DANGEROUSDANA Posted October 24, 2011 Share #1 Posted October 24, 2011 I recently bought a 2000 RSV Millennium. It had Bub slip ons that sound really good, but too loud. I couldn't hear the stereo. So, I purchased a set of stock mufflers on ebay and slipped them on. Now, I have a backfire (sometimes very LOUD) on deceleration, just as the engine reaches idle. I have greatly reduced the frequency of this backfire by raising the idle. However, it still backfires occasionally, and I really don't like the higher idle. (I'm guessing 1200-1300 as opposed to 950 or 1000, hard to tell without a tach.) I'm thinking I could adjust this backfire out. First by getting someone to follow me and see which side the backfire is on and then by adjusting the pilot screws in the carbs on the offending side. I'm just wondering...Can the Pilot screws be reached without removing the tank? Thanks. dana Link to comment Share on other sites More sharing options...
V7Goose Posted October 24, 2011 Share #2 Posted October 24, 2011 (edited) Yes, the pilot screws can be reached without removing anything (except the anti-tamper caps on them). You can see them with a flashlight from the opposite side of the bike, meaning you access the left side carbs from the right side. If the caps are still on, look for brass cone shaped nipples fairly close to the drain screws. If the caps have been removed, you will see brass screw heads with two flat slots in an X - even though these are not philips head screws, I find a philips driver works best on them because it will not slip off. Factory setting is between 2-2.5 turns out. Best setting will be between 3.5-4 turns out if your pilot jets are totally clean and the floats are set correctly (they are ALWAYS too high from the factory). If you are going to touch them at all, start by turning each one in to verify the idle speed drops - this will prove your pilot jet is not plugged. With a tach or sensitive ear, just set for max RPM on each cylinder; otherwise, set them at 3 and forget it. I suggest "3 out" in this case because you will have no way of knowing if the floats are set correctly - if they are still at the very high factory setting, then 4 out will be too rich. But, that is not the cause of your afterfire (99.875642% certainty here). And it is a bad idea to go cranking on the mixture screws until you are sure that the rest of the bike is running correctly. In completely stock trim, with all stock settings on the carbs, these bikes will NOT pop on decel unless something is wrong. This has been discussed in many older threads on this site, so you can get all the details if you really want them. The fact that you have less of a problem by cranking up idle speed suggests to me that you have some plugged pilot jets, and you are over-coming that problem by running more off the main jets. Another quick check of the pilot jets is how much vacuum the engine is pulling at idle - if the rings and valves are good, that engine should show 11" Hg - if it is showing less than 10", then the slides are being held partly open by the idle setting to compensate for plugged pilot circuits. On the other hand, it is very strange and quite uncommon if your bike did not pop with aftermarket pipes, but does with stock pipes. This suggests that you introduced an exhaust leak. Most common cause are (in this order): bad carb sync/dirty carbs vacuum leak - either from rotted caps or nicked vacuum lines exhaust leak from bad Y pipe joints, loose header bolts, or missing/damaged gaskets at slip-on points High resistance in the plug caps Bad spark plugs Dirty air filters Goose Edited October 24, 2011 by V7Goose suggested mixture screw setting Link to comment Share on other sites More sharing options...
RedRider Posted October 24, 2011 Share #3 Posted October 24, 2011 Dana, Welcome to the VR Family. Since you are new, I will offer this one piece of very solid advice. When Goose speaks, listen. His diagnostic skills and knowledge about these machines is VERY good. Put out a request for some help doing a carb sync. (#1 on the Goose list). It requires a 4 line manometer (vacuum gauge) and several members have one. In my experience, this will take care of the backfiring in most cases. It is also the least intrusive - easiest to do - of the carb diagnostics. It might also be helpful to run some Seafoam (mix 1/2 can in a tank of gas) and see if that clears up the carbs. If you are able to get with another member, they can also point out the pilot screw locations. If the caps are on, they are kind of hard to find if you don't know what you are looking for. And no, you don't need to replace the caps once/if you make an adjustment. Again, welcome. RR Link to comment Share on other sites More sharing options...
