Yeah I'm an Old Rookie Running without carb manifold gaskets for 2 years

OLD ROOKIE

Go Slow and Wave at Your Neighbors.
XS650.com Supporter
Messages
94
Reaction score
189
Points
33
Location
20832
Hey Everyone,
I just realized that I never had carb intake gaskets since I got my 81'. I didn't know they existed or were needed. So I ordered some.
What would the absence of gaskets cause in regards to how the bike runs ? I tried the carb cleaner spray test before and I did not detect any leaks.

I recently pulled the carbs and cleaned them and installed new air jets and went from 132.5 to 135 on the main and from 42.5 to 44 with the pilot.
Bike runs well but the idle is to high 1750 with the idle screw backed out. I am 3 turns out on the air jets. The PO had 132.5/42.5 with the pods and aftermarket shorter pipes, I ran it like that for 5k and it ran well then a couple weeks back it starting popping on the left pipe. The popping precipitated the re-jetting.

What now ? Thanks for everything. Old Rookie
 
Last edited:
If your manifolds weren't leaking before you installed gaskets, nothing will change after you install them. You'll be less likely to develop a leak. Air leaks there will make your engine run lean. 42.5 and 132.5 was the factory jetting. It may have been fine.
 
High idle sounds like a vacuum leak. Maybe check again. But I think 5T has it in post below.
 
Last edited:
If the idle won't drop any lower than 1750 with the idle speed adjustment screw backed all the way out so it no longer touches the cable arm, the carbs are probably out of sync. Backing that speed screw all the way out like that effectively shuts the carbs off and should stall the motor.
 
I forgot to say that I just replaced the OEM petcock with an aftermarket one. I took the tank off to clean it and took the petcock apart at the same time.
Everything was real clean. I put it back together than of course the old petcock was leaking. Getting the new petcock spigot pointed in the right direction took some work. I put a couple extra little washers on.

I found out part of reason the idle was high. The hand grip on the right was jammed up to close to where the cable attaches to the throttle.
I loosened the handlebar end cap.. getting there. IT STILL IDLES AT 3k at startup. Will check for leaks.
 
I smile, particularly with 5twins Input. I have heard(read) a thousand times w/regard to engine running, ignition, battery, charging. But having had a sync problem, I think 5twins may nail it here.Time for a manometer.
 
I bench sync'ed it. I wish I had more capacity. I work on it in my urban front yard LOL.
When I run with an auxiliary tank to tune, I'll park it near a tree on the edge of the drive way and hang the tank there.
 
I bench sync'ed it. I wish I had more capacity. I work on it in my urban front yard LOL.
When I run with an auxiliary tank to tune, I'll park it near a tree on the edge of the drive way and hang the tank there.

Nice looking bike!
1682516336396.png


A synch can be done without fancy tools.
Start by ensuring there is some slack in the throttle cable while the motor's at idle. easily checked at the LH carb. If not a R&R of the throttle cable is first up. Rusty, misrouted, kinked cables happen. Ditto the twist throttle mechanism.
Prolly hardest part of it is being able to get at the synch screw while the motor is running. You mention your test tank tree, so it seems you have the tools. There are some fancy screw turners that can get you on the synch screw while the tank is in place also.
It's simple as loosely placing a hand over each muffler outlet while at idle, the goal is an even amount of exhaust pressure from both sides.
Should be able to slowly hunt back and forth, one side or the other being stronger then find the mid point. If it is a sync issue your idle speed will rapidly drop off while you are closing the strong RH cylinder's carb via the sync screw.
 
It's simple as loosely placing a hand over each muffler outlet while at idle, the goal is an even amount of exhaust pressure from both sides.
Should be able to slowly hunt back and forth, one side or the other being stronger then find the mid point.
And that's a tried and true method. Once you develop an ear and feel for it you can get pretty damn close. Close enough that the bike will run just fine.

One trick to the sync screw is to put a bit of fuel line on it. That stops the screwdriver from walking/vibrating off the head of the screw.



1682518226628.png
 
I have a looong #1 (skinny) and am able to reach that tip in and nudge the sync screw in either direction. Be prepared for idle to go up alot as your sync gets close to correct. Because only one cylinder was pulling the load. Good luck.
 
Back
Top