A 1975 CB400F high mileage complete engine rebuild

[stl360+450]

I was wondering if you ever made trips to the US. Let me know if you ever find yourself headed to St. Louis.

That's a great photograph and I can imagine it was a really nice trip. I'm glad you were able to get away from work for that length of time and imagine you have many things to take care of now that you're back, including motorcycles.

 

[Richard Pitman]

Regarding four cylinder bikes and hot centre cylinders.

As stock, my CB600f has same float height settings for all carbs, but has 100 main jets in the outer cylinders and 102 main jets in the inner pair, presumably due to heat issues. Water cooled engine though.

 

[jensen]

Yes, I've bin to the US several times (mainly for work but also for fun, being bikes). States I've bin too are CA, AL, KY NC, SC and MI. CA for the bikes only, the rest for work. Most trips are 2-3 days (meetings), but some where a longer period (few weeks), for commissioning machines. Once to Canada (Ontario) also for commissioning machines. In most cases I don't know when I have to go, it's decided on a short notice. For commissioning, when sh.t hits the fan, me and my team are the ones to "fix" it. When a machine is not working in good order before a certain date, the fines we have to pay to the customer can be over 40.000 USD per week delay, so quick action is mandatory. This is also why I can't take goodies with me to the US, no time, and pressure is immense.

 

[jensen]

As stock, my CB600f has same float height settings for all carbs, but has 100 main jets in the outer cylinders and 102 main jets in the inner pair, presumably due to heat issues. Water cooled engine though.

The main jet works only in the higher rpm regions, my CB400F is air cooled, and mostly working in the low and mid rpm range. That's why I choose to change the float height because it influences that specific area. However, I'll see what is available for the CB400f carbs.

 

[jensen]

Is the CB400F still on the lift?

Not anymore (since yesterday), I completed the carb adjustment, and put them back, checked the valve play and took it of the lift.

 

[stl360+450]

Not anymore (since yesterday), I completed the carb adjustment, and put them back, checked the valve play and took it of the lift.

Sounds like a productive weekend! I'll look forward to more well-framed shots of the 400F out in the world.

 

[jensen]

Today, I took the CB400f to work, the maiden ride after the carburetor adjustment and re-torque the head bolts. The 2 mm difference in float height makes all the difference in the world. Now the bike is very smooth, from stationary to max rpm. Next week the bike will be on the dynojet for the final adjustments regarding the stationery part and the connection between mid-range and main jet (needle).

 

[stl360+450]

Today, I took the CB400f to work, the maiden ride after the carburetor adjustment and re-torque the head bolts. The 2 mm difference in float height makes all the difference in the world.

Awesome. Float height was something I took for granted when I first started to learn about motorcycle maintenance and carburetor adjustments. I didn't appreciate it until I was able to notice its effect on performance. This is a great example of how important it can be.

 

[Maraakate]

It's funny how much of a difference that can make sometimes from a couple mm difference. Glad to hear it's sorted out!

 

[jensen]

Another 250 added km on the odo, 180 km of backroads and 70 km highway. I took the highway from 19.00 hours, because after 19.00 pm (and before 6.00 am) the speed limit in the Netherlands is 130 km/hr (80 mls/hr) instead of 100 km/hr (65 mls/hr). It was a warm day 30 degrees Celcus (86 Fharenheit). The bike felt strong on the highway, it's fun to play the six speed gearbox when taking over. You go from fifth / sixth to third / fourth, and from 6K rpm to 8K rpm. The sound at those rpm are really nice.








Yesterday I finally got a large shipment from the US, a very special CB450 K1 in parts. Now, everything is in place for the thread https://www.vintagehondatwins.com/forums/index.php?threads/35.

 

[stl360+450]

Another 250 added km on the odo, 180 km of backroads and 70 km highway. I took the highway from 19.00 hours, because after 19.00 pm (and before 6.00 am) the speed limit in the Netherlands is 130 km/hr (80 mls/hr) instead of 100 km/hr (65 mls/hr). It was a warm day 30 degrees Celcus (86 Fharenheit). The bike felt strong on the highway, it's fun to play the six speed gearbox when taking over. You go from fifth / sixth to third / fourth, and from 6K rpm to 8K rpm. The sound at those rpm are really nice.

