Bigroach Posted July 20, 2011 Report Share Posted July 20, 2011 Friday I started replace the cams in my '79 CB750 with some 900 cams from a CB900. Easy process except I broke eight cam cap bolts. The weekend hit, and no fastener stores were open to buy the new bolts. Monday got the new bolts and finished installing everything. Dropped one of my ignition coils and didnt notice the crack I put in it. Put everything on started it up and smoke started coming out of the ignition coil. Tuesday was spent getting a new coil that worked and charging the battery and continuously turning the engine over until it finally roared back to life at about 4pm.The cam swap itself was really easy, and I had no problems getting the broken bolts out of the aluminum engine. It was so hot in my non A/C garage though. Good thing I'm used to the heat. The biggest irk for me was having to wait two days just to buy eight high grade socket head cap screws. Quote Link to comment Share on other sites More sharing options...
Casper Posted July 20, 2011 Report Share Posted July 20, 2011 Tractor Supply is your friend when you need grade 8 fasteners. Glad you got it all back together and running though. Quote Link to comment Share on other sites More sharing options...
Bigroach Posted July 20, 2011 Author Report Share Posted July 20, 2011 I got some 12.9s, the stock were 10s. The 8s are way to soft for this old bike, even with 10s you can only torque it to the bottom range of the torque spec. Quote Link to comment Share on other sites More sharing options...
Casper Posted July 20, 2011 Report Share Posted July 20, 2011 I'd still check TSC. If it'll hold on a tractor, it'll surely hold on a motorcycle. Quote Link to comment Share on other sites More sharing options...
Bigroach Posted July 20, 2011 Author Report Share Posted July 20, 2011 Note to self: Don't let OP wrench on my bike. Check.Yeah, I have a mean habit of breaking bolts. That was a given when I decided to install the new cams. And was a reason why I put it off for so long. Quote Link to comment Share on other sites More sharing options...
Disclaimer Posted July 20, 2011 Report Share Posted July 20, 2011 What'd you torque the new bolts down to?FingertightFingertight + 1/4-turnSnugSnug + 1/2-turnUltratight with 1/4" ratchetor Ultratight with 3/8" ratchet? 1 Quote Link to comment Share on other sites More sharing options...
demitrix Posted July 22, 2011 Report Share Posted July 22, 2011 Itsnotgoingtofallout ft-lbs. 1 Quote Link to comment Share on other sites More sharing options...
ReconRat Posted July 22, 2011 Report Share Posted July 22, 2011 From experience, there's a lot of poor quality sources on grade 5 and up. Some of it is just junk or completely a fake ripoff. So buying from a good quality source is important.Examples: the bolts that come with Monroe shocks are crap and will snap off the first chance they get. But replace them with low cost correct grade bolts from NAPA, and they will work fine.Cheapo products made overseas *cough* often have butter soft hardware. I've replaced quite a few, and so has everyone else.Grade 8 hardware that won't meet it's spec, will often be marked grade 5 and sold. Works, but it's not what was wanted. Can be brittle or worse.Military projects switched from mil spec to commercial specs, and went the ISO9000 route where everyone is trusted to be honest and sell good stuff. A number of companies immediately dumped all of their old out of spec hardware stock on the market, because no one would check. Most got caught. They no longer do business with anyone that's ISO9000 compliant, but I'm sure they sell it somewhere, and still do business dishonestly. This was also the reason the first C-5B Galaxy almost crashed on first flight. All the poor quality sheet metal rivets unzipped and got sucked up by the engines. Entire sheet metal panels were flapping in the wind. Three of the four engines were shut down before making it back on the ground. Heads rolled all the way to congress on that one. Quote Link to comment Share on other sites More sharing options...
Bigroach Posted July 22, 2011 Author Report Share Posted July 22, 2011 No no, when I undo them. The bike is 30 years old and some of these bolts haven't been touch in all that time, in an aluminum engine that has heated and cooled numerous times during that 30 years.Broke a couple of other bolts in the carbs also. And that was even after soaking the bolts a couple of days in penetrating spray.Easy outs and time-serts are my friends. After WD-40 and duct tape. Quote Link to comment Share on other sites More sharing options...
ReconRat Posted July 22, 2011 Report Share Posted July 22, 2011 (edited) And yeah, old cb750 engines can be a bear to work on. Corrosion mostly, making it hard to dismantle. So snapping bolts on removal isn't a surprise. Impact drivers help a lot. I've even snapped hardware on purpose, it's sometimes just quicker. But snapping hardware off really should not be happening on assembly. Edited July 22, 2011 by ReconRat Quote Link to comment Share on other sites More sharing options...
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