Big problem this time - bike sounds like a sewing machine and no power

**xwhatsit** · 20th October 2006, 21:21

Ah here we go. Now, not being able to kickstart my bike due to rooting plugs every 2 days I can handle. Replacing a rear tyre I can handle. Borrowing wing mirrors I can handle. Aralditing the dash unit 3 times I can handle. I can even handle crashing with no gloves.

But I've never been more sad and upset today on my way to my exam. Coming along the top of Symonds St, just where you leave Khyber Pass, I was tootling along then suddenly... what's that very loud clacking noise? Why does the bike have no power? Why has the engine stopped? I pull to the side of the road onto the footpath, try to turn it over... no cigar (expected due to problems starting it hot anyway) so I bump start it. Get a good head of steam up and jump side saddle like normal, drop the clutch in 1st gear (2nd gear runs engine too slow). Wtf?! It just keeps rolling, but it's making that horrible clicking noise again. Is it in gear? Yep. I roll it back like I normally do, until it hits compression... what compression? It just keeps turning over. Shit.

So I turn off the ignition, put it in neutral, and roll down the hill side saddle scooting along with my foot along the footpath. Get to exam, which I think I failed (can you get an aegrotat for bike-related stress? lol). Was thinking about calling AA but thought I'll try and start it one more time. Pull plug out - thread looks fine, plug looks ok (not smashed in -- I had images of a piston hitting the sparkplug or something lol). There's good spark when I kick it over. Put it in, get the bike started off the kick! But it still clacks away like a mofo. I thought... fuck it... I'll ride it home... I was so angry I didnt' care if I did any more damage. Well, it got me home, even on the motorway, but making an awful noise (it sounds louder in my helmet than the engine many times), and it might be my imagination due to preoccupation with engine but it felt like it had shit-all power.

Now, when I got home, it occured to me the decompression lever might be doing funny thigns. But it appears to be working like normal -- when I pull down the kickstart, the decompression lever rolls back about 10 degrees then forward about 45 degrees+ as you move the kickstart through. So, I don't know about the insides of this thing, but could the decompression mechanism be broken inside? Have I done something worse, like fucked the exhaust valve?

Now, here's a disclaimer. My father (who was a marine engineer and used to do offroad racing) happened to be in the country this morning, and helped me clean the carburettor. [It was pretty clean, actually]. Now, put back together, mixture adjusted, the engine felt really nice. Felt way more powerful than before. Revved easier, didn't die when you pull the throttle quickly from idle (the automatic fuel pump thing connected to the throttle was sticky before). Everything was all packaged up nicely -- but after he caught plane home and I went to uni, it died about 45 minutes after being put back together. Could fooling around with the carburettor cause (what seems like) compression issues?

Man I'm stressed. It's funny how quick I've become attached to this bike and it's kind of breaking my heart when I listen to it and rode it home like that. I hope it's nothing major -- she's done 50,000km+.

Does anybody have any advice?

**JMemonic** · 21st October 2006, 04:32

I suspect unless you dropped chunk of something that does not belong in a motor then your maintance work is unlikely to be the cause of the problem, so dont go kicking youself over that one.

Sounds like either a trip to the mechanics or time to learn how to rebuild an engine, if you have any internal damage its pretty hard to tell how much and how bad it is from the outside with out getting the motor apart.

Best of luck with it.

**TonyB** · 21st October 2006, 05:31

Its not something simple like the chain slipping is it?

If it turns out that the engine needs a rebuild, send me a PM. I can do piston kits, conrods, big and small end bearings and crank pins. All seriously cheap.

**bungbung** · 21st October 2006, 07:57

Honda ohv + clack clack clack = broken valve stem (in my case) but as yours still ran, how about super wide valve clearance?

**MSTRS:Me** · 21st October 2006, 08:54

Is it possible that the camchain has jumped one tooth?

**TLDV8** · 21st October 2006, 09:59

I think you need to remove the valve cover and check the various components.
If you need a hand,send me a PM.I am local.

Having access to a workshop manual would be a bonus so cam timing,decompressor action,ignition/coils etc etc could be checked.

**cowpoos** · 21st October 2006, 11:34

buy a new bike......

**xwhatsit** · 21st October 2006, 21:19

OK here's the story.

Thinking it sounded and felt like it would be if the decompression lever was stuck open, I checked that out and it looked fine. The spark plug was taken out and I put my finger over the spark plug socket and turned the engine over and there seemed to be piss-all compression. The tappet covers were pulled off, inlet and exhaust, and I had a look around. Couldn't see much, so I turned the engine over until it hid TDC and had a look again. Hang on a minute -- there's 4 valves, 2 for intake, 2 for exhaust -- and each of those pairs should line up, right? Well at TDC the exhaust valves don't line up. One valve is closed, the other is still open. WTF?

So off comes the top of the engine. Can't see too much, camchain/cam seems fine. It was decided that the head would have to come off. Hehehe. So, the cam/camchain assembly has to come out -- and the chain tensioner, right? Holy mofo, that chain tensioner I have no idea how that a) works and b) comes out. Pulled out a bolt and it seemed to be free but still seemed to be attached. So that has to stay put lol. Had a hell of a time taking the cam sprocket and chain and camshaft out -- does anybody know how to do this properly? It was bloody impossible and to get it out was a fluke. Anyhow it came off eventually, and so did the cylinder head. Man there was a lot of black shit on the cylinder and head -- should it be like that? Maybe that relates to the spark-plug-rooting-problem? At any rate, look at the cylinder head (it's very pretty haha with the four valves all lined up) and work out why the left exhaust valve is stuck open. The valve seat/ring/thing has popped out and is preventing the exhaust valve from returning. Ok. So I just have to replace it, right?

