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Post by apothecary on Oct 27, 2011 22:55:38 GMT -6
All right, it's definitely a bent exhaust valve. Took a few shots after I managed to get the valve out. Here's how everything looks currently (actually in the process of cleaning the underside of the head so it's a wee bit better than the pics now): Here's the valve next to my camera case. DEFINITELY bent.  Here are a couple of the underside of the head:   |
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Post by apothecary on Oct 20, 2011 20:05:08 GMT -6
  You can see the exhaust valve is just slightly bent but obviously enough to give a 0 compression the entire combustion cycle. I'll take a few shots of the piston and cylinder tomorrow morning you guys can tell me what you think. |
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Post by apothecary on Oct 20, 2011 18:38:31 GMT -6
Well head is off. Looks like the piston is fine. Don't even see a mark where the piston actually contacted (Could the cam have possibly caused the valve to bend somehow?) Either way, exhaust valve is definitely bent. I'll take a few pics in a little bit after I finish my homework for college and my back stops aching a bit.
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Post by apothecary on Oct 20, 2011 14:38:01 GMT -6
Yeah that's the next step. Pulling the head and seeing what else I find in there. Hopefully the piston is in decent shape. Otherwise I may just start hunting for a new motor for it.
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Post by apothecary on Oct 20, 2011 14:15:53 GMT -6
Quick update, it's definitely not the compression tester. There is no compression exhaust valve appears to be bent. Spray starting fluid into the intake (carb off) and crank it over, the engine fires but it all shoots out the exhaust port. So the valve is stuck open it would appear. It's also difficult to push it down unlike the intake side which goes a small way fairly easily by hand. The other thing tipping me off to the exhaust valve being open is that when I attempted to adjust the exhaust rocker, it says to turn the arm outward until you hit resistance then return 1/2 mark. Well there's no resistance at all on the exhaust side.
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Post by apothecary on Oct 20, 2011 12:14:09 GMT -6
Ok I'll give the oil a shot. Then I'll rotate by hand a few cranks and then by starter and see if I get compression then. Hopefully it's not the rings. I'm also going to double check my valve lash and see if I've got that right as well. I'll set the TDC with valve cover off so I know I've got it at TDC on the compression stroke.
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Post by apothecary on Oct 20, 2011 9:45:59 GMT -6
Just did compression tests. Throttle wide open. 0 compression. That's right, nada, zip, zilch, the big goose egg. Watched the intake valve as the engine turned over and it's popping up and down and from the sound of it, the exhaust valve is working as well. So either rings, piston, or rod I'm guessing. I'm thinking of pouring a little trans fluid down the spark plug to see if it seals up and gives me anything.
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Post by apothecary on Oct 19, 2011 20:59:29 GMT -6
JR, if you look at the service manual on the CN250, I can't observe the rockers in motion. The rocker shafts go through the valve cover and the adjusters are actually on the outside. So if I remove my valve cover I'm also removing the lifters.
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Post by apothecary on Oct 19, 2011 20:07:38 GMT -6
Actually the CN250 has a VERY different valve train. The rockers are attached to the valve cover. I can watch them move at least somewhat without the cover off as I watch the adjusters move if the bolts are loose. Otherwise there's no way to see the rockers moving. I'm going through the service manual tonight to see if there's a good measurement for the height of the valve stem from the top of the head while in place to see if there's a possibility I can measure the valve length to tell if it's fully seated.
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Post by apothecary on Oct 19, 2011 17:09:27 GMT -6
Ok, I adjusted teh valves all the way in which SHOULD have given me a closed position on the valves through the entire cycle right? Still no compression. I'll take the tester out tomorrow and get readings on it but I'm not holding any hopes. I have a feeling the previous owner did some valve damage.
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Post by apothecary on Oct 19, 2011 16:36:17 GMT -6
I hadn't thought about that. No I haven't adjusted the valve gaps yet and those can be done without even removing the cover. I guess I assumed that since it ran before the cam self destructed, it would run now as is. Let me review that procedure and give it a shot.
