Author Topic: Rebirth of paulages' cb735 (Read 117213 times)

paulages · « **on:** August 16, 2009, 11:34:53 AM »

When i originally built my cb550, the engine was simply cleaned up and painted, and all bearings and bushings replaced, etc.

http://forums.sohc4.net/index.php?topic=6254.msg54310#msg54310

then, i eventually built the 718cc powerplant, and found that the rest of the bike wasn't quite what the engine needed....

http://forums.sohc4.net/index.php?topic=40414.0

This spring i had a few problems with the engine (brand new OEM cam chain failure for example??), and while i was waiting for some parts, i decided to go ahead with the extra frame i had, and weld up the things missing from the old frame. all unnecessary bits were removed, and tabs for the rearset mounting plates and steering damper were added. i also added some gussets here and there, and welded up a few places on the frame that were only spot welded at the factory. i may race this someday, so i figured i'd get all of this out of the way.

a few pictures of some of the gussets:

steering damper mount:

...and you'll notice that just below this is one of the spots where the frame lugs were riveted (or spot welded? i couldn't exactly tell..). i ground these flush, and welded the joints solid.

anyway, i just need to finish fabricating the mount for the fairing and the new tank and seat. more pictures to come...

BlindJoe · « **Reply #1 on:** August 16, 2009, 11:37:02 AM »

nice looking welds

paulages · « **Reply #2 on:** August 16, 2009, 11:56:39 AM »

Quote from: KottkeHead on August 16, 2009, 11:37:02 AM

nice looking welds

thanks! i love the TIG welding. i taught myself on aluminum, so steel is a breeze.

the back sides don't look quite as nice.. they were hard to get to with the torch.

Pinhead · « **Reply #3 on:** August 16, 2009, 02:01:00 PM »

Nice! I've always wondered what a stiffened SOHC4 frame would ride like. I'm very interested to hear about your results!

Do0ki3 PWNS · « **Reply #4 on:** August 16, 2009, 05:31:26 PM »

wow great welds.

Bill/BentON Racing · « **Reply #5 on:** August 16, 2009, 05:41:09 PM »

Looks excellent ,pack welder and come on down,CB590 awaits you,what swingarm do you run,mods?Bill,718cc I'm jealous!

paulages · « **Reply #6 on:** August 16, 2009, 11:22:38 PM »

Quote from: bellcow54 on August 16, 2009, 05:41:09 PM

Looks excellent ,pack welder and come on down,CB590 awaits you,what swingarm do you run,mods?Bill,718cc I'm jealous!

ha! i don't even own it... i just borrow whatever i can. i shopmate has a nice lincoln, but before that i had a miller syncro-something-or-other 200. dynsasty i think? really spoiled with the available stuff to borrow. stock swingarm for now, though i'd love to fabricate or find something stiffer.

Retro Rocket · « **Reply #7 on:** August 17, 2009, 02:02:01 AM »

Quote

Nice! I've always wondered what a stiffened SOHC4 frame would ride like. I'm very interested to hear about your results!

I have always braced the frames om my Old Hondas, makes the whole bike a bit tighter on the road. Paul, are you going to brace between the down tubes above the swingarm pivot ?
Thats where these things flexed the most..

Mick

paulages · « **Reply #8 on:** August 17, 2009, 10:28:36 AM »

Quote from: retro rocket on August 17, 2009, 02:02:01 AM

Quote
Nice! I've always wondered what a stiffened SOHC4 frame would ride like. I'm very interested to hear about your results!

I have always braced the frames om my Old Hondas, makes the whole bike a bit tighter on the road. Paul, are you going to brace between the down tubes above the swingarm pivot ?
Thats where these things flexed the most..

Mick

yes- there and between the downtubes below the head stock. i'm stealing turboguzzi's idea and welding tabs for removable cross members or a plate to go there.

Retro Rocket · « **Reply #9 on:** August 17, 2009, 03:21:13 PM »

Nice...

Mick

Ecosse · « **Reply #10 on:** August 17, 2009, 04:34:09 PM »

ok, i'm following this one!

Quote from: retro rocket on August 17, 2009, 02:02:01 AM

I have always braced the frames om my Old Hondas, makes the whole bike a bit tighter on the road. Paul, are you going to brace between the down tubes above the swingarm pivot ?
Thats where these things flexed the most..

good to know, thanks!

bwaller · « **Reply #11 on:** August 17, 2009, 04:56:06 PM »

Hey Paul just make sure you do what's needed to the swingarm pivot, and torque it, before you install any braces in the back.

Is the engine back together?

paulages · « **Reply #12 on:** August 17, 2009, 08:44:05 PM »

Quote from: bwaller on August 17, 2009, 04:56:06 PM

Hey Paul just make sure you do what's needed to the swingarm pivot, and torque it, before you install any braces in the back.

Is the engine back together?

Yeah, I've waited to weld them until I had it rolling, but if I just do tabs that a plate or braces bolt to (probably not as stiff is solid braces, but I can always weld them solid later) it shouldn't distort.

I did get my cam back from megacycle, but have been concentrating on this stuff. Once all of the mounts for the bodywork are finished, I'll install the cam and engine. Soon...

turboguzzi · « **Reply #13 on:** August 17, 2009, 11:35:31 PM »

looks cool man.

are you fitting the rear sets to that small triangle?

let me know if you need some parts, little sohc's seem to grow on trees here in SF

yesterday a "mint" 1979 CBX parked next to me, all complete, but corroded as hell and chain dragging on the ground.

such a nice toy destroyed, guy deserves to have his %$^& cut off!

