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Author Topic: CB 750, one sided swingarm, Ducati rear wheel, GSX/R forks, Motogadget  (Read 4521 times)

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Offline SOHC4 Cafe Racer Fan

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Re: CB 750, one sided swingarm, Ducati rear wheel, GSX/R forks, Motogadget
« Reply #25 on: June 23, 2020, 06:32:32 PM »
Quote from: anotherCB on June 23, 2020, 01:01:39 PM
No, I haven't, just focused on getting it running first, but I am getting there eventually. There are a few things I need to address before I can go on a longer test ride.
I know that I can push the fork tubes through to get the bike lower in the front, not sure if that would make a difference, but what else is there I could do to adjust geometry? I am not very familiar with custom bikes so need to look into that.

You could alter the trail by using a different fork offset with the triple trees.  I believe you are using a Cognitomoto triple tree with the GSXR front.  In selecting the offset, however, did you mention to Devin at Cognitomoto that you would be running a longer swingarm?  If so, he may have already taken this into consideration.  If not, Devin may let you exchange it for a different offset if needed.  You should measure your fork offset, rake and trail and see how it compares to stock geometry.
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1975 CB550K1 "Blue" Stockish Restomod (http://forums.sohc4.net/index.php?topic=135005.0)
1975 CB550F1 frame/CB650 engine hybrid "The Hot Mess" (http://forums.sohc4.net/index.php/topic,150220.0.html)
2008 Triumph Thruxton (http://forums.sohc4.net/index.php/topic,190956.0.html)
2014 MV Agusta Brutale Dragster 800
2015 Yamaha FZ-09 (http://forums.sohc4.net/index.php/topic,186861.0.html)

"There are some things nobody needs in this world, and a bright-red, hunch-back, warp-speed 900cc cafe racer is one of them — but I want one anyway, and on some days I actually believe I need one.... Being shot out of a cannon will always be better than being squeezed out of a tube. That is why God made fast motorcycles, Bubba." Hunter S. Thompson, Song of the Sausage Creature, Cycle World, March 1995.  (http://www.latexnet.org/~csmith/sausage.html and https://magazine.cycleworld.com/article/1995/3/1/song-of-the-sausage-creature)

Sold/Emeritus
1973 CB750K2 "Bionic Mongrel" (http://forums.sohc4.net/index.php?topic=132734.0) - Sold
1977 CB750K7 "Nine Lives" Restomod (http://forums.sohc4.net/index.php?topic=50490.0) - Sold
2005 RVT1000RR RC51-SP2 "El Diablo" - Sold
2016+ Triumph Thruxton 1200 R (http://forums.sohc4.net/index.php/topic,170198.0.html) - Sold

Offline anotherCB

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Re: CB 750, one sided swingarm, Ducati rear wheel, GSX/R forks, Motogadget
« Reply #26 on: June 23, 2020, 07:31:41 PM »
You could alter the trail by using a different fork offset with the triple trees.  I believe you are using a Cognitomoto triple tree with the GSXR front.  In selecting the offset, however, did you mention to Devin at Cognitomoto that you would be running a longer swingarm?  If so, he may have already taken this into consideration.  If not, Devin may let you exchange it for a different offset if needed.  You should measure your fork offset, rake and trail and see how it compares to stock geometry.
[/quote]

I bought the bike as is, with forks and swingarm installed, not running with carbs apart. I know that the PO dealt quite a bit with the guys at Cognito Moto. My plan is to get it running right first, get the carbs adjusted and then look into the geometry. That is something I don't have much experience with, so should be a fun learning exercise! Thanks for pointing it out!
« Last Edit: June 23, 2020, 07:33:24 PM by anotherCB »
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1978 CB750K, 2016 R1200 GS/LC, 1973 R75/5

Offline anotherCB

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Re: CB 750, one sided swingarm, Ducati rear wheel, GSX/R forks, Motogadget
« Reply #27 on: July 14, 2020, 07:43:36 PM »
Well, I guess I screwed up....

