Topic: retapping exhaust holes

[exdrocca]

Everything was going so well. I just had to hook up the pipes, then I could turn it over for the first time in 4 months. When all of the sudden I came to a sudden stop. Apparently, there was a lot of sand build up in the holes where the bolts go to mount the exhaust. This is for a '74 cb 750. Long story short. I over torqued the bolts cause of all the sand in there. I couldn't even srew them in enough to touch the flanges.

Now I'm stuck with about 6 f'd up holes that need to be drilled and tapped. I guess I'm just looking for some advice, or some way around retapping them. It looks like the first couple threads in the holes are destroyed. After unbolting the bolts, the first couple threads were gone too.

frustrated,
mike

[kettlesd]

No way around it. Depending on the severity of damage, you're either going to have to drill and tap to a larger thread, or fill the holes and drill to the original diam thread.

The alloy is so soft, its almost a little disconcerting how easy it is to tap.............. just be sure you don't go too large as to leave enough "meat" on the aluminum to ensure a secure bite.

[nteek754]

Hey Kett here is another option and that is the heli coil thang   cause if you just go bigger bolt well then you may have to drill out the  flanges on the pipe heli coil lets you  use the same size bolts and they are all available at the local hardware store good luck seven fifty four ever Craig in Maine

[BobbyR]

You may want to chase the threads with a tap that is the same thread as the original. This may give you a decent start thread a bit further down.You can sometimes save a thread on a bolt by running it through a dye. Easier than helicoil which you can do if the tap fails.

[kettlesd]

Heli coils do allow you to use the original size bolt of course, but the stress-loading on a helicoil repair is transfered to the head by the outer coil itself offering no real advantage to drilling a single size larger.  Around here, metric pitch helicoil inserts are pretty dear, plus you need the insert tool, while stainless bolts are dirt cheap in comparison.