In reply to APEowner :
I have cleaned those. They come out with the jets each time.
I suppose it's possible that there's still junk in there but I would be surprised. I've physically cleaned them, carb cleaned them and chem dipped them. But that seems to be the standard answer.
The bike has shorty mufflers and supposedly modern fuel is different or something so I'm aiming for a moving target.
I left last time thinking the bike was running too rich at idle since I had the air screws out double the factory spec.
Yesterday I tried moving the low speed jet down from a 38 to a 35. Still wouldn't idle. Now however the revs would hang noticeably longer which is a tell tale lean condition. No amount of air screw adjustment helped. Back to the 38s
Still wouldn't idle. I couldn't even repeat the result I was getting before. Ugh
I learned that I am having intermittent fuel delivery to the right side carb. I'm not sure what's going on there but I suspect the fuel filter or petcock. I know the carb is clean and the float isn't the problem. I dropped the bowl and watched the needle fall and still no fuel. So I need to spend some time tracking down that issue.
Round and round we go. I'm genuinely surprised I'm having this much trouble making it run.
Will the main jet size affect idle? The pipes and plugs are sooty so I know generally the bike is rich. I'm wondering if I should chase that problem and see what effect it has. I'm fine with it running rich as long as it runs at this point, but maybe it matters.
In reply to spandak :
I really want to grab that article and go through your bike step by step, so I can scarcely imagine how frustrated you must be! :)
Referring back to that Kevin Cameron article, and this sounds like one of those rough guideline things, the carb starts transitioning from idle to main at ~1/8 throttle (guessing that specifying 1/8 sounds a lot more specific than the reality is). So... if you're having to set the idle speed pretty high to get it to idle... could you be in the foothills of main jet influence? I wouldn't think so, on the WAG that that much throttle and no load would be screaming, but I could easily be way off.
So I've got two thoughts, and if I had to put money down I'd bet against either of them being right, but maybe they'll shake something loose:
I read through that article and found it pretty helpful. There's a sort of black magic to this stuff and info is either very general to way too specific. I'm trying to take a step back and learn the system instead of just blindly doing stuff.
Here's what I know:
Above idle (~1/8th throttle) the bike runs smoothly and predictably though quite rich. My plugs are black and the pipes are sooty. Not ideal but predictable and that's fine for now. Only full throttle is questionable and if I whack the throttle open it hiccups badly. Not too worried about that at the moment though.
At idle it's very unpredictable. Some days it cold starts great and dies as it warms up (rich I think.) Some days it doesn't start at all without generous throttle openings. Recently I was able to get it idle kinda. During clutch application it would hesitate and then move off. Leaning out the needle significantly seemed to help but not fix it. At this point it was in idle range, maybe 200rpm higher.
Yesterday when the smaller jet experiment failed I put it all back the way I had it when it sort of idled and it wouldn't Same symptoms as a month ago where it slowly drop in revs for a few seconds until it died. I had a few events where it would zoom up to 7k and then slowly continue to climb on a closed throttle. It feels like trying to balance on an edge and it can't seem to do it. It revs or it dies. This might support the mains fueling theory
When we bought the bike it was a mess. The ride home it wouldn't run between 2 and 5k rpm so the clutch saw some real abuse, but it idled reliably and ran fine up top. We pulled the carbs apart and set everything back to stock setting. I cleaned the carbs with everything I could think of including a few hours in professional grade chem dip, the stuff they don't sell anymore. I've run guitar strings down the passages and carb cleaner. All of them have been checked and I get carb cleaner through all of them.
I should have recorded the carb setting when cleaning them but I did not. I do remember everything was off enough that I was alarmed. What bugs me is that something I did fixed the mid rpm issues but now it won't idle when before it would. So it's capable of doing it but I'm missing something.
I did discover the fuel supply problem yesterday and I want to try and work that out first. Then back to the carbs.
This thing is making a fool of me.