DANGEROUSDANA Posted October 24, 2011 Author Share #4 Posted October 24, 2011 Well, I just called my local Yamaha dealer, (since I don't have the gauges) and they said that a carb sync is a 3 to 4 hour job at $100 per hour. I though it would take closer to 30 minutes. Am I wrong, or am I correct in my assumption that I don't need to be taking my bike to THAT dealership? Guess I'll be buying a set of gauges. Today, I will also check the tightness on the connection between the exhaust pipe and the muffler, at the gasket where they slip on. Maybe, I need to tighten that some more. Could a leak there cause an afterfire? Also, I am at work now, but I took a flashlight outside and looked and the caps have been removed, so they have probably been adjusted before. But Goose got me to thinkin'. Before I switched back to the stock pipes, I had a little "blub blub blub on decel, but never a loud backfire. The only change was the mufflers. I was thinking the extra back pressure might be causing it, but EXTRA back pressure would more likely be preventative to backfiring. Maybe my slip on connection is not sealed well. I will check this. Do you really think that could be the problem? We'll see. dana Link to comment Share on other sites More sharing options...
Freebird Posted October 24, 2011 Share #5 Posted October 24, 2011 A carb sync takes about 10 minutes. It is also very simple to do. I wish you lived closer and I would do it for free. Link to comment Share on other sites More sharing options...
Cougar Posted October 24, 2011 Share #6 Posted October 24, 2011 This is what the brass cap looks like above the bend in the allen wrench that Goose is talking about. hope it helps [ATTACH]61959[/ATTACH] Link to comment Share on other sites More sharing options...
V7Goose Posted October 24, 2011 Share #7 Posted October 24, 2011 Well, I just called my local Yamaha dealer, (since I don't have the gauges) and they said that a carb sync is a 3 to 4 hour job at $100 per hour. I though it would take closer to 30 minutes. Am I wrong, or am I correct in my assumption that I don't need to be taking my bike to THAT dealership? Guess I'll be buying a set of gauges. Today, I will also check the tightness on the connection between the exhaust pipe and the muffler, at the gasket where they slip on. Maybe, I need to tighten that some more. Could a leak there cause an afterfire? Also, I am at work now, but I took a flashlight outside and looked and the caps have been removed, so they have probably been adjusted before. But Goose got me to thinkin'. Before I switched back to the stock pipes, I had a little "blub blub blub on decel, but never a loud backfire. The only change was the mufflers. I was thinking the extra back pressure might be causing it, but EXTRA back pressure would more likely be preventative to backfiring. Maybe my slip on connection is not sealed well. I will check this. Do you really think that could be the problem? We'll see. danaAs Don Said, a carb sync can be done in about 10 minutes. If you are REALLY a perfectionist and have a bike that won't cooperate, maybe 30 minutes. There are about four different types of sync tools available, and of course, you will find lots of different opinions about them - the one that is most popular here, I think is junk. The only sync tool I recommend is the four vacuum gauge set (mechanical gauges). You can still buy them for about $50 or a bit less. LOTS of threads on this site with discussion of these tools, including links on where to buy. An exhaust leak anywhere from the header pipe connection all the way to the muffler slip-on point will cause an afterfire. Stock mufflers should have a silver asbestos (?) gasket inside the end, but when you buy something from the junk market, no telling what you got. That gasket is quite thick, so if it is missing or damaged, the clamp cannot seal the connection. But even if you find an exhaust problem, do not ignore those vacuum caps and lines. The caps do not last more than two years if the bike is being ridden - pull them off and bend them - ANY SIGN of cracking, no matter how small, means they MUST be replaced. That vacuum leak will always cause this problem. Do not waste time and money ordering new caps from Yamahaha - just go to any auto parts store and buy 5.5mm vacuum caps. Also remove the two vacuum lines and carefully inspect them near the end - many careless mechanics using pliers to try and pull them off will cut them around the end of the nipple. And if somebody has stupidly removed those vacuum lines and plugged the AIS system, then you are absolutely guaranteed that your problem is an exhaust leak, no matter what else is wrong with the bike. Goose Link to comment Share on other sites More sharing options...
muaymendez1 Posted October 24, 2011 Share #8 Posted October 24, 2011 Wow. This thread makes me anna go through my bike with a fine tooth comb. i also have been getting the popping but after talk with several new venture owners with the same prob I put it off as nature of the beast. I have the 96 rstc and it has after market pipes put on by PO. The vacuum cas have been replaced and th mixture screws urned in and out. still popping on decel. I have seen minor cracks on therubber connection from carb to head I think that wll be the first to get replaced. Link to comment Share on other sites More sharing options...
