Broken Bolt on Cam Chain Tensioner

Not having good luck today with my 1983 V45 Interceptor! I have been fighting with a rattle in the motor for months now! I replaced the cam chain tensioners, still had the rattle, took the bike back apart today to check the valves, they needed some adjustment, and the front cam chain was still loose on the cam gears. SO i took the took the tensioner back out, and checked it, then re-installed it. The chain seemed tighter right away! HOWEVER, while tightening the bolts back to spec, one of the four bolts that holds the tensioner in place broke off at the head of the bolt!!! WTF!!! can i run this thing on the remaining three bolts??

PLEASE offer some suggestions, or let me rest assured that this will be ok on the three remaining bolts!!


:unsure:

 

Is the bolt in an area that you can get to and back out with the proper tools?
That would be the best option-remove and replace.

 

Since the bolt cap is off, there should virtually no tension on the bolt. See a dentist's pick or an awl can unscrew the bolt. Here are your options:

1. Drill and use an EZ out. Just be sure no shavings get into the engine. Don't use a crescent wrench to turn the EZ out - use a T-wrench like what is used with a tap and die kit.

2. You can also find reverse drill bits at Sears etc... that will bite into the bolt and help spin it out.

3. I don't remember how deep the bolt hole/threads go, but if the bolt goes into the block, when you remove the head, the bolt should be standing up and you can probably use your fingers to unthread it.

Upon re-installation, be sure to coat the threads and bolt with some sort of anti-seize.

 

MasonV45 has you covered.

Take your Q from Mason. Consider that the reason that you had the chain go loose was because the bolt was damaged when you first replaced it. Did you replace the old bolts with common steel bolts? Did you reuse a stretched bolt that could not hold the chain tensioner in place in the first place? Hardened bolts have pattern lines in the bolt heads. Three, four, six lines on the head of a bolt indicate its hardness. The greater the number of lines the harder the harder the bolt. A good manual will indicate the desired hardness of torqued bolts.

When you stretched the bolt to the point of loosing the head you released the stretch which creates the friction between the holes thread and the bolts stretched thread. What you are actually doing when you "torque" a bolt is stretching it in what is called the "elastic zone" of the steel the bolt is made of. Once you broke the bolt head off, the remainder of the bolt thread shrank back to its normal length and relieved the friction caused by stretching the bolt. Like Mason said, you should be able, by working patiently, to back the remainder of the snapped bolt back out of the threaded hole.

Sometimes its not that easy. If you did subsitute a common steel bolt for a hard bolt there is a possibility that you have permanently deformed the thread of the snapped bolt. This will make backing it out difficult. You may have to use an eazy out. Mason is correct about Sears having special "easy outs" that work like reverse drill bits. You need to have a clear straight shot at the hole to use them successfully. Traditional eazyouts require drilling a hole down the centerline of the snapped bolt. You need a clear straight shot at the broken end of the bolt to do that. I don't envy you the task you have ahead of you. Extraction of a bolt threaded portion is one of the worst jobs in the mechanics lexicon. Don't give up, pray that it will turn in the threaded hole. Consider every way you can of getting purchase on the threaded portion and making it turn in or out, dentist picks, pins, hemostats, roach clips,continuity testers, VOM wire leads, tweesers, finger nail sissors, anything that will fit. Keep teasing it if it will turn. Use liberal amounts of spray light oil to free things up. Last resort is to drill it out crooked and to over bore and tap for the next larger diameter thread. Never a nice solution.

Hardening makes the steel capable of more or greater stretching. When you use a torque wrench what you are actually doing is measuring that you do not exceed the amount of stretching that the bolt can sustain in order to allow it to resume its original length when loosened again. You can stretch the bolt a limited amount and have it return to its original length if you remain in the elastic zone when the bolt is fastened down. If you over stretch the bolt t it never returns to its original length, It goes "plastic" and stays permanently stretched out. It never goes back into the threaded hole correctly after that and you end up jamming the thread or stripping it if you are unlucky.

Next time make sure you have the proper hardened bolts for the job and use an inch/lb or SI equivalent torque wrench when making the bolts fast. Sometimes torque, or turning force, is specified as a known # of flats turned (arc) after the shoulder or head of the bolt meets the flat surface that the bolt is fastening against. Either method is valid. The # of flats method obviates the need for a torque wrench.

GOOD LUCK