Topic: Dorothy III - CB750

[Stev-o]

Done with that one, now what?

I'd say you are due a cold beer! Well done Mate...

That's given 

But what am I going to do about cylinders and pistons, that is the question. 

I have always entrusted my machinist to accurately measure the bores to determine exactly what is needed. Hopefully just a hone and re-ring as boring [$50+ x4] and a piston kit [$200+] can get expensive.

I'm a "Wiseco Piston" guy but many guys, including Hondaman, have had success with the Cruzinimage piston kits.

https://www.ebay.com/itm/165843069051?chn=ps&_trkparms=ispr%3D1&amdata=enc%3A1MHJOWr_xQOiMs6nIZusdnQ42&norover=1&mkevt=1&mkrid=711-117182-37290-0&mkcid=2&mkscid=101&itemid=165843069051&targetid=1644837434363&device=c&mktype=&googleloc=9028253&poi=&campaignid=16743749222&mkgroupid=138744546207&rlsatarget=pla-1644837434363&abcId=9300842&merchantid=101648401&gclid=CjwKCAiArNOeBhAHEiwAze_nKC9QxjYoZ9NBRLC0n-E38JFFcrAo3siPTAykdpf_rOIwhpClE6kEuxoCuAcQAvD_BwE

[70CB750]

Done with that one, now what?

I'd say you are due a cold beer! Well done Mate...

That's given 

But what am I going to do about cylinders and pistons, that is the question. 

I have always entrusted my machinist to accurately measure the bores to determine exactly what is needed. Hopefully just a hone and re-ring as boring [$50+ x4] and a piston kit [$200+] can get expensive.

I'm a "Wiseco Piston" guy but many guys, including Hondaman, have had success with the Cruzinimage piston kits.

https://www.ebay.com/itm/165843069051?chn=ps&_trkparms=ispr%3D1&amdata=enc%3A1MHJOWr_xQOiMs6nIZusdnQ42&norover=1&mkevt=1&mkrid=711-117182-37290-0&mkcid=2&mkscid=101&itemid=165843069051&targetid=1644837434363&device=c&mktype=&googleloc=9028253&poi=&campaignid=16743749222&mkgroupid=138744546207&rlsatarget=pla-1644837434363&abcId=9300842&merchantid=101648401&gclid=CjwKCAiArNOeBhAHEiwAze_nKC9QxjYoZ9NBRLC0n-E38JFFcrAo3siPTAykdpf_rOIwhpClE6kEuxoCuAcQAvD_BwE

Aren't you a machinist, too? 

I did new rings and hone for Red but I read from Hondaman that it is only short term solution - good for 15K or so. 

[BenelliSEI]

After I repair the bent fins on my S/C project I’m giving it a light home to get back a decent crosshatch. If the new RIK rings (std.) measure with spec gap, the original pistons are going back in. I feel th simplest solution is always the best..... At my age, 15000 miles is good!

[Stev-o]

Done with that one, now what?

I'd say you are due a cold beer! Well done Mate...

That's given 

But what am I going to do about cylinders and pistons, that is the question. 

I have always entrusted my machinist to accurately measure the bores to determine exactly what is needed. Hopefully just a hone and re-ring as boring [$50+ x4] and a piston kit [$200+] can get expensive.

I'm a "Wiseco Piston" guy but many guys, including Hondaman, have had success with the Cruzinimage piston kits.

https://www.ebay.com/itm/165843069051?chn=ps&_trkparms=ispr%3D1&amdata=enc%3A1MHJOWr_xQOiMs6nIZusdnQ42&norover=1&mkevt=1&mkrid=711-117182-37290-0&mkcid=2&mkscid=101&itemid=165843069051&targetid=1644837434363&device=c&mktype=&googleloc=9028253&poi=&campaignid=16743749222&mkgroupid=138744546207&rlsatarget=pla-1644837434363&abcId=9300842&merchantid=101648401&gclid=CjwKCAiArNOeBhAHEiwAze_nKC9QxjYoZ9NBRLC0n-E38JFFcrAo3siPTAykdpf_rOIwhpClE6kEuxoCuAcQAvD_BwE

Aren't you a machinist, too? 

