bswinn

Okay...my bike is the magical mystery bike. It's a walking contradiction. That or I know nothing about what i'm doing. I adjusted the idle speed screw to JUST on the verge of stalling the bike. That means it's either tacking at 3000 or stalling. I assume that this means that the butterfly valves are only SLIGHTLY open so the bike will actually run. The idle mixture screws are anywhere from 4.5 to 6 turns out. They started at 3 when I first started this thread. The bike is STILL running at 3000 RPM and the plugs are carbon fouled (light powdery black coating) after running in idle fro 10 to 15 minutes. I've searched and this means that the carbs are running too rich correct? So I'm at a loss now. The idle mixture screws being turned anticlockwise make the mixture richer (more gas)? If this is the case then I must have to go the opposite right? Screw them clockwise to make the mixture leaner? But wont this cause the RPM's to go up?

Thanx guys. I'm gonna head out and adjust those mixture screws right now and see what happens. If they ever successfully clone a human being I'm gonna make sure they clone Drewpy so I can have my own copy here at home whenever I run into an issue

Alright I hate to beat a dead horse....and by dead....I mean nothing left but bones since all the flesh is LONG gone. It's just that I've spent HOURS reading through these forums about carb issues/information and can't seem to nail down what I need to know. The bike. 1977 XS400D. The carbs. Mikuni BS32 I think. The issue. Cold bike, pull the slide choke or enricher or whatever all the way out. Start bike. Revs spike and then slide the choke in half way and revs go down and then spike again. Choke is all the way in now and revs seem to be okay around 1500. Take the bike on the road and hit a stop light. Revs hold steady at 3000+. The only way I can get them down is to hold the brake and let the clutch out and bog the engine down. It'll stay at 1500 for a bit but then shoots back up to 3000+. What I've tried. Adjusting the idle speed screw that lies between the carbs. This doesn't seem to do squat. The idle mixture screws are out about 1.5 to 2 turns. Balancing doesn't seem to work at all. When I think it's balanced and I rev up the engine the balance is WAY off and wont go back even at a steady idle. What I've read. If the idle mixture screws are making the mixture too lean it can cause a high rev. If this is the case is there some way of adjusting the mixture screws so that they are at a good level? Broken carb holder boots can cause a bad idle. But I have brand new gaskets and boots on it so I doubt it's this. Lack of a good filter (letting too much air through) can cause a high idle. If I decide to put new filters on then I would have to buy pods and rejet the carbs. Does anyone know the correct jet sizes for a poded carburator on this bike? Could this also be due to bad float levels? I adjusted them to what is in the haynes manual, but the manual contradicts itself with two levels. Does anyone know the correct float level and where exactly it's measured from? I know these issues have been hammered to death and I apologize for making yet another post about this. But it's riding season and this is the last thing I need to get done on the bike. I have the bike out and running but I know the carbs aren't adjusted correctly. Any help would be greatly appreciated.

I'm not sure if it ran like this before. Like I said earlier the guy I bought it off never got it running. The guy he bought it off said that it ran but was unable to get it started when the trade was made. I examined the cylinder head and it's mating surface for flatness and it's flat to with a .001" I just finished building the engine back up with the old gaskets I rebuilt it with (yeah I know you shouldn't do that but hear me out)just to do a leak down test. Was able to make a tester. They're so easy to make I don't know why anyone would bother spending $60 on one. Anyways...I found only 10% leakdown. Everywhere I've read says that this is right in the good range. I listened VERY closely to any place where air could escape. The only thing I found was an EXTREMELY small amount of air coming out of an exhaust port. I swear I bought the magic bike and it's performing a magic trick on me with this oil leak.

I don't know if it was sucking in oil before I dismantled the engine. I checked the ring end gaps. They were slightly larger, about .005" larger, but that shouldn't lead to the amount of oil in the pistons. Cylinder bores are in spec, valve guide diameter are in spec, valve stem diameter is in spec, nothing is loose. The only thing I've seen that could result in the amount of oil was the oil on the head gasket. But I checked the head and cylinder housing mating surface and they are at a maximum of .001" out of true flat. I torqued the cylinder bolts to spec so I have no idea how this is happening. Should I torque the nuts down slightly tighter? I guess it could have been valve stem guide oil seals but they were super tight on the guides and on the valve stems. When I took them off I inspected them and they looked in good working order.

Alright, been lagging behind on what I thought I'd get done. Here are some images I've taken of something I've found. Imageshack link to photos. I hope that link works. If not just let me know. So one exhaust port is soaked with oil, while the other is dry but is quite charred. Now remember the bike has probably only run about 30 minutes and before that it was cleaned out thoroughly. There are little pools of oil around the valve guides but I can't be sure that's not just from having to move the head around to get the valves out. I haven't checked the seals or the guide tolerances yet. What I found the most interesting was the amount of oil that made it's way between the cylinder head and the head gasket. So much so that it got up to the metal part of the gasket. Does this mean that the cylinders are sucking in oil through the gasket? That would be pretty shitty right? Warped head? Any advice based on the images?

