New xs400 problems.

[Onetype]

Thanks for the tip and the link, I still havent had the time to read it all. I think im going to boil them in lemon juice and go from there. Will this require rebuild kits?

It seems my petcock is giving me problems as well, I can only get it to flow gas on reserve but its not really flowing very well. I pulled it apart and blew air through it all and theres nothing blocking it or anything so im kinda stumped. My main goal for this bike was to keep it cheap so im hoping I can still use it before throwing down the cash for a manual one.

I was however able to make a seat for it and swap the brake light guts into the turn signal housing for a tail light. Its starting to look more rideable haha.

 

[Onetype]

Boiled the carbs last night in lemon juice. It turns out my pilot jets were completely plugged up. Put it all back together this morning and it will now run without the choke, I can also rev it. I cannot however get it to run without holding the throttle open (It did idle with the idle screw all the way in). So we rode it up the street twice and when you give it gas it kinda doesnt respond and then suddenly it will jump up and start hauling. On the last trial run you couldnt give it any gas in gear to really get it going even when I opened up the throttle all the way, it just didnt respond. Now I know I need to go up in jets which Im going to order an assortment tonight. Would this be a symptom of the carbs still not being clean enough? I mean we tore them all the way down and took everything apart.

 

[XSLeo]

When you say idle screw, do you mean idle speed or idle mix? If idle mix then thats why it won't idle well. You need to set the mix screws to whatever you year carbs spec is.
It sounds like the idle passage ways ae till blocked.
Clean them more. Their are very small passages in the carb body. Remove the idle mix screws, spray carb cleaner in there. It shoud come out into the float bowl and two or three small holes by the throttle plates.
Spray carb cleaner then blow through with air.
Leo

 

[Onetype]

Sorry, im still learning about the carbs. I meant the idle speed. What i would assume are the idle mixture screws are set at 3.5 turns. Im boiling them again and still see a bunch of crud coming out so i guess they didnt get as clean as i thought. Im taking them to a buddies house to use his air compressor.

 

[Onetype]

Well I boiled the carbs for like the 5th time last night, I think I may have found the issue. The air jets for the mains are clogged. I shot some air and carb cleaner into them and it just shot right back out at me. How do I clean them? It seems boiling isnt working.

 

[drewpy]

ultrasonics will clean them

 

[Onetype]

Ok, cleaned them out as much as I could with a piece of small copper wire (it seems the air passage is super tiny, when I tried to double up on wires it wouldnt go through, is this correct?) Pulled the emulsion tubes (didnt know about these until now), threw them in some boiling water with the carbs again, shot out all the passages with carb cleaner, new o-rings/washers on the mixture screws, new carb boots, new spark plugs , went 2 sizes up on the jets.

I've cleaned the carbs probably like 10 times now, maybe more. I can't possibly imagine this could still be the issue but as im still new to this im not sure. I started it up and everything sounded good so I rode it up the street and it died on me and wouldnt start back up. It did sorta start on full choke but died once I started giving it gas. The closer I got towards the top of my street the less/longer it took to respond when I gave it gas . It still has some hesitating when you give it throttle. Floats are set at 26 and the mixture screws are 2 turns out right now.

This was the first start on the new plugs, left one is already almost completely black and the right one still looks good. The last time I ran it before all the stuff above, it died on me and when I pulled the plugs both were fouled. I would say I maybe got 7-8 starts/rides out of those, and thats just up and down the street. Im sorta confused as I thought the pod filters and open exhaust would lean it out. It seems its still running too rich, at least on the left side. Any ideas, im stumped.

 

[XSLeo]

This is for the XS650 carbs but the xs400 carbs are very simular. www.amckayltd.com/carbguide.pdf It explains trouble shooting your carbs and how to tune them.
Leo

 

[Onetype]

Thanks for that link, that will definately help. I realize part of the problem is they do need to be tuned before I ride it and thats my fault but its sooo hard not to want to just hop on and take off haha. I did get quite a few compliments as I was pushing it back down the hill to my house though .

 

[XS-Time]

Your on the right track. Keep reading all the info you can find and clean, clean, clean.
Most people are scared of carbs so you are already ahead of the game. Just a couple of thougts though. Don't use metal wire when cleaning the jets. You don't want to scratch the inside. It should be ok for the passages though. Also check the rubber on the CV slides. An air leak here cause problems. There are "o" rings on either side of the butter fly valves. Most carb kits don't come with them but I think you can get them from Sirusonic ( however I can't seem to find there website right now ?). Also how badly cracked are your carb boots?
The bike is looking good. I like the stretch. Also putting the indicator lights in the switch housing is brilliant.

 

[Onetype]

Thankyou sir for the kind words, I may end up putting the leds in the drag bars between the mounts at some point and ditch the housing. As for the stretch its definately cool because its a bit different but I still dig the hardtails. I have another 400 on the side of my house that may go that route. Its frustrating when you get this close... I've been through these things sooo many times now, i've double checked and tripple checked everything. I can take apart these things in my sleep. All the jets are new except the air jets in the front and the needle jets. Can you get the air jets in bigger sizes? The slides are good, I held the vent and they drop slowly as they should. The carb boots are brand new. I haven't replaced the butterfly seals and now that you mention it I thought I did see some fuel spray out of the clips once, I didnt really think anything of it at the time. It seems everytime I clean them the bike will run real good and then it dies and I have to repeat. Obviously I still have some experimenting when it comes to jet sizes so I will update every now and then. Heres some recent pics, I saw a super clean silver vette and got inspired. Most of the rear has been done in black appliance epoxy and the tins are stainless steel appliance epoxy. Also cleaned up some wiring and moved the ignition.

