Excess smoke through the PVC.

chief_of_smoke · Aug 19, 2024

So after sitting idle for a few years, I decided to get the blastetcase running again for my son. He just got him motorcycle license. I took the carb off and got it all cleaned up. Kind of messed up with took off the tps. I got it set though. Had to put a new boot on. Got it started on ether. Idle was off a bit, but got it set close. It would die and I could get it to start back up. Once it was running at idle, I started to notice a lot of smoke coming from the top of the head and air box. Shut it down. No leaks from the head or cylinder. Opened the air box, lots of smoke. I guess it is choking itself out. Pulled the tank off and just let it run out of gas. And to watch for smoke. Looks like it is coming from the PVC valve, which feeds into the carb. My question is what would be causing the excess smoke? On the plus side, it not smoking through the exhaust. Unless the exhaust is plugged up?

Barrett · Aug 20, 2024

Hey Chris how you doing????

In the automotive world....that combination of engine not fired for several years along with excess smoke and pressure now coming from the PVC feed area and the PVC valve itself is almost always piston/cylinder related.
Check that your exhaust is flowing freely then perhaps start googling "piston ring blow-by from long term storage" and see what you find.

chief_of_smoke · Aug 20, 2024

It's going bud. How are you doing? That's one thing I was worried about. That or valve seat and seals. I was suspecting the exhaust as well. Didn't notice any smoke from there. Of course when I got the new boot and fired the blast up it was 830 at night. Ill give it a google. Thanks again.

chief_of_smoke · Aug 20, 2024

So I bypassed the breather and added mystery oil to the fuel and let it run for a good while. Looks like the smoke is old residue. And what I was getting out of the PVC valve seemed more like exhaust that burning oil. Oil is still full. Still messing with the idle and the primary chain needs a tweak. Worst case scenario is I do a top end rebuild. Going to soak the cylinder and see what happens. Here are a few videos.

Barrett · Aug 21, 2024

Chris: Got your PM and IMO the color of the vapor plus the "huffing" nature of the vapor pulses sure seems consistent with piston rings failing to fully seal. Perhaps, on a room temp motor, remove the plug and squirt an ounce or so of either Kano Kroil or diesel into the cylinder....let it sit for 2 days and soak....crank with plug out to expel excess....then start and see what you have?

chief_of_smoke · Aug 22, 2024

That's what I'm doing now. Plug looked surprisingly good. Thanks for the help. Just had a bunch of things going this past couple months. Not thinking things though as clearly as usual.

chief_of_smoke · Aug 24, 2024

Well it's running better. Got some strange results. So I soaked the cylinder with marvel mystery oil, went to clear the cylinder and nothing came out. So I sprayed a bunch of pb into it and let it sit for a bit. Cleared the cylinder and soaked the rag with PB that came out. Put a bunch of marvel back in to soak another day or so. Cleared the cylinder like before. That turned into damn mess. Fired it up. Boy did it smoke out of the exhaust. Took a while to clear up. After it got warmed up, it started to smoke out the breather again. Not as bad and this time with a bit of water dripping every so often. Did a clutch adjustment and rode it a bit around town. Shifting isn't as smooth as it should be in 1st and 2nd. Had to adjust the idle a bit. Let my son for a ride. He told me it started to smooth out. Guess I'll give her the beans then. Here is a picture of him on his maiden voyage.

Excess smoke through the PVC.

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