Topic: My GF broke her 400F ... Carnage pics on page 2.

[Scott S]

 This Spring, my GF picked up a '76 CB400F from a friend. Great price on a neat little bike. He had done a top end rebuild (I'll have to ask him exactly what he did, but I'm pretty sure he did rings) and the bike ran like a top. No leaks, no smoke, no drips, no problems.



 All that lay ahead of us were some minor cosmetic issues.

 While I was at work yesterday, she went on a ride with a small group of VJMC people. Beautiful day on the Blue Ridge Parkway, 181, etc.
 She rode 240 miles. However.....the ride was 295 miles long. DOH!

 One of the riders said he had noticed the bike smoking, either on down shifting or lifting off the throttle. They stopped to check oil and it was low on the dip stick. (Never used excessive oil before).
  Then he noticed oil on the rear tire. When they stopped, the bike left a puddle on the ground. They parked it and went back after it with the truck.

 It was a long day and after dark when they got home, but it appears to me the oil is coming from the breather. It's very oily there and around the top of  the swing arm pivot, etc.

 With this admittedly scarce information, where would you start looking? Think a ring went south? She did say she was riding the snot out of it; 7 or 8 grand on stretches on the twisties. But that bike should have easily handled that.
  What can I do to find the cause of sudden oil consumption and an oil filled, puking breather?

[becken]

I would start off by doing a compression test and compare it with the one you took after getting the bike and doing the 3000 mile service. It does sound like you're going to have to take the top end down and check the bore and piston condition, check for a broken ring and also check the valve guides for excessive wear. Is the engine making any unusual noises? Any new discoloration on the pipes? What do the spark plugs look like? What else do you see or hear that is different from before?
Nice looking bike, by the way.

[bryanj]

I agree with the compression test but straight off the bat I would say it is unusual for any Honda to break a ring unless thrashed from cold, which did not happen from your description, If it was putting oil out of the exhaust I would say a valve guide seal

[Bankerdanny]

To be fair (and to avoid Annoyed Girlfriend Syndrome) I would say "My girlfriend's 400 broke" not "My girlfriend broke her 400".

[lucky]

If it broke a ring the oil would be dripping out the exhaust.
Also it would be making a LOT OF SMOKE.

IF the breather is clogged up then the oil will try to push out of any place it could ,
like a seal.

[MoMo]

To be fair (and to avoid Annoyed Girlfriend Syndrome) I would say "My girlfriend's 400 broke" not "My girlfriend broke her 400".

Good point BD...Larry

If it broke a ring the oil would be dripping out the exhaust.
Also it would be making a LOT OF SMOKE.

IF the breather is clogged up then the oil will try to push out of any place it could ,
like a seal.

That scenario seems more likely...Larry

[Scott S]

I would start off by doing a compression test and compare it with the one you took after getting the bike and doing the 3000 mile service. It does sound like you're going to have to take the top end down and check the bore and piston condition, check for a broken ring and also check the valve guides for excessive wear. Is the engine making any unusual noises? Any new discoloration on the pipes? What do the spark plugs look like? What else do you see or hear that is different from before?
Nice looking bike, by the way.

 I didn't do a compression test when we got the bike. Had a chance to look it over (briefly) tonight and the only unusual noise is a little valve noise that wasn't there before. Nothing horrible, nothing that an adjustment shouldn't take care of.
 I will pull a plug or two soon....I work 12 hour shift rotations and I'm getting slammed with OT right now.

 

[Scott S]

To be fair (and to avoid Annoyed Girlfriend Syndrome) I would say "My girlfriend's 400 broke" not "My girlfriend broke her 400".

 If you knew how proud she was of this bike and of this particular ride, you'd understand....