 

[XS-Time]

I'm thinking that your worried about the jet size too much right now. You have replaced the air filters and exhaust only. They will require a change in jet size but I don't think it should cause the problems you are describing. ( I could be wrong though and encourage more input)
The problems shouldn't change during a ride. You might want to start out back on square one. We are working on certan assumptions right now. Compression good, Valves adjusted properly, Coil and wires good, Fuel in tank, Vaccume caps on carb boots, Petcock not leaking, No rust in tank, Floats adjusted properly and not leaking, Ect.
Go back and recheck everything. I have seen people trying to find an electical problem when the kill switch was set to off. It's the simple stuff that gives us the most problems. Don't assume anything. Keep trying and you will get it.

 

[Onetype]

Well im not sure if this has anything to do with it but I ordered 142.5/145 main jets and 45/47.5 pilot. I had the 145 main in with what I thought was the 47.5 pilot but was actually the smaller one. Switched it out and it ran ALOT better, actually idled this time and I didnt get any noticeable surging. Maybe its not the whole problem but it seems I am getting closer. I feel like an idiot for pointing this out but I honestly havent checked the valve clearances, timing or compression. In my head, i've been stuck on the carbs as the issue. Plus I wasnt planning on it starting the first time it did and kinda got sidetracked when it did. Checked the carb boots for leaks and none showed up so im good there. As for the rust, there are spots in the tank but compared to other tanks i've seen I didnt think it looked bad.

 

[lhaolpa]

Mine is a '82 Dt400rj seca,and has 127/117 mains and I think 45 pilots.That should be close to stock on most of these bikes.Enriching the jets is sometimes necessary when modifying the intake and/or exhaust,but should be done at a moderate scale[one size or two at a time],then ran a bit and checked by plug condition,not just guessing.I'm not saying that's what you did,but you've got a big difference from stock.Just my $0.02. lha

 

[kindest]

Well im not sure if this has anything to do with it but I ordered 142.5/145 main jets and 45/47.5 pilot. I had the 145 main in with what I thought was the 47.5 pilot but was actually the smaller one. Switched it out and it ran ALOT better, actually idled this time and I didnt get any noticeable surging. Maybe its not the whole problem but it seems I am getting closer. I feel like an idiot for pointing this out but I honestly havent checked the valve clearances, timing or compression. In my head, i've been stuck on the carbs as the issue. Plus I wasnt planning on it starting the first time it did and kinda got sidetracked when it did. Checked the carb boots for leaks and none showed up so im good there. As for the rust, there are spots in the tank but compared to other tanks i've seen I didnt think it looked bad.

if you have an electronic ignition then your not supposed to mess with the timing so you can cross that off the list. The haynes manual I have says that it should be trouble free and I should never have to mess with the TCI system and that "regular timing adjustments aren't needed". you will know if its electronic if you have plugs instead of screws holding the timing plate on on the left side above the spark plug.

 

[XS-Time]

Well if the PO adjusted the valves to tight the engine would run fine till it heated up then after everything expanded the valves would not close compleatly and it would not run good at all. I was asking about rust in the tank because you don't want the fuel to bring rust from the tank to your newly cleaned carbs and clogg up your jets. An inline fuel filter is pretty well a must at this point. Also you said" the slides are good, you held the vent and they dropped slowly like they should." I`m not sure I understand. When you apply vaccume the slide should stay up and not drop. Increasing vaccume should open up the slides more.

 

[lhaolpa]

Mis-adjusted valves would allow vacuum to be lost through leaking valves,and if allowed to continue,will burn the valves.You will then have to replace the valves,seats,etc. It's much easier to check/adjust them than to replace burned ones.If you have adjusters,it's fairly simple to reset them,otherwise you have to mess with adjusting shims,a little more difficult in that you have to remove more. lha

 

[Onetype]

I wasnt sure what type of ignition I have, My cover definately looks like yours but in the recessed hole I have a flat head screw. So im assuming someone has been in there before. Honestly how hard is it to check the valves? Im worried I could mess something up in the process since i've never done it before. Anyone have a link to a tutorial, that would definately make me feel better before tearing into the motor. I've had an inline filter on it for a while now and when I pulled out the petcock the filter on it was still real clean. As for the slides this is what I did to determine they were good.

Slide diaphragm function can be tested as follows. If carb top screws were removed
above, reinstall them. Then look at the backs of the carburetors. At the top of each
intake bell there is a curved hole which opens into the chamber below the diaphragm,
exposing it to atmosphere. If you raise a slide, cover the port firmly with a thumb, then
release the slide, it should fall very slowly. If it falls quickly, the diaphragm is breached,
and the slide/diaphragm assembly must be replaced.

Heres a video of my twin brother starting it right before thanksgiving, this was the first time we were able to actually give it throttle.

 

[drewpy]

still sounds too weak that's where your getting spitting back.

your running pods and open exhaust go for a 50 pilot and leave the mains alone as your not getting that far up the rev range to bring them in.

I'm assuming the float level is correct? you could lower it a mm to richen the whole range!

 

[Onetype]

Thankyou all for your insight so far, I love this site and the vast amount of knowledge you guys have. I have another xs400 that will need quite a bit of work to bring it back so I may start a new thread at some point for that one.

I will try the 50's next, I was going to order them the first time but I hear every bike is different so I wanted to work my way up if needed. The floats are set at 26 right now from the gasket.