V7Goose Posted October 24, 2011 Share #9 Posted October 24, 2011 (edited) Wow. This thread makes me anna go through my bike with a fine tooth comb. i also have been getting the popping but after talk with several new venture owners with the same prob I put it off as nature of the beast. I have the 96 rstc and it has after market pipes put on by PO. The vacuum cas have been replaced and th mixture screws urned in and out. still popping on decel. I have seen minor cracks on therubber connection from carb to head I think that wll be the first to get replaced. It is unlikely that those intake boots ("manifolds") need to be replaced. We have seen a lot of these older RSVs with heavy cracking on them, and lots of visible flexing from the intake vacuum pulses, but they just do not seem to leak - cannot really explain why, but it is a good thing! To test it, make sure the bike is warm, then with the engine idling, spray starting fluid all around the boots and vacuum ports. If there is any leak at all, the engine will pick up speed. Carb cleaner will work too, but then you should wash the area good just to make sure there is no long term negative effect of the carb cleaner chemicals on the rubber. Goose Edited October 24, 2011 by V7Goose Link to comment Share on other sites More sharing options...
DANGEROUSDANA Posted October 25, 2011 Author Share #10 Posted October 25, 2011 Okay. I am going to buy a carb sync tool today. And I know this has been discussed several times. gauges/vs manometer, which brand is best, etc. But, I have noticed that most of these, for sale on the Internet say that they come with 5mm adapters and that the 6mm adapters for the Yamaha should be purchased separately. I have studied "Synchronizing The Carburetors" from the technical section and it really looks straight forward and simple, however, I don't see these adapters. What do you do with the adapters? Are they even necessary? What is the best deal on a good Carb sync tool that includes everything I need? Give me a link. I'm ready to buy. Thanks. dana Link to comment Share on other sites More sharing options...
Cougar Posted October 25, 2011 Share #11 Posted October 25, 2011 http://www.carbtune.com/ Link to comment Share on other sites More sharing options...
RedRider Posted October 25, 2011 Share #12 Posted October 25, 2011 No adapters are needed for the Carbtune (or for any others that I know of). RR Link to comment Share on other sites More sharing options...
54chevybelair Posted October 25, 2011 Share #13 Posted October 25, 2011 Could it be that this bike was set up for the aftermarket pipes, as far as jetting. Now with the stock pipes, the bike is running too rich. I have always thought decel popping could be caused from a too lean or rich condition. I'm sure one of the experts will comment on this. Just my thoughts. Link to comment Share on other sites More sharing options...
V7Goose Posted October 25, 2011 Share #14 Posted October 25, 2011 Could it be that this bike was set up for the aftermarket pipes, as far as jetting. Now with the stock pipes, the bike is running too rich. I have always thought decel popping could be caused from a too lean or rich condition. I'm sure one of the experts will comment on this. Just my thoughts. Decel popping is caused by anything that upsets the full clean burn of the available fuel, combined with available oxygen in the exhaust pipe. On today's engines, which are designed to run on the ragged edge of too lean, this typically means something causing a too lean mixture or fresh air in the header pipe when it should not be there. Once somebody starts modifying a machine, then all bets are off. These bikes almost never benefit at all from rejetting, even when changing the exhaust. I know that there are still some people who still feel they just have to do that, even when it is pointless, but we generally assume the bike has stock jets simply because they are so rarely changed on the 2nd gens. Goose Link to comment Share on other sites More sharing options...
V7Goose Posted October 25, 2011 Share #15 Posted October 25, 2011 I don't usually comment on mechanical stuff but mine started backfiring recently on decel.(loud at times close to idle) Had the AIS blocked off and that cured the problem. Mechanic thought he had done this years ago. Common problem he said. Not saying this is your issue. Your bike has something wrong with it. You have not fixed it at all. By disabling the passive AIS system you have gained nothing at all except to tell your bike to quit telling you that something needs to be repaired. Goose Link to comment Share on other sites More sharing options...
relic Posted October 25, 2011 Share #16 Posted October 25, 2011 I agree with you entirely Goose that this is a bypass of the air cut off valve and not a fix. To fix the problem I would have to change the AIS. It does not backfire anymore so I would believe the mechanic has isolated the problem. It seems better to check this than fool with jetting or other issues. He specifically asked if it was on decel and checked the y pipes for leaks again as they have both been replaced. He says this valve in the AIS weakens over time and does not fully close on decel and causes the backfiring. I am not mechanically inclined with automotive issues and rely on this mechanic that races hi own Vmax and has worked on yamaha's as well as other bikes his whole life. He keeps my bike on the road so all I have to do is ride it. Your bike has something wrong with it. You have not fixed it at all. By disabling the passive AIS system you have gained nothing at all except to tell your bike to quit telling you that something needs to be repaired. Goose Link to comment Share on other sites More sharing options...