Yesterday I finally got a large shipment from the US, a very special CB450 K1 in parts. Now, everything is in place for the thread https://www.vintagehondatwins.com/f...-an-inquiry-into-Differences-and-Similarities.

Great shots. Did you have to reposition your bike to line up all six(?) of those wind turbines?

 

[jensen]

The shots are taken 10 km apart from each other. When riding from work to my home, I mostly ride 60-70 km along open water, just a few km's where I can't see open water.

 

[jensen]

After adjusting the carburettors and another 1000 km on the road, the bike was ready for it's first dynorun after rebuild, here you go:

Shifting through the gears :

https://flic.kr/p/2oLqQT2

Pull in 5th gear only:

https://flic.kr/p/2oLknpP

Top speed on the road matches with the top speed on the dyno, 186 km/hr (115 mls/hr) flat out @ 9.500 rpm in sixth gear

Not finished jet, some more carb work ahead. The needles 1 position lower, main jet maybe one step smaller (has to be decided after the needle work).

 

[stl360+450]

That was neat to see! I've never witnessed a dyno run, so thank you for sharing.

 

[ballbearian]

Thanks for the vids. Would love to hear your thoughts/rationale for needle position changes versus jet change. I've heard it said, "the dyno doesn't lie", so all performance data supercedes any plug condition readings or even Exhaust Gas Analyzer readings, I assume.

Seems a highly successful rebuild. Congratulations.

 

[jensen]

The runs are done with exhaust gas analyzer, and is one of the most important source of data in combination with load, rpm and throttle position, and logically with the torque and power curves.

 

[Maraakate]

EGA is a great tool. It be nice if you get them at prices for the people, but any decent shop that is serious about working on these vintage 4-cycle carb bikes should have one and know how to use it. There are quality portable units out there, but they're around $2000-$3000, such as this one https://www.bridgeanalyzers.com/engine-performance/2-gas-analyzer-exhaust-gas-analyzer/. I've been on the hunt for the 1990s era snap-on portables with a monitor, but they come up infrequently. Right now all I have is an old 1970s Allen EGA that is need of some repair. Right now the CO side of it works, which is good for some diagnostics and tuning, but you really want the HC as well. Gunson sells a simple one that only does CO which is intended for idle mixture adjustments only. It can be a useful tool, but this assumes everything else is correct on your bike. And it may very well not be. For those interested, it's available at: https://www.gunson.co.uk/Product/G4125/Gastester-Digital.

 

[Maraakate]

Out of curiosity... what is your target CO range at idle? Most bikes it should be around 2-3, but some pre-1980s bikes (such as yours) may favour a 4-5 in order to get a smooth idle and good take off from idle.

 

[jensen]

6% CO

 

[jensen]

Today, I took my CB400F to the yearly old-timer day. There was a lot of strong competition, but I managed to be in the first place.

It was a very rainy day, and all the bikes did a 50 km tour. Made some friends, had some beers, and enjoyed the competition.









Many classic cars, this is a nice one (and that's how far my knowledge of cars goes .....)

 

[ancientdad]

Congratulations, looks like there was some strong competition. Quite an assemblage of vintage Hondas in the second picture alone.

 

[jensen]

Yes indeed, an almost perfect, new CB500, in candy gold / black too, and a nice CB250 K2. Many BMW's, including a very fast and original R50s '62 (high compression race version, max rpm 8000, only 1633 made). However, I took him out on top speed easily while shifting in fifth :lol: (145 km/hr). The normal R50 has 26 HP, the R50s has 10 more (and there was also a black standard R50, the sound alone was very different).



And this Benly looks very expensive too. As I live in one of the richest area's of the Netherlands (t'gooi), many very special and expensive cars where present.

 

[stl360+450]

It's great to see so many well-maintained bikes and impressive that all of the owners took their bikes on the ride. in sure it's fun talking to the other owners about their bikes, too. I see a ribbon and a trophy. Was there really a prize to finish the tour first or were the bikes judged on their condition, etc.? In any case, congratulations! What a fun day!

 

[jensen]

Judged on condition, originality, etc. Nothing to do with the tour. The jury was 5 experts in the field on cars, mopeds and bikes. Authentic was the most important weigh factor, and the originality of my bike, including the original dealer stickers at the front and rear mudguard, together with the original paint made it a 98 pointer (2 points subtracted for the tires and battery, the BT46 weren't available in 1975, as Yuasa). They even checked the originality of the tool tray.