 In fact, this is from a post on her Facebook page today:

So, yesterday was sort of a big deal for me. Here's some backstory:
 When I was in college, my boyfriend had a 1976 KZ1000 and we would ride that thing all over southwestern Virginia. We put 100s of miles on that old bike almost every weekend. My personal favorite route was along the Blue Ridge Parkway. The scenery; the wide, sweeping turns; the other motorcyclists: I knew I had found my place in the world.
 I was always on the back of the bike, too scared to learn to ride that big honking beast. I wanted a bike of my own, but I was a broke 20-year-old student. I coveted just about every bike I saw, but in the meantime I was very content to ride on the back of that bike and just take it all in.
 Well, I parted ways with that boyfriend at the end of college, 1996. I decided I still very much wanted to have a motorcycle in my life. Somehow, though, I convinced myself I would never own one and would just have to date someone who did. I spent quite a few years dating boys with bikes and being disappointed (for one reason or another) or dating nice guys without bikes and being unfulfilled. I decided I would have to just have a bike of my own...some day.
 Fast forward to 2006...I had been dating Scott for a year, was totally in love and happy and all that, but he didn't have a bike. Scott restored VWs, he didn't know the first thing about motorbikes (or so he thought). I had told him of my dream of motorcycle ownership, how very important it was to me, how I had been unable (or too scared) to buy one for myself. And he made it happen. One of his co-workers was looking to sell his bike. I fell in love with it on sight and Scott matched the money I had saved. I finally had a bike of my own.
 In the 7 years that I have been riding, I've converted Scott into a bike guy. (In truth, I created a monster, but that's another story. Be careful what you wish for.) We have made some fantastic friends; we have joined motorcycle clubs; we attend motorcycle festivals. I even bought a 2nd bike! And I haven't ridden on the back in 15 years. But, to fulfill the rest of The Dream, I wouldn't be satisfied until I returned to the Blue Ridge Parkway.
 I did that yesterday.
 Our friends, Patrick and Lloyd, invited me on a group ride up to the hills of North Carolina. The ride would include a portion of the BRP near Linville Falls, NC. I decided I would take my 1976 CB400. Pat and Lloyd were unaware what a big deal this was to me. They had no idea, until now, that when I saw that Parkway sign, I literally teared up inside my helmet. They didn't know I had waited 20 years to get back to that roadway--on my own bike. I had waited 20 years to see that glorious scenery, to navigate those sweeping turns, to wave at the other motorcyclists. That giant hawk that swooped down on us was just icing on the cake! Those street curve signs that looked like question marks made me giggle out loud.
 And the funny thing about dreams? Sometimes, just sometimes, they're not as good as real life. After we rode that portion of the Parkway, Pat and Lloyd took us on the craziest road I have seen yet: NC80 "The Devil's Whip". I rode harder yesterday than I ever thought I could. I took corners where I swear I was looking at my own rear end. I was better than I thought, but far from good. I almost wiped out twice, but I made it. I made it. Me. And it only took me 20 years to do it. Thank you, Pat and Lloyd.
 So, yesterday was sort of a big deal for me.

 This is just part of where they rode. I'm still waiting on them to upload pics from that day...hopefully, he got a good shot of her!
https://www.thedevilnc80.com/

[Scott S]

If it broke a ring the oil would be dripping out the exhaust.
Also it would be making a LOT OF SMOKE.

IF the breather is clogged up then the oil will try to push out of any place it could ,
like a seal.

 Very preliminary testing at this point (see earlier comment about 12 hour shifts and massive OT), but this is what I'm leaning towards.

 It's DEFINITELY coming from the breather. I can see a little mist there when I rev the bike. I was unable to make it smoke, really, out of the exhaust. Nothing that I would say is an issue, anyway.



 I'll try to pull the air cleaner and look into the breather system tomorrow. I'm sort of unfamiliar with the CB400 set-up; I'm a 500/550 guy.

[Bill/BentON Racing]

When was last oil change? What weight? Petcock and carbs ok,no overflowing or contaminated oil,I'd do compression and or leak down,change oil and filter,check for leaks and see what happens,just my .02.Bill Good Luck,have a 400F engine anyone interested!

[Powderman]

So how does it feel to know you come second in that relationship?