After a moment's reflection, the question pops up: why did it come out? Shouldn't these things stay put? I put it back in, and use a ball hammer to gently pin-tap the aluminium around it over it so it can't come out again (it's there for good now lol). In the sunlight doing this, something makes my heart drop all of a sudden. There is a crack running through between the spark plug socket and the exhaust valves. It's long too, you can see it from the top of the cylinder head and out the bottom too.

Shit.

Cracked cylinder head.

So that's it, I think. New cylinder head. How much are they? I'm thinking at least a couple of notes, maybe five. I don't have $500. But then, after thinking for a while, I wonder. That crack didn't just appear yesterday. It must have been there for a while, right? And it was only yesterday when it finally caused the valve seat to come loose. That's nice and stuck in tight now. So, I think, well, lets put it back together... and sell it! Muhahahaah!. But then that's too evil, so I think OK I'll just ride the fscking thing until it breaks again. Cylinder head cracking won't be too fatal. There's nothing to come loose and root the piston or anything. So the whole engine goes back together again, tank back on, seat back on, wires all plugged back. It's waaaay harder putting an engine back together than taking one apart hahah! And that camshaft/gear... WTF?! How the hell do you do that? Can't wait til I have a Haynes manual and they tell me the proper way. Make sure all the camgear is in phase with the piston and all of that. Everything goes back together, noticing on the way that quite a few of the cylinder head bolts have odd threads and don't look standard. One or two of the threads on the head are threaded too, so a new cylinder head is useful for that too.

Kick it over. Nothing. Kick it over again, keep kicking, wtf?! Why won't this start. I can smell fuel. This sucks. I've fscked the engine for good. Oh wait... spark plug lead

. I laughed for a while about that ^_^. Now it starts, really easily! Yay! Sounds right too. Leave it to idle for a while to make sure nothing will come loose and blow up the garage in a Hollywood-style explosion. No it's all cool.

I take it for a ride. Everything works OK. The only issue with it that worries me is that it feels slightly less power and a bit stiff, not as free as it was before. I wonder if this is psychological or not? There's plenty of oil in it.

I rode it to work, a ~30km round trip, with motorway bits, and it didn't fly to pieces. It stalled quite a few times, while idling at the lights and when I went to pull away. I think it's being starved of fuel. I wonder if after putting it back together I need to adjust the mixture again? I also noticed that the automatic fuel pump thing on the carb which connects to the throttle is sticky once again. This is probably why it dies when I turn the throttle after idling for a while. Will have to look into that later, I can live with it for now.

So yeah. My first engine. Interesting, I can't believe how much stuff is inside it lol! It's beautiful though, in a strange way. I'm a musician, and I can't help but use the tired old orchestra analogy. Everything is in harmony. At least until some buffoon drops their cello and tries to play it out of tune. Then it all comes to pieces.

Of course I'm now looking for a cylinder head for it. Any idea where/if I can get one? How much will it cost me? The bike runs... but for how long. So I'l need a new head eventually. I feel sad in a way that I'm running her knowingly broken, but in another way there was a huge sense of joy when it fired up after being in a million bits in my garage. I took some photos... might include them in a later post when I can arsed to get them off the camera.

Buying this bike is the best thing I ever did. I'm sort of taking a crash course in engineering and coordination by trying to ride the thing around. I love bikes.

Cheers for all your help,

-Tom

**Ixion** · 21st October 2006, 21:32

Profane oath. That is one tough little bitch of a motor to run at all in that state. Honda sure build em tough

props for getting it all back together well enough to run at any rate.

the cracked head will bite you sooner or later, prolly sooner so you need to source a second hand (uncraked) head. These models did have a head cracking problem if I recall correctly.

**xwhatsit** · 21st October 2006, 21:37

Hahaha. It starts easier than it did before ^_^. I'm thinking that the reason it was impossible to start when hot was due to the crack (metal expanding and less compression than normal).

Yeah I want a cylinder head ASAP. I'm too fond of the bike to want to hurt it again. I know a wreckers online (they're in Wellington or summat) that's got a CB250RS but I don't think they'd let me buy just the head, would they? They'd want to sell the whole engine.

I haven't heard much about them cracking heads. Have heard nasty things about the balancer shafts and the like but the last thing I was expecting was a cracked head.

**Ixion** · 21st October 2006, 21:44

Wreckers will, often sell a head separate.

Someone has most of an XL250 including engine on Trademe , closes tomorrow. current at $151, met reserve

http://www.trademe.co.nz/Trade-Me-Mo...n-74044587.htm

**xwhatsit** · 21st October 2006, 21:50

Arse! Quick, does anybody know if it's the same engine as the XL250S? I know for sure the XL250S is the same engine as CB250RS, but is the XL250 the same? That would be wicked...

Cheers

**xwhatsit** · 21st October 2006, 21:53

Oooh he has a photo... shit the engine looks close! Holding the laptop next to my bike, it looks identical... should I go for it? Can anybody confirm that's the same engine? It's old though maybe the engine's shagged on it too lol. Man I'd love to get it though, loads of spares... and then I'd be a real biker! Two bikes! One fscked one!