Topic: 400f cam chain tensioner bolt problem

[andrsn]

My bike rattles, a lot. I went to adjust the cam chain and discovered that the previous owner sheered the bolt head clean off. When you look at it, the bolt is flush with the engine case (possible slightly recessed). There is no way to grab the bolt, I tried an extractor, but that resulted in a piece of extractor bit stuck in the hole I drilled in the 6mm bolt. I was thinking of just drilling the hole larger and tapping it to a bigger thread. My question is where are all of the metal flakes going to end up? If they fall in there, will they pass through the filter and not be an issue or will they get me into trouble? Anyone have any good ideas? I really don't want to take the engine off and tear it apart.

[schwebel]

 This happened to me as well. I found a fix using an old set of feeler guages. Take off the valve cover. Look for the dampener holder at the rear of the engine, it is a black piece secured by two bolts behind the camchain. Take out the dampener holder and dampener. The dampener will be stuck inside the holder, pull it out. Cut some squares of feeler guages so that they fit inside the holder and place them inside. This causes the dampener to stick out of the holder a bit. This will push on the slipper more, causing the chain to tighten up. I did this about a year ago and so far it has worked great.

 It took me about 3 tries to find the right amount of gauges. Start will a couple thin ones. It only take 10-15 minutes to take off the cover and do this and put it back together, beats the hell out of an engine teardown. The downside is that every once in a while you will have to repeat the process to get rid of the noise. Next time I do it I will post pics so it is easier to understand.

[Bodi]

You won't be able to drill again with the broken hardened extractor in there. I've tried, and the drill just walks around making a big mess but not cutting the extractor which is harder metal than almost any drill you can get.
I've heard of chemical ways to dissolve a steel bolt in aluminum but never tried.
I have had broken studs and such removed by EDM, electrical discharge machining. This is done rather often to remove exhaust studs that have broken off in engines. I doubt if it can be done on an assembled engine  but haven't ever asked about it. The part has to be in a fluid, but possibly a dam of some sort could be formed around the hole with putty or something.

[bryanj]

Only way to do the job properly is engine out and stripped down, any other way is a big risk of expensive failure