Wont start!

[Junkyard Johnny]

Well, I've got more n a couple hours trying to find the source of my problems online. Bike problems that is. I have a 77 I picked up for a descent price. It was basically just the engine in the frame which is what I was looking for. Ive been putting this off as far as I can go. I have compression spark and fuel, but still wont start. Ive gone through the battery probably 6 times and have kicked till im sore. Once in while itll pop through the carbs and sometimes itll pop through the pipes, but thats it. I currently have the carbs off and apart. It has a 122.5 main and I think it was a 145 pilot if that sounds right??? Ive searched averywhere for an answer. I cant seem to find what the stock jetting was so I at least have a place to start. Ive looked at all the tuning guides, but they arent doing me much good if I dont have something to base off of. Any help would be appreciated!

 

[grepper]

Pilot would be 25. See the carb guides and info http://www.xs650.com/forum/showthread.php?t=43

May be ignition timing. Once I had the ATU loose it's pin, bike would fire irregularly, pulled the little chrome cover off the left side and saw my advance unit was spinning.

 

[Junkyard Johnny]

Ill have to get some jets and see if Thats my problem. I hooked up a timing light and just cranked it over. Right side seems a bit erratic but nothing that would prevent it from starting. Left side is on, so I dont think timing is my issue. I set the timing chain tension and set the valves. I guess we'll see.

 

[FrkyMnky]

If you think its the carbs, pull them off and use a gas soaked rag or started fluid over the intake. If it pops off then it is the carbs. If that doesn't work, start pulling the spark plugs or get a plug light to tell you if it is firing. If your getting fuel and spark then your not getting them at the right time and your timing is jacked up somewhere.

 

[XSLeo]

You say you have read the tuning guides, have you read the repair manual? If not get one and read it. You might be surprized just what you can learn reading the repair manual. If you don't have one, biker.net has them to download.
www.amckatltd.com/carbguide.pdf is the best thing you will find to work on these carbs.
The carb guide has a chart showing the stock jetting for the US models.
The carb jetting should be in your repair manual it.
It tells how to gap the points and set the timing.
Have you checked the spark by pulling a plug and holding it against the engine while cranking the engine to see if the plugs spark?
Have you checked the compression with a gauge? Or just by feel? Stock engine in good shape should have at least 145 PSI. Fresh engine around 165 lbs. The bike will run ok with it as low as 125 PSI. Much lower and might not run.
If you think the compression is good and have spark at the right time, get a pump style oil can. Fill it with gas. Pull the plugs, put a squirt or two in each plug hole. Try starting.
If it fires and runs a second or two then you know it's in the fuel delivery system. Carbs most likely, could be the petcocks, or even in the tank.
Leo

 

[Junkyard Johnny]

I have spark on both plugs. I have bout 100 psi on both sides. Gas does seem to be getting where it needs to be only on the compression stroke I can see very small bubbles on the edge of the intake valve. I've tried everything. Im guessing compression is probably it.

 

[XSLeo]

It should run on 100 psi, try the oil can/gas suggestion? It works for me. If the oilcan/gas trick gets it to fire up, read the carb guide, the problem is most likely there.
Leo

 

[Junkyard Johnny]

Well, I read up on the helful info posted and the carbs had the stock jets in em yet, so I put everything back together and put the donor tank on it to see what it would do before I try the oil can thing. She fired right up. Runs like a bitch, but it runs. Once I shut er down it chugs gas out of the little brass barbs on the bottom. At first it was just the left and then both. I have to shut the petcock off or else it'll drain out the whole tank. I first suspected a stuck float, but it's both and they swing freely.

 

[CDNTX650]

what carbs? bs34 or bs38? float seat orings could be bad...

 

[Junkyard Johnny]

BS38's...

 

[XSLeo]

If the floats are set wrong the fuel can over flow. If the seats and needles in the foat valve are damaged it will over flow. If the seats and needles are dirty they can over flow.
I might suggest taking the carbs apart and cleaning them well. The carb guide tells how. Not just the float valves but the whole carb. Many tiny passages that are hard to get clean.
Leo