Well since I had the Cylinder housing off the bike I had the guys at work check it for me and it's hardly worn at all. When I get home I'm checking the rings. Fairly certain they aren't upside down or in the wrong order but ya never know. Also gonna check the gaps and make sure those are right too. I believe the breather is fine. I know it's not plugged in actual crank case. I'll check the breather tube that goes up to he carbs but I believe that to be clean. Maybe the hole in the breather gasket was installed poorly? It's a solid square of a gasket with a rectangle cut out near one edge. Should that be closest to the actual hole in the crank case, or further away in case of oil being flung up? I would install new rings in a hearbeat, but I can't seem to find the stock size. All I appear to find are the oversize rings. And those go from the cheapest at $20 a set up to $50. I'll be checking the valve stems, valve guides, and valve guide seals tonight along with the rings and let ya'll know what I find. I really do appreciate all the replies to this thread. It's helped out a lot.

Alright, took the engine out of the motorcycle and disassembled the top half. Took the valve cover off and it looked good. Took the cylinder head off and found what I considered substantial pooling of oil on the top of the pistons. The piston walls were also wet with oil. Wetter than I imagine they should be. The vertical distance between the piston rings was also substantially wet with oil. In my last hopes how do I check to see if it's bad valve stem guide oil seals? Also, is there a good way of measuring the inner diameter of the piston sleeves? I personally don't have an internal micrometer. I could possibly find one at the machine shop I work above but it's no guarantee. Could this oil that appears to be leaking from between the piston and piston sleeve be due to the fact that I didn't hone the piston sleeve? Would a smooth internal surface really cause this much oil to leak?

Well the right hand side muffler gets AWFULLY hot for it NOT to be firing. Perhaps it's not firing ALL the time? I did notice that the right hand muffler is quite a bit quieter then the left hand muffler.

I just got home and checked. It's in fact a 20W50 motor oil. So motor oil could foul up the clutch huh? What's so different about a motorcycle oil? The engine never ran for the previous owner. He was a fellow college student who didn't have the time or patience to put into the motorcycle. So I have no way of knowing how the engine ran before it was broken down and reassembled. I pulled the plugs and found wet standing dark oil on the right hand plug, and the left hand plug while dry looked like it had some pretty decent build up after only running for like 15 minutes and they are brand new plugs. More and more it's looking like I'm going to have to pull the engine and rip apart the top end to find the source I guess.

I can't remember off the top of my head, not at home to look at the bottle, but it's whatever is recommended in the Haynes manual. I think it might be 10W40 or something. I bought it at the local auto parts store just based off the recommended weight. Is there something specific that I should be using?

Oh...one more piece of info that might help. If the engine is cold and I start it up there is no smoke and it's running fine. Once the engine starts to warm up is when the smoke starts appearing. Once the engine is at running them the smoke is at it's worse. And in addition once it's hot the idle jumps form around 1000-1500 RPM all the way up to 4500 RPM.

I know I didn't mix up the pistons and rings. I only did one at a time. I can't say with 100% certainty I didn't mix up the pistons to bores. Would it make that BIG of a difference? I guess it could be the valve guide seals, but they were brand new.

Greetings and salutations to everyone!!! Alright, to the quick and dirty. Posted a couple questions a number of months ago when I started the rebuild of my '77 XS400D. Over the past year or so I tore the thing down to all it's bits and pieces. Cleaned it all up, repainted it...unfortunately a rattle can was all I could afford, and rebuilt it with mostly original parts. I FINALLY got the thing started this morning and as far as I can tell it's running top notch except for a high idle which I think I can fix with a carb adjustment. Now to my problem. As soon as it started there appeared some blue smoke in the left side exhaust. I thought not to worry since there is oil in the cylinders from lubing them up to slide the pistons in. After a couple of 3-5 minute start up cycles the right hand exhaust shows the same amount of blue smoke. It doesn't appear to be going away. So my question is this...after tearing the engine down, cleaning it, reinstalling the original rings, pistons, etc. will there be a break in period where the rings have to seat themselves in the sleeves? Is this the reason for the blue smoke? If this is due to a break in period how long before I should see the smoke go away? I know the worst case scenarios would be bad rings, worn out sleeves, bad or over worn valve stem guides, and/or a bad gasket somewhere. I'm crossing my fingers this isn't the cause because I DO NOT want to have to tear my baby apart again. Nor do I want to go through the process or re-boring, honing, finding new rings, or replacing a valve stem guide. So please tell me it's a break in period....but please don't lie to me to make me feel better either I eagerly away anyones advice.

Hello all. A quick question for those in the know on xs400's. I'm in the process of stripping down, cleaning, and rebuilding the engine on my xs400 and I want to make sure I haven't done the ole switcheroo on my rocker arms. Each rocker arm has a number stamped on it's side. It looks to be 14 degrees and 15 degrees but i'm not certain. The odd thing is that it looks like both 15's are on one cylinder, and the 14's are on the other cylinder. This just seems odd to me and I figured that there would be one of each per cylinder. So if anyone has seen this could you let me know if this is normal or if I switched them?