jrhendryx Posted August 17, 2007 Share Posted August 17, 2007 hey guys, im new to motorcycles, and am trying to teach myself about the engine, and engines in general. heres the deal. i own a 75 xs500b. it has been running fine, but yesterday i noticed a slight backfire when i rolled off the throttle. today, it was even worse, to the point where the engine actually died when i got to work. coming home from work, i was just wondering if i was going to make it. when i roll on the throttle the engine bogs down and tries to die (or just dies). when i pull in the clutch and roll off the throttle, all of a sudden the rpm's dont drop for quite a while (5 seconds or more) and then once it does die off, it just dies. doesnt want to start. backfires a lot. im hoping that this is just a carburetor adjustment issue, that its maybe running way too rich. any ideas or help would really be appreciated. thanks. jeff Link to comment Share on other sites More sharing options...
Moderator drewpy Posted August 18, 2007 Moderator Share Posted August 18, 2007 hey guys, im new to motorcycles, and am trying to teach myself about the engine, and engines in general. heres the deal. i own a 75 xs500b. it has been running fine, but yesterday i noticed a slight backfire when i rolled off the throttle. today, it was even worse, to the point where the engine actually died when i got to work. coming home from work, i was just wondering if i was going to make it. when i roll on the throttle the engine bogs down and tries to die (or just dies). when i pull in the clutch and roll off the throttle, all of a sudden the rpm's dont drop for quite a while (5 seconds or more) and then once it does die off, it just dies. doesnt want to start. backfires a lot. im hoping that this is just a carburetor adjustment issue, that its maybe running way too rich. any ideas or help would really be appreciated. thanks. jeff check out spark plugs to see if they are rich, I doubt they are. I have a feeling that you have some crud in your carbs especially the pilot jets as they give the rpm idle you describe. The only fix is to strip and ultrasonic clean the carbs and fit new jets whilst your at it. get the keyster kits from ebay http://www.siriusconinc.com/rebuilding_tips.asp Link to comment Share on other sites More sharing options...
jrhendryx Posted August 18, 2007 Author Share Posted August 18, 2007 check out spark plugs to see if they are rich, I doubt they are. I have a feeling that you have some crud in your carbs especially the pilot jets as they give the rpm idle you describe. The only fix is to strip and ultrasonic clean the carbs and fit new jets whilst your at it. get the keyster kits from ebay http://www.siriusconinc.com/rebuilding_tips.asp you are correct, in fact, i noticed that the engine was running a little warm at that point too, so after reading up a bit on what lean/rich looks like, im leaning towards lean, and since i dont have the right tools (the pressure gauges mainly) i will be having everything cleaned with new jets at a local classic bike shop. Link to comment Share on other sites More sharing options...
jrhendryx Posted August 23, 2007 Author Share Posted August 23, 2007 i dropped the bike off yesterday, and i trust this shop because it comes highly recommended, but a couple of things that the guy said to me kind of put me on edge a bit. first, he told me that these bikes were huge pieces of crap, etc etc, which i already knew, but the ones still running somehow missed most of those problems, gave me the huge song and dance about how parts are discontinued and they dont stock any. heres the real thing that worried me a bit. he said that the problem wasnt in the carbs....... without ever starting the bike up or anything, he said that it was electrical, and that it was a problem with the generator. that more than likely the brushes were worn.... problem is, that kicked up a red flag, and sure enough, when i checked my factory manual, the generator on this bike doesnt have brushes........... after talking to other yamaha shops, heres what ive come up with... 1) the high rpm problem sounds like a vacuum leak 2) the carbs are out of sync more than i thought they were 3) there could possibly be an electrical issue with bad plugs, or the points being worn or something to that effect. does this sound like an electrical issue to you guys? Link to comment Share on other sites More sharing options...
Moderator YamaHead Posted August 23, 2007 Moderator Share Posted August 23, 2007 More than likely, the carbs are the guilty culprit here..... But the points being worn or dirty could also have an effect with these symptoms. Link to comment Share on other sites More sharing options...