I was a machinist, but that was many moons ago!  I now leave it to the Pros...

[HondaMan]

I was a machinist, but that was many moons ago!  I now leave it to the Pros...

Steve-O:
I'm curious, as I worked in several machine shops (I was the Controls guy who made the machines they built 'go') and would like to have a Bridgeport or similar mill: would you consider a mill rigid enough to bore these cylinders accurately? Mine are currently being done in a [large] engine boring machine with things like 3" thick top and side plates and 5" thick bottom plate, boring 1 hole at a time (used for inline car engines). It is rigid like Gibraltar!

[Stev-o]

I was a machinist, but that was many moons ago!  I now leave it to the Pros...

Steve-O:
I'm curious, as I worked in several machine shops (I was the Controls guy who made the machines they built 'go') and would like to have a Bridgeport or similar mill: would you consider a mill rigid enough to bore these cylinders accurately? Mine are currently being done in a [large] engine boring machine with things like 3" thick top and side plates and 5" thick bottom plate, boring 1 hole at a time (used for inline car engines). It is rigid like Gibraltar!

Hey HM...I never did cylinder boring but my machinist uses an automotive type boring machine too.  I'd say that is the best way to go.

[HondaMan]

I was a machinist, but that was many moons ago!  I now leave it to the Pros...

Steve-O:
I'm curious, as I worked in several machine shops (I was the Controls guy who made the machines they built 'go') and would like to have a Bridgeport or similar mill: would you consider a mill rigid enough to bore these cylinders accurately? Mine are currently being done in a [large] engine boring machine with things like 3" thick top and side plates and 5" thick bottom plate, boring 1 hole at a time (used for inline car engines). It is rigid like Gibraltar!

Hey HM...I never did cylinder boring but my machinist uses an automotive type boring machine too.  I'd say that is the best way to go.

One of the machinists at my former employer decided to rebuild his Trumpet Bonneville twin after it sat for 30+ years. He made a 1" thick mounting plate for it to bolt onto the head of the biggest lathe in the shop, then bored each cylinder using a specially-made (he made it) bit holder in the traveler. Then he took a video of it being bored, which I had until my 2nd-to-last computer just stopped working one day, before I had backed up that video file.

It looked pretty cool, never saw it done that way before. It worked fine, too.

[70CB750]

I was a machinist, but that was many moons ago!  I now leave it to the Pros...

Steve-O:
I'm curious, as I worked in several machine shops (I was the Controls guy who made the machines they built 'go') and would like to have a Bridgeport or similar mill: would you consider a mill rigid enough to bore these cylinders accurately? Mine are currently being done in a [large] engine boring machine with things like 3" thick top and side plates and 5" thick bottom plate, boring 1 hole at a time (used for inline car engines). It is rigid like Gibraltar!

Hey HM...I never did cylinder boring but my machinist uses an automotive type boring machine too.  I'd say that is the best way to go.

One of the machinists at my former employer decided to rebuild his Trumpet Bonneville twin after it sat for 30+ years. He made a 1" thick mounting plate for it to bolt onto the head of the biggest lathe in the shop, then bored each cylinder using a specially-made (he made it) bit holder in the traveler. Then he took a video of it being bored, which I had until my 2nd-to-last computer just stopped working one day, before I had backed up that video file.

It looked pretty cool, never saw it done that way before. It worked fine, too.

I have seen something like that many times in the tool and die factory.  Aluminum casting form had always inserts made from tool steel while the form "frame" (say 1000 x 1000mm) was made from cheaper steel.  On a big, big lathe this old timer would bore the hot aluminum entrance inserted in the frame. 

Ways to get by before CNC.   

[Don R]

I guess this will come handy 

  I printed this "cb750 changes" to hang in the garage next to the serial number list.  The link didn't come along with the quote.  Reply #413.

