Stripped exhaust bolts??

[jamezgreen]

Hello, new to the forum and new to the GZ250 world. Seem to have come across my first dilemma. Noticed the exhaust got progressively louder on my way home from work yesterday. Took a peak when I got home to find one of the bolts missing off one of the 2 exhaust tubes where they connect to the engine (sorry if I'm not using the correct technical terms!) So, bought and put in a replacement bolt and it fell out the next day. They seem to tighten up but loosen up rather quickly as soon as I start the bike and the louder exhuast hasn't gone away, even with the bolts tight, since the original inciddent Are my threads stripped? What are my options? Could I use a tap larger threads and use bigger bolts? Or maybe I just need new gaskets? Any help would be appreciated. Thanks.

[Vinci]

what are you tightening the bolts with? They have to be torqued to a specific amount using a torque wrench..I believe 10 lbs for the headers and 20 lbs for the actual muffler

[Easy Rider]

Originally Posted by jamezgreen

Are my threads stripped? What are my options? Could I use a tap larger threads and use bigger bolts? Or maybe I just need new gaskets? Any help would be appreciated. Thanks.

TIME OUT!!

Right now, you have a fairly simple problem (probably) that could turn into a BIG mess if you keep going with it yourself. At the very least, you need a new gasket where the pipe meets the engine. At the worst, the original bolt broke off half way down the hole.

At this point, my advice is to have the dealer order a gasket and take it in to them. Best case, it's in and out in 1/2 hour....or less....and costs you almost nothing. Worst case, they have to drill and tap the hole, which takes maybe an hour and still isn't real expensive.

Worst case if YOU continue.......you damage the block and it costs you BIG $$$ to fix.

[ppronti]

Originally Posted by Easy Rider

At the worst, the original bolt broke off half way down the hole.

One good way to tell whether or not your bolt is broken is to measure it’s length! I just completed a head-gasket job on my bike and I was successful in removing the exhaust pipe, at the head, in at least 2 ways… I was successful in backing out three of the 4 exhaust bolts… and (therefore… drum roll…) I was successful in breaking the forth!

Anyway, the length of the exhaust bolt is 25 mm… (nominally 1”). So, if what keeps backing out is less than 1” (measured from the underside of the head to the end of the thread), you have a broken bolt as Easy suggested above.

If the bolt is not broken, I find it odd your bolt is backing out, unless you or a previous owner reworked this hole-in-the-head (hah!) or over-torqued the bolt (thus stripping the aluminum threads) on a previous occasion. In that case… Locktite the bolts after replacing the gasket (probably a joke)? However, from what you are saying it sounds like the bolts don’t tighten enough to stop the exhaust leak (the loud noise) anyway? In that case Locktite wont work!

Did you purchase the correct replacement bolt? The bolt should be an M6-1.00 x 25 (That reads a 6mm dia thread with a 1.00 pitch, 25mm long). I ask because if you purchased an undersized (in diameter) bolt then it would/could back out. Otherwise, anything much anybody could suggest about why the bolt would back out would be speculation.

As far as what I went through with the broken bolt (and I offer the following to help you in the case that you have a broken bolt – not to complain… lol… but…)… what a pain in the @$$! I worked the problem to the extent of my competency (and tooling constraints) and hand drilled & taped the broken bolt on a bench in the basement. The steel of the bolt is harder than the aluminum head, and I could NOT keep the drill straight by hand – the deeper I went, the further the bit drifted into the adjacent aluminum – the resulting thread was a functional success, but I wasn’t thrilled with the result because of the off-center and slightly-off-of-perpendicular hole.

And, if your bolt is broken, I offer two recommendations:
1) If you are capable of doing extensive/detailed mechanical work, disassemble the engine to the extent of removing the head from the engine to drill/tap this bolt out. However, reference the service manual though… there are details/specifications you need the manual for to be aware of how to rebuild it. Otherwise, take it to a competent individual. (Please note: at least as far as my available tooling was concerned, there was no way I could work the head in-place on the bike… the frame member down-tube in front of the exhaust ports, where the horn/reflectors are mounted, made it impossible for me to get a drill in place with the head on the bike.)

2) And, unless you have one yourself, take the head to someone who has at least a drill press and a means to fixture the head to hold it in place while drilling so the drill hole will be straight. I recommend this because the top two exhaust bolts (one above each exhaust port) are blind-tapped holes… those two below the exhaust ports are thru-taps (there is a core-relief in the cast aluminum head the hole opens up into). Therefore, the bottom bolts are exposed to moisture/air and are likely to rust much more than the top two. If you have one of these two bolts broken (it was one of these bottom bolts that I broke) and there isn’t much aluminum about the hole toward the bottom side of the head (which is, of course, the direction the drill bit wanted to go). And otherwise, I doubt you would want either of the other holes messed up toward inner workings of the engine – so this the main reason you should take this someplace if you can’t do it yourself.

Hope this helps!!!

[kaput]

Try a new gasket some locktite. Couldnt hurt and should be less than 10 bucks and a half hour.

Tapping it could be a big headache.

[dhgeyer]

These header bolts breaking off seems to be a recurring headache on Suzukis. I gad a GS500E that had one seize. That's what happens: the bolt seizes in the hole. Steel bolts, especially if they are a little rough, can seize up in aluminum at high temps. If you try to take it out after it locks up, you either break the bolt or strip the threads in the head. Either way, it's a fine mess to play in.

As soon as I got the GZ, I applied high temp anti-seize compound to those bolts. And I don't tighten them very tight. I put the same stuff on the spark plug threads also. Had one of those seize on the same GS500E. The threads came out with the spark plug. The good news is, that's a fairly easy fix for a shop - not something I could do. They install a Helicoil. Big self tapping on the outside, spark plug thread size on the inside. And it's steel, so you don't have to worry about seizing again.

All this is also a good reason to pay attention to how hot the engine is getting if you have to sit in traffic with an air cooled engine. If it starts getting too hot, I'll shut mine off for a while and let it cool.