gsxr renegade Posted April 11, 2012 Report Share Posted April 11, 2012 Last night I decided to take the engine apart on my little 250 to further investigate why it was making a ticking/rattling noise – mainly to see if it was anything obvious. I took the head off the engine and had a look at the pistons, and there seems to be quite a lot of carbon build up on the pistons. Left Right Firstly, is this a normal-ish level of build up to be on the pistons, or would it indicate that something isn’t quite right? I’ve never had an engine apart to this level before so don’t know what’s normal and what isn’t. The bike is 32 years old and done 17000 miles (although I do suspect this is the second time it’s hit that figure....) Secondly – Is there any way to safely remove some of the deposits, as I imagine the pistons being a little cleaner can only improve things. I was thinking about using either a bit of carb cleaner and a rough sponge, or a dab of metal polish left on for a few hours then coaxed off with the aforementioned sponge? Nothing seemed loose, I couldn’t move the pistons from side to side in the cylinders, and they moved up and down smoothly in the bores with no knocking noises– so I’m guessing this rules out piston slap? I’m hoping the noise was just an incorrectly adjusted cam chain as it seemed a little loose when I was prying about before taking the head off, but I’ll find out once the engine is back together. Link to comment Share on other sites More sharing options...
peter30 Posted April 11, 2012 Report Share Posted April 11, 2012 Brake fluid is excellent for decoking engines. Link to comment Share on other sites More sharing options...
lorenzo Posted April 11, 2012 Report Share Posted April 11, 2012 For 17000 miles they look a bit sooty, for 117000 they look great! Link to comment Share on other sites More sharing options...
Alex_H Posted April 11, 2012 Report Share Posted April 11, 2012 Put neat redex on the pistons and leave overnight, that'll soften it for you. But carbon build up = more compression lol Link to comment Share on other sites More sharing options...
kaighn80 Posted April 11, 2012 Report Share Posted April 11, 2012 think i've spotted the problem theres a spanner in there. Link to comment Share on other sites More sharing options...
gsxr renegade Posted April 12, 2012 Author Report Share Posted April 12, 2012 Brake fluid is excellent for decoking engines. Winnar!! Scrubbed them wih a bit of brake fluid last night and they came up a treat, hardly any coke left on them - stuck the engine back together and i did notice it was a bit easier to start and ran a tiny bit smoother, but weather that was just in my head, i don't know. The rattling noise is still there, except now it's happening on the right hand side of the engine, instead of the left. AARRRRGGGHHHH!! At least I know now that it’s definitely the valve clearances making the noise, so I’ll just have to keep adjusting them tonight. It did dawn on me on the way to work – I’ve been adjusting them back to the gap stated in the handbook, but if the bike really has done 117000 miles (which I think it has) then they’d probably need adjusting further than the gap stated. Oh well, I’ll have a play around tonight and see if I can make the nasty noise go away. Thanks for the help peeps! p.s. I removed the spanner before putting the engine back together. Link to comment Share on other sites More sharing options...
gsxr renegade Posted April 12, 2012 Author Report Share Posted April 12, 2012 How are the valves and valve seats? are they clean enough? Sometimes you get a strange noise when carbs arn't properly balanced, could see if that helps They seemed ok, they all seated properly and weren't loose - although i don't really know what i was looking for, but they seemed ok. All the valve springs were intact as well. The faces of the valves were a little sooty, like the pistons were, but i didn't want to scrub them really for fear of damaging them. I don't think it's the carbs, the noise is definitely coming from the rocker cover/cylinder area, and the carbs are set a little way back from the engine. Link to comment Share on other sites More sharing options...
Kaos Theory Posted April 12, 2012 Report Share Posted April 12, 2012 The rattling noise is still there, except now it's happening on the right hand side of the engine, instead of the left. AARRRRGGGHHHH!! Thats cause you installed the engine back to front, easy mistake to make. Link to comment Share on other sites More sharing options...
Liamo Posted April 12, 2012 Report Share Posted April 12, 2012 I don't think it's the carbs, the noise is definitely coming from the rocker cover/cylinder area, and the carbs are set a little way back from the engine. The noise wont be coming from the carbs, but out of balance carbs can cause the engine to run lumpy and sound a bit funny. Link to comment Share on other sites More sharing options...
lorenzo Posted April 12, 2012 Report Share Posted April 12, 2012 Out of balance carbs will cause the engine to be really much noisier than you thought a set of out of balance carbs would make it, if you know what I mean. What I'm saying is that you'd be surprised what the effects are. I guess it's from one cylinder getting a bit of a bigger bang than the other, which makes it run a bit rough, which then causes clonking noises. As the revs pick up this roughness tends to become less pronounced. The other thing with them is that they can cause the engine to be a little hesitant to pull away, but on a 117k mile 250 I suspect hesitancy is going to be masked somewhat by the lack of power! With regards valves, why would a high milage engine cause your valve clearances to need to be set up any differently to a low milage one? All you're doing is taking into account the amount of wear on the valves and the seat, and adjusting that wear out. In fact, if there's one thing that you can get back to new in terms of tolerances on a worn engine, it should be valve clearances! Link to comment Share on other sites More sharing options...
gsxr renegade Posted April 12, 2012 Author Report Share Posted April 12, 2012 Yep, your right re; clearances. Ignore me, I was having a brain fart!! I’ll double check it again tonight. In my haste to get the engine back together again, it’s very possible that I’ve not set them properly. I’ll try and get a recording of the noise as well so you can see what I mean. Link to comment Share on other sites More sharing options...
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