So, I've been fighting SVS recently. Finally found some Deep Creep Sea Foam and did a big treatment on her. Pipes off and everything.

When I pulled the pipes, I noticed the left rear exhaust valve stem had about 3/4 of an inch of shiny on it, like it was pushed way in. The right one didn't, in other words, it was dark and discolored (not totally carboned up though) and looked like the other three. I didn't think to try to manually move the left valve, I just sprayed like crazy and let it sit about five hours.

Now, the bike seems to run ok...I guess. Truth be known, I've been blasting around on it so much, revving the piss out of it to hit the limiter a bunch, that i sorta can't even tell if it's got all its power back or not. Blew most of the packing out of the baffle and so it sounded weird from that. Now the weather's bad so I don't know what it's going to run like when I get to ride again. Man, what a mess. I'll never go rich again!!!

OK, here's a SERIOUS question. Could I have bent a valve? Is it possible in all this revving and wailing on it to blow the carbon out that the valve stuck and the piston hit it? Are these "interference engines"? I'm worried because, while I've been out thrashing her she seems to start to run like normal again, but not quite. The idle is really uneven....like "potato potato" with a heavy accent. And the power....well, I dunno. I think it was faster right after I ported it the other week, and now it's just sorta ok. Thoughts?

Mike

Guess you could pull the pipes off again, pull the plugs and hit the starter button and watch...

I've had a couple of bouts of SVS. It starts with a noticeable exhaust sounds (especially at idle), and vibration at certain engine RPMs.

This latest time I could not shake it with "the cure" until I read a post from Doc.

I first sprayed a de-carboning spray into the carb at fast idle and then gunned it a while to blow out as much carbon as possible.

Then I sprayed in Deep Creep for 30 seconds at high idle and then choked it with Deep Creep to stall while spraying. Let it sit for overnight and ran it and sprayed it for 30 seconds again.

I left the air cleaner off and drove her to work (30 minutes). Parked and sprayed for 30 seconds and stalled it while spraying.

Ran it for lunch and sprayed again when I got back. Sprayed it again when I got home.

Did that for about four or five rounds and it cleared up. I can tell it's gone because the vibration from SVS is gone and the engine is running smoother.

Hope this helps.

EDIT: Poor quality gas and low compression conspire to cause carbon build-up in the heads and gunk up the valve stems. I purchased an extra set of heads with 2000 miles on them and they had a lot of carbon over all the combustion chamber surfaces and the valves - especially the intake valves of each head on the carb's side.

Thanks guys.

What about my bent valve question. Any thoughts?

Mike

I don't know if you could hit the valves with a piston or not, haven't been that far into it yet, but from pics I've seen of the heads and pistons, my guess is no..but you could still warp one if its sticking, and the only way to tell is to remove and measure..roll it on a flat surface and you'll be able to see an obvious warp. The thing is, if you go to the trouble to do all this, you may as well take it to a machinist and have it done right..

Make darn sure you don't have a leak at the intake manifold. If no leak then I think you may be running still a little rich doesn't take much to get that back cylinder carboned up. Also check check tye choke knob and make sure it is all the way in you might want to do Musky's choke knob trim.

Midstar,
A cylender leakage test will show a bent valve.
This is a test where you put compressed air in
the spark plug hole and mesure amount of leakage,
it also lets you know where the leakage is;Valves,
rings.
With exhaust off you can see witch valve if any.

http://www.gregsengine.com/clt.htm


Mike

Curt wrote:
Make darn sure you don't have a leak at the intake manifold. If no leak then I think you may be running still a little rich doesn't take much to get that back cylinder carboned up. Also check check tye choke knob and make sure it is all the way in you might want to do Musky's choke knob trim.


I've got no strong popping on decel, so I don't suspect an air leak. I was worried that my needle was floating around due to the slide problem I have (one of the four prongs that hold the needle is cracked), but it feels fine when I've been in there to Deep Creep it. New slide is on it's way. When I put it in I will read the plugs and maybe go even leaner on the needle, currently at 3rd with a washer. I've got a 167.5 main with Barons needle.

And...I've trimmed the choke knob

We are supposed to have some nice weather returning to PA on Tue, Wed, Thurs...so, depending on work schedule I'm going to put some miles on. I'd like to get to the bottom of this before winter hits!

parttime wrote:
Midstar,
A cylender leakage test will show a bent valve.
This is a test where you put compressed air in
the spark plug hole and mesure amount of leakage,
it also lets you know where the leakage is;Valves,
rings.
With exhaust off you can see witch valve if any.

http://www.gregsengine.com/clt.htm


Mike

Thanks for the info, Mike. I'm hopeful that this won't be necessary, but hey, at least it's not the beginning of the season !! If it comes to replacing a valve, I'll just call it my "winter project."

Mike

If most of your riding is short in town stop and go then it may just need a good 300 mile blow out at 70 mph. I know after a couple of weeks of riding mine to work after I take a long ride at 70+ it does run much better.