Wednesday, September 04, 2019

Fiona's High Idle issue is better now.....maybe

Got the parts I ordered for Fiona's carburetors last week, today.

Basically, I replaced the O-Rings for both the Idle and Main Jets, the return springs for the choke levers I added a new spring to the existing old one to ensure the lever closes fully when I close the choke.  Eventually I will have to take the carburetors completely apart to clean them out thoroughly I suspect.

Cleaned out some more gunk from the jet wells, to include surprisingly a bit of red gasket sealant material....

I adjusted both idle air mixture screws to 1 full turn out for base adjustment.

Finally, I replaced the rubber tubes which mate the carburetors to the respective cylinder heads.

She started right up as usual, with the choke on, I let it warm up for a couple of minutes while I geared up.  Turned off the choke before heading out and she seemed OK, there was no hanging idle in the short ride to the local store for camping supplies; but the idle was too high (around 1500 rpm) which was understandable since I had dinked with the throttle stop screws last week.

Rode her home the long way to get her engine up to 300 degrees or so and got the Harmonizer balancing gizmo hooked up.

I made sure the throttle stop screws weren't in play, then adjusted the idle air mixture screws inward till the idle was barely around 700 rpm.  I then bumped up the idle with the throttle stop screws till it was around 840-900 rpm and the Harmonizer reported balanced carbs.

Went out for another ride and the hanging high idle seems to have gone away!  The RPMs drop as expected when coming to a stop and hover around 1000 RPMs, sometimes a bit higher, sometimes a bit lower.

As I go up in gears, I don't hear the RPMs drop at all between gears but then again, not sure that's something to worry about for now.  I just seem to have a recollection that it should be a noticeable drop when one pulls in the clutch to change gears?

The only time the idle seemed to hang high was when I got her home but then I wiggled the throttle cables and it seemed to immediately drop down as desired.  Hmmmmm.

I added some 3-in-1 oil where the cables seat into the carburetor, perhaps they're sticking?

More riding and testing to follow, but things look OK for now on Fiona.  I'll be taking her camping tomorrow to Monte Vista, Colorado where a mini Ural Rally is scheduled for this weekend.  Not a big rally, just a gathering of Denver Metro area Uralisti, hopefully some newbies, a few of the core group of riders.

Update, September 6.  Turns out, while the o-rings and springs did need work, the throttle cables are sticking where they come of the throttle control assembly!  Every time I come to a stop and the idle isn't going down as expected, I just jiggle the cables where they connect to the handlebar control and voila, the RPMs drop!

Have looked at it, no moving parts really except for the chain used by the throttle grip to pull on the cables simultaneously.  Must research further, don't want to force things while I'm camping and break the throttle assembly mechanism somehow.  For now, I jiggle the cable when stopping.

Update, September 7:  More riding and I determined it was the cable that goes to the left carburetor that seems to "hang up" with the control housing, causing the hanging high RPMs.  During the riding today, I taped a small rock to the cable to weigh it down, no more hanging high RPMs when closing the throttle!  Eureka.


RichardM said...

Maybe the throttle cables themselves are sticking. Or whatever the thing is called where the cable splits into two cables under the tank...

redlegsrides said...

That’s what I’m suspecting as well RichardM, no splitter though, each throttle cable runs free to each carb but they do start off “together” at the throttle control so will examine that next.

CCjon said...

Good thing you have lots of rocks laying about... lol

Good detective work, tracing down the catch so to speak. When was the last time you lubricated the throttle cables?

redlegsrides said...

I have never lubed the cables CCjon, it's not the inside cable that's catching, its something in the outside housing at the throttle control assembly end I think. Still, it wouldn't hurt the lube the inside cables either eh?