Mid last year I was driving with SVS for 3 months... afetr thet time stock valves destroy lifters and wince tapes... Olso my cylinder head was olmoust destroyed, my outlet valve is brown now not silwer... So beter chek it quickly. You must anscrew only few screws

Doc, wykrzyknik, and all,

Thanks for all the input. I'll be outta town for a few days and will tackle float height and whatever else like a big dog next week. Gotta have this figured out this season for sure.

MS07

Mid star are yuof fix ypur bike?
Ihave SVS again... Seafoam didn help... I clean cylinder heads and vavlves. now its ok but I must found reason why SVS come back so quickly

Just an observation..since the svs is always in the rear cylinder..wouldn't heat be a big factor as the rear jug runs hotter..?? Is this just a carb only issue or does the fuel injected models get this problem..?? I dont have it in my 2 roadies,but i am running seafoam in them now to try and keep from getting the svs disease..

The only sticky valve problem I have ever had was on the Pratt&Whitney R1340!! It was due to runing the mixture to lean, and causeing the cylinders to run hot, which causes the valves to stick in the guides!! When I would get the valves sticking would run a lot of Marvel mystery oil to aleviate the problem. I have not had a problem with my Roadstar. According to most of you guys I am runninng alittle rich, but on an aircooled engine, I would lot rather be alittle rich than to lean..a lean condition can cause you lots of problems... Oh by the way I get any where from 45 to 60 mpg!!!

wykrzyknik wrote:
Mid star are yuof fix ypur bike?
Ihave SVS again... Seafoam didn help... I clean cylinder heads and vavlves. now its ok but I must found reason why SVS come back so quickly

Normally it's because you have an overly rich mixture as a result of rich jetting, overuse of the choke, or too many very short trips which don't allow the engine to reach full operating tempeature.

Doc

I've been struggling with SVS on and off for quite a while. My scoot seems to run GREAT , and the next time I ride, I get a vibration - the telltale sign of SVS.

I just took off the exhaust and one plug on each cylinder and sprayed Deep Creep on the valve stems and piston heads. I will get her back on the road tomorrow.

It seems that when I don't use Sea Foam, I get SVS. I think it's due to the bad gas I get around here. I need to find a good source and stay with it. I will strap a can of Sea Foam to the risers to use when I get a fill-up.

Ray

Hi wykrzyknik,

Thanks for asking. Well, I "fixed" it, only to have it return. Now I think I might just have a MASSIVE intake leak that occurs only with about ten minutes of warm up on the bike. I'll tell ya, I'm not exactly sure what to think. Yamaha dealer says (not that I trust dealers much, but it was a local call ) that if it were really SVS that I'd hear a tremendous hammering noise. What do you guys think? I've never read that as part of the description, I've been assuming that the heavy carbon on the valves, the fact that sea Foam clears it for a while, and that it seems to totally shut down one cylinder, that, well, it's SVS. But nothing seems to cure it for good, and I had been running it uncomfortably lean.

So, I'm going to go back to the oversize o rings ONE MORE TIME and see if it helps. After that, I'll try a different manifold and perhaps get the mating surface lapped. After that...well....might just pack it in and buy something else. I can't spend all my time with the short PA riding season just trying to seal a manifold. I'd like to ride a bit, too

Here is the Yamaha Bulletin for SVS that I got from my dealer:

http://weislake.com/sig/mucker/2-16-07.pdf

note what they have to say on oil level, checking oil level and jetting.
Also over the yrs on other possible causes that I have read are, valve guides that are not exactly with-in spec too.

What I have also come across for those that had the SVS multiple times but cleared it temporarily with Ring free, that most have had much better long term results by reaming the valve guides, and either going with Patrick Racing valve springs, or the Speedstar valve springs, and not using more than 4qts for an oil and filter change.

Erb,
Thanks for the info.

I installed Nemesis valve springs when I did the heads, but I think they may have been a stock replacement. I was under the impression that they were a *racing* or at least a stiffer spring when I ordered them.

I was going to ream out the guides, but could not find a ream. Ended up using a rifle bore cleaning brush which did a great job on the bench.

I make every attempt to avoid it but SVS keeps on returning. I run the lungs out of her in 1st or 2nd gear for a few miles to clear it up - I mean wind her up till she sounds like she will erupt.

I think that I may have to put her on a dyno for tuning or get one of those O2 sensors with computer hook-up so I can do it myself.

(If I get one of those units, I would make it available to other members of the clinic for a small fee and shipping to help pay for costs. We'll see.)

Like MidStar07 I am either going to invest in some means to conquer this bane or use it as an excuse to move to an FJR 1300.

Ray