top end rebuild>*bang*>wtf was that noise?

[mike-s]

As per the title, i've had a number of dramas with my GS(x)250e. I bought it as a bit of a burnt out old bike that needed tlc to get going properly again, i replaced a broken valve, the rings, headstuds (one original stud snapped when refitting the head meaning i had to wait for new studs to come from japan!). Anyway, final assembly took place, i had a bit of fun with the cct and got it set up correctly (grub screw out & pinchnut on), timing correct, and measured the gap fron the cams to the followers.

Anyway after a a slight bit of reluctance i manage to start it, it purrs like a kitten. So i give it some throttle and let it spool up to about 5k rpm or so. i do this a couple of times and i hear an almighty bang which franky nearly made me make a mess of my pants. I hit the kill switch immediately, then out of curiosity, fire her up again. She works, and is firing correctly with both pots (meaning that there is a reduced likelyhood of things going pear shaped within the valves / chamber) and i can feel warm air coming out of the exhausts. I don't rev her, but she seems alright apart from this large smacking noise that sounds like i've set the valve clearance to a couple of mm instead of 0.08-0.13. listening to her it very much sounds like the noise is localised to the top end and seemingly towards the exhaust side of everything.

I take the rocker cover off, no physical damage noticeable anywhere on the cam cogs, valve surface or any gobs of metal floating about anywhere. I *think* i may have some play on the cam caps (honestly i wouldnt be surprised if i missed this, i was keen to get her re-assembled) i can also notice a noticeable level of play on the followers to the cams (still seems less than 0.25mm though). Also the timing needs to be checked but is likely ok (and naturally i doubt the timing jumped a tooth or anything), given the fact that the cam chain tensioner seemed to be doing its job and the chain had near zero play.

Also after reading through the other threads in here, i couldnt discern any cam side-to-side play as others have described previously. My plan, put spring washers under the cam cap bolts and make SURE they are all torqued up correctly, the more i think about it the more there is a possibility i may have missed this rather important step in my exuberance.

My questions are though:

1) Does any of those items sound like they could account for the noises i heard? If there are any other possible sources of noise i would love to hear what they are, please note i wont be checking the headlight fluid any time soon though ;-).

2) what are the chances of permenant damage, either to any of the bearing surfaces (in particular the cam caps)

3) anything it sounds like i've missed? Doing this has been a learning experience, and theres been a few mistakes on my part, but also a few showstopping doosy events simply due to components passing away due to old age or over-use (i.e. the head stud that waves goodbye).

[82Shafty]

Start it up with the cam cover off and find the tick. Then evalute the individual system.

[chef1366]

Too much play in a rod bearing and the piston is clipping a valve??

[mike-s]

Too much play in a rod bearing and the piston is clipping a valve??

Doubt it would come on this suddenly, i've run the bike in the past (i reassembled her and started her and ran her for a good while, and THEN realised i goofed something & took the head off again) so I doubt it's the clearances on the bearings going south so quickly, but then again with the number of things that have crapped themselves one after the other on this bike, NOTHING would surprise me.

Start it up with the cam cover off and find the tick. Then evalute the individual system.

I thought of that, then i started wondering just how much oil would spurt everywhere if i did that, my garage is a bit untidy but im not that keen on adding "oily" to the list of gripes for down there. That being said, if adding a flat & spring washer (as well as redoing the clearances back to mid-spec of 0.10mm) doesn't do the trick then this is certainly going to be my next option.

Cheers for the suggestions though, this is certainly one of those times where i agree that there is no such thing as a silly answer.

Oh one last thing that may be relevant, is it a bad thing that i put a little anti-seize compound on the thread of the cam-cap bolts? i did it because the head is aluminium & the bolts themselves are high tensile steel and i figured the last thing i need is for these baby's to seize on me as its liable to do some form of damage.

