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Author Topic: CB400f engine in a CB350f frame?  (Read 9660 times)

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Offline schwebel

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CB400f engine in a CB350f frame?
« on: June 12, 2009, 06:11:10 PM »
I have sourced a CB400f and was wonder if there were any issues putting it into a 350 frame. I will be using my carbs, seems the jetting is the same, just the air screws are let out further?...is this correct? And the clutch housing looks different? Anything special from the 400 I will need. The engine is complete minus carbs.
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Offline kghost

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Re: CB400f engine in a CB350f frame?
« Reply #1 on: June 12, 2009, 06:56:10 PM »
I dunno....

I have a 350 and a 400...they look like they would interchange....

I have a spare 400...been thinking about putting it in the 350.....

As far as I can tell the frames are the same....Might need a 400 sprocket set up front/rear
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Offline Owned

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Re: CB400f engine in a CB350f frame?
« Reply #2 on: June 12, 2009, 07:58:43 PM »
The 400 will bolt right up into the 350.  As far as the carbs, the only additional difference is thee slow jet size.  I believe you'll need 40's.

I have a 400 motor sitting on a shelf I'm just waiting to start tearing into.  It will be placed into my 350 soon.

-Brad
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Offline many408

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Re: CB400f engine in a CB350f frame?
« Reply #3 on: June 14, 2009, 03:53:12 AM »
Quote from: schwebel on June 12, 2009, 06:11:10 PM
I have sourced a CB400f and was wonder if there were any issues putting it into a 350 frame. I will be using my carbs, seems the jetting is the same, just the air screws are let out further?...is this correct? And the clutch housing looks different? Anything special from the 400 I will need. The engine is complete minus carbs.

I did this.

Fits right in.

350f has rear footpeg mounts on the frame (so does the UK spec 400f frame).  Much nicer for the pillion.

Plus you'll go faster.
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Offline fishman_Phil

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Re: CB400f engine in a CB350f frame?
« Reply #4 on: December 05, 2009, 11:35:10 PM »
The 400 will go straight into the 350f frame. In fact, the engine I worked on this weekend is one of my CB350F bikes, has a 400F bottom end with a 350F cylinder and head installed. This gives the 350F a 6-speed gearbox. The reason I needed to work on her was the valve seals required replacing.
Cheers ...
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Offline fmctm1sw

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Re: CB400f engine in a CB350f frame?
« Reply #5 on: December 06, 2009, 07:28:04 AM »
Something keeps telling me the gearshifter is a problem.  I think someone said the case is wider so you'd have to use the 400F footpeg setup.  Not really a problem though...
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Offline socalenduro

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Re: CB400f engine in a CB350f frame?
« Reply #6 on: December 06, 2009, 11:02:14 AM »
how much more powerful is the 400 vs the 350?
how much smaller is the frame of a 350?
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Offline fmctm1sw

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Re: CB400f engine in a CB350f frame?
« Reply #7 on: December 06, 2009, 05:57:09 PM »
Quote from: socalenduro on December 06, 2009, 11:02:14 AM
how much more powerful is the 400 vs the 350?
how much smaller is the frame of a 350?

There's a 10HP difference IIRC.  Frame is the same size (I think)...
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Quote from: 754
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Quote from: inkscars
This is not a pod thread
This is not a #$%* on my vacuum gauges thread
This is a help or GTFO thread.

1973 CB350F
1973 CB350G
1975 CB550K
1983 GL650I
1973 CB750K3 (http://forums.sohc4.net/index.php?topic=92888.0)
1984 Kawasaki KLT-250 (AKA 3 wheeler of death)
1994 Honda TRX300
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Offline fishman_Phil

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Re: CB400f engine in a CB350f frame?
« Reply #8 on: December 06, 2009, 07:26:00 PM »
To answer a couple of questions: The frame is the same size (400 just has different footpegs, tank, seat and indicator mounts). Putting the 400 into the 350 frame you can retain your existing footpegs as I have. Where the case differs in the engine is on the right hand side. See in the photo for how close the footpeg fits. The muffler not fitted in this pic as I am busy putting things back on to the bike after renewing the valve seals during the weekend, but you will not have trouble with anything that is currently on your 350 bike including the wiring. Cheers
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edmer79

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Re: CB400f engine in a CB350f frame?
« Reply #9 on: December 08, 2009, 07:46:41 PM »
Quote from: fishman_Phil on December 06, 2009, 07:26:00 PM
To answer a couple of questions: The frame is the same size (400 just has different footpegs, tank, seat and indicator mounts). Putting the 400 into the 350 frame you can retain your existing footpegs as I have. Where the case differs in the engine is on the right hand side. See in the photo for how close the footpeg fits. The muffler not fitted in this pic as I am busy putting things back on to the bike after renewing the valve seals during the weekend, but you will not have trouble with anything that is currently on your 350 bike including the wiring. Cheers


Hi,I am also interested in putting a 400f engine in a cb350f,do you need change the gear shift linkage to a 400f type?
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Offline socalenduro

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Re: CB400f engine in a CB350f frame?
« Reply #10 on: December 11, 2009, 05:09:31 PM »
so im curious.... why all the interest in putting a 400 into a 350.
i mean 10hp bump would be nice.... but is it really worth all the effort vs getting a 400 into good running order?
i have  350 and LOVE the size and love the idea of more power... sell me!
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Offline hoodellyhoo

