bralkan

Had to, go out of town. I messed with the floats again today and bam! She lives! Thanks so much for the help. I do have another question... W The rear brake (drum) likes to catch really bad. When I press the pedal it doesn't engage immediately and then it will catch causing the wheel to lock. If I depress and repress the pedal it works normally. Once I travel the brake will catch again. Can this be renewed or otherwise fixed?

I had a 750 for awhile. Fun bike!

Never would have thought vice grips would work, but it did the trick. Thanks! Thankfully, I have some screws from a set of donor carbs. I should be 3 turns out on the pilot mix. I'll double check. Unless both of the pilot screws broke at the same place they should be ok. One I had renewed awhile ago (it was missing!), so I think the are good. Spray bars (also called needle jet?) are being soaked in Chemtool right now. The bar on the left in the pic was in the left carb (looking forward). Pretty nasty. Also, on the floats - where should the tang be when the carbs are upside down? Fully depressing the float needle? Sitting just above?

Ok! I lowered the floats. I first tried 26mm but my left (looking forward) carb was leaking fuel out of the air inlet. I raised it to around 28mm and it seemed to do ok on the center stand. It will now idle off choke. There are still some issues, however. Once warm, if I blip over 4k rpm it is still sticking at 4krpm. I was unable to clean the spray bar - there are 3 screws stripped on one hat and 1 screw stripped on the other. I don't have a lot of experience drilling out screws, particularly ones on a part that isn't easily replaceable. I may see if I can get a local shop to remove them for me. I am getting backfire (exhaust) and the pops in the carbs when off the enrichener. Off enrichener, the throttle response is a bit sluggish on the low end though it may have gotten slightly better once warmed up. I have a video below... http://dl.dropbox.com/u/12150479/20120102_081140.mp4

Thanks! I'll clean the spray bar and adjust the floats and report back!

Not that I know of. Where is this located? I didn't see it mentioned on my diagrams. This was one of the first things I adjusted. When I started messing with the bike, I pulled it with a lawn mower and noticed that fuel would spit out the intake side of the carb. I took the float bowls off and "raised" the floats to ~32mm from the top of the float to the carb body. I thought that was spec? If its 26mm, I would need to lower them. Could this cause the pilot circuit to be starved of fuel? I'll renew these if nothing else above seems to be it! I have the brass floats. I am running stock airboxes at the moment, although the original air filter element has been removed and it is a sketchy piece of foam in its place. Thanks Drewpy! I remember you when I first started posting here 2 years ago. Thanks once again for the help.

I've combed the forum for topics that address the issue and made some progress, but I'm at my wits end. I have replaced the intake boots / gasket. I have pulled main jets, pilot jets, pilot screw, starter jet (Air inlet) and soaked in carb cleaner. I have replaced the rubber o ring, metal oring, and spring on the pilot screw. I upped the pilot jets to 47.5 from the 42.5 (I was going to go to 45 but I seemed to have lost one....). Main jets are still stock (135 I think). Now, the issue. About 2 years ago the bike started doing the "Stick at 4k RPM" issue. I let it sit for awhile and finally started looking at it again. What is it doing now? After tinkering with it I have it starting rather quick on full enrichener. If I blip the throttle after it is warm and I blip it over 4k, it will stick at 4k RPM. If I ride and load the bike to get it below 4k rpm, it will idle at 1.2k (Full choke/enrichener). If I get it over 4k RPM and turn off the enrichener I can keep the bike running. If I turn the enrichener off and let it drop to 3-4k RPM, it will stall and die. From what I understand, this is an issue with the pilot screw / pilot circuit. However, I have soaked and cleaned and soaked again. If I spray carb cleaner into the pilot jet housing (with jet removed), it will spray straight out of the hole at the outlet to the manifold (where the pilot screw rests). The spark plugs are grey. I'm not sure what else to do at this point.... right now the Pilot screws are at 2.5 or 3 turns out (I forget at the moment). Increase the pilot jets again? Back the pilot screw out more? Any ideas / help is greatly appreciated!

I would definitely look at the voltage regulator / rectifier. It was causing my bike not to recharge.

Picked up an 80s Suzuki with mikunis just like my xs400. Anyways, two carbs have pilot jets snapped off inside. Any suggestions for getting them out?

Yep, I just used a little jeweler's screwdriver.

Alright, well I upped the pilot jets. Still getting stuck at 4k. =( any other ideas?

Well, I finally got some time off work to mess with the bike. Its still sticking at 4k rpms with the new jets and adjustments. Diaphragm maybe?

If its like mine, your pilot jet(s) are blocked and your floats are set wrong.

Unplug the starter motor's positive cable from the solenoid and touch it to the battery. It will turn the motor if its not dead. Does the solenoid click when you hit the starter? It should if its in working order.

