Helix CN250 no start By apothecary (Read 6,224 times)

[alleyoop]

BUMMER, yea pour a little oil down the spark plug and see if you get a HINT of compression.
You can also check the valves a little better. When the valves come up grab the rocker and see if you can wiggle it, same with the exhaust valve when it comes up. You should be able to wiggle them a little because they should have just a slight play.
Alleyoop

[apothecary]

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.

[apothecary]

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.

[alleyoop]

Yep, you found your problem, that was was I was saying to take the valve cover off and notice if the valve springs are compressed a little which would mean a bent valve not letting come back up to close.
Well at least it is not that bad(SO FAR), but you will have to check your piston. The valve did not bend by itself it was hit by the piston so there could be more damage.
Alleyoop

[apothecary]

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.

[alleyoop]

If the piston is shot I was thinking maybe a BBK but maybe the price of a bbk and a new engine are pretty close. Well lets hope its just the Valve or Valves bent and you can either get a new head and or just the valves.
Good luck on your further investigation.
Alleyoop

[cruiser]

If the piston and/or cylinder are damaged, here's the set from BPNW for $125:

.buggypartsnw.com/home?page=shop.product_details&flypage=flypage.tpl&product_id=416&category_id=43" rel="nofollow" target="_blank">.buggypartsnw.com/home?page=shop.product_details&flypage=flypage.tpl&product_id=416&category_id=43

A new engine is closer to $1000.

[apothecary]

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.

[alleyoop]

That is good news.
Alleyoop

[apothecary]

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.

[apothecary]

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:

[apothecary]

Here's a shot of the piston. You can see where the valve dinged the top but I'm thinking no major damage. Looks like everything else is fine so I'm not going to replace the piston or jug.


At least I'm assuming there's no damage. It's got a nice nick in the piston head you can see towards the top but that's about it that I can tell.