Barely starts, won't run, why?

[mr72]

I dropped in a used set of carbs that I gave a cursory check/cleaning and adjusted the pilot screws to 2.5 turns out.

Now the bike will barely start with the throttle wide open (choke on) and won't even attempt to start with the throttle closed. Then it runs with WOT but just barely and just for like 5 seconds.

See the video:

https://www.youtube.com/watch?v=MA9jmxpkeCk

What say ye? What should I be looking for?

BTW it ran, only wouldn't consistently idle, with the other carbs.

I know, I know, next I'm gonna be pulling the carbs back off, I just want to know what to check/fix/look for.

Grr. Have I mentioned how much I hate carbs?

[kapiteinkoek]

What exactly would you call a cursory check/cleaning?

[rscottlow]

Do you have proper fuel flow? No pinched or clogged fuel lines?

I know you've been through hell trying to get this bike running right...I'm rooting for ya...

[mr72]

cursory check / cleaning --- by this I mean, I just made sure things that were supposed to move would move (slides, throttles, etc.) without sticking, and swabbed with some q-tips and carb cleaner. First time around I didn't do any tearing down and detailed cleaning of every orifice and passageway, verifying everything, etc.

As far as fuel flow, well it turns out I had a serious fuel flow problem: stuck float needle valve resulting in zero fuel to one carb. Plus a leak in the petcock vacuum hose causing likely fuel flow restriction at the very least.

I did pull the carbs and found the stuck float needle valve and the vacuum hose issue, plus a problem with the diaphragm spring on the other carb. Anyway, I fixed this stuff and cleaned them much more thoroughly and put them back. Gonna go try to start it again this afternoon.

[3imo]

Did you pull the jets?

[rscottlow]

Just read through the rest of your other thread, I'm all caught up now

I hope it fires right up for you after work. If not, I hope you can stick with it long enough to get it running right. Switching it to prime may make all the difference in the world...I know from having taken off my tank and carbs so many times. I've even forgotten to turn the tank petcock back to the "on" position before bolting the tank back onto the frame--it's easy to get excited when putting everything back together after you think you've fixed it. Good luck!

[mr72]

Did you pull the jets?

Yeah I replaced them actually, with a known working set from my other carbs. But I haven't gotten it started yet with the newly reworked and verified configuration.

[mr72]

OK. Put it on prime and it started up!! Then it proceeded to rev to 7,000 rpm while on choke!

I adjusted the idle down to like 2-3K rpm on choke but I don't know where it's actually supposed to be. I ran it for like 5 minutes and it revs and runs and acts like it's ready to go rippin' down the backroads, but I didn't have time to actually get on it and ride. When I turned off the choke it would not idle and died, then wouldn't start back up. I suppose I'll have to wait until it's stone cold and then restart it on choke? Or who knows what. I don't know the startup routine for this motorcycle.

Anyway, I am pretty sure I sorted my barely-start-no-run issue. Now on to the original issue, make it idle AND run reliably.

Thanks for the input guys-

[3imo]

Sweet!
I'd pull the plugs. Hit em with a wire brush. Might help . won't hurt.

[Bluesmudge]

After 5 or 10 seconds the bike should idle at 5,000 rpm with the choke on. You are supposed to adjust the idle with the choke off and the bike fully warmed up. Setting the rpms to 2-3k on choke means the bike will die when you take off the choke.

[qcbaker]

After 5 or 10 seconds the bike should idle at 5,000 rpm with the choke on. You are supposed to adjust the idle with the choke off and the bike fully warmed up. Setting the rpms to 2-3k on choke means the bike will die when you take off the choke.

+1 to this, was going to say something similar. When I start the bike with choke fully on it idles 4Kish RPM. after a few seconds it goes up to around 4.5K. Then when I take the choke off, it idles around 1.25-1.5K

[mr72]

Yeah, so I went out today and it started right up. I adjusted the idle speed (while cold, on choke) so it'd idle at ~5K rpm after about 10 seconds running on choke.

Question: how long do you ordinarily keep the choke on and let it run at 5000 rpm?

Well I adjusted it to about half choke and about 2500 rpm idle after about 20 or 30 seconds, moved my car out of the way and then came back up to try and take it for a spin to adjust the idle. My driveway is rather steep. Once I got back up I took it down to about 1/4 choke or less and it was idling at about 1500 rpm. I then aimed it down hill on the driveway and as soon as I started to roll it down hill the revs shot up to like 5K again. It seems to rev high on its own when pointing down hill. What's up with that?

I took it all the way off choke and it died, so I just coasted it down the driveway and tried to start it back up. Won't start.

Ideas?

Revs high aimed down hill.

Won't start when partially warmed up.

What does it mean?

[qcbaker]

Yeah, so I went out today and it started right up. I adjusted the idle speed (while cold, on choke) so it'd idle at ~5K rpm after about 10 seconds running on choke.

Question: how long do you ordinarily keep the choke on and let it run at 5000 rpm?

A minute or two, however long it takes me to put on my jacket, helmet, and gloves. Usually by that time if I turn the choke off, it idles fine around 1.5K.

Well I adjusted it to about half choke and about 2500 rpm idle after about 20 or 30 seconds, moved my car out of the way and then came back up to try and take it for a spin to adjust the idle. My driveway is rather steep. Once I got back up I took it down to about 1/4 choke or less and it was idling at about 1500 rpm. I then aimed it down hill on the driveway and as soon as I started to roll it down hill the revs shot up to like 5K again. It seems to rev high on its own when pointing down hill. What's up with that?

I took it all the way off choke and it died, so I just coasted it down the driveway and tried to start it back up. Won't start.

Ideas?

Revs high aimed down hill.

Won't start when partially warmed up.

What does it mean?

Gut says the downhill thing must be linked to the carbs, maybe something with the float height?

As for the dying off choke and not starting when warm, I would try starting the bike on choke, letting it sit about a minute or two to warm up, then ease off the choke and see if it idles properly on flat ground. If the revs seem correct with choke on, but it dies when you close the choke completely, wouldn't that mean your mixture is too lean?

[HPP8140]

Check that your exhaust valves are not tight

[mr72]

Well it won't start at all now. So my bigger problem is getting it back up into my garage. It's too heavy to push up my steep driveway.

There's a good independent motorcycle shop near my house. I may go ask the owner his opinion and maybe get them to order me some carb parts. I'm thinking the downhill surge thing may be float needles and seats. And the no-start may be that it's flooding, or not flowing fuel.

Crazy thing is, when it was running on the center stand, it was running GREAT.

[mr72]

Quick update .. bike still will not start.

Left carb is obviously flooding. The plug on that side is wet with gas and if I pull the plug and turn the starter it blows droplets of fuel out of the plug hole.

Right carb is  Seems like it should start if at least one carb is working.

Pulling it apart again tomorrow. Advice? What causes this? What part do I need to replace?