Topic: Disaster!!! (updated...fixed)

[Cuts Crooked]

Well I'm on the skids now! A couple of weeks ago I was riding home from work on Kate and was running about 45 MPH on a city through-way at 0600 hours, when the back wheel locked up. It was still dark and was misting lightly and I really couldn't see what had happened. I rocked the bike back & forth a bit and it broke loose, I drove it to an intersection and look it over but still could not see what the problem was, all seemed ok so I continued my ride home, parked it, and went to bed thinking that I would look it over good when I woke up.......

When I did wake up, I had a raging case of pneumonia that landed me in the hospital. Yesterday I finally had a chance to look Kate over. NOT GOOD! The mounting brackets had broken on the aftermarket chain guard The and the chain had launched the guard forward into the cases! both upper and lower cases are cracked right through the mating surfaces, and there is a hairline crack that almost touches the output shaft seal.

I guess I'll be looking for a new/used engine. (although I'm thinking about trying JB weld on it and see if I can get by until fall?)

[jrboyce1983]

your really lucky to have walked away from that one, sorry to hear about the pneumonia. good luck with the search, ill post a link if i see a used engine online

[domer]

hate to say it, but where did said aftermarket chain guard come from? so as others know what to look for...

[Cuts Crooked]

Here's a pic of the damage.

You can barely see the crack extending into the upper case and the hairline crack nearly into the output shaft seal.

( lower left of the big bolt)

[Cuts Crooked]

hate to say it, but where did said aftermarket chain guard come from? so as others know what to look for...

Donno, it was something put on her by a PO.

[faux fiddy]

 JB weld should work if you clean everything up really well. Might get you through the season.

[Cuts Crooked]

Here's  pic of the remains of the chain guard: 

[TwoTired]

hate to say it, but where did said aftermarket chain guard come from? so as others know what to look for...

Donno, it was something put on her by a PO.

And still, I get lambasted for recommending the stock bits on the bike.   

Sorry, to hear about the pneumonia I've had it twice, now.  Not fun.

Hope you get your bike fixed up.

Cheers,

[Kong]

Looks to me like it can be welded.  Make a few phone calls.

[fire113]

...YES! it can be welded, I had a K0 engine that was welded at the same area but if You have no time for taking out the engine You can glue it, to be sure take better pictures of the broken area and post them please.

good luck...fire113

[Bakeoff]

Using an epoxy now may contaminate the metal to the point that tig welding it later might not be an option without doing some excessive grinding.  Do it right.  Do it once.

[Anti-Johnny]

Sad story. And I get a nasty chest cold about once a year. Mucinex and an antihistamine are the only thing that keep it from getting too bad. And lots of water, that Mucinex will dry you out.

[Spiider]

I swear by wild Oregano Oil.  You can get it at your local health food store.

First sign of a cold, a couple drops under the tongue for a few days and no cold ever follows.

My father recommended it after a 2 month spell of lingering cough, within an hour of taking it the first time I stopped coughing.

Sounds crazy but try it.

[Cuts Crooked]

Found a local shop that sayz they can weld cast aluminum so I think I'm going to go that route. However there are two hair line gracks that I'm not real sure about. One that gets pretty close to the out-put shaft seal.

[KingCustomCycles.com]

It can be welded on the bike, in the frame.  I have never heard the one about the epoxy needing to be ground out of the metal.  Epoxy is a surface adhesive.  I wonder about the validity of the comment because my last repair like this my welder had to remove a gob of JB weld and then tig welded without grinding, and without problems. 

[Cuts Crooked]

It can be welded on the bike, in the frame.  I have never heard the one about the epoxy needing to be ground out of the metal.  Epoxy is a surface adhesive.  I wonder about the validity of the comment because my last repair like this my welder had to remove a gob of JB weld and then tig welded without grinding, and without problems.

I donno about welding "in the frame". You must know some welders with some pretty small tools to get into that area and lay a good bead! Also....Those cracks run through the mating surfaces of the cases. I'm thinking that I'll have to take down the engine, have the cases welded and then machined. The more I think about it, the more I think I should just JB it, get through this season, and look for another motor this winter.

[MasterChief750]

believe hednut had his cases welded..... i think could be wrong. he didnt machine them but he did use some jb to level the mating surface

[daytonajoker]

There is a previous thread on this topic....I used JB Weld on my CB750 5 years ago and no leaks for over 12,000miles....use fiberglass patches between the coats of JB

[Roach]

does the crack have any movement to it? if it does then jb weld might not do a thing if you can move it. it can vibrate and no amount of jb weld will fix it. the jb weld would just crack.

[Cuts Crooked]

Roach,
No it doesn't appear to have any movement to it. My current plan is to sand all the surface area and start applying JB weld in several coats.

Daytona,
Fiberglass? What screen size? I've never known anyone to use fiberglass with JB. Do you need to saturate the stuff like you do when fiberglassing  bodywork?

[bryanj]

Are you sure that the mark by the seal is a crack and not just a casting mark?

[KingCustomCycles.com]

JB weld is epoxy resin with various fillers to strengthen the matrix.  It is more flexible than the cast alloy, although it does get more brittle with time.  It will soften briefly when the engine is started due to "post cure" heating.  It will then reharden at the new higher temperature.  Fiberglass cloth saturated with the adhesive is a good idea.  It strengthens the overall repair much like rebar and wire mesh in concrete.  What most people refer to as "fiberglassing" is very different in that a polyster resin is used with the fiberglass fibers.  A coarse weave glass will be most effective with the thick JB weld.  A heat gun will soften and thin the epoxy for good cloth saturation but be careful, the heat can cure it prematurely resulting in a weakened repair.

[gregimotis]

There is a previous thread on this topic....I used JB Weld on my CB750 5 years ago and no leaks for over 12,000miles....use fiberglass patches between the coats of JB

I have the same experience.  Wrapped my chain and did almost identical damage to the OP's pic.

Cleaned it up, scuffed up the area, did several layers of JB and now have about 17,000miles and six years.



Still, though welding is surely better if done well.

[Cuts Crooked]

Ok, It's fixed..sorta!

I went the JB weld route to at least get through this season. Cleaned it up real good, used my dremel tool with the flex shaft to get a small grinding head in there to rough up the surfaces. Then started putting layers of JB weld and fiber glass in there. Towards the end I got a bit sloppy with the final layers but I think it's sealed pretty good now. I've put a couple hundred miles on the repair and so far no drips. Word of caution for others who might follow this trail: I almost over did it!!! Came close to not having enough clearance for the chain/sprocket! (mostly because of getting radical with the final layer and some "sagging" at the bottom)

Now I gotta find a new chain guard. I've got a lead on one locally, feller has a couple of barn bikes, and gave me his phone number, but he couldn't tell me what year they are. So.......I know the 77/78 750s are longer by about two inches overall, than the earlier bikes. Anyone know if the chain guard from an earlier model will fit a 78? Or does part of that length come from a longer swing arm, making it unlikely that a guard from an earlier bike will fit?