I/S Running Rough After Warm-Up

[stratnick]

I know this topic has been dealt with before, but I am going to ask about it for myself. My 2000 I/S Starts up fine without fuel enricher (unless it's really cold) and runs almost perfectly throughout rpms. After it warms up, some or all of the cylinders on the right bank (1,3,5) pop and snap at idle, and stumbles just above idle, sometime even at higher rpms. Using the "choke" (I know it's technically not a choke) evens things out, so I know it's a fuel mixture problem. Left bank cylinders (2,4,6) run nice and smooth. I ran a tank of gas with some seafoam and it helped a little, but now that seafoam is used up, it's back to popping and stumbling. After reading posts on here, I suspect the slow jets or pair valve, or intake O-rings but wanted to throw it out there and see what you all might say about it. I'm very mechanically inclined, but can't wrap my head around why it runs worse warmed up. Seems to me that it would be worse at cold start up. I checked valve clearances today and cyl. 3 intake was a little tight, but otherwise all good. Thanks for any insight!
Nathan

[Valker]

Try tightening the screws on the rubber parts that run from the air cleaner box to the top of the carbs.

[NITRO]

Try tightening the screws on the rubber parts that run from the air cleaner box to the top of the carbs.

And keep in mind that there are two per boot, you need to remove the linkage cover just above the carbs to get at the others.

[stratnick]

Problem resolved! Removed carbs, cleaned, replaced slow jets and main jets, desmogged, rebuilt petcock (after hydrolock), new spark plugs, and replaced all associated o-rings, seals, etc. The difference is amazing...runs perfectly with absolutely no hesitation, stumbling, popping, or backfiring...and is "scary fast". It was definitely worth the time and trouble.

[salty]

Stratnick any idea what specifically may have caused the original problem or was it a combination of issues? I think it's important to try and bring issues to a specific closure if possible. What say you? 

[stratnick]

Stratnick any idea what specifically may have caused the original problem or was it a combination of issues? I think it's important to try and bring issues to a specific closure if possible. What say you?  

Good point. I'm happy to share what I found. The carb bowls had residue from what appeared to be diluted varnish (I had run several tanks of sea-foam through her prior to the repair. The jets were highly varnished, rough, and crusty, and pilot screw o-rings were flattened and hard. Intake runner o-rings had shrunk, were stiff, and some did not even touch both mating surfaces, obviously creating a vacuum leak. One of the intake nipples had a torn plug, another potential vacuum leak.

What I did:
Thoroughly cleaned carbs with cleaner and blew out with air. Replaced slow jets with #35s and mains with #100s. Replaced pilot jet o-rings. Rebuilt petcock due to hydrolock just prior to repair. Since carbs were out, I did a desmog using a Redeye kit. Put carbs back with new Viton intake runner o-rings, and plugged all intake nipples except for the one that operates the petcock. Turned pilot screws out 2.5 turns. Changed oil due to hydrolock. Replaced fuel drail hose kit.

The result:
She fired right up, and after adjusting the idle speed, she ran perfectly from the get-go with no additional pilot screw adjustments necessary. All the symptoms had disappeared. She is now a total pleasure to ride, and I can't wipe the smile off my face as she goes through the gears without missing a beat.

What I think was wrong:
A combination of several things. Flattened, hard intake runner o-rings definitely caused vacuum leaks. The torn intake nipple plug most likely caused a vacuum leak as well. Slow jets were definitely dirty. They didn't seem to be clogged, but had a rough coating on them that surely affected the flow of fuel through them.

My advice:
If your Valk runs like mine did before I repaired it, think seriously about doing this job, or having it done. Sea foam temporarily helped some of the symptoms, but did not alleviate them completely. Some have stated that Sea foam or equivalent products have cleaned out their fuel systems, but it did not fix my problem, possibly due to vacuum leak issues. With reasonable mechanical skills, anyone can do this job. One more thing... if your Valk suffers a hydrolock, change the oil! My oil had gas in it. Thankfully I knew enough not to attempt to start it.

Hope this is what you had in mind Salty.

[salty]

IT WAS!    Excellent review of your work. Do you synch your carbs? I know you said it was running well, but maybe even better after synchronization. Thanks for the great reply.

[stratnick]

IT WAS!    Excellent review of your work. Do you synch your carbs? I know you said it was running well, but maybe even better after synchronization. Thanks for the great reply.

I did not sync the carbs. Dont have guages yet. It would probably benefit from it.
Thanks!