Topic: Dead CB750 Mystery Solved

[BobbyR]

I went down in my driveway on some wet leaves. It happened so fast I was on the ground before I knew it. The bike came out fine, the case guards did their job and my body pinned between the bike and the blacktop did the rest. The bike stalled and gas was pouring out of everywhere.
I decide to let it sit and dry out while I ran my errands on four wheels. The bike would not start the next day. I determined I had no spark.
Terry and some others gave me advice and I got out my trusty multimeter and in fits and starts began checking stuff. Long story short I had voltage everywhere I should.
I have a Dyna so I figured something came loose in there since I had 12V at the coils and the kill switch turned that on and off.
While pulling the points cover I noticed the wire coming out looked odd. Well the case cut through the wire. I routed the Dyna wire which is thicker as the old one. I soldered the wires back together and she fired right up. I am going to see if I can find a replacement cable since it bothers me to have a splice. 

[Johnie]

Glad to hear all survived Bobby.  What case guards do you use?  I have not put any on my KO as I wanted it all stock.  But listening to your story I would sure hate to mess up my covers.

[BobbyR]

John, they are just stock I think. They just cover the side cases. So far in a couple of tip overs, the cases had no damage. I don;t have pic on me, but they look proper for the bike.

[BobbyR]

THis is not my bike but these are what they look like.

[MCRider]

John, they are just stock I think. They just cover the side cases. So far in a couple of tip overs, the cases had no damage. I don;t have pic on me, but they look proper for the bike.

Case guards were not stock, all offered aftermarket. There are always some on eBay. Here's some 3 pointers  

http://cgi.ebay.com/ebaymotors/_Motorcycle-Parts-Accessories__1970-71-Honda-CB750-Engine-Guards-Crash-Bars_W0QQitemZ220354057146QQadiZ2863QQadnZMotorcycleQ20PartsQ20Q26Q20AccessoriesQQcmdZViewItemQQptZMotorcycles_Parts_Accessories?hash=item220354057146&_trksid=p4506.c0.m245&_trkparms=72%3A543%7C65%3A12%7C39%3A1%7C240%3A1318  

which are not available new. I bought some on eBay a few months ago, paid a lot more than $35 for them. There was a bidding war for a while on 3 pointers. The 2 points work fine, but do bend on contact, still preserving the cases...usually.

The 2 pointers are available new from Whitney, Dennis Kirk etc. Always worked for me, many times. I have poked holes in a few dyno covers without them.

[Terry in Australia]

Here's what you need John, they even come with forward pegs!

http://cgi.ebay.com/ebaymotors/_Motorcycle-Parts-Accessories__Honda-CB750-CB-750-Chrome-Crash-Bar_W0QQitemZ140298070020QQadiZ2863QQadnZMotorcycleQ20PartsQ20Q26Q20AccessoriesQQcmdZViewItemQQptZMotorcycles_Parts_Accessories?hash=item140298070020&_trksid=p4506.c0.m245&_trkparms=72%3A543|65%3A12|39%3A1|240%3A1318

 

On a more serious note, I looked for some engine bars like Bobby's, but these were all I could find.

http://cgi.ebay.com/ebaymotors/_Motorcycle-Parts-Accessories__1970-71-Honda-CB750-Engine-Guards-Crash-Bars_W0QQitemZ220354057146QQadiZ2863QQadnZMotorcycleQ20PartsQ20Q26Q20AccessoriesQQcmdZViewItemQQptZMotorcycles_Parts_Accessories?hash=item220354057146&_trksid=p4506.c0.m245&_trkparms=72%3A543|65%3A12|39%3A1|240%3A1318

Cheers, Terry.

[MCRider]

Duh, hello Terry: I beat you to it in the post before yours.   

BTW: I'll be workin on mine in the AM. We dug out from our 6th worst snowstorm in history this week.

[Johnie]

Thanks guys...I like those 3 pointers.  Sort of small and not so visual to detract from the rest of the bike.

[MCRider]

Thanks guys...I like those 3 pointers.  Sort of small and not so visual to detract from the rest of the bike.

The hardware tends to get separated from those used items. You'll have to spend some time at the hardware store. Most will be easy.