Bike was running really well, it just needed a carb sync and I wanted to double-check a few other things, one of those being cam chain tension. According to the Clymer cylinders 1-4 need to be at TDC + a few degress (whatever the book said). I didn't pay attention that there 2 different TDCs, one after the compression stroke and the other one after the exhaust stroke and from what I know now is that I think I had set the cam chain tensioner with the valves of Cyl 1 open. Long story short, I think the timing chain must have jumped over and I am afraid a valve hit a piston...Or what else could have happened?

I had thought about pulling the engine before this happened to strip off the ugly paint job, this makes the decision easier. Out it will go.

I will let y'all know what I find.
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1978 CB750K, 2016 R1200 GS/LC, 1973 R75/5

Offline SOHC4 Cafe Racer Fan

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Re: CB 750, one sided swingarm, Ducati rear wheel, GSX/R forks, Motogadget
« Reply #28 on: July 15, 2020, 11:06:09 AM »
That's a bummer. 
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1975 CB550K1 "Blue" Stockish Restomod (http://forums.sohc4.net/index.php?topic=135005.0)
1975 CB550F1 frame/CB650 engine hybrid "The Hot Mess" (http://forums.sohc4.net/index.php/topic,150220.0.html)
2008 Triumph Thruxton (http://forums.sohc4.net/index.php/topic,190956.0.html)
2014 MV Agusta Brutale Dragster 800
2015 Yamaha FZ-09 (http://forums.sohc4.net/index.php/topic,186861.0.html)

"There are some things nobody needs in this world, and a bright-red, hunch-back, warp-speed 900cc cafe racer is one of them — but I want one anyway, and on some days I actually believe I need one.... Being shot out of a cannon will always be better than being squeezed out of a tube. That is why God made fast motorcycles, Bubba." Hunter S. Thompson, Song of the Sausage Creature, Cycle World, March 1995.  (http://www.latexnet.org/~csmith/sausage.html and https://magazine.cycleworld.com/article/1995/3/1/song-of-the-sausage-creature)

Sold/Emeritus
1973 CB750K2 "Bionic Mongrel" (http://forums.sohc4.net/index.php?topic=132734.0) - Sold
1977 CB750K7 "Nine Lives" Restomod (http://forums.sohc4.net/index.php?topic=50490.0) - Sold
2005 RVT1000RR RC51-SP2 "El Diablo" - Sold
2016+ Triumph Thruxton 1200 R (http://forums.sohc4.net/index.php/topic,170198.0.html) - Sold

Offline anotherCB

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Re: CB 750, one sided swingarm, Ducati rear wheel, GSX/R forks, Motogadget
« Reply #29 on: July 15, 2020, 12:59:42 PM »
Quote from: SOHC4 Cafe Racer Fan on July 15, 2020, 11:06:09 AM
That's a bummer.

Indeed. Only good thing, I wanted to pull the engine anyways to strip off the horrible paint job, but hopefully I don't have to spend to many $$$ for parts.
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1978 CB750K, 2016 R1200 GS/LC, 1973 R75/5

Offline anotherCB

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Re: CB 750, one sided swingarm, Ducati rear wheel, GSX/R forks, Motogadget
« Reply #30 on: July 17, 2020, 12:21:02 PM »
Collateral damage....I'll start another thread in the SOHC4 forum titled "K8 Engine Damage - cam shaft sprocket in pieces".
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1978 CB750K, 2016 R1200 GS/LC, 1973 R75/5

Offline SOHC4 Cafe Racer Fan

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Re: CB 750, one sided swingarm, Ducati rear wheel, GSX/R forks, Motogadget
« Reply #31 on: July 17, 2020, 05:10:10 PM »
Quote from: anotherCB on July 17, 2020, 12:21:02 PM
Collateral damage....I'll start another thread in the SOHC4 forum titled "K8 Engine Damage - cam shaft sprocket in pieces".

