Moderator drewpy Posted August 4, 2009 Moderator Share Posted August 4, 2009 sounds like its running a little weak, adjust your pilot settings front of carbs. until you get the floats sorted, you can't expect too much in the way of performance!! I do like the quiet surburban backdrop, then start revving the bike up and the dog starts barking etc Link to comment Share on other sites More sharing options...
JimR Posted August 13, 2009 Share Posted August 13, 2009 sounds like its running a little weak, adjust your pilot settings front of carbs. until you get the floats sorted, you can't expect too much in the way of performance!! I do like the quiet surburban backdrop, then start revving the bike up and the dog starts barking etc Well it could be just an XS400 they were well odd to set up, in the UK as they tended to sit in crates as no one wanted them until the SE days (1980) so its correct that the older bikes will never run too well and there will be struggles getting a 2A2 to run correctly (now a few years on) but as a "fix" setting the dwell & timming correctly tended to make them run ok Regards Jim Link to comment Share on other sites More sharing options...
gazampa Posted August 18, 2009 Author Share Posted August 18, 2009 Project is moving along, after replacing punctured floats im working on high idle with a warm engine, i understand its a lean mixture problem most likely caused by too low a fuel level in the bowl, its about 8mm under the lip. Im going to reset float heights and am using a fuel level gauge. So far adjusting the idle screws is not affecting it. I posted a seperate thread about the float work. First of all the floats were stuck, then punctured, now too low. Grrrr, floats. And the new floats fall so low in the bowl allowing the needle to fall out low enough to jam them. The tang on the back that hits off the post is not big enough. I am walking in the shoes of Torakusu Yamaha as he endeavored to tune his first reed organ. The air show came to town, I pedal powered over on my bicycle. Ive got enough progress to be reasonably content with but its not air show quality just yet. The idle is very high and in a crowded area with a fairly rusty driver, it would not be very cool. Getting the carbs right is taking me some time, a rebuild from the sirius kit with new floats was in order from the outset. Here a couple of photos from the papers, i dont think any of these guys would drive a bike with high idle and who knows what else just yet. ( At least thats one thing i might have in common with them ) I have used it to jet down to the store though and the circumference around my appartment which I am driving is increasing. Im not flooding the engine anymore but its very dry. photo1 photo 2 Link to comment Share on other sites More sharing options...
gazampa Posted August 25, 2009 Author Share Posted August 25, 2009 Am completely stuck. I cant get the engine to idle. Is there a secret handshake involved, then again this is my first time tuning carbs, I say that to myself to stay calm but I am going #$%# banannas throwing myself against this. Utter frustration. 1 ) 2 New carb kits from sirius. Able to spray air through the passageways. Two new Idle screws. 2 ) 2 New floats ( genuine yamaha brass float for this model ). Fuel Level set about 5 mm below the lip, thats as good as I could do, I could get higher by taking out the washer in the fuel valve assembly. 3 ) 2 new air filters. Genuine yamaha parts for this model. 4 ) Sprayed WD40 around the boots and no change in anything, sprayed it around carb and no change in anything ( the engine was on ) 5) Before I set the fuel level in the bowls, I was getting backfires on deceleration and shutoff. Now, thats cleared up. Started with the idle screws fully screwed in and backed them off, I did start to get backfires in the left exhaust. But with the screws full out there was an idle of 5k, i think that was just the engine getting fully warmed up though and the idle rising with it. Any ideas, Are these carbs just garbage ? Are there specific settings for the pilot air and fuel jets ? Mine are in all way, thats the way they were when I got them, should they be turned out a little or seated firmly. Is the choke circuit toast ? When I pull the choke out, rpm increases. I figured that was normal for a choke, I dont understand why enriching the mixture didnt slow it down. Is the hgh rpm due to a too rich mixture. Ive been assuming its lean as evidenced by the lean backfiring earlier. Do the idle screws need o-rings, mine dont have any ? Im very grateful for any contributions. Link to comment Share on other sites More sharing options...
Cy Welch Posted August 26, 2009 Share Posted August 26, 2009 You need to start out with the idle mixture screws out about 1 1/2 turns. Then slowly turn them out one carb at a time to highest idle speed (and then adjust the idle speed, there is a knob between the two carbs for that) then turn them down just a bit (it should be slightly lean but not too much). Lean idle will cause it to hang coming back to idle when warm, and if the idle speed is set too high (which it sounds like it is) the mixture screws will have little if any affect, so turn it down with the knob in between the carbs and work your way from there. These things can run very well and idle pretty smooth for a two cylinder with no counter shafts or other vibration reducing devices). I ended up with my mixture screws at about 5 turns out with our crap california gas, but the 80's are known (at least in the U.S.) as being way too lean in stock condition. Link to comment Share on other sites More sharing options...
duaneage Posted August 26, 2009 Share Posted August 26, 2009 Do the idle screws need o-rings, mine dont have any ? Im very grateful for any contributions. Yes. Go to cycle-orings.com and get one of his CV carb kits. It will have enough for 4 carbs but you only need 2. I used the same kit of orings on my carbs and they fit perfectly. If you don't have CV carbs ask the site owner if he has the o rings for yours. Link to comment Share on other sites More sharing options...