Kielohawk Posted August 23, 2007 Share Posted August 23, 2007 I had a simlar issue. My 75 XS500B started dying at stops, and was getting hard to start especially when already warmed up. When I first got the bike, it seemed really cold blooded and took awhile before I could turn the choke off or it would die. The low idle screw acted really funny also. I could adjust it down to about 1100 RPMs and when I would try to raise the idle just a tad by turning the idle screw, the RPMs would race to about 2500 and stay there. When I would slowly rotate the idle screw back a tad, the idle would drop to 1200 RPMs pretty fast. I could not adjust in between. WHen I turned the choke on for a cold start, the bike would start but would only idle around 1300 RPMs then slowly fall for about 45 Seconds then it would die unless I gave it gas. I broke open the Clymer manual. Here's what I did to fix my bike... I set the fuel/air mixture screws to factory settings. all the way in till they gently seat, then back out 1 full turn +/- 1/4 That didn't really help. My mixture screws were out about 4 full turns. It had to be running rich. Then I checked for spark. The plugs didn't seem torqued all the way and the spark was good on both plugs. I took the points cover off on the right side of the bike and checked gaps on both points. The gaps were no where near what they needed to be according the Clymer. The gap was about half what it was supposed to be. I adjusted the gaps on both points, then advanced the timing a tad. (turning the whole point base a bit) WOW, what a difference. The bike started right up and ran much better. The choke works normally. Choke on, the RPMs are up around 2000 to 2200 RPMs, after about 30 seconds, choke off and normal idle at around 1200 RPMs. The idle set screw is now fully adjustable from 1000 RPMs and up smoothly. The engine doesn't want to die when you give it a fast throttle advance. It also has a bit more power when running. And best of all, I got another 12 Miles on the tank before I had to kick in reserve. That's another 4 MPG from what I was getting. I also ordered a original owner's manual which has a ton of info in it. I was pretty dissapointed with the Clymer manual. It's kinda like a Haines or Chiltons. It covers a bunch of years and the pictures and directions never seem to exactly match what you got. The owners manual says the tank size is only 3.4 US Gallons. I thought it was 3.96 Gallons. That makes a HUGE difference when you are depending on a certain amount of fuel in reserve!! The manual says that when you have to kick in reserve, you only have 20 to 25 Miles left before the tank is empty. I can verify this!! I had 21 Miles on the reserve when my engine died. I thought I could go 40 Miles with a 1 gallon reserve. Hope this helps. Check your points for condition and gap. It's what fixed my bike. Dan Link to comment Share on other sites More sharing options...
jrhendryx Posted August 24, 2007 Author Share Posted August 24, 2007 awesome, very helpful. i got the bike back today, and i realized that it was a problem i could have fixed myself, but hey.... i will just call it an $80 learning experience. problem 1: old plugs Problem 2: bad plug caps problem 3: petcock screens so clogged with rust that it looked like someone had packed chewing tobacco into the hoses. still, this means that there is the underlying problem of a rusty gas tank that needs to be solved, so i need to find a NOS tank, or find a way to get this one sealed or something. any suggestions on that? Link to comment Share on other sites More sharing options...
yoda Posted August 24, 2007 Share Posted August 24, 2007 Take the tank off the bike and have it steamed out. This should remove any loose scale and rust. Do not put old fuel in petrol tanks as the fuel is hydroscopic. Make sure that the tank top seals are in good condition and not letting water in. Seal them with waterproof sealant. Fit a fuel filter after the petcock. Link to comment Share on other sites More sharing options...
Moderator drewpy Posted August 24, 2007 Moderator Share Posted August 24, 2007 Take the tank off the bike and have it steamed out. This should remove any loose scale and rust. Do not put old fuel in petrol tanks as the fuel is hydroscopic. Make sure that the tank top seals are in good condition and not letting water in. Seal them with waterproof sealant. Fit a fuel filter after the petcock. Far as I know fuel is not hydroscopic (like brake fluid) water is present in the air (and in tank) and condeses. As water is heavier than fuel it sinks and guess where your fuel tap is? that's why tanks are rustier at the bottom. drewpy Link to comment Share on other sites More sharing options...
Moderator YamaHead Posted August 24, 2007 Moderator Share Posted August 24, 2007 Take that tank off & pour a little Deisel fuel & a handful of nails into it.......then shake the Hell out of it! Rinse....& Repeat if necessary.........Poor Mans way to prep the tank Link to comment Share on other sites More sharing options...
