Troubleshooting rough cold running and carb backfire

For both of youse guys, lipSTick is suffering the same cold start symptoms. Runs fine and gets good mileage when warm, but doesn't wanna start even as warm as 50. I had to use ether to get'er started in New Boston, TX on Monday morning at 28?. Hadn't thought of the enrichener circuits, I'll run some Sea Foam thru her on the next tank. BTW, this has come on slowly, just really noticed it the last couple months. With generally warm weather until this most recent trip, hasn't been a problem.

Jonathan, I don't recognize that piece of torn rubber either, and I've been into many STs. Wonder if it's part of the rubber sheet which should be UNDER the carbs, got replaced wrong at one time or another? (Just a guess.)

Anyhoo, the "valley plumbing" referred to are the coolant hoses under the carbs. Recommend replacement before 122,000 miles (STick blew a hose at 122,000 plus. :D) With the carbs off, check the right front coolant hose and the PAIR valve hose clamp underneath. On mine that clamp rubbed a hole after those many miles. On several bikes with fewer miles, I've found that clamp intruding. Look closely, could save ya a headache. Mike Martin's maintenance site has the complete list of parts needed to refresh the coolant system, hoses, thermostat, etc.

Checking the valves is no big deal but changing the shims (if necessary) is more problematic. I suggest getting an experienced hand to help if ya do need changes. At least, the first time.

(Have I written this up before?)
To check the valves, pull the maintenance covers and knee panels. Pull the valve covers. Put the bike in fifth gear and turn it over by rotating the back wheel forward. As each cam lobe stands straight out from the head, measure with a good set of gauges. I use "go-no go" as best indicator for correct setting, no need to be anal UNLESS one of'em indicates out-of-spec. Using this method, no need to remove the lower cowl or timing mark cover, no need to check any of the other settings. Yur just looking for the loose or tight valve.

If ya DO find valves out of spec (too tight or too loose) then you can get anal and start following the book.

Agree you probably need a new timing belt.

Anyhoo, both of ya please keep us poSTed as to your final solutions. Always interesting reading.
 
None of my bikes has had that on them. I am guessing they all go away the first time the filter housing is removed. I wouldn't worry about that.
Thanks Mark. No, not worried about having it or not. Just was alarmed at the fact that it was laying where the airbox is supposed to seal.

And thanks for the info on the plumbing. Diving right in is what I do best. I do love spinning me some wrenches. :)
 
Anyhoo, both of ya please keep us poSTed as to your final solutions. Always interesting reading.

Thanks a lot George. Yup, I'm no stranger to slingin' valve shims. Shouldn't be a big deal; but now I know where to call if there's a problem. :D

I just want to say... what a great bike! :eek: I've only had dual sports since my '75 Yamaha XS400, which barely ran. So needless to say this is a long time coming with my long-day habits.
 
.... Wonder if it's part of the rubber sheet which should be UNDER the carbs, got replaced wrong at one time or another? (Just a guess.)....

I've no doubt that's what it is! Compromised the air cleaner box seal... unfiltered air entering the carbs. =8<O


John OoSTerhuis STOC 1058

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I wonder John. You can see the mat in the pic too and the stuff that should not be there looks thin to me compared to the mat. As always, I reserve the right to be wrong. I think an owner up the line thought they had come up with the next great farkel.
 
Looks to me like the mat is torn and the left side of it is flopped back into the carb body, leaving the handlebar wires' connectors behind the steering stem exposed.


John OoSTerhuis STOC 1058

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For both of youse guys, lipSTick is suffering the same cold start symptoms. Runs fine and gets good mileage when warm, but doesn't wanna start even as warm as 50. I had to use ether to get'er started in New Boston, TX on Monday morning at 28?. Hadn't thought of the enrichener circuits, I'll run some Sea Foam thru her on the next tank. BTW, this has come on slowly, just really noticed it the last couple months. With generally warm weather until this most recent trip, hasn't been a problem.

J.

George,
The problem with running a cleaner in the fuel to clean the enrichner valves is, they are closed once the bike is operating temp and NO fuel with the cleaner is running through the circuit. If I were to try and clean them this way, I would use Berryman's Chemtool and ride the bike with the enrichners open so the fuel will flow through the circuit. Berrymans is stronger than SeaFoam and lots cheaper to boot. Don't be surprised if you have to remove them.
 
George,
The problem with running a cleaner in the fuel to clean the enrichner valves is, they are closed once the bike is operating temp and NO fuel with the cleaner is running through the circuit. If I were to try and clean them this way, I would use Berryman's Chemtool and ride the bike with the enrichners open so the fuel will flow through the circuit. Berrymans is stronger than SeaFoam and lots cheaper to boot. Don't be surprised if you have to remove them.

Thanks, Ralph. I've never used the Berryman's before, where do ya find it?

