like magnifying a picture - outside dimensions grow, and so do inside dimensions.  So the ID of the rod journal will increase as the rod heats up, not decrease.

[leogriss]

no video yet!!!? we would like to hear her!

[vames]

Jessezm -- Nice bike, and glad to see it's running. I have a question that goes back to the first page of this build. I'm about to put the same gauges on my 400f and would like a little more info about how you mounted them. Did you grind off the original guage mounting tabs, or are the sitting in between them? If you could give any description or detailed pictures of the gauges/tree setup, i'd greatly appreciate it.

[jessezm]

Jessezm -- Nice bike, and glad to see it's running. I have a question that goes back to the first page of this build. I'm about to put the same gauges on my 400f and would like a little more info about how you mounted them. Did you grind off the original guage mounting tabs, or are the sitting in between them? If you could give any description or detailed pictures of the gauges/tree setup, i'd greatly appreciate it.

Actually, I used the two mounting tabs, but I had to (carefully) grind them down to about have the thickness, so that the mounting bolts/posts on the mini-gauges would reach through enough to thread on a nut.  So basically, I just mounted them directly to the tabs that originally held the instrument cluster, using only one of the two bolts/posts on each gauge.  Make sense?  It aint the best, but it works and looks clean...

[jessezm]

no video yet!!!? we would like to hear her!

Gah, I don't even own my own camera!!!

[Sparked]

Beautiful bike.   I love the engine colour, and the alloy tank looks sharp.