Topic: Rebuilt Carbs - Now My Choke is WHACK!

[OakBehringer]

Timing is good. Point gaps good.

Took carbs off gave them a good cleaning. Replaced main jets b/c rubber washer was worn. Float heights are dead on. Patched some leaks in my exhaust. Put carbs back on the bike. Installed new air filter. Pulled choke lever up. Wont start. Hmm.... push choke lever down halfway, bike starts and shoots up to ~ 5000 rpm. Playing with choke lever, I can get it to idle at a happy 1100 rpm by setting it to about 90% of the way up. If I pull it all the way up it dies. Pushing it down blasts it to very high rpms.

So what does this mean? I have some ideas, but I'd like to get some of your expert advice before going in there again

Thanks,
Adam

[OakBehringer]

One thing that I'm not sure about: My exhaust pipes had small holes in the ends under the main ones. I assumed these were a result of corrosion so I patched them. That's correct, right?

See attached drawing of pipe end.

Thanks.

[Johnie]

I am not sure on your particular bike, but sometimes those holes are to get moisture out so it does not rust.  Were they rusted holes or did they look like they were supposed to be there. 

[BobbyR]

I an not sure what bike you have. My 78K has a fast idle cam, I think it is adjustable. 

[Johnie]

It's a 350 Four.  So where is hoodleyhoo...he will know what to do!!!   

[OakBehringer]

Yes, it's a 350F - says that in my signature, but everyone seems to miss it so I figure I'll start putting that in my posts

[OakBehringer]

I'm wondering if maybe the throttle slides are just set too high. Does that sound right?

[Steve F]

First place that I would check is to make sure the carb boots (between the carbs and the engine) are tight and not leaking vacuum and /or there are no cracks somewhere on them.
It also sounds to me like your idle jets are clogged, and you're relying on the mains to maintain rpm's, which is why you have to keep the choke mostly closed to keep it running.  Check fuel level in the float bowls too.  If they're too low, you could be having similar problems.

[OakBehringer]

Thanks for the reply.  I will check the boots today. I don't think it's the idle jets. I spent days clening out those carbs and jets. I know for a fact that I could see light straight through them. I shot plenty of carb cleaner through the passage ways.

[OakBehringer]

Not to mention, unless my throttle slide are set too high,it can't be running off the main jets. If the trlhrottle is closed that should be impossible. 

[OakBehringer]

screwed throttle slides all the way down and backed out a 180 degrees, same problem, just a little bit slower peak rpm when choke is open.

[OakBehringer]

Tried spraying propane and wd40 on boots, no changes. What the heck

[OakBehringer]

Carbs are back off. Gotta work for a few hours, then I will go though them again. Jets were clean, though

[Bodi]

If you didn't mess with the choke system, this is a puzzler. The choke lever has a cam that advances the idle... but I don't see how it could be messed up enough to do what you describe. Inspect the way it works, it is pretty simple... it should lift the slides slightly when the choke is on, but have a bit of free space between the adjusting screw and  throttle bellcrank assembly with choke off.
Otherwise, possibly your slides are up too far at idle and have some slow jet/airscrew problem? With choke on the engine is way rich and won't run, at part choke you have a decent mixture but too much throttle, no choke it's leaning out too much and won't run?

[OakBehringer]

If you didn't mess with the choke system, this is a puzzler. The choke lever has a cam that advances the idle... but I don't see how it could be messed up enough to do what you describe. Inspect the way it works, it is pretty simple... it should lift the slides slightly when the choke is on, but have a bit of free space between the adjusting screw and  throttle bellcrank assembly with choke off.
Otherwise, possibly your slides are up too far at idle and have some slow jet/airscrew problem? With choke on the engine is way rich and won't run, at part choke you have a decent mixture but too much throttle, no choke it's leaning out too much and won't run?

First, let me just point out that the bike was running a little rich before, but nothing major. Except that one cyl was not firing @ idle. That's why I pulled and cleaned the carbs.

So, that being said, good point about the idle advancement cam / choke lever. I never adjusted that, so it's still set in a good spot as my choke and idle were fine before. Now - the fact that it raises the slides a bit at full opening might be why it dies @ full choke, but a bit under full choke and it will idle. I hadn't thought of that.

One thing to point out though, the last thing you said:  "no choke it's leaning out too much and won't run" - this is not true - at no choke it is blazing rpms  I believe around 4500.

OK... what does this mean...

All I can think is that the choke being opened is pulling enough air in to burn all of the fuel that is being pulled in because the slides are set too high and, as a result, blasts up to major rpms.

I'm going to blow some compressed air though the carb ducts, bench sync (I didn't do this the first time), and put 'em back on. I'll let ya know what happens.

Thanks for the reply.