Helps to have gas Its still sticking at around 4k when on and still having some problems getting it to come off the choke. I think it had better luck on the 145s than the 135s. I will try going back to those this weekend while I wait for 140s to come in. I also need to replace the throttle cable - anyone have clubmans and know the length they used? The stock length is a little long. Same for the front break cable.

Well, messed with the floats and its running and doesn't die on throttle. I put the 147 size mains in, but I need to pull the plugs and see how they look. I had moved up from 135s which where lean... I had the bike running on choke and off, but later in the night I couldn't get it going again. Like I said, need to pull the plugs and look at those. Should I need to do anything to the pilot jets? Clean them again? Just go to a more reasonable main jet (137.5?).

I've got a 76 XS750. It only need the stator wires reconnected after a bad batt leaked fluid on them and they snapped in half. Other than that, it runs great. Don't have to much technical knowledge though on it, as nothing has needed to be fixed.

So I am retarded - what do I bend to adjust the float height? I just want to be sure before I go bending metal

I have the 1980 carbs, so I think its a non-adjustable needle. I will try the washers.

I did pull the plugs and they where not wet at all. They are colored from running previously so I am not sure if its lean or rich or whatnot. I need to go pick up a clean pair. They are sparking though, checked that. Gapped and all. It has to be something fuel related. I will check the floats. What should I do about the jets? Go back to the 135s until I can get 137.5s or 140s? Or go ahead and use 145s? Thanks again Drewpy.

Alrighty... So, got some chopping and painting done. I put the carbs and filters back on and tried to get it going. Well, no go. I got a few put puts but nothing staying on. Took carbs off and decided it was time to mess with the jets. I took the bowls off and looked around. The main jets (center shaft; adjacent to a shaft with a rubber plug and what looks like the pilot jet underneith) where 135s. Hmm, supposed to be 142. Shit. I orded 145s and 147.5s. Guess it serves me for ordering jets without seeing what is really in there. Anyways, I put the 145s in and put the carbs back on. This time I left the air filters off (new, pod filters). Success! She runs....but, once I give her any throttle she quits. Won't start off full choke. Do I just need to bump down the main jets to 140s or so? Could it be anything else in the carbs? Fuel mix screws (top of carbs, close to engine) wrong? Starter jets? (these looked dirty). Try and find an ultrasonic cleaner and take the whole bloody carbs apart?

So, I know a lot of this has been posted in various threads but I want to try and collect it all so I make sure I do this right. I put clubman's on and I like the sit. However, it feels like they might be vibrating more. Any suggestions? Heavier weights in the bar? Carbs - the last place I was at with these: I was adjusting the mixture screws (idle or fuel? I think I've seen it called both?? Anyways, mix screw on engine side, top of carbs). Well, I loosened one to much and I can't find it. I ordered a new one from mikexs. I also ordered 145 and 147.5 jets; as well as larger pilots just in case. Why bigger jets? Well, I want to go to pods so I can try and get rid of the battery box. But I know there are / have a few issues. Will I need anything to support the carbs with the stock airboxes no longer "holding" them? I bought the cheapo EMGO filters. Apparently, the lip on these can get in the way of the main jet. Anyone here have any experience with these? Also, looking at MikeXS I see they have K&N style pods for the XS650 BS34 carbs. Should these be safe for my BS34? I only ask because on MikeXS they are sized at 52mm and the EMGOs are sized at 48mm. I will mention, these EMGOs are a pain in the A$$ to get on. I barely got them on the carbs off the bike. No idea how I would get them on with the carbs on the bike. Removing the battery box - I understand that the XS has to have a power supply to power the magnet to generate electricity. But how small of a battery can I go to? I've seen mention of car alarm batteries - will the lower Ah be ok? Stock XS is 12Ah? I found one that might fit, but its only rated at 7Ah. Anyone actually try it? Thats all I can think of for now. Thanks in advance.

I had a similar problem. Smoke all out of the exhaust port on the head. It turned out to be bad valve seals. Just replace those. My valve springs where a bitch to get off, but it isn't a bad job. The valve cover is only sealed with liquid gasket. It was the later year XS (post 83?) that had a valve cover gasket.

make sure there is a house coming from the top of the petcock to the inlet boot of the engine. The petcocks on the xs400 are vacuum. Meaning, that as the piston moves up and down it creates the pressure (via the hose from the inlets to the petcock) needed to drain fuel out of the tank and into the carbs. There is on - normal vacuum. RES - normal vacuum, however the fuel comes from a lower position in the tank. PRI is for "prime". This is free flow. Used to refill the carbs after working on them.

This is the place to be, for sure. Over a year drewps and others helped me get my $200 rat bike running. Its turning into a cafe racer this winter as well. Doing similar things - dropping the bat box, new bars and a fairing. I am going to try the 12v car alarm bat in the elec. starter housing to drop the full battery. We'll see how it goes!