TG

paulages · « **Reply #14 on:** August 18, 2009, 12:13:06 AM »

Quote from: turboguzzi on August 17, 2009, 11:35:31 PM

looks cool man.

are you fitting the rear sets to that small triangle?

let me know if you need some parts, little sohc's seem to grow on trees here in SF

yesterday a "mint" 1979 CBX parked next to me, all complete, but corroded as hell and chain dragging on the ground.

such a nice toy destroyed, guy deserves to have his %$^& cut off!

TG

Yeah, there are some nice old hondas down there. About as many here too... the rusty CBX is a shame, but only a few blocks from my shop is a ducati 850GT sitting rusting its life away. Granted it's no 750/900SS, but it's definitely a classic. I've left many notes on that bike, begging to allow me to give it a nice dry home.

Anyway... yes, the aluminum triangles you see are for the rearsets. Once I find the right position, I'll cut the excess out and it'll look more like a "C". I finished fabricating the mounts for the half fairing tonight. Just have to figure out how to attach the aluminum seat, and the mechanical stuff will be easy. Wire harness, engine, exhaust etc are from the old bike. New steering damper, fork brace, and rearsets are on the way. One of these days I'll finish my paton lookalike rearsets, but for now I'll use tarrozzis.

BobbyR · « **Reply #15 on:** August 18, 2009, 06:18:06 AM »

Paul, nice work. I had to do some courses on crack inspection and repair. The Consultant had a degree in enginnering with a speciality in welding. Grinding welds is not only cosmetic, it makes the weld structually stronger. The edges concentrate the strsses. The most critical welded plates on railroad wheel trucks look like one piece of metal after they are fininshed grinding.

paulages · « **Reply #16 on:** August 18, 2009, 11:42:46 AM »

Quote from: BobbyR on August 18, 2009, 06:18:06 AM

Paul, nice work. I had to do some courses on crack inspection and repair. The Consultant had a degree in enginnering with a speciality in welding. Grinding welds is not only cosmetic, it makes the weld structually stronger. The edges concentrate the strsses. The most critical welded plates on railroad wheel trucks look like one piece of metal after they are fininshed grinding.

yeah, i know bobby. they could also be stronger if i built up the welds more. my thinking though about these particular gussets is that they are meant to supplement strength, not totally transfer it, not to mention the fact that the stress forces the welds will see aren't exactly train-strength. the welds are larger on the rearset mounts, but i'll still probably leave the beads as-is. advice from TG and other racers is that the bike will likely outperform me for a while anyway... if i still feel flex if and when this hits the track i'll go back into it with a better look.

yossef- i just realized that you might have been talking about the triangles where you mounted your rearsets. or did you notice the tabs behind that holding a plate of aluminum?

turboguzzi · « **Reply #17 on:** August 18, 2009, 05:00:51 PM »

yossef- i just realized that you might have been talking about the triangles where you mounted your rearsets. or did you notice the tabs behind that holding a plate of aluminum?
[/quote]

OK, now I see.....

seen some people solving it like you did.

I felt that in a crash welded ears will bend before the ally plate does, so I went with stronger mounts and weaker ally 5/16" X 1" flat bars for footpeg support.

In the two crashes I had so far, all I had to repalce were those flat bars (easy to make) and the CBR 900 levers I am using.

TG

paulages · « **Reply #18 on:** August 19, 2009, 12:12:25 AM »

tank, seat and fairing are mounted. i need to finish foaming the seat pan so my friend the upholsterer can put some vinyl on it... going out of town for a few days, but when i get back i should be able to install the cam and get the engine ready to drop in.

Ecosse · « **Reply #19 on:** August 19, 2009, 01:58:12 AM »

god that's lust worthy.

BobbyR · « **Reply #20 on:** August 19, 2009, 05:49:19 AM »

BEAUTIFUL!!!!!!!

78CB750CAFE · « **Reply #21 on:** August 19, 2009, 07:32:42 AM »

beautiful work!

hmm... gets me thinking about winter project in welding school

I will follow this one closely

paulages · « **Reply #22 on:** August 19, 2009, 08:46:42 AM »

thanks guys. i wanted to get the seat foamed and have it covered while i'm in the woods for a few days, but other things caught up to me. back at it this weekend...

mlinder · « **Reply #23 on:** August 19, 2009, 11:30:29 AM »

Quote from: paulages on August 19, 2009, 08:46:42 AM

thanks guys. i wanted to get the seat foamed and have it covered while i'm in the woods for a few days, but other things caught up to me. back at it this weekend...

In the woods...?
http://tonebendermusic.net/pictures/displayimage.php?album=3&pos=15

Kemp · « **Reply #24 on:** August 19, 2009, 01:42:56 PM »

Hi Paul,
Curious as to how you arrived at the "bracing" areas and how you determined what to use for bracing. Steering head, swingarm area are similar areas to bracing that was done on old superbike racers. Some of these handled badly after bracing and I know of one local CB550 racer that was braced and became a real handful to ride afterwards! I think you're on the right track as 70bhp and sticky tires will stress the old hoop but what constitutes a balance to build a good handling CB550?
My old AHRMA CB350 racer with 47bhp was an interesting case. The frame is your std pressed steel affair spot welded together from the factory. Most of the guys would just weld up the seams and added bronze swingarm bushings. With these small changes (plus a steering damper just in case), the bike handled really well and would slide predictably under power. Seems almost unbelieveable since you could actually defect the swing arm with your arm. I think in the case of these bikes, a little flexing of the frame worked and there wasn't one particular area that was significantly stronger or more rigid.
Very curious about frame mods as I am slowly building up a CB550 for serious cafe racer duty ( taking forever!!)

Kemp

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Author Topic: Rebirth of paulages' cb735 (Read 117213 times)

Do0ki3 PWNS