[tone]

I guess that as you said it was reluctant to start at first the bang will have been unburnt fuel igniting in the exhaust, makes you jump but rarely does any harm

As for the rest is suggest a ignition timing check, setting the valves accurately & doing a compression test

cheers tone

[mike-s]

I guess that as you said it was reluctant to start at first the bang will have been unburnt fuel igniting in the exhaust, makes you jump but rarely does any harm

I've had my share of backfires, and as fun as they can be (cruising along at 50, hit the kill switch, open throttle wide for 2-3 seconds, close it & kill switch off again, *crack!*) it sounded more of a mechanical what'd-i-break noise.

As for the rest is suggest a ignition timing check, setting the valves accurately & doing a compression test

as said before, exactly what im planning to do!

cheers tone

Thanks for the input.

P.s. im reading a few interesting stories about loose cam caps on random car/bike forums, fingers crossed no helicoiling is needed here either.

[mike-s]

good & bad news
good: i figured out what was making that awful racket.
bad: what was making the racket.

Looking at things this morning in sunlight (everything else was done at night due to time constraints) and i noticed that one of the valve follower locknuts wasn't nipped as tight as i thought and the whole shebang, locknut and adjuster made their way out of their retainer and are located somewhere within the innards of the engine!!!

Next step is to drain the oil and see if there are any chunks of metal aside from the small silver filings i am expecting (brand new rings just got installed) and if im lucky, i may well see the locknut & screw come out. However at the very least im expecting to take the barrels most if not all the way off and try to extract the nut & adjuster in question. Somehow i don't think that they'll be reusable, so it might be in my interests to call the bikeshop now and order in a new pair of them... at the very least.

That is if i am really really really lucky. If im moderately unfortunate i may be up for a new crank (if the primary timing cog has been chewn out), but i can get them a nearby wrecker pretty cheaply. I don't know how tightly the bottom end of the chain is retained / if it has gaps for bits to come out into the rest of the bottom end. If its pretty close down there then that will work for my advantage and any/all damage will be localised, if not, well, this project may just get a whole lot more freaking expensive.

Also goes to show that every single time you check or re-assemble anything there is absolutely no substitute for thoroughness.

I just came off nightshift, im going to go have something to eat, and cry myself to sleep.

[chef1366]

Don't cry too hard. It's probably in the sump.

[mike-s]

Well im not that worried, moreso nervous about it than anything else (hey the bikes thrown me more curveballs than i care for already, whats one more?). Thinking about it as the slapping metallic sound was running as regularly as the engine and pretty much varied with the revs, add to that the fact there were no metallic horrible crunching noises aside from when the screw & nut were first slung off the rocker cover

. I think the god awful noise i heard while the engine was running was the cam follower slapping the top of the valve, which would account for my saying "it sounds like the clearance is 2mm" as it is close to a centimeter in its current state.

I've erred on the side of caution and have already ordered in a new adjusting nut & screw from my local bike shop, he thinks it should be in tomorrow . Which works fine for me as that is the earliest i can see me being able to touch the bike anyway.

Will follow up with updates (and pics if there is any gory damage that the morbid in here may find interesting). Cheers again.

[mike-s]

ok, you know how they say "the right tool for the right job?" well tonights effort of extracting bits of ferrous metal from within my engines crankcase proved that along with "using the right technique" right.

Much dicking about previously occurred in an effort to get the blasted bit of metal out before i got it out tonight courtesy of a high power neyodium magnet that is on a telescopic rod that i picked up from the local auto store.

Fishing around wildly didnt do it, but as soon as i 9/10ths installed the front chain guide i remembered that there is a flippy bit of metal under the crankshaft that the guide flicks up into position (keeping the chain very close to the crankshaft & unable to skip off/skip the timing.). So chain guide went in with only about 7-8mm left to push into place, i then used the telescopic magnet and fished about and got it into the tiny recess hidden underneath the flippy guide and IMMEDIATELY i picked up this sad little fellow. I tried a few times to have a go at getting the nut, but that is hopefully sitting in oil at the bottom of the engine now and i shant go after it as the adjuster seems relatively ok, the master timing gear seems unscathed and there was little to no ferrous materials sitting in the sump.

