Why has Sheniqua turned into a bear?

[nitrofish1]

Hi. If you've been following me for a while now, you'll know that my 81 xs400 special in all black is Sheniqua. And lately she has been living up to her name more than normal, one hard to start black b****.....

The year prior to this, if i went and started her the night before i would go on a ride, she would fire right up. If i didnt start her for more than 3 days, she required starting fluid to get going.

When she get her refresh for the beginning of the year, new air filters, new oil filter, new plugs, fresh oil.... I was able to start her with one kick and she had more power than I had ever experience from her. about a week later, she would not start without fluid, then after one day of riding when i ended up killing the battery trying to start her, ended up starting it with alot of fluid and a well placed kickstart.

After some troubleshooting last night with my father, we found that the cylinders are just not drawing fuel into the cylinders upon start. once its going, runs alright, but will not draw gas to start. last we checked we were also getting plenty of vacuum between the airbox and the carbs. so there is something going wrong in between the carbs and the cylinders. the carbs were thoroughly cleaned prior to this year's service as well.

 

[MechNewb]

Possible air leak in the carb boots? Are they cracked or old? Are the vacuum ports properly hooked up/ blocked off?

How did you determine that you weren't able to draw fuel in at start up?

 

[nitrofish1]

Possible air leak in the carb boots? Are they cracked or old? Are the vacuum ports properly hooked up/ blocked off?

How did you determine that you weren't able to draw fuel in at start up?

Cranked it for like 10 seconds and pulled the plugs, no smell of gas in cylinder or on plugs, plugs also dry.

 

[Buccaneer]

Hi nitrofish,

I have a similar problem on my bike. All I can tell you is I have done

Points gap
Static timing
Valve clearances
Check battery and voltage at points
New condenser
Very Thorough carb clean (boil, careful probes with brass wire, then carb cleaner shoot through)
New inlet stubs
New high octane fuel

.. and nothing has made much difference (static timing seemed to help a bit). VERY hard to start but pulls like a tank once going; on latest test was virtually wheelie-ing on its own in second gear!

I'm guessing my carb clean wasn't good enough and there is still blocked pilot circuit... pilot jets are 100% perfect, done VERY carefully, but maybe a blocked passage somewhere? Odd that this seems to affect both sides!!

Will keep an eye on your thread - good luck indeed, hope you solve it easier than me!

 

[MechNewb]

Cranked it for like 10 seconds and pulled the plugs, no smell of gas in cylinder or on plugs, plugs also dry.

Id have to guess that something is plugged or dirty in your carbs then. If the motor is cranking it will create vacuum and suck air in. Do you have an in-line filter installed?

 

[nitrofish1]

I do have an inline fuel filter, but I replaced it this year and so far it is clean.

 

[nitrofish1]

My dad dug around in the carbs, found some rubber plugs (?) that were too tall and blocked off the flow downstream in the venturi of the pilot jets. She ran like a pig sliced in half off the start until she reached the main jets, then i had to wring the shit out of her to get fast.

Shaved those down, drilled out the pilot jets, now she starts every time even cold, runs like a champ on two cylinders too. Back to her former torquey lower end self!

 

[16VGTIDave]

Now that you know that the problem was, you can order some pilot jets to get it running even better. Drilling jets is only a temporary fix, according to the pros...