THe front long lower motor mount is compromised. THe right side guard is threaded and the long bolt threads into it without a nut. Not much thread to grab without stripping it.

I drilled out the threaded part and used some threaded rod with nuts on both ends to get a good torque on it.

I'm looking to buy a proper bolt for my current project.

Don't let this scare you though. Anything is better than being stranded with a damaged dyno cover or a damaged ignition.  THose 3 pointers are indestructable.

[Terry in Australia]

Duh, hello Terry: I beat you to it in the post before yours.   

BTW: I'll be workin on mine in the AM. We dug out from our 6th worst snowstorm in history this week.

Ha ha, oh well, John shouldn't mind that we're both trying to help him, I guess?

I actually like that big bugger, I've had, or seen, both 2 and 3 point engine case guards fold back into the cases in a big "off", so I like the idea of the big police style crash bars on a touring bike, but (and it's a very big "but") BMW recommended against installing big asssed crash bars on their bikes because in a crash, the crash bars (usually mounted to the frame downtubes via "U" bolt clamps) could actually twist the bike's frame out of shape.

I guess it's kind of a difficult choice when in a big crash either bars can actually exacerbate the damage, but in a light fall over like Bobby's, either bar would be good to protect against a punctured alternator cover, or worse, a smashed ignition and broken engine cases. Cheers, Terry.

[Johnie]

Excellent...great points to ponder fellas.  I really should do something.  I rode a year with no dumps, but scares the heck out of me to think "what if".  It would kill me to smack those cases after all the time I put into them.  I have not bid on those 3 pointers because the road rash on them has me thinking they are bent.  No good if the bolts will not line up.

[BobbyR]

Duh, hello Terry: I beat you to it in the post before yours.   

BTW: I'll be workin on mine in the AM. We dug out from our 6th worst snowstorm in history this week.

Ha ha, oh well, John shouldn't mind that we're both trying to help him, I guess?

I actually like that big bugger, I've had, or seen, both 2 and 3 point engine case guards fold back into the cases in a big "off", so I like the idea of the big police style crash bars on a touring bike, but (and it's a very big "but") BMW recommended against installing big asssed crash bars on their bikes because in a crash, the crash bars (usually mounted to the frame downtubes via "U" bolt clamps) could actually twist the bike's frame out of shape.

I guess it's kind of a difficult choice when in a big crash either bars can actually exacerbate the damage, but in a light fall over like Bobby's, either bar would be good to protect against a punctured alternator cover, or worse, a smashed ignition and broken engine cases. Cheers, Terry.

Yes in a mild tip over anything should protect the cases. I also had a supplemental system on this spill. It was my right leg, very effective in protecting everything aft of the bars.   

[Terry in Australia]

I know what you mean Bobby, many years ago I took off from work on my Yamaha 250 dirt bike, I'd been drinking a couple of beers and forgot about knobby tires vs wet tarmac, anyway, I managed to throw the bike down on it's left side, still inside the compound.

We'd had a parade that day, so I was only wearing my light polyester summer uniform, and the steel peg went thru my left shoe, pinning me under the bike, which, being a two stroke, was happily idling at about 10,000 RPM, with fuel gushing out of the filler cap, all over the engine, and me!

Luckily Fred, my staff sergeant, ran out and physically picked the bike off my poor broken body and threw it about 20 feet! It didn't catch fire, and after cleaning myself up, (and changing into my jungle greens and boots) I bought Fred some beer, and rode home.......... 

[MCRider]

Excellent...great points to ponder fellas.  I really should do something.  I rode a year with no dumps, but scares the heck out of me to think "what if".  It would kill me to smack those cases after all the time I put into them.  I have not bid on those 3 pointers because the road rash on them has me thinking they are bent.  No good if the bolts will not line up.

The ones I bought off eBay were physically much worse shape, but I'd been looking for a year and running out of patience. The mounting holes are mostly cut in slots so lining up even bent ones were easy. I bolted mine up and used a hockey stick to straighten them. Of course the engine is out of the frame so i had a lot of angles to come from.

A little give is preferred otherwise all the shock is transferred to the frame.

One other piece of hardware is the "u"bolt used on the left side to clamp the center point to the frame. Common hardware.

I've had a tab welded to my frame and the guard to do away with the U bolt.