Next up, refit a new sump washer and then refit the carbs, re-compression test her and give her another bash.

In the meantime before i had gotten the magnet on a telescopic rod i had stripped her down to barrel-off naked before so had to deal with that little bit of fun (yet again). I'm hoping once and for all that this is the end of this headache from this bike and i can just go out and RIDE her.

[tkent02]

ok, you know how they say "the right tool for the right job?" well tonights effort of extracting bits of ferrous metal from within my engines crankcase proved that along with "using the right technique" right.

Much dicking about previously occurred in an effort to get the blasted bit of metal out before i got it out tonight courtesy of a high power neyodium magnet that is on a telescopic rod that i picked up from the local auto store.

Fishing around wildly didnt do it, but as soon as i 9/10ths installed the front chain guide i remembered that there is a flippy bit of metal under the crankshaft that the guide flicks up into position (keeping the chain very close to the crankshaft & unable to skip off/skip the timing.). So chain guide went in with only about 7-8mm left to push into place, i then used the telescopic magnet and fished about and got it into the tiny recess hidden underneath the flippy guide and IMMEDIATELY i picked up this sad little fellow. I tried a few times to have a go at getting the nut, but that is hopefully sitting in oil at the bottom of the engine now and i shant go after it as the adjuster seems relatively ok, the master timing gear seems unscathed and there was little to no ferrous materials sitting in the sump.

Next up, refit a new sump washer and then refit the carbs, re-compression test her and give her another bash.

In the meantime before i had gotten the magnet on a telescopic rod i had stripped her down to barrel-off naked before so had to deal with that little bit of fun (yet again). I'm hoping once and for all that this is the end of this headache from this bike and i can just go out and RIDE her.

Magnetic drain plug catch the nut?

Maybe poke the magnet up through the oil drain and swivel it around until it catches it?

[Stefnwolf]

Magnetic drain plug catch the nut?

Maybe poke the magnet up through the oil drain and swivel it around until it catches it?

Just a wild thought, and others more knowlegable than I may advise against it.
With the drain plug removed, and a bowl underneath, pour a load of diesel in through the top. Repeat a few times, and it may flush the nut out, or nearer the drain so a magnet will hook it.

[mike-s]

it wont work, theres a metal mesh between the top of the crankcase and the region containing the sump plug, so it'll never get through unless it defies the laws of physics.

oh and ive already stuck the magnet up there and swirled it around to see what i'd get, just a couple of fragments of metal under 1mm in diameter, just like elsewhere when i tried that (aside from the adjuster i pulled out that is).

edit: clarification, there are two major areas seperated by a mesh capture screen, and theres a smaller area enclosing the bottom end of the cam chain that was the headache to get to.

[mike-s]

Brief update,
I got her running yesterday and today i took her the 20km (14 miles) to work and she seems alright. I certainly forgot how much harder you have to work the gearbox to get things going when your riding a 250 compared to my 900 (god i love the torque in my 900!) where above second gear your just choosing a gear to select how much noise you want to make (at any legal speed that is).

I'll have to go take her home shortly on another test ride as i forgot to get my RSA security token and can't do any work without it.

[mike-s]

Well it seems that mechanical issue is all sorted out now as the more i ran her, she seemed to get a bit better. Blowing out the cobwebs so to speak. Now there's no smoke blowing from the exhaust and theres a waft of smoke billowing out from underneath her (that'll be my leaving oil everywhere when reassembling her).

Next up is a problem im not going to bother this board with, which is the battery seems to not be able to turn the bike over. I'm guessing that from how quickly the battery went flat the alternator or rectifier isn't doing its thing, but at least i was able to get the bike home.

Let the electrical troubleshooting begin!