[CBSigmund]

Ready for the head.I have ported the head and will upload some pics of it as I put it on. As you can see in this pic, I use a battery clip to hold the cam chain during assembly. 450 base and head gasket are used. Don't forget the rubber seals on the oil supply holes.

 

[longdistancerider]

Good progress being made with this, it'll be interesting when you get it up and running to find out what the power increase is.

 

[CBSigmund]

Head porting-A pic before the valves went in would have showed more.

All new valves. The head is on now!

 

[BEEFKING69]

Will this work on the CB400A?

 

[longdistancerider]

Will this work on the CB400A?

Yes, you can do this with the A model BUT you need to use the A model parts from a CM450A like the pistons and entire head ass'y. There's been attempts at using the manual trans part on the A model and while it works the power results are very poor.

 

[CBSigmund]

It started! It runs, but it was late so I could not do much. It idled perfectly and sounded a bit throatier when reved. Will adjust the cam chain and finish it off tomorrow for a test ride.

 

[CBSigmund]

I rode the bike, it ran fine but had a slight oil leak on the left side that I noticed today. Knocked the oil seal in a bit more so that should be it. I have also noticed that there is a lot of crankcase pressure. When the dipstick is just sitting in and I crank the bike over, it jumps up about an inch! I don't remember that happening before? I'll check the valve clearances before leak down etc.

 

[longdistancerider]

Yes, they do have a lot of crank case pressure normally so the dipstick jumping I would expect.

 

[CBSigmund]

I re adjusted the tappet screws and the engine is very quiet now- I did a quick job and they were noisy. Unfortunately my tank needs work before I break the engine in, but I started it up with my IVF tank and it's sounding very smooth now. I'll test ride again asap.
One thing I noticed is that the 400 and 450 heads have different part numbers, but everything I have read says they are all the same? LDR (the part number king) Can you ease my mind? I'm just making sure that I'll have the same compression ratio. Also, I'm not sure how necessary it is to re-torque the head on these engines after a few hundred KM or *Miles* ?

 

[longdistancerider]

Yes they do have different part numbers because they are different. Head/cam oiling on a 450 is from the center main bearing thru a external pipe. $00's oil the head/cam via the rear outer head bolts. I don't know what the cc's of the combustion chamber on the 450 are, somewhere I've got notes about the 400's.
Head re-torque is 600 miles with an oil/filter change at the same time.

 

[CBSigmund]

Just an update: I'd say the big bore/rebuild is a success. After a few hundred km's, the engine came alive and it's very quick now! All working as planned.

 

[longdistancerider]

Good deal. This thread is now a"sticky" so you can expect questions from time to time

 

[CBSigmund]

I just Let my brother in law ride it. He has a 2017 Ducati scrambler (400cc) and he agreed that my CB450t is much faster, especially after 5,000rpm. Ported head might of helped too. It's very fun to ride! Happy days.

 

[HamHock]

So you used a 1977 400 head right? That'd be the pent roof head I believe. Interesting pairing with the flat top 450 pistons. Seemed to be the ticket for you though. Do you by chance have the marking from your head written down?

 

[colvinry]

So you used a 1977 400 head right? That'd be the pent roof head I believe. Interesting pairing with the flat top 450 pistons. Seemed to be the ticket for you though. Do you by chance have the marking from your head written down?

I was under the impression that all of the heads on the 400s and 450s were domed. Is this true or was there a flat top offering?


Sent from my iPhone using Tapatalk

 

[HamHock]

I was under the impression that all of the heads on the 400s and 450s were domed. Is this true or was there a flat top offering?


Sent from my iPhone using Tapatalk

78/79 had a domed piston and a different cylinder head.

This thread will explain more
https://www.hondatwins.net/forums/62-engine-discussion/18981-400t-e-400a-head-differences.html

 

[CBSigmund]

So you used a 1977 400 head right? That'd be the pent roof head I believe. Interesting pairing with the flat top 450 pistons. Seemed to be the ticket for you though. Do you by chance have the marking from your head written down?

Yes, from LDR's head thread:
Production date: 1977
Country designation: Australia
Model: CB400T
H code from the head: H2

 

[Bigstinka]

Would the 400 carbs work on a 450?

 

[CBSigmund]

Would the 400 carbs work on a 450?

Yes. Some later CB450's had a spacer and different jetting, but essentialy the same CV carbs.