Woof! You don't see that everyday.
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1975 CB550K1 "Blue" Stockish Restomod (http://forums.sohc4.net/index.php?topic=135005.0)
1975 CB550F1 frame/CB650 engine hybrid "The Hot Mess" (http://forums.sohc4.net/index.php/topic,150220.0.html)
2008 Triumph Thruxton (http://forums.sohc4.net/index.php/topic,190956.0.html)
2014 MV Agusta Brutale Dragster 800
2015 Yamaha FZ-09 (http://forums.sohc4.net/index.php/topic,186861.0.html)

"There are some things nobody needs in this world, and a bright-red, hunch-back, warp-speed 900cc cafe racer is one of them — but I want one anyway, and on some days I actually believe I need one.... Being shot out of a cannon will always be better than being squeezed out of a tube. That is why God made fast motorcycles, Bubba." Hunter S. Thompson, Song of the Sausage Creature, Cycle World, March 1995.  (http://www.latexnet.org/~csmith/sausage.html and https://magazine.cycleworld.com/article/1995/3/1/song-of-the-sausage-creature)

Sold/Emeritus
1973 CB750K2 "Bionic Mongrel" (http://forums.sohc4.net/index.php?topic=132734.0) - Sold
1977 CB750K7 "Nine Lives" Restomod (http://forums.sohc4.net/index.php?topic=50490.0) - Sold
2005 RVT1000RR RC51-SP2 "El Diablo" - Sold
2016+ Triumph Thruxton 1200 R (http://forums.sohc4.net/index.php/topic,170198.0.html) - Sold

Offline anotherCB

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Re: CB 750, one sided swingarm, Ducati rear wheel, GSX/R forks, Motogadget
« Reply #32 on: July 17, 2020, 06:23:13 PM »
At least now I am thinking the cam sprocket wasn't tightened down to the cam properly, doesn't make me feel that bad. Although I learned my lesson, I guess if you buy a bike "ran when parked" anything can happen!
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1978 CB750K, 2016 R1200 GS/LC, 1973 R75/5

Offline rickmoore24

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Re: CB 750, one sided swingarm, Ducati rear wheel, GSX/R forks, Motogadget
« Reply #33 on: July 17, 2020, 07:36:51 PM »
Man that sucks! You really cant trust it unless you put it together yourself, even then its sketchy. LOL Bummed for you man.  ;(
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1972 CB750 K2 (Sold)
1973 CB750 K3 (Hardtail 836cc)
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Offline PeWe

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Re: CB 750, one sided swingarm, Ducati rear wheel, GSX/R forks, Motogadget
« Reply #34 on: July 18, 2020, 11:06:09 AM »
Quote from: calj737 on April 18, 2020, 03:55:26 AM
Might want to replace that battery NEG cable and move it to a more suitable location. Grounding in that thin stamped area of the frame likely won’t get you the best results.
+3
Bad grounding in frame one reason of melted green wire to rectifier and sometimes more melted green wires in main harness. There are some posts about it.
I have also seen that many used rectifiers have melted green insulation or even connector housing where the pin sit on rectifier harness.

I have recently added extra ground wires to ensure good voltage with less drops.
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CB750 K6-76  970cc (Earlier 1005cc JMR Billet block on the shelf waiting for a comeback)
CB750 K2-75 Parts assembled to a stock K2

Updates of the CB750 K6 -1976
http://forums.sohc4.net/index.php/topic,180468.msg2092136.html#msg2092136
The billet block build thread
http://forums.sohc4.net/index.php/topic,49438.msg1863571.html#msg1863571
CB750 K2 -1975  build thread
http://forums.sohc4.net/index.php/topic,168243.msg1948381.html#msg1948381
K2 engine build thread. For a complete CB750 -75
http://forums.sohc4.net/index.php/topic,180088.msg2088008.html#msg2088008
Carb jetting, a long story Mikuni TMR32
http://forums.sohc4.net/index.php/topic,179479.msg2104967.html#msg2104967

Offline anotherCB

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Re: CB 750, one sided swingarm, Ducati rear wheel, GSX/R forks, Motogadget
« Reply #35 on: July 19, 2020, 04:17:24 PM »
For whoever is interested, I started a new thread with just the engine issues here:

http://forums.sohc4.net/index.php/topic,183590.0.html
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