V7Goose Posted October 25, 2011 Share #17 Posted October 25, 2011 (edited) I agree with you entirely Goose that this is a bypass of the air cut off valve and not a fix. To fix the problem I would have to change the AIS. It does not backfire anymore so I would believe the mechanic has isolated the problem. It seems better to check this than fool with jetting or other issues. He specifically asked if it was on decel and checked the y pipes for leaks again as they have both been replaced. He says this valve in the AIS weakens over time and does not fully close on decel and causes the backfiring. I am not mechanically inclined with automotive issues and rely on this mechanic that races hi own Vmax and has worked on yamaha's as well as other bikes his whole life. He keeps my bike on the road so all I have to do is ride it. The problem is not your AIS valve - that statement from your mechanic is simply a copout. The AIS valve is an extremely simple device and very easy to test, and it is NOT a typical failure point. Most likely, your problem is nothing more than a simple vacuum leak or a poor spark, either from a high-resistance plug cap or old/defective spark plug, or maybe even a simple carb sync or partially plugged pilot jets. Of course I have no way of knowing exactly what is working and not working on your bike from just reading a couple of posts on the internet, but the odds are WAY in my favor to say that the problem is a real issue with your bike and not a defective AIS valve. Generally, this problem is easy to find and fix, but not always. And too many people are just not interested in doing it right. If you are happy just hiding the symptoms instead of fixing your bike, well, that is your prerogative - after all, it is your bike. I just do not think you should fool yourself into believing that there is not a real problem that you just do not care to fix. Please do not misunderstand - I know that you were simply taking the advice of a mechanic you trusted. But I am telling you that you need to look a bit further now - perhaps that trust is misplaced. Your mechanic may be very knowlegeable about a lot of things, but he is not doing you any favors on this specific problem. Goose Edited October 25, 2011 by V7Goose Link to comment Share on other sites More sharing options...
RedRider Posted October 26, 2011 Share #18 Posted October 26, 2011 Dang, Goose. When did you start getting all diplomatic and stuff. (good answer though). RR Link to comment Share on other sites More sharing options...
allwx Posted October 26, 2011 Share #19 Posted October 26, 2011 It is unlikely that those intake boots ("manifolds") need to be replaced. We have seen a lot of these older RSVs with heavy cracking on them, and lots of visible flexing from the intake vacuum pulses, but they just do not seem to leak - cannot really explain why, but it is a good thing! After two years I saw my intake boots cracking on my 97 RSTD. The dealer mech looked at them and said they had to be replaced, and ordered new. I talked him into letting me do the work, and was able to examine the boots, both new and old, off the bike. They are very thick!! Cracks on the exterior of the boots don't mean anything in terms of leaks. Not saying they will NEVER leak, but they are probably not worth worrying about before ten years old. That was 13 years ago, and I have since seen cracks in most intake boots on most RSTDs and Ventures I've seen that are more than a couple of years old. Some of the cracks look horrible, but apparently do not leak. As for decel popping, my Venture, like my 05 Roadie, "burbles" on decel. I would not call this "backfire" since my understanding of "backfire" is a completely different type of animal involving fire coming out of a carbuetor. I might call this sound "popping" but it is actually more of a "burble" and thus we arrive at the limitations of the printed word. I removed the AIS from my Roadie and this eliminated the burble. I took this to mean that the AIS, which allows the post exhaust-valve burning of unburnt fuel, causes a certain amount of combustion in the pipes. Minus the AIS, the unburnt fuel just goes out the back in raw form, which is why the EPA wanted such a system installed on our bikes in the first place, to burn this fuel before it gets into our air. Not a bad idea. I put the AIS back on the Roadie before I sold it, and the burble returned with it. I don't worry much about this burble, because I think it is a sign that the AIS is working properly. I stand to be corrected. Link to comment Share on other sites More sharing options...
DANGEROUSDANA Posted October 26, 2011 Author Share #20 Posted October 26, 2011 What does AIS stand for and where is this device located? Link to comment Share on other sites More sharing options...
muaymendez1 Posted October 26, 2011 Share #21 Posted October 26, 2011 I guess your burble can be my ruble rubble. On decel especially comming down hill I ill hear popping and many times it will get loud enough that lead andfollowing riders hear it. My 96 shadow had this happen hen i put on cobra straight pipes and I know the bike shouldnt do that. Went to a local shop had it dynoed and rejetted. no more after burn ( burble) ( rummble) (Burp) ( Pop) this was when i was richer and had less bills. I cant afford nor do I want to have a shop touch my bike. Another site I vist had a post here a guy got larger pilot jets and it cured not only the popping but the cold b,loodedness of thebeast. i now have those jets in my dresser waiting to get installed. They have been waiting 2 months Link to comment Share on other sites More sharing options...
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