Thought about calling you the other evening but too early for me to stop as I passed by area. Made it all the way to New Boston, TX before stopping for the night.
 
Update, still not resolved but working thru it,

So here's where I'm at, it's in at the dealer for a valve adjustment, curious to see if this helps but won't know until next weekend.

A couple of other self inflected issues, I set the fuel mixture at 1.5 turns out, uh I guess I don't like to take everyone's advice, it' way too lean, really tough to get a 1200 rpm idle (idle stop fully turned in) and the engine speed hovers for 20-30 seconds before dropping to an idle. It's a 96 ABS California model, 2 or 2.5 turns out? They were at almost 3 turns out and did smell very rich at idle and couldn't get much response from the choke/fast idle.

I also cross threaded a couple of the PAIR tube bolts and then a coolant leak appeared, darn....So after it comes back from the dealer the carbs will be coming off again...I'm baffled on the coolant leak, I replaced the hoses under the carbs last summer but the area it's dripping from is dead on where a leak some where in the valley would occur. I guess I just need to slow down a bit on this and take my time.

One good point out this latest exercise, I tested the coils, primary leads and spark plug caps according to the manual. I found one lead with the cap on out of spec limits, not by a lot 31-32k ohms versus to of the spec limit of 25k, am I onto something here? I was actually able to get it to jump quite bit higher by wiggling the stem of the plug cap and was not able to get much fluctuation on the other caps doing this. Anyway, plug cap is on order.

So, the plan is when I get the ST back next weekend, with the valves adjusted is to pull the carbs, set fuel mixture to 2.5 turns, diagnose the coolant leak, remove PAIR valves and install block off plates, replace the questionable spark plug cap and sync the carbs.

To be honest the most improvement I have seen thru this (discounting what I broke the process) is running Berrymans thru the carbs and then adding 1/2 can to the full tank...

More to come, if this all turns out to be that plug cap I'm going to kick myself.....
 
Ok,

Most recent update, dealer called this afternoon and the valve adjustment is complete but I won't be able to pick it up until this weekend, they finished three days early.....that's a first

Conclusion without exact specifics, two intake valves were tight, not sure by how much until I pick it up. Asked if they heard any carb backfires, they asked what carb backfires.....promising....

Hoping this is part of the puzzle is solved.....

I will bring it home this weekend and access myself, then replace the out of spec spark plug cap, test....Then move the mixture screws out to at least 2 turns if not 2.5 from the 1.5 and re-sync the carbs and see how it goes. Then on to the coolant leak....
 
Just a double check, John. You do know turning the pilot screws out leans the mixture.

Do you have the procedure for adjusting the pilot screws, and a tach which can accurately sense 50 RPM changes?
 
Just a double check, John. You do know turning the pilot screws out leans the mixture.

Pilot screws are either fuel screws or air screws You can tell if a carb has an air screw or a fuel screw by it's location on the carb. An air screw will be on the intake side of the carb while a fuel screw will be on the engine side of the carb.

They sort of work opposite one another. An air screw adjusts how much air is being delivered thru the pilot circuit: in is rich (less air) and out is lean (more air). A fuel screw adjust how much fuel (or air/fuel mixture) is being delivered from the pilot circuit. In is lean (less fuel) and out is rich (more fuel).

If my memory is working OK, ST1100 has a fuel screw.
 
D'oh! :doh1: Yeah, I had it backwards. Had to re-read the high altitude adjustment procedure to get my head straight: "Turn each pilot screw clockwise 1/2 turn..." Clockwise = In = Lean for high altitude.

Sorry for the error. Thanks to Ralph 'n John for straightening me out.

Procedures for setting the pilot screws are in Chapter 5 of the service manual, high altitude setting on pg 5-16,
 
Ok, quick update to keep this going,

Picked it up from the dealer hoping to see some improvement after the valve adjustment, none that I can tell...To clarify a previous post, when icalled they said tight intake valves but when I picked it up it was two exhaust valves. It was a real bear to start when I picked it up because it has been in the 30's here at night, took 5 tries, thought I was going to have to ask for a jump.

Definitely still hunting at idle by at 250 rpm and random popping from the carbs. I did gas it up on the way back since since it was at a quarter tank after the 1/2 can of berrymans in the tank, was thinking before I start anything else it would be good to get as much straight fuel running thru again.

So, next steps

I know for sure it's really lean, currently 1.5 turns on the mixture screws so the carbs come off again and will move them out to 2.5 turns, it's a CA model and the Honda manual says 2 5/8, go with 2.5 or the 2 5/8?. I regularly run into higher elevations. I"ll re-sync one more time since the valves have been done also. The new elbows and orings are in so I'll fix the coolant leak while the carbs are out again.

The spark plug cap that showed over the limit was not in yet so that will go on at the same time.

Anything else to consider? Plugs just to be safe, they are new iradiums, about 1k miles on them?
 
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