Topic: 73-75 Denvers choppers CB750 period correct build thread

[754]

Any thoughts of matching the old paint?
 When lifting the motor in, most use slings like tiedown straps to hold the motor..

[lxcoupe89]

That was some impressively careful sanding!  It really is a shame what people paint over.

I like experimenting with the old bread boxes too.  I am currently running one with OEM air box boots installed and black UNI foam for the filter material.  I ended up with 135 mains, everything else stock in 086a carbs.  Super smooth idle and just off idle performance which is usually where carb adjustments get tricky.  I feel like the very top of the rpm range is lacking slightly compared to the stock airbox.  Probably due to the breadbox not being as big.  I plan to try to maximize the size by bending a new mesh piece if I can find suitable material.

Once I figured out what color was the first repaint, I'd gently sand through that coat and it would instantly go through in spots, at first I kept thinking I was blowing though the paint but I realized that it probably wasn't me. I think when it was sanded for the repaint they broke through.

The rubber boots on my bread box aren't large enough to fit my carbs. The spacing looks perfect though. I'm hoping I can get some oem boots to fit the bread box without modification.

I was planning to by the foam filter material also. Nearly all of the material is falling apart and gone out of this one.

I have PD42B Carbs I'm starting with 42 slow jets and 120 main jets. Brand new Keihin Jets.

Check out the attachment, Have you seen it? That dude blocks off some of the breadbox on the inside. I thought about trying that. It sounds like you want to open your up more though.

[lxcoupe89]

Any thoughts of matching the old paint?
 When lifting the motor in, most use slings like tiedown straps to hold the motor..

I have a car engine lift and thought about using it. The gantry I made is easy to get into my basement and it holds the motor still which is nice. I think I may be able to use it for other stuff also. It was an evening project with some steel I already had.

I'm not exactly sure what I'm going to do on the paint. Once I get the bike all together, running,  and try it out then I'm planning to decide how much I'm going to spend on paint. I'm thinking about something totally new but in the style of the old Denver's bikes. Similar loud flashy colors and striping patterns. If I could find a picture of the bike with original paint I would try copying it but since that's not likely it'll probably be something new.

If the frame and tank had paint like the fender I'd just clear them and run it. Frame has been stripped to metal though.

[lxcoupe89]

So far on the paint I like this the best. I like how the continuous striping takes advantage of the molding job, you can't really pull off paint like this unless the stuff is all molded. I'd go with different colors and a different pattern but similar in style.

The problem is these choppers seem to only be worth about $6K and I'm getting close to that already. As much as I'd like it I'm not sure I can spend thousands on the paint. We'll see. I'm, actually surprised these bikes aren't worth closer to $10K.

[slikwilli420]

Excellent work. I really like the period Honda choppers. Unfortunately, around here choppers even in nice condition sit unsold for less than half of your $6k you have into yours. Very small following and not too difficult to find.

[seanbarney41]

That was some impressively careful sanding!  It really is a shame what people paint over.

I like experimenting with the old bread boxes too.  I am currently running one with OEM air box boots installed and black UNI foam for the filter material.  I ended up with 135 mains, everything else stock in 086a carbs.  Super smooth idle and just off idle performance which is usually where carb adjustments get tricky.  I feel like the very top of the rpm range is lacking slightly compared to the stock airbox.  Probably due to the breadbox not being as big.  I plan to try to maximize the size by bending a new mesh piece if I can find suitable material.

Once I figured out what color was the first repaint, I'd gently sand through that coat and it would instantly go through in spots, at first I kept thinking I was blowing though the paint but I realized that it probably wasn't me. I think when it was sanded for the repaint they broke through.

The rubber boots on my bread box aren't large enough to fit my carbs. The spacing looks perfect though. I'm hoping I can get some oem boots to fit the bread box without modification.

I was planning to by the foam filter material also. Nearly all of the material is falling apart and gone out of this one.

I have PD42B Carbs I'm starting with 42 slow jets and 120 main jets. Brand new Keihin Jets.

Check out the attachment, Have you seen it? That dude blocks off some of the breadbox on the inside. I thought about trying that. It sounds like you want to open your up more though.