[Scott S]

So how does it feel to know you come second in that relationship?

 In this instance....just fine!

[Stev-o]

+1 compression check.

love her FB post, great story.  So you're a monster?!

[Scott S]

When was last oil change? What weight? Petcock and carbs ok,no overflowing or contaminated oil,I'd do compression and or leak down,change oil and filter,check for leaks and see what happens,just my .02.Bill Good Luck,have a 400F engine anyone interested!

 My plan is to totally de-grease it tomorrow. Not sure when I can get around to the valves...I have three days off in the next three weeks. Ugh.
 I'll do a compression check when I have the tank off to do the valves.

 Carbs seem fine. I know the P.O. did a synch shortly before we bought it, because he used my gauges. It's never leaked or smoked before.

 I have a theory: One of the guys she was riding with said he was seeing a little smoke from the exhaust. Now, mind you, she rode it for 6-8 hours, interstate speeds and then wailing on it in the mountains, with stops only for fuel.
 They stopped and checked the oil since it was "smoking". Said it was near the "LOW" line, so they added oil. The next time they stopped, it was puking oil and the parked it.
 I'm wondering if they over-reacted and over-filled it and it started blowing oil out the breather system?

[Scott S]

 Can someone go over the 400F breather/air box for me? I can't seem to find a good pic or diagram.

 I take it the breather on top of the engine is vented to that white cup thing (what's it's purpose, anyway?), and that is then breathed in through the air box/filter and recirculated through the engine....right?

 Is there anything in the white cup? Filter, etc.?

[Lyle]

Great FB post.  it's just not that often that you read about a young women who seems that passionate about bikes.  I trust that she didn't really "almost wipe out" two times.  If so, has she taken the MSF or similar? 

[Scott S]

 Yes, she's taken the MSF course. Look up NC80 on YouTube....you'll see why she almost wiped out.

[RAFster122s]

Scott, PM MoMo, he is very experienced with the cb400 and can assist you in diagnosing and the like...

[bryanj]

The tube comming out of the bottom(labelled drain tube in parts book) looks to be way too short if comparing to the parts book i have and on the bottom end is a sort of split that you pinch to let water out

[Scott S]

 I started to unscrew the white cup from the air box last night just to take a look inside, then realized I couldn't fit my hand between the frame to re-install it.
 Is there anything inside it that needs servicing?

[MoMo]

Have you looked at the air filter? ...Larry

[Scott S]

Have you looked at the air filter? ...Larry

 Just last night.... it has a pretty oily spot where the breather goes in but otherwise seems clean.



 I blew it out with compressed air. I'll start looking for a replacement. I also cleaned out the air box and made a new foam piece for the breather apparatus.

[Scott S]

 I spoke to one of the guys she rode with today. Pretty seasoned rider and a good mechanic. He said it was smoking when the throttle/slides were closed or closing.
 He said it was a little more than a puff, but that was after they added oil.

 I checked the oil today and I added maybe 2-3 ounces. I've cleaned up around the breather and swing arm and I can't replicate what was happening that day.
 No smoke, no drips, etc.

 I hear a little valve train noise, so I'll do the full tune up soon. Here's a vid from this morning:

1976 CB400F

[Scott S]

 Took a look at the plugs, too. #2 and 4 look OK, a little dark tan, but I'd run 'em if I were having no other issues.
 The #3 plug was a little darker but, again, passable. The #4 plug wasn't fouled but had some pretty heavy carbon deposits on it.

 None of the plugs showed signs of oil fouling.

 The bike has NGK D8EA plugs in it....is that what the 400F calls for? What if I went with a little hotter plug....NGK D7EA...in an effort to clean them up a little without getting into jetting, since the bike seems to run really well, otherwise?

[Stev-o]

Motor sounds very healthy.....great.  I'd be a little concerned about the oil in the filter, that does not seem normal.
If an excessive amount of oil/fumes was entering the carbs, could that have caused the smoking?
Have you ridden the bike? If yes, running normally now??