Guest Brian Bonner Posted August 24, 2007 Share Posted August 24, 2007 Take that tank off & pour a little Deisel fuel & a handful of nails into it.......then shake the Hell out of it! Rinse....& Repeat if necessary.........Poor Mans way to prep the tank That's the first time I've heard that solution, the other solution I heard was to use water and sand. Just put some water in and dump the sand in and shake and then rinse and repeat. The last step being to put some 2 stroke oil in and cover the inside of the tank to provide some resistance to it rusting again. Link to comment Share on other sites More sharing options...
jrhendryx Posted August 25, 2007 Author Share Posted August 25, 2007 thanks for the help guys. i talked to my dad about this because we had the same problem with an old honda 3wheeler that we bought when i was about 12. we ended up buying a new tank, because they were so readily available, but he also suggested taking it to a radiator shop and having them steam/boil it out. do you think that this is going to be a problem when i park the bike for the winter? if i top off the tank and put in some stabilizer, it shouldnt be a problem right? the tank should only have rusted where the gas was not touching, so if it sat half full for a while, the top half of the tank would be rusted. right? Link to comment Share on other sites More sharing options...
Moderator drewpy Posted August 26, 2007 Moderator Share Posted August 26, 2007 thanks for the help guys. i talked to my dad about this because we had the same problem with an old honda 3wheeler that we bought when i was about 12. we ended up buying a new tank, because they were so readily available, but he also suggested taking it to a radiator shop and having them steam/boil it out. do you think that this is going to be a problem when i park the bike for the winter? if i top off the tank and put in some stabilizer, it shouldnt be a problem right? the tank should only have rusted where the gas was not touching, so if it sat half full for a while, the top half of the tank would be rusted. right? you could always try this and engine wise do a lay-up kit Link to comment Share on other sites More sharing options...
jrhendryx Posted August 28, 2007 Author Share Posted August 28, 2007 you could always try this and engine wise do a lay-up kit using electrolosis would be nice, but wouldnt it damage the paint? i assume i would have to submerge the entire tank to get it to work. and what is a "lay up kit?" is it something to winterproof the engine? i was told to just drain all of the gas out of the carburetors, top off the tank, and add a stabilizer. what will the lay up kit do differently? Link to comment Share on other sites More sharing options...
Moderator drewpy Posted August 28, 2007 Moderator Share Posted August 28, 2007 using electrolosis would be nice, but wouldnt it damage the paint? i assume i would have to submerge the entire tank to get it to work. and what is a "lay up kit?" is it something to winterproof the engine? i was told to just drain all of the gas out of the carburetors, top off the tank, and add a stabilizer. what will the lay up kit do differently? Just google "engine wise" and the top search is the kit!! I thought that if you could seal the area around the pet cock after t has been removed and pour in the solution into the tank, you could achieve the same result. I have used this method on brackets etc in a bath and it will remove the paint. It also get hot depending on how much you insert the cathode (stainless rod) you do this at your own risk BTW don't come back to me with tales of woe Link to comment Share on other sites More sharing options...
yoda Posted August 28, 2007 Share Posted August 28, 2007 Far as I know fuel is not hydroscopic (like brake fluid) water is present in the air (and in tank) and condeses. As water is heavier than fuel it sinks and guess where your fuel tap is? that's why tanks are rustier at the bottom. drewpy Temperature. Link to comment Share on other sites More sharing options...
jrhendryx Posted August 28, 2007 Author Share Posted August 28, 2007 Just google "engine wise" and the top search is the kit!! I thought that if you could seal the area around the pet cock after t has been removed and pour in the solution into the tank, you could achieve the same result. I have used this method on brackets etc in a bath and it will remove the paint. It also get hot depending on how much you insert the cathode (stainless rod) you do this at your own risk BTW don't come back to me with tales of woe yeah, this actually sounds like it might work.... plug up the petcock holes with a rubber stopper, and fill it with solution, but i would probably immerse it almost all the way in a cold water bath. perhaps i should purchase a tank i have no intention of putting on the bike to give it a try.... thanks. Link to comment Share on other sites More sharing options...
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