Poor idling and starting

Nicko

XS650 Member
Messages
22
Reaction score
38
Points
13
Location
Yarm
Hello,
I have recently renovated an xs650 a 1974 and have what I believe to be carb problems, the bike has a new Boyer ignition and has been set up as per the instructions. The carbs are standard for the bike and were stripped and cleaned, with all passages checked, the bike is fitted with standard filter boxes, however the mesh is now wrapped with 10mm filter foam, silencers are pretty standard and from xs650 in Germany.
On initial start up the bike ran, but not very well throughout its range, I completed about 60 miles on it, but it was running very rich, with sooty plugs. I fitted keyster carb kits with standard jets for this model and Road tested again for 60 miles. It ran ok and the plugs were pretty good, (see photo), however did not run as good as my previous xs650b.

Still difficult to start. Choke seems to help but starts best on a closed throttle and then coaxed into life with throttle.
Idled on one cylinder until warm (no2)
Cylinder no 1 fumbles when you open the individual carb and pops back on closed throttle at very low revs
When you open the throttle and both cylinders kick in it accelerates strongly, however runs out of power at about 65mph, not missing
but just creeps up slowly from there. I have tried different mixture settings but start from the 3/4 of a turn recommended setting, balanced the carbs and adjusted tick over settings many times.

Any one got any advice on what my course of action should be, do I need to change jet sizes, especially pilots or play around with timing
 

Attachments

  • IMG_6318.jpeg
    IMG_6318.jpeg
    495.8 KB · Views: 37
  • IMG_6276.jpeg
    IMG_6276.jpeg
    402.9 KB · Views: 34
Yes, it sounds like the idle circuits, or at least the one in that cylinder that doesn't run at idle, are blocked or partially blocked. Also, did your rebuild kits come with a generic Y-22 replacement slide needle, and did you install it? If so then that may be the root of your higher speed running issues. It's wrong for your carb set, about 5mm too short.
 
The flat slide tooters on my runner XS suffered intermittent no-idle and sometimes not much go on left side jug. Careful exam revealed that a sharp edge of a brass fitting had sliced off a fragment of the fuel hose lining, capturing this as in effect a valve...sometimes. Vexatious tooters those two are.. An' ah got me a box of stockers...oneadezedays the mukunis go away... Meantime honey-do-chores...

I would like a "Y" manifold cast, like the old Brit twins..and a tooter with the tickler... call me old. Maybe I shall make one... first the frame must change a bit.... ;) I can cast al and cu alloys out back the shop, but cores and patterns are what take all the work...

One tooter solves many difficulties...

If I had built the scooter I would have paid better attention to detail...
 
No they were from a keystar carb kit suppled by yambits, 127.5 main 45 pilot, I think you are correct about the crud, but I am running filters so discounted that.
 
No they were from a keystar carb kit suppled by yambits, 127.5 main 45 pilot, I think you are correct about the crud, but I am running filters so discounted that.
The intermittent obstruction was between filter and tooter... I made same assumption. But you're probably not suffering from that... crud somewheres tho, is my hunch
 
Thanks for the info so far, have checked pilot jets and circuit, so far clean, picture of needles with regards to 5 twins post.

Any other advice greatly appreciated
 

Attachments

  • IMG_6323.jpeg
    IMG_6323.jpeg
    534.8 KB · Views: 26
OK, it looks like your kits came with the correct generic Y-31 needle, so you should be OK using it. But needles are something that don't usually don't wear much and I rarely replace them, just clean them and re-use.
 
Back
Top