Your boots are too small because the PD42's have a bigger throat than the earlier roundtop carbs which your breadbox was probably designed for.  So if you are gonna order boots, make sure and order them for a 77/78 750.  I have not had any success trying to tune PD's for modified intake and/or exhaust...not saying it can't be done, just not cheap or easy.  Also UNI offers foam sheets that you can cut into replacement filters in two colors/density's, black is less dense and green/blue is more dense.  I have used either successfully, the black is gonna require more main jet and the blue/green probably has better filtration.  Also the black is slightly easier to fit into the breadbox, as it is thinner.

I have found no reason to partially block off the breadbox, although I have heard of many doing this.  I think it is a misguided way to avoid the tedium of proper jetting.  I also have experienced no running issues due to wind or rain.  I can imagine being on a long ride in steady rain could cause problems.

[lxcoupe89]

[/quote]Your boots are too small because the PD42's have a bigger throat than the earlier roundtop carbs which your breadbox was probably designed for.  So if you are gonna order boots, make sure and order them for a 77/78 750.  I have not had any success trying to tune PD's for modified intake and/or exhaust...not saying it can't be done, just not cheap or easy.  Also UNI offers foam sheets that you can cut into replacement filters in two colors/density's, black is less dense and green/blue is more dense.  I have used either successfully, the black is gonna require more main jet and the blue/green probably has better filtration.  Also the black is slightly easier to fit into the breadbox, as it is thinner.

I have found no reason to partially block off the breadbox, although I have heard of many doing this.  I think it is a misguided way to avoid the tedium of proper jetting.  I also have experienced no running issues due to wind or rain.  I can imagine being on a long ride in steady rain could cause problems.
[/quote]

Thanks for the info, I thought the throats were bigger on these carbs than the older ones. Do you know if the boots for the factory  77/78 airbox will work on the sheetmetal plate of the bread box?

https://goo.gl/images/8q8t4c

I'll keep the air filter foam notes in mind until I get to it.

[seanbarney41]

I don't know right off hand, but I can get you some measurements if you give me a few days.

[Medyo Bastos]

[/quote]
I have found no reason to partially block off the breadbox, although I have heard of many doing this.  I think it is a misguided way to avoid the tedium of proper jetting.  I also have experienced no running issues due to wind or rain.  I can imagine being on a long ride in steady rain could cause problems.
[/quote]

Question,
How many stock airboxes are vented all the way around? Why didn’t Honda do it?



Sent from my iPhone using Tapatalk

[seanbarney41]

I have found no reason to partially block off the breadbox, although I have heard of many doing this.  I think it is a misguided way to avoid the tedium of proper jetting.  I also have experienced no running issues due to wind or rain.  I can imagine being on a long ride in steady rain could cause problems.
[/quote]

Question,
How many stock airboxes are vented all the way around? Why didn’t Honda do it?



Sent from my iPhone using Tapatalk
[/quote]because still air works the best and that is why the stock airbox works the best, it supplies a rather large volume of still air.  The breadbox is not big enough to supply enough still air, so you have to supplant it with moving air which thus requires re-jetting.  Block off half the breadbox's airflow and then you cannot even flow enough air and you have created a restriction.  That is gonna hurt power.  Realistically, the breadbox is already a restriction without blocking off any of it.  So if you have not greatly increased cylinder head port flow, the stock airbox is gonna make the most power.  Breadbox is just for looks and fun to experiment with.  It certainly performs better than pod filters

[lxcoupe89]

I don't know right off hand, but I can get you some measurements if you give me a few days.

I've got plenty of time to wait. I appreciate you checking it out

[754]

Excellent work. I really like the period Honda choppers. Unfortunately, around here choppers even in nice condition sit unsold for less than half of your $6k you have into yours. Very small following and not too difficult to find.

There is nice choppers, and mediocre choppers,  and POS choppers.
 The Denver ones tend to be pro built and have a certain look to them. I suspect this look still appeals to many and that drives the price up.
 Many of the ones for sale are just a good starting point., and thus command less money.

Now that you have an idea of the original paint, you may be able to figure out the first owner..

[Desert-SOHC]

I don't know right off hand, but I can get you some measurements if you give me a few days.

I've got plenty of time to wait. I appreciate you checking it out

Do you need the diameter of the stock air horns?  I just replaced mine and have the old set still.

[lxcoupe89]

I don't know right off hand, but I can get you some measurements if you give me a few days.

I've got plenty of time to wait. I appreciate you checking it out

Do you need the diameter of the stock air horns?  I just replaced mine and have the old set still.

Yes if its not much trouble. Are you going to hang onto your old ones or throw them away?

