Topic: The Hot Mess - 1975 CB550F1 Frame/1981 CB650 Engine

[MessnerMoto]

The engine really can't be considered a stressed member without ream fitting larger mounting bolts. The original bolts are just too sloppy. Both turboguzzi designed a "head steady" for his CB500 racer and friends do the same with their CR750. However it's the pressed steel surround of the steering head that would be best supported and that isn't easily done.

The swingarm pivot area is another spot that is often stiffened. Originally I used a bolt in alloy brace here using high grade splined bolts plus welded braces underneath.




As far as welding in braces. They should be welded on the outside of the tube not the middle, and a saddle style brace is best. Note where the welds start & end, don't weld solid.




Where Honda joined the front downtubes they made three spot welds. That area can be welded down the joints.

Kemp's bolt in brace in the front is a good idea.

Most often all we're doing is adding weight as the frames are quite adequate as is. The Italian 500 class champ that races a CB500 has no frame bracing at all. Makes you wonder! 

Hope you don't mind Don.

Thank you for this info. Can you elaborate more on this: "ream fitting larger mounting bolts"... Can you point me to some pictures, more info?

Also "head steady" means you can brace top of the engine to frame? I found http://forums.sohc4.net/index.php?topic=23539.0 post from turboguzzi.....

Sorry for asking these question in your thread Don

[Retro Rocket]

The swingarm pivot area is another spot that is often stiffened. Originally I used a bolt in alloy brace here using high grade splined bolts plus welded braces underneath.

That brace looks pretty thin, Brent. What thickness was used?

As far as welding in braces. They should be welded on the outside of the tube not the middle, and a saddle style brace is best. Note where the welds start & end, don't weld solid.

Im curious as to why not fully weld the seam?

Most often all we're doing is adding weight as the frames are quite adequate as is. The Italian 500 class champ that races a CB500 has no frame bracing at all. Makes you wonder! 

No fork brace either? Don't tell "those other guys" 

I've said this before, a good rider can ride around a lot of handling querks, I could easily show anyone the twist in an unbraced sohc front end, its surprisingly easy to do..

[Retro Rocket]

Fish on!  That was like throwing a topwater bait in the spring time... Easy, Retro, I was only poking a bit of fun. You know we are mates to the end and that I do value your input. 

No animosity mate, just a comment...    We call them "poppers" here...

[SOHC4 Cafe Racer Fan]

I'm open to more advice on the frame mods, especially the tried and tested wisdom from Brent!

I just spoke with Mike. I'll be packing my '79 CB750 head for a Stage 2.5 job.  My guess is that I'll have the finished head long before I will have  coating, paint and wiring (to come after fabrication and wheel building).  (I might just shelve the '81 head and stock CV carbs for now. . .)

[Retro Rocket]

I'm open to more advice on the frame mods, especially the tried and tested wisdom from Brent!

I just spoke with Mike. I'll be packing my '79 CB750 head for a Stage 2.5 job.  My guess is that I'll have the finished head long before I will have  coating, paint and wiring (to come after fabrication and wheel building).  (I might just shelve the '81 head and stock CV carbs for now. . .)

Brents gussets are the cats meow...

[SOHC4 Cafe Racer Fan]

His 550 is awfully pretty but it is all tested and proven on the track.

[Retro Rocket]

His 550 is awfully pretty but it is all tested and proven on the track.

Yep, its a pretty well thought out and sorted bike....

[GV1390]

Damn, this one is cool as well! I'm jealous. I will be looking into one of those exhaust setups as well, they look pretty!

[SOHC4 Cafe Racer Fan]

Damn, this one is cool as well! I'm jealous. I will be looking into one of those exhaust setups as well, they look pretty!

With the CB650 engine, there are more limited options.  Up to discovering the Hindle (via Jim), I was looking at having a custom one made, since I did not want the stock or Mac system. 

[SOHC4 Cafe Racer Fan]

Christmas came early today.  My Hindle 4-2-1 exhaust arrived from Kemp/Ripple Rocker Racers, and it is beautiful.  It is also much lighter than my MGP pipe.  I won't be fitting it for a while (engine head is out for porting, and frame is undergoing fab), but I am very happy with what I received.  The welds are nice and clean.  It was also packed carefully with plenty of cushioning material.  The slash reverse megaphone looks very well made.  Along with tab welded to the muffler, Kemp also included a hanger strap to secure it to the frame.  Teaser pic:

image_zps4rfnhpkr by Donald Leonhardt, on Flickr

The frame brace is also a very high quality finished piece.  I think I am going to use it on my 550 bike and simply weld a cross-member on the 650/550.

image_zpswgomscv0 by Donald Leonhardt, on Flickr

[Restoration Fan]

Good looking pipes, Don.  It appears from the photo that they're just a bolt-on and might need the little 2-piece collar inserts.  Is that correct or will you still need those and the copper crush washer to install them?

