Author Topic: 75 cb400f  (Read 11694 times)

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Offline thestratomaster

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75 cb400f
« on: April 22, 2013, 05:51:10 PM »
Recently traded my old enduro for this....


Essentially cost me about 300 bucks, which I'm satisfied with!

Didn't run when I got it and had a dead battery.  Got it running via a car battery and some starting fluid and it had a very bad overflow problem.  Picked up a new battery, had the carbs apart to clean 3 entirely clogged pilot jets and two clogged main jets.  2 of the carbs still overflow, but not out of the overflow tube anymore, now they leak from the float bowl gasket which is undoubtedly garbage after taking it apart.  On the two that leak, the floats don't quite spring back up like the other two.  I think it's likely due to faulty float needles?

Besides that, the bike now runs and rides pretty well.  It doesn't like to have the idle set much below 1800rpm and it bogs a bit below 4k but pulls very hard after that.  It's quite a blast to ride so far I have to say. 

Up next on my plate are finding some suitable carb replacement parts, new front and rear tires, new pads on the front brakes and bleed the system (very squishy right now).  After that I'm going to put some low swept renthal mx bars I have laying around and possibly fab a seat and try to find proper side covers before I try to hand fab a set from aluminum. 

I've heard the keyster carb kits are garbage.  What exactly is wrong with them?  I really would like to replace all the needle valve assemblies and the important gaskets and o-rings.  The most cost effective way is to go with a kit from Keyster, or the one on DCC.  The genuine honda parts add up a little too quickly for me at this point. 

For tires I'm thinking about either IRC nr55 rear/nr53 front, or Kenda K657 challengers f/r.  Anyone have any experience with these tires?

Offline MoMo

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Re: 75 cb400f
« Reply #1 on: April 22, 2013, 06:04:10 PM »
I had the Kenda tires on a 400f-for the price and my 66 year old riding style they were fine.

You will need to rebuild both the master cylinder and caliper, possbily the caliper piston will be pitted-depends on how long the bike sat.

The jets in the Keyster kits are not manufactured to the same physical size as stock.  I rarely replace jets just gaskets and o-rings.. Again, depending on how long the bike sat you will need to take the carbs apart to clean the emulsifier tubes.  I have never worked on a 400f in which they were not clogged(probably done 10 in the past 5 years). 

A set of New side covers are available on Ebay for 72 .  I bought a set and am happy with the quality...Larry

Offline thestratomaster

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Re: 75 cb400f
« Reply #2 on: April 22, 2013, 06:21:18 PM »
I had the Kenda tires on a 400f-for the price and my 66 year old riding style they were fine.

You will need to rebuild both the master cylinder and caliper, possbily the caliper piston will be pitted-depends on how long the bike sat.

The jets in the Keyster kits are not manufactured to the same physical size as stock.  I rarely replace jets just gaskets and o-rings.. Again, depending on how long the bike sat you will need to take the carbs apart to clean the emulsifier tubes.  I have never worked on a 400f in which they were not clogged(probably done 10 in the past 5 years). 

A set of New side covers are available on Ebay for 72 .  I bought a set and am happy with the quality...Larry

Perhaps I'll just buy their kits and use everything except the jets.  The float needles in the kits are fine? My jets should be fine now, just need new orings on the mains.  Are the emulsifier tubes your referring to the tube the slide needle plunges into and the main jet sits in?  That could likely cause my bogging problem eh?

Did you have the kenda front tire too?  It seems to say it is not tube type, which presents a problem I believe.  $72 is decent for some new side covers.  Most sets I saw were ~100. 

The bike has been ridden, but not on the road since 1999.  The brake works ok, just not much feel in it.  I also discovered there was almost no fluid in the reservoir so I'm going to try flushing and bleeding it first!

