Quick Intro, and usual Carb issues...

S

SteveH

XS400 Member
Messages
14
Reaction score
0
Points
1
Location
Del
Hello,
Great spot you have here ! I've been sucking down the bandwith for the past week or so :)
I picked up an '81 xs400 'Special' last weekend. I was told at that time that the PO could get the bike running- just real rough. He had put in a new battery, changed the oil, cleaned the carbs, new plugs, etc.
I brought it home, gave it the once over, and started it up. Started easily on full enrichment, but was only running on the RH cylinder. I checked all the usual suspects (spark, compression, etc), and it all boiled down to the carbs (Bike only has 2100mi on it...so they've been sitting.). Even though the PO rebuilt them not too long ago, there was still gunk and varnish, and the floats were way off. I also executed the sphinctor-testor step (Removal of EPA plugs over the pilot screws), and cleaned everything up as best I could.
Re-installed the carbs, and the bike fired right up on both cyls with full enrichment. About 5s later the idle climbed to 4k, so I went for 1/2 enrichment and the bike died. It will not start on 1/2 enrichment at all, and I was leery about it running at 4k for very long when cold.
So where Im at right now, is I need to get the O-rings on the pilot screws, as the ones in there now looked shot, but I tried to baby them. Are these a standard sized item, or am I going to have to order them ?
Also, where else should I start to look ? Think that the lack of the O-rings can be the sole cause of the crap running ?

Thanks !
Steve
 
Welcome to the forum. I still can't believe that there are 30 year old bikes out there with only a few thousand miles - nice find.

Regarding the idle problem, have you checked for air leaks?

Posted via Mobile
 
Thanks ! I did check for leaks and didn't find any. The carb mounts are new; and the intake manifolds look brand new as well.
I think I need to take another look at the floats...Just a gut feeling.
My game plan is is to try to find the O-rings locally tomorrow and see if that helps (I can do that with the carbs on the bike). If not, guess the carbs are coming off again.
 
That 4000rpm sounds like the vacuum hose to the fuel petcock..if you havn't checked that already. More than once Ive gotten into the carbs,put it all back together, and forgotton that little vacuum hose. Starts, runs alittle bit, revs up to about 4000rpms, then is hard to start.If your lucky thats all it is.
 
Thanks for the tip...But unfortunately this issue isn't that easy =(
I will check the hose though to assure there aren't any cracks/holes/leaks elsewhere.

-Steve
 
Thanks for the link !

So here's the update:
I picked up two spark plugs, and two O-rings (believe it or not, I was able to find some...). I went home and tore into the carbs - cleaning everything out again. I fitted the O-Rings and turned the pilot needle out 2.5 turns. I set the floats right about 25mm. Bolted everything up, and gave it a go...
Success ! The bike started immediately up on full enrichment, and then easily went down to 1/2. When the engine rev'd up on 1/2, I fully closed the enrichment and it idled fine. Took it for a quick ride around the block and noticed some hesitation and popping. So I did a high-rpm ride back to the garage and cut the ignition.
When I inspected the plugs, the LH side looks almost perfect; but the RH side looks very lean. I suppose this means I need to adjust the float on that side ?

Getting ever closer....

Thanks !
Steve
 
Also, some pics !

Here's how it looked the evening I picked it up:
IMG_00316.jpg


And now with the windshield removed; hanging out with its' new friends:
IMG_00318.jpg

IMG_00317.jpg

IMG_00319.jpg

IMG_00320.jpg
IMG_00321.jpg
 
Thanks !

I got the O-ring from True Value. The original measured 5.7mmx1mm. They have 1/4" O-rings which are close enough. $0.49/ea.
 
OK guys....
So today I went out to replace the tach and speedo cable. Of course, the ones dennis kirk sent me aren't the right ones. Crap.
I gave the idle pilot screw another 1/2 turn, so Im at 3.25 turns. Started it up - starts very easily. Let it warm and then put the mercury sticks to it. RH side is low, so I bring it up and the bike is idling nicely. Decide to take it for a quick spin, and instantly when I give it gas the I have hesitation. I open the throttle and nothing happens for a second or two, then the motor catches up. I then notice that it hangs at about 3k rpm for a couple of seconds, then will fall back into the idle.
It starts easy, idles fine - but hangs at around 3k before settling back down. I let it cool, and again starts fine, etc - but the same issue.
I gave it another good high speed run, and the plugs look ok - but the RH side is still leaner than the left. The carb mounts are new, the intake runners (between the carbs and airfilters) are new. New airfilters (stock), stock exhaust. The only thing left would be to replace the vac line from the RH cylinder to the petcock. I guess I'll try that tomorrow. Any other suggestions ? Maybe the float is off ? This will be the 7th time the carbs have been off in as many days....
 
Some misinformation in my previous posts. The 1/4" O-ring at truevalue will NOT work. When I took the carbs apart today, I noticed that it never really seated at the bottom of the carb. On a good note, it seems as if in one of the Harbor Freight O-ring sets they have what we need ($5.99 for the kit). They have it listed as size 'P3': 5.5mm OD.I'll pick some of these up and try them out tomorrow.

That said, I checked the floats today using the clear tube method, and both floats were right where they should be (fuel height about 1mm below the seam). I tore down the carbs, discovered the O-ring issue, and blasted them again with the compressor.

I hope this will be the last time they're gonna have to come back off...
 
Ah yes, also forgot to mention that I picked up new Vac line for the petcock -> carb holder.
 

Similar threads

A
1980 XS400 Special, jet issues.
Replies
2
Views
513
Archilles
A
Mjerrold
Help...anyone?! Carb identification & general chaos...
Replies
12
Views
1K
gpounce32768
G
E
78 XS 400 2E won't start!
Replies
6
Views
470
Ed Dunham
E
G
'82 Seca 400 hard starting when cold
Replies
6
Views
622
gpounce32768
G
E
Sparkplugs- What is everyone using?
Replies
3
Views
341
Ed Dunham
E
Back
Top