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Post by apothecary on Oct 19, 2011 16:02:33 GMT -6
Ok good news and bad news. Good news, I'm not sure WHAT exactly happened but as soon as I took the side off, the motor started spinning. Put everything back in place and it's still spinning. It's cranking over now just fine.
Bad news, I think I have no compression. The timing is right but the engine is still spinning easy as can be. AND to top it off, my carb just started leaking fuel. So back to the drawing board...
So I'm guessing the valves are bent. Is this a strong possibility knowing that the cam bearing shattered while the engine was running? I thought these weren't a non-interference engine so valves were highly unlikely to be bent...
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Post by apothecary on Oct 18, 2011 7:10:37 GMT -6
Well just tested the relay the way you described and I'm getting 12.7V on the output side to the starter. Looks like it's time to bench test the starter and see what happens.
A bench test (though MUCH cruder than the one you described) shows me the starter is working quite well. So now to get that pain in the backside reinstalled and see if maybe I just had it jammed a little...
Ok well another update. I got the starter back in (THAT was a pain I NEVER wish to experience again). Took the left engine cover off (Why the HEX didn't I do this in the FIRST place...) and the engine is locked up tight as can be. Can't turn by hand or wrench. I'm wondering if I overtightened the not on the opposite side of the motor? The engine turned easy enough before I put the flywheel back on... Looks like it's back to the drawing board and a removal of the RIGHT side again with fingers crossed I didn't do any MAJOR damage in my attempts...
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Post by apothecary on Oct 17, 2011 22:13:37 GMT -6
Ok I'll give that a shot tomorrow. It's dark now and I've never been good at holding a flashlight and turning a wrench.
It just baffles me that the starter worked great when the guy was showing me the bike and just from sitting and me doing that work on it, it's gone south? Maybe I knocked it when I was reinstalling everything but I'll check voltage tomorrow and if I'm getting good voltage I'll likely pull the starter tomorrow and thing about pulling it apart.
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Post by apothecary on Oct 17, 2011 19:10:21 GMT -6
Well I've been referred here by a member of another board. So a quick run down of the issue I'm having.
I bought an '87 Helix the owner said the only problem was the cam chain had snapped. So the price was too good to pass up and everything else seemed kosher on the bike.
Start looking into the issue of the cam chain to find it DIDN'T in fact snap but popped off the the cam sprocket. The reason it did so was due to the right side bearing self destructing.
So I removed the side cover to start the replacement of the chain (I still thought the chain had snapped at that time). I found the oil pump chain had also removed itself from position. So I removed the flywheel, the oil pump shaft, the starter gear, the starter idler gear, and both chains.
Though not broken, the cam chain WAS bent so I'm glad I had a new one on hand. Replaced the cam chain and put the oil pump gear and circlip back in place along with its chain. Reinstalled everything else. Add oil, add coolant, hook the battery back up, turn the key, hit the button NOTHING...
Replace the battery and try again. The starter solenoid/relay clicks but the engine doesn't turn over. Battery is registering 13.2 volts now. The solenoid makes a rather loud and quite audible click when you hit the start button.
I've double checked the off/run switch to ensure it's in RUN position and I KNOW the bike turned over prior to me working on it. I've tried with the kickstand down and the kickstand up with no difference (I don't remember which way it's supposed to be anymore).
The only other thing I've noticed is the horn isn't working either. I'm not sure if these are related or if the horn doesn't work unless the engine is running or if I just have a bad horn.
I'll be arcing the starter relay tomorrow to see if it's the relay or if it's some other problem but I HAVE checked the ground from starter to battery and it's giving a good solid connection. The other thing I'll check when attempting to start is voltage at the starter when hitting the button.
Anyways if anyone can shed some light, I'd really appreciate it. Thanks.
Ok, patience not being my greatest virtue when working on something like this that I've been trying to get going for a few weeks now, I went outside with a flashlight and pliers and tried arcing the relay/solenoid. No joy. Starter STILL didn't turn over. I'm wondering if I did something to bind it up or if it's just gone south...
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