[SOHC4 Cafe Racer Fan]

Ron,

I haven't looked at the installation specs but I believe they install just like the MGP pipes with the exhaust flanges and springs.

[FunJimmy]

I've got the exact same stuff arriving next week.
I'll be fitting mine as soon as I can. Gonna polish it up too.
Can't wait.

[Bigsam302]

Don,

Those pipes look sweet!  I can't wait to see them installed.

Sam

[SOHC4 Cafe Racer Fan]

I was planning not to coat the outside, but I will likely ceramic coat just the inside of the pipe due the tube wall thickness.

[bwaller]

Well Merry Christmas to you Don.  Sweet looking pipe.

[SOHC4 Cafe Racer Fan]

The 1979 head arrived at Dr. Mike Rieck's mad scientist laboratory. Thanks Mike for accommodating the head into your busy schedule!  Since the 650 head is a little more efficient than the 550 and 750 heads, this one is getting what Mike calls a Stage 2.5 job.

In the interim, the replacement ring set went on and the cylinder block is now on the engine -- ready for the killer Mike Rieck head!

image_zpsrursht7b by Donald Leonhardt, on Flickr

[SOHC4 Cafe Racer Fan]

I checked in with Mike Rieck today.  My head is about 2-3 weeks out.  Mike is trying to get some last minute winterizing and repairs done before Mass. starts getting winter weather. 

He confirmed the head is in good condition and a strategy for porting. 

As for carburetors, Mike recommended (for the 1979-1980 head) looking into 30mm CV carbs if available (as they are very streetable), CR26s or possibly CB750 carbs.

Does anyone have experience using 30mm CV carbs with a 650 engine?  I am going to ask on the 650 forum too, but there's not much posting there.

[Retro Rocket]

I checked in with Mike Rieck today.  My head is about 2-3 weeks out.  Mike is trying to get some last minute winterizing and repairs done before Mass. starts getting winter weather. 

He confirmed the head is in good condition and a strategy for porting. 

As for carburetors, Mike recommended (for the 1979-1980 head) looking into 30mm CV carbs if available (as they are very streetable), CR26s or possibly CB750 carbs.

Does anyone have experience using 30mm CV carbs with a 650 engine?  I am going to ask on the 650 forum too, but there's not much posting there.

The Aussie model CBX550 has 30mm Keihin CV's...   

[grcamna2]

This bike is going to be Nice !

[SOHC4 Cafe Racer Fan]

I checked in with Mike Rieck today.  My head is about 2-3 weeks out.  Mike is trying to get some last minute winterizing and repairs done before Mass. starts getting winter weather. 

He confirmed the head is in good condition and a strategy for porting. 

As for carburetors, Mike recommended (for the 1979-1980 head) looking into 30mm CV carbs if available (as they are very streetable), CR26s or possibly CB750 carbs.

Does anyone have experience using 30mm CV carbs with a 650 engine?  I am going to ask on the 650 forum too, but there's not much posting there.

The Aussie model CBX550 has 30mm Keihin CV's...   

Thanks for the tip, Mick.  I wonder if they will match up or can be re-racked easily enough.

[Retro Rocket]

I checked in with Mike Rieck today.  My head is about 2-3 weeks out.  Mike is trying to get some last minute winterizing and repairs done before Mass. starts getting winter weather. 

He confirmed the head is in good condition and a strategy for porting. 

As for carburetors, Mike recommended (for the 1979-1980 head) looking into 30mm CV carbs if available (as they are very streetable), CR26s or possibly CB750 carbs.

Does anyone have experience using 30mm CV carbs with a 650 engine?  I am going to ask on the 650 forum too, but there's not much posting there.

The Aussie model CBX550 has 30mm Keihin CV's...   

Thanks for the tip, Mick.  I wonder if they will match up or can be re-racked easily enough.

I've never compared the CBX750 to the 550 but I know that the CBX750 carbs can fit the 750 with some patience and manipulation without any mods, if the 550 engine is a bit smaller they might just fit straight on, the CBX550 had 65HP stock at 10,000RPM so they would be a good match...

[SOHC4 Cafe Racer Fan]

Well there is some up-side to our single season California weather. I took the bikes out this weekend in the mid to high 70s weather. It's getting chilly at night but the days have been perfect. 

[SOHC4 Cafe Racer Fan]

I spoke too soon.  California is now in Fall/Winter.  Daytime temperatures are in the mid 60s!

[Bigsam302]

I spoke too soon.  California is now in Fall/Winter.  Daytime temperatures are in the mid 60s!

Very true, but it's still decent weather to ride in.  Plus you never have to put your bikes away for the winter!