Offline MoMo

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Re: 75 cb400f
« Reply #3 on: April 23, 2013, 12:17:38 AM »
I had the Kenda front and rear set, tubeless with tubes(no problem doing that). The emulsion tubes are the midrange tube that holds the main and guides the needle.  There are holes in the tubes that get clogged, plus the crap builds up and coats the carb body-all that prevents the gas and air from properly mixing...Larry

I have used the parts from the Keyster kits along with the stock jets, results were OK

Offline thestratomaster

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Re: 75 cb400f
« Reply #4 on: April 23, 2013, 02:15:15 PM »
I had the Kenda front and rear set, tubeless with tubes(no problem doing that). The emulsion tubes are the midrange tube that holds the main and guides the needle.  There are holes in the tubes that get clogged, plus the crap builds up and coats the carb body-all that prevents the gas and air from properly mixing...Larry

I have used the parts from the Keyster kits along with the stock jets, results were OK

Looking like the only way to get them out is to remove the slide and punch them out?

I also think I'm going to go with the IRC tire setup based on looks/cost/size

Offline MoMo

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Re: 75 cb400f
« Reply #5 on: April 23, 2013, 07:15:41 PM »
Yep, you have to remove the slides(be careful not to lose the little pins that are inside the linkage) and tap the tubes up-many people use a hard wooden dowel, I use the round end of an old walnut pick...Larry

Offline thestratomaster

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Re: 75 cb400f
« Reply #6 on: April 24, 2013, 06:21:46 PM »
Yep, you have to remove the slides(be careful not to lose the little pins that are inside the linkage) and tap the tubes up-many people use a hard wooden dowel, I use the round end of an old walnut pick...Larry

I'll have to try this over the weekend to see how dirty they are.  Is there a seat that the tube sits on when it gets pounded back in? Or is it a good idea to measure or mark where they sit before they come out?

Offline MoMo

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Re: 75 cb400f
« Reply #7 on: April 24, 2013, 08:33:52 PM »
Yep, you have to remove the slides(be careful not to lose the little pins that are inside the linkage) and tap the tubes up-many people use a hard wooden dowel, I use the round end of an old walnut pick...Larry

I'll have to try this over the weekend to see how dirty they are.  Is there a seat that the tube sits on when it gets pounded back in? Or is it a good idea to measure or mark where they sit before they come out?



Tap is a waaay better verb than pound, be gentle and if they do not move right away use a heat gun.  The tubes have a notch so they only go in one way and so far...Larry

Offline thestratomaster

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Re: 75 cb400f
« Reply #8 on: April 24, 2013, 09:46:45 PM »
Yep, you have to remove the slides(be careful not to lose the little pins that are inside the linkage) and tap the tubes up-many people use a hard wooden dowel, I use the round end of an old walnut pick...Larry

I'll have to try this over the weekend to see how dirty they are.  Is there a seat that the tube sits on when it gets pounded back in? Or is it a good idea to measure or mark where they sit before they come out?



Tap is a waaay better verb than pound, be gentle and if they do not move right away use a heat gun.  The tubes have a notch so they only go in one way and so far...Larry

Poor phrasing hah.    I ordered a set of IRC NR55's for front and rear, new tubes, tape, new oil filter, and 4 carb kits tonight.  I also picked up a center stand from someone on the forum.  Excited to get everything in! Not much I can do at the moment other than cleaning stuff up and waiting.  I'll post an update when things come in!

Offline braveg

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Re: 75 cb400f
« Reply #9 on: April 25, 2013, 06:19:54 AM »
If you dont have a manual and parts book yet, get them while you are waiting for stuff and read, read, read :)

Offline thestratomaster

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Re: 75 cb400f
« Reply #10 on: April 25, 2013, 01:29:30 PM »
If you dont have a manual and parts book yet, get them while you are waiting for stuff and read, read, read :)

I don't have a clymer's or anything yet, but I do have the service manual and parts manual online

http://dl.dropboxusercontent.com/u/19494889/CB350F%20CB400F%20Shop%20Manuals%20Part%20Lists%20%26%20More.pdf

Offline thestratomaster

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Re: 75 cb400f
« Reply #11 on: April 30, 2013, 11:40:22 AM »
Yesterday my carb kits came in! Got them rebuilt and put back in.  The emulsifier tubes really were not very dirty at all. I was surprised! I was very thorough this time getting into all of the passages I could reach with some spray carb cleaner.  Overflow problem fixed with the new needles and seats!