gazampa Posted August 27, 2009 Author Share Posted August 27, 2009 turn it down with the knob in between the carbs and work your way from there Oh, you mean the big screw, the really big one...the biggest one on the whole carb. Christ, I am such an amateur...Yeah, gave that a couple of turns and down came the RPM. What can I say, I like to think it was the fumes. Man, did that feel good though. Still have to tune it in properly but just to not have a screaming idle is really really satisfying right now. Jesus, it feels good. Thank You for that. I wish i could buy you a beer. And that goes to everyone who has helped so far. How does that screw work though, I saw that it pushes open the throttle valves, does that create greater vacuum to suck up more fuel from the bowl. And how come opening up the valves via the throttle on the handlebars increases the rpm. Whats goin on there, I can read up on the internet I suppose. Go to cycle-orings.com Thanks, will do. Link to comment Share on other sites More sharing options...
Cy Welch Posted August 29, 2009 Share Posted August 29, 2009 Oh, you mean the big screw, the really big one...the biggest one on the whole carb. Christ, I am such an amateur...Yeah, gave that a couple of turns and down came the RPM. What can I say, I like to think it was the fumes. Man, did that feel good though. Still have to tune it in properly but just to not have a screaming idle is really really satisfying right now. Jesus, it feels good. Thank You for that. I wish i could buy you a beer. And that goes to everyone who has helped so far. How does that screw work though, I saw that it pushes open the throttle valves, does that create greater vacuum to suck up more fuel from the bowl. And how come opening up the valves via the throttle on the handlebars increases the rpm. Whats goin on there, I can read up on the internet I suppose. That screw controls where the throttle plates sit when you release the throttle. To lower the idle your closing them more, to raise it your opening them. If the idle it too high, the mixture screws won't work right and you can't get the mixture set like it should be. When you get it right, it should idle real nice at 1200 RPM and nice and steady. Link to comment Share on other sites More sharing options...
gazampa Posted September 2, 2009 Author Share Posted September 2, 2009 put 50 miles on it over the weekend. Took it out for two runs of about 25 miles each. I may have missed the airshow ( through my own inexperience, not the bikes fault ) but I can still give it a ride downtown along michigan avenue amidst the skyscrapers and all that, along lower wacker to get the full amphitheater effect of the pipes and up along the north shore for a hint of the cafe racer feeling. Vrooom, Vrooom. The idles not perfect but it is a work in progress, its a little on the high side about 1400, Im new to this but i think im getting the hang of tuning it in and am working on getting it down to 1200. Link to comment Share on other sites More sharing options...
jrhendryx Posted September 7, 2009 Share Posted September 7, 2009 I've recently started adding a bit of seafoam to the gas with each fill-up, and a larger dose about once per month. I have noticed an improvement in the smoothness of my idle. I don't know if this is just wishful thinking, or something else, but it seems to be running slightly better. Link to comment Share on other sites More sharing options...
gazampa Posted September 29, 2009 Author Share Posted September 29, 2009 Ive been riding each weekend now since the one before labor day and using it during the week for short trips. It could still do with a bit of polishing but for now its running well. I've put about 800 miles on it and that includes one ride of a little over six hours last weekend on a medium hot day of about 70-80F which it handled well with no complaints. Its got something to say pretty much throughout the rpm range and pulls well from mid to high. The acceleration is not comparable to anything modern I imagine which is great from a safety point of view. I understand leaning out the mix can give it a bit more burst but at the cost of higher engine temperatures. Its hard to beat the sound that it makes, its very throaty. The gear box is a little tight sometimes going from second to third, could just be this bikes gear box, and it slips out of fifth into neutral sometimes which is not cool. My tachomoter is not smooth when its warmed up, it bounces around, it can jiggle around a range of about +-250 rpm. carbs probably need better balancing im guessing. The right side was always complaining, i found that the exhaust engine port was loose on that side ( it fell out, whoops ), but after getting it back in, there was a great improvement vis a vis starting. The o-rings on the idle screws helped big time. It was starting to get there and the o-rings pretty much got it there. On early rides, the sparks carboned up a bit and made starting very hard but after a little sanding and just riding the rpm a little higher, they cleaned up and are tanned. From a starting point of view, its starting really well without any problem at all. The temperatures have been a little chilly lately but it hasnt been having a problem. The current list of fix mes runs as follows. 1 ) Forks weeping on left side. 2 ) new brake pads. 3 ) new Front Tire. 4 ) vacuum balance carbs. Idle still needs a little nursing. Outside of that, a deep off frame clean and a frame repaint would go most of the rest of the way to a full restore. If I find a place for winter where I can work I might give it a try, falling short of that I'll just store it. The pipes are pitted from standing and should be replaced going the full restore route but they are not bad for general use and in good working condition. I might just take care of the fix mes and then maybe sell it on later, hopefully to someone who will take it the full way. As of now though I would call this xs400 resurrected. I wouldnt call it fully restored but its certainly up and about. Heres a quick vid, ill maybe post a better one in a bit, just noticed the kick was a bunny ho, not really for public consumption but there it is. Video Link to comment Share on other sites More sharing options...
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