The diameter of the part where it fits into the airbox is all I need

[lxcoupe89]

Excellent work. I really like the period Honda choppers. Unfortunately, around here choppers even in nice condition sit unsold for less than half of your $6k you have into yours. Very small following and not too difficult to find.

There is nice choppers, and mediocre choppers,  and POS choppers.
 The Denver ones tend to be pro built and have a certain look to them. I suspect this look still appeals to many and that drives the price up.
 Many of the ones for sale are just a good starting point., and thus command less money.

Now that you have an idea of the original paint, you may be able to figure out the first owner..

I agree with what you've said. The difference is in the components and the quality of the build. I think the reason choppers are cheap is because:

There is no service manual to maintain and fix it. You have to figure it out and that takes skills and patience.

Many people are scared of them, because of the rigid frame, the long front end and rake angle. Typically no turn signals etc etc. I think a lot of people wish they had one but never go for it. Many probably think they will be paralyzed from hitting bumps and will crash because they can't steer it.

The great part is, it keeps choppers cheap to buy. So for those of us who love to ride em, and know how to keep them running its a great deal. Can't beat that.

I have no idea how this Denver's will handle which is why I decided to fully build it and ride it before spending the money on the paint. I don't plan to sell it so I'm not concerned with the value other than I'd like to know how much I'm throwing away when I do it. I've always wanted to build a chopper. For me, I'm paying for the experience. I could have saved a good bit of money by not having Fred weld those mounts back in and by using a cheap oil tank. I paid a lot for Fred to make me one. I don't regret it one bit.

I've had a couple other choppers but I bought them built, for about 1/3 of the build cost. Its always cheaper to buy one than build it, especially a good quality bike. Whenever someone checks them out I always give credit to the guys that built it. Its time for me to build my own.

[lxcoupe89]

Excellent work. I really like the period Honda choppers. Unfortunately, around here choppers even in nice condition sit unsold for less than half of your $6k you have into yours. Very small following and not too difficult to find.

There is nice choppers, and mediocre choppers,  and POS choppers.
 The Denver ones tend to be pro built and have a certain look to them. I suspect this look still appeals to many and that drives the price up.
 Many of the ones for sale are just a good starting point., and thus command less money.

Now that you have an idea of the original paint, you may be able to figure out the first owner..

I would love to find some past owners of the bike.

[lxcoupe89]

A few weeks ago, I ended up finding an NOS CB750 8 spoke invader wheel on ebay. So I sprung for it, because its in great condition. When it arrived, and I tore open the box like Ralphie opening his red ryder bb gun on christmas morning in the movie A Christmas Story, to my dissatisfaction I realized immediately that it was not a CB750 wheel. I should have seen it in the pics because it was easy to tell.

I messaged the seller and they gave me $50 bucks back if I wanted to keep it or they would refund me. I think it was an honest mistake on their part. The chrome on the wheel is excellent so, in true chopper fashion of use what you got, I figured I'd just try to use it. I'll talk more on this later, but I figured out its a Kawasaki Z1 or H2 wheel.






Now that I got a wheel its time to get this thing up on my lift so I can work on it easier. I made a set of stands to hold it better on the lift. (A note on my garage decorations. The flag in the background of one of the pics has a chopper on it. I am not racist in any way. I have friends of many ethnicity's. I think its stupid this day and age that I feel like i need to add that disclaimer before being judged. I hope that the thread doesn't get hijacked with any discussion on it.)








The shop supervisor was on duty that night.

[lxcoupe89]

Once I got the bike up on the lift, my main goal was to see if I can use the Kawi wheel before buying any parts for it. I needed to check the sprocket alignment with the wheel centered in the frame and fender.

I took a trip to Baltimore cycle salvage, in Baltimore md, to see if I could find some parts for my wheel. The parts were priced good and the guy took the time to dig through all his stuff trying to find parts that fit.  I ended up with a Kawi sprocket carrier and a yahama virago brake plate. He said it looks like the holes for the cush drive bushings were in the wrong spot. I figured maybe I have a blem wheel and the reason it was an NOS is because it was made wrong. Not one to give up easliy I started doing more research. Turns out the holes for the cush drive bushings appear to be in the correct spot for the early Z1 and H2. I saw a Lester wheel on ebay for a Z1 that had the max diameter for the drum cast into it. I went and measured, my wheel had the correct size drum for Z1 also.