[70CB750]

I made  bushings for the swingarn.

[MauiK3]

Any good Bridgeport (not worn out) mill should work with a good stiff setup. The sleeves are pretty easy stuff to cut, not a lot of fuss or chatter.

[70CB750]

Any good Bridgeport (not worn out) mill should work with a good stiff setup. The sleeves are pretty easy stuff to cut, not a lot of fuss or chatter.

I used my old Logan to make bushings. 

Here is the future swingarn.

[grcamna2]

Any good Bridgeport (not worn out) mill should work with a good stiff setup. The sleeves are pretty easy stuff to cut, not a lot of fuss or chatter.

I used my old Logan to make bushings. 

Here is the future swingarn.

Custom made swingarm ?

[70CB750]

Any good Bridgeport (not worn out) mill should work with a good stiff setup. The sleeves are pretty easy stuff to cut, not a lot of fuss or chatter.

I used my old Logan to make bushings. 

Here is the future swingarn.

Custom made swingarm ?

I got it many years ago from ebay. Suzuki swingarm, I think.  We shall see how it turns out.

[Stev-o]

Any good Bridgeport (not worn out) mill should work with a good stiff setup. The sleeves are pretty easy stuff to cut, not a lot of fuss or chatter.

I used my old Logan to make bushings. 

Here is the future swingarn.

Custom made swingarm ?

I got it many years ago from ebay. Suzuki swingarm, I think.  We shall see how it turns out.

Why the need for a new swinger?

[70CB750]

Any good Bridgeport (not worn out) mill should work with a good stiff setup. The sleeves are pretty easy stuff to cut, not a lot of fuss or chatter.

I used my old Logan to make bushings. 

Here is the future swingarn.

Custom made swingarm ?

I got it many years ago from ebay. Suzuki swingarm, I think.  We shall see how it turns out.

Why the need for a new swinger?

Challenge? 

The plan for Dorothy is to look stock but with improvements when you look closer. 

[grcamna2]

Any good Bridgeport (not worn out) mill should work with a good stiff setup. The sleeves are pretty easy stuff to cut, not a lot of fuss or chatter.

I used my old Logan to make bushings. 

Here is the future swingarn.

Custom made swingarm ?

I got it many years ago from ebay. Suzuki swingarm, I think.  We shall see how it turns out.

The swingarm looks very much like the ones that come on the Suz. GS1100E

[70CB750]

After several tries, I got the angle right.  Now the length.  I might make it 1" longer than the stock swingarm.

[70CB750]

Welded the donner seat bracket back on.  The frame will get stripped and powder coated.

[Stev-o]

Welded the donner seat bracket back on.  The frame will get stripped and powder coated.

Color?

[calj737]

After several tries, I got the angle right.  Now the length.  I might make it 1" longer than the stock swingarm.

The few I’ve made were about 5* for the legs to intersect the pivot tube. Looks like you have “just enough” room for the tire when it’s cold and unloaded. A 1” extension to move the axle back would be very helpful for clearance issues.

[70CB750]

Welded the donner seat bracket back on.  The frame will get stripped and powder coated.

Color?

Gloss black, I am boring 

[70CB750]

After several tries, I got the angle right.  Now the length.  I might make it 1" longer than the stock swingarm.

The few I’ve made were about 5* for the legs to intersect the pivot tube. Looks like you have “just enough” room for the tire when it’s cold and unloaded. A 1” extension to move the axle back would be very helpful for clearance issues.

Thanks, Cal.  Still working on it. 

[Stev-o]

Welded the donner seat bracket back on.  The frame will get stripped and powder coated.

Color?

Gloss black, I am boring 

Stock was semi-gloss so you are stepping it up a bit!

[70CB750]

Welded the donner seat bracket back on.  The frame will get stripped and powder coated.

Color?

Gloss black, I am boring 

Stock was semi-gloss so you are stepping it up a bit!

Good to know, guess I will do semi-gloss.