 

[LongDistanceRider]

Wow, 98/100 is a very impressive score! But then we all knew the time and effort you have in this one so it's not terribly surprising. Congratulations on the win.
Nice blue Bentley, looks to be all original. The silver restomod Bentley looks real good as well.

 

[2BrokeBikes]

Congratulations on the win Jensen!

Sent from my SM-A536U1 using Tapatalk

 

[Cycleranger]

It's those headers, gets 'em every time!
Very nice!

 

[jensen]

It's those headers, gets 'em every time!

Don't know what you mean ? maybe a saying in the US ?

 

[stl360+450]

Don't know what you mean ? maybe a saying in the US ?

That's right. "It gets them every time" basically means that "it" is very effective for producing a certain response from people. Here, "it" would be the 4-into-1 header and the response would be that people are impressed by its novelty, form, and/or function.

 

[ballbearian]

It's like the Marylin Monroe of exhaust systems.

 

[Richard Pitman]

Congrats on the win !

Slightly off topic, and apologies if I've missed this in your build thread, but what engine oil are you running ? From your 450 thread, I assume fully synthetic.

Reason I ask is that while sitting in the smallest room this morning I was reading an old copy of 'Classic Bike', which had a 400/4 buyers guide, in which David Silvers mechanic recommended use of mineral oil, rather then semi or full synthetic. To me, this makes no sense, surely the most modern bike oil ( that meets the JASO spec ) has to be best ?

 

[Richard Pitman]

That Bentley looks familiar. I saw this at a car show at Highnam Court ( Gloucester, UK ) back in 2021.

 

[jensen]

Reason I ask is that while sitting in the smallest room this morning I was reading an old copy of 'Classic Bike', which had a 400/4 buyers guide, in which David Silvers mechanic recommended use of mineral oil, rather then semi or full synthetic. To me, this makes no sense, surely the most modern bike oil ( that meets the JASO spec ) has to be best ?

Yes, I agree, and yes, your assumption is correct. I use 10W60 engine oil in this bike in the summer, and 10W50 in the spring and Autumn. I do not really care what others recommend, I go by my own experience. The modern oil are superior in every way compared to the older oils, exept for the amount of zinc. However, the zinc gets important when the oil fails.

 

[Richard Pitman]

Thanks, that's reassuring. I've recently swapped over to using Mobil 1 15w50 bike oil in my 175's. I've always used fully synth 10w40 in my (water cooled) 600.

 

[jensen]

 

[LongDistanceRider]

Great picture of the 400

 

[bilbikek411]

Another 250 added km on the odo, 180 km of backroads and 70 km highway. I took the highway from 19.00 hours, because after 19.00 pm (and before 6.00 am) the speed limit in the Netherlands is 130 km/hr (80 mls/hr) instead of 100 km/hr (65 mls/hr). It was a warm day 30 degrees Celcus (86 Fharenheit). The bike felt strong on the highway, it's fun to play the six speed gearbox when taking over. You go from fifth / sixth to third / fourth, and from 6K rpm to 8K rpm. The sound at those rpm are really nice.


View attachment 22625



View attachment 22626

Yesterday I finally got a large shipment from the US, a very special CB450 K1 in parts. Now, everything is in place for the thread https://www.vintagehondatwins.com/forums/index.php?threads/35.

I like the 'varnish blue' color CB400F SS model much better than the red color.
Which other color models(yellow,etc.?)CB400F did you get over there in The Netherlands, Jensen ?

 

[jensen]

Which other color models(yellow,etc.?)CB400F did you get over there in The Netherlands, Jensen ?

Blue and red in the first years, later the yellow version.

 

[bilbikek411]

Blue and red in the first years, later the yellow version.

Ah yes,it was the same over here in the States.

 

[ballbearian]

I'm kind of surprised that you've mounted the engine cover protector bars. They do look well made and fit nicely, but I've the impression that you might be a minimalist on accessories and too good a rider to need them.

 

[Richard Pitman]

I think those bars are neat and entirely sensible, protect those cases ( and possibly the exhaust header ) from the careless actions of other folks. I have big nylon crash bungs on my Hornet. I've no illusions that they would help much in a big crash, but they've certainly saved some damage when I've clumsily dropped the bike at low speed or when stationary.

 

[ballbearian]

An earlier pic does show the guard protecting the header from a fall over so probably worth the Kg or so extra weight.