Whacking the throttle open on non-CV, non-accelerator pump carbs does normally produce hiccups (too much air too quickly, not enough fuel) so that actually doesn't sound like an issue to me.
Do you know if the float valve is new? Some of the older ones tend to get sticky rubber tips, and then they don't open properly. Sounds like you may have that problem or one that doesn't move freely in the carb for other reasons.
I don't remember, but did you by any change check the float levels and make sure that the floats, well, err, float properly? Not uncommon on old bikes to have floats that don't float that well anymore, and that can throw out the whole mixture badly.
In reply to BoxheadTim (Forum Supporter) :
Good to know. I have read that but this is my first experience with a non injected bike. So "normal" isn't nailed down for me. I think that's part of my disadvantage here too.
The floats are original but as far as I can tell okay. There's no fuel inside of them I can hear and they move freely. The needle and housing was replaced in the rebuild kit, they are metal tipped and as far I can tell are working normally.
Float level is set at 21mm from the gasket surface. There's some mixed info online but that seems to be the generally agreed upon measurement. This has crossed my mind as being a problem but I'm not sure how to proceed.
The fuel flow issue is odd, I left the carbs attached and just dropped the bowls yesterday and even with the float dangling and the needle almost falling out I didn't get any fuel. Playing with the petcock and general poking and suddenly it was flowing again. It's only one side that has the problem. I noticed because after changing jets it was clearly running on one cylinder. I won't get to it today, work took it out of me, but I'm going to try swapping lines and seeing what happens. Maybe delete the inline filters too.
I'm looking for a good fuel system cleaner to put in with some fresh gas to see if that does anything too. Seafoam comes up a lot
edit: wanted to thank you both for following along and helping me troubleshoot. It's been helpful!
Unless you know 100% that the tank is spotlessly clean, I wouldn't get rid of the inline filters. Maybe replace them with better (or at least newer) ones, but not delete them. Old tanks tend to have lots of stuff in them that will nicely clog up your carbs.
The tank is not 100%, I can confidently say that. I did a vinegar soak and that kinda helped but someone lined the tank previously and must not have done a great job because whatever it is is peeling off in places.
You've convinced me to leave the filters. I'll blow them out a little and leave them. They aren't old
That fuel petcock issue certainly needs to be fixed first and it might solve the other issues. Does that have a vacuum line going to the petcock in addition to the fuel line? If so it's an auto shutoff and they can fail in three different modes.
I think you've got additional problems but not having the carbs synced can cause really sluggish throttle response. My approach from where you're at now would be as follows.
That has points doesn't it? If it does I'd clean, inspect and adjust those.
If the ignition is OK and the carbs are in fact clean the bike should start. You may need to crack the throttle to get it to idle. Once it's running (assuming all goes well) Adjust the idle speed turning each throttle stop screw 1/4 turn at a time.
Pick a carb and turn the idle mixture screw in the rich direction (out I think on those carbs) until the idle drops then in until the idle drops and back out 1/4 turn. Then do the same on the other side and re-adjust the idle speed, again turning the idle speed screws the same amount on each carb. If everything is working that should give you a ridable tune.
In reply to APEowner :
It's a standard petcock and I need to look in to the delivery issue but before this I had no indicator of a problem with it. I cleaned it out when I soaked the tank.
The carbs have been synced though only by feel. I put my finger on the slide and compared side to side. Theyre as close as I could get them.
Timing was set and checked. Point (one lol) is good. The advancer is not as good. There's some play in the cam but based on the direction it spins that shouldn't have an effect on timing unless it's able to bounce around and I don't think it is. I would like to replace it but I'm done spending money on the bike.
Edit for clarity, play in the centrifugal weight cam that moves the point, not the camshaft.
Ive been doing the process you laid out each time I change something and I'm still here. No luck. It will start with a cracked throttle but it won't idle consistently with the throttle closed. Even when the slide stops are run in. The closest I have gotten was leaning out the needle and double the air screw turn spec. Putting the needle back a notch and the same air screw setting worked for a day but I haven't been able to replicate it.
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