Ok so the deal is I got this xs400gs 79 a month ago and it didn't run at all so I ripped it down and rebuilt it everything except the crankcase then when I put it back together it ran but very rugh. I got to the timing part of the rebuild and just kept messing with it untill it ran good whitch was as far as the electirc timing unit gose clockwise. Now the bike is running really good at this point but then I get my hands on a strobe the timing is way off so I put it where its suppost to be (the LF Mark) it pops and studers and dies and won't start unless I have the choke on all the way then revs out to about 6000rpms so at this point I'm thinking I put the cam shaft on wrong or somthing. Anyone ever have this Issue before I've ripped the ting apart like ten times and cant finger it out thanks in advance
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bike only runs when timing is way off
- Thread starter ryan
- Start date
2eightcustoms
XS400 Enthusiast
any chance your cam chain is a tooth off?
No way it's a tooth off I went in there like 3 times and went a little bit both ways and it only runs when I have it as centered as possible and it runs the best. What would be the chance of something being bad with the carbs or the timing unit not being made for the bike this bike has been picked at by people that don't know anything about bikes that went out and got one of them hanse manuals
DARKMIDKNIGHTWARRIOR
XS400 Addict
Are the coil wires going to the right plugs?
What he is saying is, there is a large contingent of XS400 owners, who have put the coils on backwards
He meant that under the fuel tank, is both of your coils. there is a chance that the orange and red striped wires got connected to the opposite connector, making the bike need to be as you said, Because it runs really good when the timings off. unqoute
The difference is that there is one grey wire going to one, and a Orange going to the other. I will take a look at that since I have access to those wires, and post something in an hour or so.
At one point my cam was off a tooth, and my points were too worn to spark correctly AND my idle mixture screw was broken at the second taper and stuck in the carb body, so it only ran on one cylinder I would check all those thing, ohm out your coils, make sure your gettin power everywhere. I replaced my condenser and rectifier before my spark issue was resolved.
Would a bad valve do this because when it's set to the book it sounds a lot more deep on the left cylender then the right and when I synce it theres sorta low vacuum like my gages read in the read area but I have changed the rings and checked the boots I don't have acsess to a compression test gage and my electric starter is not usable untill I change the starter clutch
The fuel mixture takes time to burn. The faster the engine is revving, the sooner the spark has to fire to achieve maximum cylinder pressure to push the piston down before the exhaust valve opens. Basic Engine theory 101... 
I know you said you checked 3 times but seems to me the cam chain is a tooth off.this is the only way your bike would run with timing out of tune so bad.Its kinda like when you stick the distributor on an old school 350If the timing mark isnt lined up just right when you stab the distributor in you can advance the timing way off and the engine will run good.Then if you bring number cylinder up to tdc and stab the dis in to where the rotor is pointing exactly at number 1 the engine can be timed properly.I dont personaly have any experience with lining up the chain gear on these bikes but have read if you get them off its extremely difficult to line them back on properly.So either the cam or cam gear is off.
Ok I'll ceck again and I just want to make sure that at the LT mark has to line up and the cam shaft pin has to be at 12 o clock from the engine serfece. Also is there supost to be a gasket on the valve cover I don't think there is but just wanted to make sure
Posting Pics, I click on "Go Advanced", then in the middle of all those buttons, is a paperclip icon, with an arrow next to to it. (manage attachments) Remember any pic greater than 3 megs will processes down to a meg or so (something like that) and if you are using large images, only select 3, instead of using all 5 spaces for 5 photos. It will time out while processing, then you didn't post any pics. do 3 to 4 a shot, and once you get a feel for it, go crazy, create a photo album, I stage a lot of my photos on the photo album for consideration of what the heck I am doing. Then those who are interested to see it, can click it. where in here, everyone can see a glimpse of it, and its easier to click on, (one less or so click-age)