 

[jensen]

I'm kind of surprised that you've mounted the engine cover protector bars. They do look well made and fit nicely, but I've the impression that you might be a minimalist on accessories and too good a rider to need them.

I agree, but these where fitted by the first owner, so I put them back. A few years ago I found my bomber flat on the tarmac, coming back from the supermarket, probably due to a car driver. Lucky for my it was on the right side, only the right footstep was damaged and the muffler had a few scratches extra. Lesson learned, no parking in the neighbourhood of morons in cars...

 

[stl360+450]

I agree, but these where fitted by the first owner, so I put them back. A few years ago I found my bomber flat on the tarmac, coming back from the supermarket, probably due to a car driver. Lucky for my it was on the right side, only the right footstep was damaged and the muffler had a few scratches extra. Lesson learned, no parking in the neighbourhood of morons in cars...

I figured that was reason you had them.

It's crazy to think of a bomber being tipped in a parking lot, but I guess most people just have no idea. I've heard of situations here where someone will try to move a parked bike to take their parking spot and the result is the same. I do like you — keep far away.

 

[jensen]

Another day at the office. At the moment the weather is very good, a little chilly and foggy in the morning and warm in the evening. My bomber is collecting dust at the moment, the seat is being upholstered. I take the CB72 and the CD50H out on occasion, for a nice evening ride. Tires for the CB400f are ordered, next season the bike has fresh shoes. I choose BT46 again. On my CB72 I have more authentic tires (Heidenau), but I don't like them in the wet. I ordered Michelin Anakee for the CD50H, due the the size the choice isn't so big (17inch, 2.5 rear and 2,25 front).

The last three days I used the CB400f exclusively on the highway, changing gears between fourth, fifth and sixth gear is really fun. In the morning the constant speed is 100 km/hr (62 mls/hr), but in the evening 130 km/hr (80 mls/hr (our highways have two speeds limits, between 6.00 and 19.00 hours it is 100 km/hr, after 19.00 it is 130 km/hr). The average rpm is per ride one hour above 6K-7K, the song from the exhaust is marvelous and addictive. Overtaking a truck, just go back to fourth, open the throttle, and swiftly slide the needle close to the redline, once overtaken, put it in fifth or sixth (depending on the wind direction), and go after the next truck (no speed tickets jet ). Yesterday evening, on an empty road, I almost reached the redline in sixth, the GPS showed 173 km/hr (107 mls/hr).

This bike is a nice highway bike, smoother then the bomber, however, at the back roads the heavy throttle, the handling and the lack of instant torque is somewhat frustrating.

 

[ballbearian]

Another beautiful photo there.
It must be fun to be on the highway right when the clock strikes 1900. Sort of a rolling start grand prix, especially on that bike.

 

[jensen]

Almost the end of the season here. This morning it was 2 deg Celsius (35 Fahrenheit), raining and dark when I left my garage. The bike started quickly, and the sunrise was a joy to watch while riding. This year, I did put a lot of km's on the odo it is a joy to ride. After an hour ride with my Gerbing GT (battery) heated gloves I drove the bike into our workshop, where it is warm and dry.

 

[ancientdad]

Nice that management allows you to park inside. Rarely happens here in the US.

 

[jensen]

Nice that management allows you to park inside. Rarely happens here in the US.

Why ? In this case I'm alone in the whole building, no machines to be build in this hall (1 out of 13 factory halls), and as long I don't make doughnuts on the floor. And since I'm part of the management (Research & Development Manager), I decided it's ok

Everything is ready and shipped two weeks ago. Next month the build of a new machine starts, now waiting for parts. In the meantime I'm finishing the vision applications (software) for both machines, I like to do that in an empty office. I have my own office, meeting room, coffee machine, music, toilets and as you can see, a huge garage.

 

[jensen]

Only wet this morning, early ride, in the dark from door to door. Bike was doing well (again), and made the trip a pleasure ride. Pic is taken just before I parked it inside, dry and warm. It seems that the bike has more power in colder weather, the clutch started slipping just a little bit in the warming up. At 5K rpm, there is a "powerboost", clearly more noticeable, I think it's time to set the carbs a little leaner. When it's cold the air is denser, resulting in a leaner mixture. I did set-up the carbs a little too rich for the running in period only. Now, the running in period is finished, the carbs can be put back to a leaner set-up.