XS650 points problem

[Scully7050]

Gday guys my father has a 74 XS650 bobber his had it for years been sitting in the shed for awhile now so me and my brother thought we would pull it out and get it going for him for Christmas turns out it was harder than I thought just looking for abit of direction or input if you guys have any.... so it was low on spark got new spark plugs and checked out the points they had seen better days so I brought a second hand set with backing plate and all that where on another bike working fine so I got home put the second hand points in and went to set them up pulled off the magneto casing to realise it had a PMA set up on it so I had to refind tdc the F mark and mark them all back out so I knew where they where did all that set the points up to spec put a test light on was generating power ect now it has a dual output coil on it so I fixed the 2 points wires together and put them on one clip on the coil then I ran a Hotwire from the battery to the other clip on the coil tested it and it was running power through the coil to the points so I gave it a kick it went to fire but didn’t gave it another and it popped out of the carbs 10 more kicks after that it wanted to fire but wouldn’t then all of a sudden there was nothing when you kicked it I’d lost spark to the points got the test light out took the points wires off the coil had power running through it as soon as I put the points wires back on the coil it wasn’t generating power out of the coil I had to move around the points and backing plate to get power to them again I think iv reset the points about 10 times and I’m still getting it to want to fire but it won’t then every now and then I’ll lose spark to the points and have to move the backing plate around to get power back out of the coil again I’m pretty stumped anyone have any ideas ? Cheers

 

[Ozboy]

How did you refind TDC?
Using the piston stop method is by far the best way i have found to find TDC. Something down the ol plug hole can be ok to eyeball the stop..long wood dowel rod or plastic rod
Search on here or YouTube to double check. You can print out a gauge wheel to nail it down.
Good luck Scully and keep posting on here great crowd... oh photos ohphot...and photos post em.
Dad will be stoked his boys got it going for Xmas. I would be!!

 

[Scully7050]

Yea I did the piston stop to find tdc then I went 0.5 inches to the left (anti clockwise) to put the F mark I might be missing something or doing it wrong but iv gone off the spec diagrams iv found online set the points to 12 thou on the feeler gauges just can’t get it to run have no idea why firing sometimes just won’t start cheers mate hoping we get it sorted out before Christmas for him

 

[Scully7050]

Not anti clockwise sorry I set the f mark to the left of tdc (clockwise)

 

[650Skull]

This thread might be of use...........
http://www.xs650.com/threads/timing-help-and-info.53589/#post-573117

 

[Scully7050]

Gday fellas so I got it running thanks to 650skull and the link he put up I had to remark all the timing advance an fire mark retention the timing chain so the rod was flush with the nut ect gave it a kick and boom fired up straight away but was running pretty rough played around with it abit more starts first or second kick most times but runs better on the right cylinder then the left right exhaust gets hot but left exhaust stays cool if you rev it up to high revs it will run on both cylinders but on low revs it’a running more on the right so Im beginning to think it’s a carb issue it blows out white fuely smoke when you rev it sometimes and when I played with the mixture screws it ran a little better problem is it’s got after market single carbs on it and I don’t no how to tune them I’ll put up a pic of the carb any help would be appreciated

 

[Scully7050]

Carb

 

[gggGary]

Looks like a Mikuni VM or a knock off thereof. 34mm is the most popular,
first step is to strip and catalog all the brass so you know what you have. Genuine VM's have markings on the body also.

THe float valves on the VM series can be a bit touchy you may have one that isn't shutting off fuel.
Here's a long VM tuning thread. http://www.xs650.com/threads/help-me-id-these-and-can-they-be-tuned-mikunis.6570/
If nothing else a good primer with links for getting a handle on them. And there is a post with some "kown to work" brass set numbers

 

[Scully7050]

Gday mate there Mikuni has a sticker on the side saying (not for aircraft use Mikuni)

 

[Scully7050]

has 34 stamped on them

 

[650Skull]

Scully, Some pics of the single carb manifold.

Got to check the carb set up as gggGary suggests but the manifold could also be causing problems. Even distribution of the fuel mixture is important and another thought .........have the inlets been ported and polished........

 

[hotdog]

Skull, looking at his pic I'm assuming he means aftermarket single carbs as in - one per cylinder.
Scully, they do look like Mikuni vm34's.
My 2c is that you may have a blocked pilot jet that needs to be cleared on the left hand carb. Go to the Tech section/carbs and follow the breadcrumbs....

 

[Scully7050]

Cheers fellas everything you guys have said has been helpful turns out the old boy had another set of carbs exactly the same but newer so I chucked them on stopped the fuel smell coming out of the exhaust but still ran like crap sometimes it runs like the spark is jumping between cylinders runs one the 2 for a second then back to one I’m pretty baffled that’s pointing me towards timing but I’m pretty sure I set that up correct has a pma kit on it so I had to remark tdc fire and advance did that set the points to open just before the fire mark with the test light ect points are throwing out good blue spark but still runs between one and 2 cylinders unless held on high revs then it try’s running on 2 have I done something wrong??

 

[Scully7050]

I first went of this diagram to set it up

 

[Scully7050]

Then I printed off one of these to the exact size it should be and went off that

 

[Scully7050]

Turns out one of the carbs where buggered sitting idling and running fine now haven’t took it for a spin yet will do over the weekend... cheers for your help fellas

 

[XSsex50]

Sounds like you guys are nutting through the issues! If has been sitting for awhile I would flush the tank and replace with new fuel - hate to see all your carb work before nothing. Also oil change and check no shavings in the filture.

Just suggestion.

Where abouts in Aus are you guys?