Unfortunately, the bike still is hesitant to start.  Once it's warmed up it idles fine, starts fine, and revs fine with the exception of a delay when you bump it from idle to full throttle.  If you slowly rev into it it's fine, but it bogs down if you go WOT instantly.  It seems that could be normal to me, but what do you guys think? My airbox doesn't sit perfectly on my carbs so I'm definitely getting some amount of unwanted air through.  Could this be my problem?

I've noticed a fair amount of "chain" noise in the top end.  I'm going to check the cam chain tension today as well as the valves. 

Any thoughts on the starting problems other than it's a tired old 25k mile honda?


Offline thestratomaster

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Re: 75 cb400f
« Reply #12 on: May 02, 2013, 08:31:53 PM »
Tires got here the other day so I'm waiting on some time to put those on.

On the cam chain noise, went to look at it yesterday, and the bolt above the oil filter is sheared off half way in the case.  Great.  Any tricks or just get an EZ out?

Offline thestratomaster

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Re: 75 cb400f
« Reply #13 on: May 04, 2013, 10:56:55 AM »
Ok, so a few pics.

This is what I found when I went to find the cam tensioner bottom bolt.  It's broken off most of the way down the hole.  What size is the bolt? I thought I read a 10mm but it doesn't seem to be that.  The beginning of the hole seems like a 10mm, but the threading further in where it sheared looks smaller to me.


So while the brakes work ok, I think I'm going to have an issue when I want to rebuild them, which I really wanted to do sometime this riding season.  Bleader screw is seized, hard line fitting seized, and I'm assuming everything else is probably pretty stuck too.  It's in way worse shape than I thought, oh well.


The chrome on the muffler isn't as bad as I thought.  It looks very dull and pitted from further away, but there is really just some sort of film on top.  It doesn't really seem like oxidation, but I'm not sure what else it would be. I hit it with a bit of steel wool and then some chrome polish, it's definitely gonna take a while but it'll shine right up I think


Here she is after putting a bit of leather conditioner on the seat and wiping a little more dust off of things.  Overall it's in decent shape, but it definitely has it's bits that are grimy and beat up.


On the carbs, there are two lines coming out of the center of carbs 2 and 3.  What are these?  They don't seem to be vacuum lines and I can't see why they would be drain lines.  They mount on a clip off of one of the top slide covers.  I can't quite figure out what they are and where they should be running to.


Offline MoMo

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Re: 75 cb400f
« Reply #14 on: May 04, 2013, 12:36:31 PM »
The two lines are vents, they go up and over the air box.  Not sure of the inner thread but I think it was 6mm.  You have your work cut out but keep at it and you'll have a fun bike...Larry

Offline thestratomaster

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Re: 75 cb400f
« Reply #15 on: May 05, 2013, 03:20:35 PM »
Well I got around to replacing the tires last night.  Also took a shot at ez outing the cam tensioner bolt.  It does not want to come out at all.  Anyone suggestions from people who've had this problem?





Pretty happy with how they look and how easy they were to mount.  I sort of wish I went with a slightly larger rear but oh well.

Offline MoMo

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Re: 75 cb400f
« Reply #16 on: May 05, 2013, 04:57:42 PM »
I had to buy a little round bit for my Dremel and grind the broken piece and then retap.  Not a fun job...Larry

Offline thestratomaster

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Re: 75 cb400f
« Reply #17 on: May 05, 2013, 07:17:21 PM »
I had to buy a little round bit for my Dremel and grind the broken piece and then retap.  Not a fun job...Larry

What about the portion that goes inside the case? Wouldn't that just fall off if you dremeled the threaded portion off?  I may give that a try other wise

Offline braveg

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Re: 75 cb400f
« Reply #18 on: May 06, 2013, 02:13:44 AM »
If you don't manage to get this out there is a very good chance that you are going to have to open up the engine and sort that out. Unfortunately the cam chain tensioner is a weak spot for these engines and guys tend to break this bolt off easily die to overtightening. Depending on the mileage, the horseshoe tensioner has probably seized and will need an overhaul in any case, so be prepared to get elbow deep in the engine...