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Re: CB400f engine in a CB350f frame?
« Reply #11 on: December 11, 2009, 06:15:13 PM »
more horsepower plus a 6 speed trans.
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Offline socalenduro

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Re: CB400f engine in a CB350f frame?
« Reply #12 on: December 12, 2009, 09:20:54 AM »
right, but when i asked before it was said that the frame was the same size...
so whats the advantage of a 350f with a 400 engine over a 400?
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Offline patricke9

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Re: CB400f engine in a CB350f frame?
« Reply #13 on: December 13, 2009, 10:51:49 AM »
Found some pics of a buddy's 350/400 hybrid- in his case the 350 blew up & all he had was a 400.  The head is off in the pics, he wound up selling it after buying a modern bike, I almost bought it, but he got a lot more for it than I would have paid.  Neat little bike, when it was stock 350 he couldn't keep up with the rest of us, with the 400, it was much quicker (until the head went bad anyway).


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Offline Gordon

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Re: CB400f engine in a CB350f frame?
« Reply #14 on: December 13, 2009, 10:54:12 AM »
Quote from: socalenduro on December 12, 2009, 09:20:54 AM
right, but when i asked before it was said that the frame was the same size...
so whats the advantage of a 350f with a 400 engine over a 400?

Some people might prefer the 350 design but want the 400's power.  
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Offline socalenduro

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Re: CB400f engine in a CB350f frame?
« Reply #15 on: December 22, 2009, 05:48:03 PM »
great now i want a 400 in my 350.....
actually that kinda works...my 350 runs fine, but not great and makes alot of valve noise...
i think ill ket the rest of the bike the way i want it...then when i have a garage start rebuilding a 400 the way it should be and install.....

in the mean im i need to regear to get some pep
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Offline schwebel

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Re: CB400f engine in a CB350f frame?
« Reply #16 on: December 23, 2009, 01:27:36 AM »

[/quote]

Some people might prefer the 350 design but want the 400's power.  
[/quote]

Bingo, I ended up doing this and am very happy with the results. The 6spd makes a word of difference. The 350f would struggle on the highway, the 400 just zips along and can blast past traffic when needed. The 400f is a wonderful engine. I have two extra teeth on my rear sprocket which keeps the rpms down. It'll cruise at 70-75 all day easy.  I really would like to find the right sprocket for stock gearing, but I have a wider 450 rim to accomodate my larger rear tire. And 450 twin sprockets and 350/400f sprockets don't fit that rim.

Like said, the brake lever is a little weird, but other than that I love the bike. It gives my 500f a serious run for it's money. I really like the 350f's styling over the 400f's.
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Offline kghost

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Re: CB400f engine in a CB350f frame?
« Reply #17 on: March 13, 2010, 03:03:48 PM »
Or.....

You could do what I did.



Get one of each
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Offline Kevin400F

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Re: CB400f engine in a CB350f frame?
« Reply #18 on: March 14, 2010, 01:49:31 AM »
Or, in my case, the 350F frame footpeg brackets come in handy to hang the exhaust meggas.  400f tank fits the 350F frame as well.
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Offline fmctm1sw

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Re: CB400f engine in a CB350f frame?
« Reply #19 on: March 14, 2010, 07:20:59 AM »
Quote from: schwebel on December 23, 2009, 01:27:36 AM


Some people might prefer the 350 design but want the 400's power.  
[/quote]

I have two extra teeth on my rear sprocket which keeps the rpms down.  
[/quote]

Doesn't that have the opposite effect?  I thought more on the front or less on the back make the RPM come down... 
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Quote from: 754
Dude is that a tire ? or an O-ring..??

Quote from: inkscars
This is not a pod thread
This is not a #$%* on my vacuum gauges thread
This is a help or GTFO thread.

1973 CB350F
1973 CB350G
1975 CB550K
1983 GL650I
1973 CB750K3 (http://forums.sohc4.net/index.php?topic=92888.0)
1984 Kawasaki KLT-250 (AKA 3 wheeler of death)
1994 Honda TRX300
1999 Honda TRX250

Offline horror

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Re: CB400f engine in a CB350f frame?
« Reply #20 on: July 06, 2010, 04:08:06 PM »
Does this mean that a 350f exhaust system fits straight onto a 400f?

I like the 2 into 2 system on the 350. I hate the 400f 4 into 1 system. Can they be swapped?
Thanks
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Offline camelman

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Re: CB400f engine in a CB350f frame?
« Reply #21 on: July 06, 2010, 10:25:11 PM »
They could be swapped, but you'd need to fashion up some mounts.  The 400F has one mount on the right side of the frame to support the muffler.  The 350F uses the rear foot peg mounts to hang the exhaust brackets for the 4-2 exhaust options.  The 400F has the rear foot pegs on the swing arm, so there is nothing on the frame on the left side to hang a muffler from.

Camelman
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Offline horror

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Re: CB400f engine in a CB350f frame?
« Reply #22 on: July 06, 2010, 11:53:07 PM »
aha. thanks, I'm in the UK and my 400f has the footpeg mounts on the frame, so there would be a place to hang those.
cheers nice one.
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Marc Cutler

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Re: CB400f engine in a CB350f frame?
« Reply #23 on: July 09, 2010, 11:19:01 AM »
I'm clear on everything about swapping the 400 into the 350 frame except for the gearshifter. I see in one of the photos that it has the 400 shifter mounted. Would that include the foot peg mount to make it all work. Has anyone done a workaround to use the 350 shifter?
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