I found a chrome sprocket carrier and brake plate on ebay. Supposed to be early Z1 parts. Once I got them, They both seemed to fit good. After doing some research I learned that the Kawi Z1's and H2's used the same size rear axle as a early CB750. In fact they use the same wheel bearings (6304-2RS). The sprocket carrier bearing is larger on the Kawi but there is a spacer that goes inside the bearing and it fits the CB750 axle size.

Since the wheel didn't have bearings in it, I zip tied the sprocket carrier and Brake Plate to the wheel so I could put it on the bike.

With the wheel centered in the frame, I used a straight edge to line up the sprockets and it looked like the alignment is damn near perfect.






I had to put the front end back on to see it again up on the lift.



Now that I knew it "should" work. I figured I'd better do a dimensional stack up and compare to the Honda Wheel set up to see if they indeed do line up the same. This is also a great way to figure out the correct size for axle spacers.

I took everything apart and took the best measurements I could. I made some rough 3D models to lay the stuff out. Seeing the parts in cad is much easier than just calculating the numbers out on paper. plus I can take other measurements from it and refer back to it easily. It can be done on paper though if you do not have access to a cad system. Its simple math and anyone can do it. According to my measurements the sprockets on the honda wheel and the Kawi wheel set up I had were within 1/32" of one another.









Once I received my bearings and bearing spacer for the wheel hub, I put them in and put everything back on the bike. Centered the wheel again and re-checked the sprockets with a straight edge.

[754]

 I like the axle adjuster being inboard...cleaner look..
I started cleaning up my savior frame yesterday, some one had welded a bunch of plate on the sides, messy to clean up.

 Show a pic of the paint to  Fred at the frame shop  he may remember..

[lxcoupe89]

I like the axle adjuster being inboard...cleaner look..
I started cleaning up my savior frame yesterday, some one had welded a bunch of plate on the sides, messy to clean up.

That's one of the reasons I appreciate the denver's stuff so much. Everything was clean, and they did a nice job of designing and building the stuff. Not like a lot of the home built hack jobs.

Those amen frames are cool. a long time ago I had a chance to buy a plunger frame and long springer, I didn't,  I was young and didn't know #$%* about them then. I wish I could go back and buy some of the cool stuff i saw for sale within the last 20 years. I also knew a guy that had a super long 59 harley chopper chassis and another guy that had a triumph long chopper. I was tempted to buy them but I figured I'd never be able to get them running.

[Desert-SOHC]

I don't know right off hand, but I can get you some measurements if you give me a few days.

I've got plenty of time to wait. I appreciate you checking it out

Do you need the diameter of the stock air horns?  I just replaced mine and have the old set still.

Yes if its not much trouble. Are you going to hang onto your old ones or throw them away?

The diameter of the part where it fits into the airbox is all I need

The ones I replaced were aftermarket and measure 50 mm outside diameter.  OEM's are still available and I recommend them over aftermarket.  I had to replace them because they were cracking and falling apart after 7k miles.

[Jerry Rxman Griffin aka MuthaF'er]

Excellent work. I really like the period Honda choppers. Unfortunately, around here choppers even in nice condition sit unsold for less than half of your $6k you have into yours. Very small following and not too difficult to find.

There is nice choppers, and mediocre choppers,  and POS choppers.
 The Denver ones tend to be pro built and have a certain look to them. I suspect this look still appeals to many and that drives the price up.
 Many of the ones for sale are just a good starting point., and thus command less money.

Now that you have an idea of the original paint, you may be able to figure out the first owner..

I would love to find some past owners of the bike.

We have Denvers Choppers members onboard just don't remember who?? They have some REALLY sweet rides. Perhaps a resource for you?

[seanbarney41]

Hi LX...I measured some brand new OEM Honda 78 cb750f boots.  I am seeing 50mm maybe a couple mm less.  Kinda hard to get an accurate measurement with out smooshing them with the calipers.  I am totally estimating that if the holes in your breadbox are like up to 20mm bigger, they would still seal.  If your holes are too small, it would be real easy to clearance the holes with a die grinder or something.

[lxcoupe89]

Thanks I appreciate the help.

I checked out my bread box, They should fit perfect. The holes measure about 49.5mm.

[lxcoupe89]

Got my tire mounted up last night. J&B Moto in Wrightsville, PA helped me out with that. Stop in to check them out if you are nearby. The owners name is Brian. They have been on Cafe Racer TV.

https://www.facebook.com/jbmotoco/