2007 Rsmv Backfiring

[V7Goose]

Very nice explanation Goose. Understand that a whale of a lot better now. So my next question is this:

 

The gurgle on decel that I'm getting doesn't sound like it fits into the "afterfire" category given this explanation. Is that a correct assumption or is it still a type of afterfire.

This is a very tough question to answer without hearing it (and comparing it to other Royal Stars). An afterfire is an explosion, which causes a "bang" or "pop," and it would be exceedingly rare to have a condition that allowed so many of them to be fairly quiet and so close together to be described as a burble. So I'd be tempted to just say it was normal deceleration sounds. The AIS valve should be closed during most deceleration, and even if it was defective and leaking, then you probably would be getting obvious afterfires. One way to test that is to just pull off the vacuum hoses that activate the AIS valve (and temporarily cap the nipples, of course; you don't want an excessively lean condition to foul up the test). With the vacuum hoses off, go for a ride and see if anything changes. If it does not, I'd suspect a bad AIS valve, Unfortunately, you said you plugged it once, so that kind of rules that out already.

 

Does it sound different than other RSVs? Do you have stock pipes and air filters? Have you balanced the carbs recently? I suppose it is possible that it is just running on the ragged edge of lean, so there might be just slightly elevated hydrocarbons in the pipes during decel, which burn off just short of a bang? That condition is normal on some bike designs (like the W650 I had), but I have not noticed it on the RSV. I'll keep thinking about it.

Goose

[gibvel]

This is a very tough question to answer without hearing it (and comparing it to other Royal Stars). An afterfire is an explosion, which causes a "bang" or "pop," and it would be exceedingly rare to have a condition that allowed so many of them to be fairly quiet and so close together to be described as a burble. So I'd be tempted to just say it was normal deceleration sounds. The AIS valve should be closed during most deceleration, and even if it was defective and leaking, then you probably would be getting obvious afterfires. One way to test that is to just pull off the vacuum hoses that activate the AIS valve (and temporarily cap the nipples, of course; you don't want an excessively lean condition to foul up the test). With the vacuum hoses off, go for a ride and see if anything changes. If it does not, I'd suspect a bad AIS valve, Unfortunately, you said you plugged it once, so that kind of rules that out already.

 

Does it sound different than other RSVs? Do you have stock pipes and air filters? Have you balanced the carbs recently? I suppose it is possible that it is just running on the ragged edge of lean, so there might be just slightly elevated hydrocarbons in the pipes during decel, which burn off just short of a bang? That condition is normal on some bike designs (like the W650 I had), but I have not noticed it on the RSV. I'll keep thinking about it.

Goose

Bought it in Texas and drove it back. Aftermarket pipes that were on it when I got it. Was told they were BUBs but they have no markings like BUBs. Someone, on this site, did have photos of pipes that looked exactly like mine and he called them BUBs too. I put in K&N filters but, after that, I was going to have the carbs rejetted but the shop said they only needed to be adjusted. They adjusted them for slightly rich, since I am planning on going down in altitude (if I can ever get away from this bloody job ). I think they said they set them for 13 and normal was something like 10 or so on the EGA. The carbs had been rebuilt before I got it. Just changed the plugs not more than 100 miles ago, did a resync this last weekend. Sounds, pretty much the same now as it did when I first got it, even changing out the filters and the re-adjust.

 

My son-in-law, however, does think it sounds pretty cool though so I may just have to leave it this way... :rotf: But, to me, it would make the bike lots better if I could get rid of it.

 

When I had my 89 I was consciously listening when I'd decel and I swear that I could hear sounds that sounded similar on that one but the pipes were so much quieter that I couldn't be sure.

Edited May 29, 2008 by gibvel

[V7Goose]

Wow, any one of those changes could contribute to a change in exhaust sound! But I'd guess it is just a natural sound for those pipes. Easiest way to test that would be to swap pipes for a test ride with someone who has stock pipes. Any chance you are going to one of the maintenance days or rallies this year? We might be able to hook up and do the test - I'd like to hear it and learn about the cause myself. If not, maybe somebody in your area would be willing to do it? The pipes are supper easy to pull off, and even pulling the saddlebags to get to the bolt is pretty danged quick with a T-handle wrench.

Goose

[gibvel]

Wow, any one of those changes could contribute to a change in exhaust sound! But I'd guess it is just a natural sound for those pipes. Easiest way to test that would be to swap pipes for a test ride with someone who has stock pipes. Any chance you are going to one of the maintenance days or rallies this year? We might be able to hook up and do the test - I'd like to hear it and learn about the cause myself. If not, maybe somebody in your area would be willing to do it? The pipes are supper easy to pull off, and even pulling the saddlebags to get to the bolt is pretty danged quick with a T-handle wrench.

Goose

 

I actually have the stock pipes from the bike and the saddle bags would be even easier than that because I've got the thumbscrew set-up. Would I be able to leave the K&Ns on to do that? I don't think that any of the changes I made or the re-adjust actually did anything to it as the exhaust sounds exactly the same now as it did when I rode it home on the 1st day. Some day, when I get time, I may swap the pipes back and take a little ride.

 

I wish I were close enough to a maintenance day to get there. I still have to check the "Y" for a leak though. Actually haven't found my way around the AIS hoses to check that either but I need to make dead sure there are no vacuum leaks in those as well.

[V7Goose]

Nothing you have done should affect the stock pipes at all - the K&N is a standard Yamaha accessory that does not require you to make any changes. Just pop those pipes back on and see if the burble goes away - that should tell you everything you need to know. If it goes away, then it is the pipes and there is probably not much you can do about it. If it does not go away, we still have an opportunity to figure it out.

 

The vacuum hoses that activate the AIS valve are just the two hoses on the intake manifold nipples that are not capped. All you need to do is go to an auto parts store and buy a couple of rubber caps, then just pull the hoses off and let them hang free for a test ride. You don't need to plug those vacuum lines for the test, just cap the nipples. You can also do a quick check for a vacuum leak by just spraying around the nipples with carb cleaner.

Edited May 29, 2008 by V7Goose

[curtisb]

cranked the scoot last night and felt for exhaust leaks. found pinhole leaks at both left and right side y pipes. would this cause the slight popping sound on decel?

[V7Goose]

cranked the scoot last night and felt for exhaust leaks. found pinhole leaks at both left and right side y pipes. would this cause the slight popping sound on decel?

Not really sure about a "pinhole leak," usually the problem is at the crimp with a large raised section that leaks - the hole is about the size of a broom straw. Leaks in this area DO cause popping on decel; because, they defeat the purpose of the AIS valve. When the valve is supposed to be closed, shutting off fresh air, the leak around the Y joint allows the fresh air in anyway.

Goose

[curtisb]

it was at the crimp on both sides. tried j-b weld on it last night. still setting up so have not tested it yet.

[V7Goose]

it was at the crimp on both sides. tried j-b weld on it last night. still setting up so have not tested it yet.

You described it perfectly. In addition to the ocasional popping, those leaks usually put a gray film of exhaust gasses on the chrome shields over time - JBW should be a perfect solution. These leaks do cause popping, but not near as bad as a vacuum leak or bad AIS valve would.

Goose