Offline MoMo

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Re: 75 cb400f
« Reply #19 on: May 06, 2013, 05:34:57 AM »
I had to buy a little round bit for my Dremel and grind the broken piece and then retap.  Not a fun job...Larry

What about the portion that goes inside the case? Wouldn't that just fall off if you dremeled the threaded portion off?  I may give that a try other wise



That is a problem.  I used a lot of grease on the bolt and kept blowing it away and regreasing.  Did that until the bit went all the way through, then I  used a tap to rethread.  Changed the oil right away.  It is best to pull the motor and remove the lower case to do the repair...Larry

Offline thestratomaster

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Re: 75 cb400f
« Reply #20 on: May 08, 2013, 09:40:13 PM »
I had to buy a little round bit for my Dremel and grind the broken piece and then retap.  Not a fun job...Larry

What about the portion that goes inside the case? Wouldn't that just fall off if you dremeled the threaded portion off?  I may give that a try other wise



That is a problem.  I used a lot of grease on the bolt and kept blowing it away and regreasing.  Did that until the bit went all the way through, then I  used a tap to rethread.  Changed the oil right away.  It is best to pull the motor and remove the lower case to do the repair...Larry

Well, got the easy out to work today, until the point where it sheared off and broke inside the bolt.  This sucks.  I guess I'm going to have to open it up :(  Is there any immediate danger of things going very badly if I run the engine or ride the bike in general?  There's a few other issues I'm trying to solve to and really would like to ride it. 

Offline MoMo

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Re: 75 cb400f
« Reply #21 on: May 09, 2013, 01:05:14 AM »
Broken easy out ???  ??? ??? >:(.  I have had that happen so many times with the smaller bits that I am very hesitant to even try to use one.  If your cam chain is not noisy there should not be any risk in riding.  How many miles on the bike?...Larry

Offline Powderman

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Re: 75 cb400f
« Reply #22 on: May 09, 2013, 09:17:32 AM »
Broken easy out ???  ??? ??? >:(.  I have had that happen so many times with the smaller bits that I am very hesitant to even try to use one.  If your cam chain is not noisy there should not be any risk in riding.  How many miles on the bike?...Larry
I'm with you, I dread getting the easy outs out of the drawer. Seems more often than not you will end up breaking one off and then you're screwed because there is no easy out for broken easy outs.

Offline thestratomaster

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Re: 75 cb400f
« Reply #23 on: May 09, 2013, 09:42:01 AM »
Broken easy out ???  ??? ??? >:(.  I have had that happen so many times with the smaller bits that I am very hesitant to even try to use one.  If your cam chain is not noisy there should not be any risk in riding.  How many miles on the bike?...Larry

The chain makes some noise but they are noisy to begin with on these bikes right? I have no basis for how much louder this one is than how loud it's supposed to be unfortunately. The bike has 25k but only 1k of those in the last 15 years.

Offline MoMo

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Re: 75 cb400f
« Reply #24 on: May 09, 2013, 10:21:06 AM »
Broken easy out ???  ??? ??? >:(.  I have had that happen so many times with the smaller bits that I am very hesitant to even try to use one.  If your cam chain is not noisy there should not be any risk in riding.  How many miles on the bike?...Larry
I'm with you, I dread getting the easy outs out of the drawer. Seems more often than not you will end up breaking one off and then you're screwed because there is no easy out for broken easy outs.



That's when the cobalt bit on a Dremel comes into play.