I've rebuilt the carb. New jets, float gasket blahblah... The book says when you replace the pilot screw, go from lock down to 2 and 5/8s out to start and then use the throttle adjustment to fine tune.It says a bunch of other stuff, and I get that, but I'm experiencing backfires through the carb -- or coughing -- whatever you want to call it. I've backed the pilot screw out in 1/2 turn increments and am currently at 4 complete turns out. Also when the choke is pulled out it runs okay, but as I slowly release it, it begins to stall out. Increasing the throttle at that point causes backfires/misses and stalling.

Is the Pilot Screw the right place to look?

Thanks for any advice.
(will post pics later to maybe help someone else)

R

 

Try moving the main jet needle a notch to increase fuel. Never been one to play with the pilot air/fuel mix, it is really only for idle speeds. Never been one to fit carb kits either, I bet it ran better before you rebuilt it.

One point, if you can see it spitting back you haven't got the air filter on, and if you haven't got the air filter on and airbox closed up, you are not getting the right air fuel mix anyway.

 

Well...duh. SMH. Thanks. I didn't even make that connection. (between the air filter and the air fuel mix screw). I wasn't sure what the "pilot screw" (as the manual refers to it) actually did. Calling it the Air/Fuel mix screw makes a difference. Not that it would have dawned on me anyway, without you hitting me in the face with it.
This whole thing started when it stalled out on me a month or so ago. Checked the plug. It was getting regular spark. Sprayed starter fuel and it fired up. So no fuel. Gas was good and delivery was good, so I pulled the carb. Took it apart, cleaned it blew it out, put it back together and re-installed. same issue. Replaced the plug. No change. After reading a couple of your posts, I traced the issue to the voltage regulator. That fixed the no start issue, but now it ran rough. Sooo...here I am and that's the genesis of the rebuild. I'm really close.

And yeah, messing with the "pilot screw" is a real PIA -- unless you pull off the air filter and air box so you can turn the carb sideways to get at it. Armed with new information, I'll have at it again and report back with pics. Maybe it will help someone else.

I knew nothing about carbs other than the basics, so this is a great learning experience. Thank you for your help.

 

@merryman Took the carb off and took it apart again just to go back through it and make sure I didn't leave anything out and reassembled it. Backed the Air/fuel pilot screw out the recommended 2 and 5/8s out. Idle screw was at zero - just touching the throttle plate(?). Put it back in- this time with the air box and filter in place. Pulled out the choke and cranked. It started, died. Primed it a little, repeat. It took a couple of tries, but eventually it started. I kept the choke out while i adjusted the idle screw (not the air/fuel screw). Got it to run pretty decent but it seems like it runs better with the choke out even after a few minutes. And I still get the occasional hiccup in the carb spitting back like it's getting too much fuel.

I know I need to adjust the Air/Fuel pilot screw some - according the manual anyway - but I think I'm going to get the special tool that they mention because getting to that air/fuel pilot screw is a super pain.

Will post some pics after I get them sorted..

 

Finally got the tool. It is convenient, but takes some getting used to. Probably could have accomplished the same thing with a stubby screwdriver, but, oh well. Having a hard time finding the right balance with the Air/Fuel pilot screw. I started with 2-1/2w turns out with no assist from the throttle adjustment screw and cable adjustment.. Seems like it runs much smoother with the Air/Fuel pilot screw way out -- too far out - to the point where I think it's almost ready to fall out.

Is that normal?

Here are some pics. Sorry they are so large. Tried to scale them down, but I obviously don't know what I am doing.







:

 

No pics of the main jet, did you change it? I never do, but then I never change any jets as a rule. I do change the main jet needle sometimes as this does wear, in fact I have had a few wear clean through and drop into the jet, blocking it, almost always Honda 500s for some reason. As I wrote above, this needle should be adjusted upwards if you think the bike is running lean. Makes far more difference than fiddling about with the idle jet screw. That jet bridge I can see in the box of bits can be put in the wrong way up, but I don't think it would run at all if you did that.

 

Thank you so much for your response.
Yes I did replace the main jet. I just didn't want to bore everyone with even more :"fascinating" images of carb guts.
There are 4 or five notches on the end of the jet. I replaced the retaining clip into the center or third slot as recommended.





is this the "jet bridge?"



If so, then yes, I did put it in wrong, but as I was going back through the images I took, I caught the mistakes before reassembling.

I'll remove the main jet and move the retaining clip as you suggest and let you know how it turns out.

Again, thanks a bunch for your expertise.

R

 

Please bear with me as I am learning as I go...Running lean means more air than fuel? By adjusting the jet "upwards", I think that means moving the retaining clip towards the pointy-end, so that it protrudes less into the cavity, allowing more fuel and less air? Or is it just the opposite?



Right now I have the clip positioned at the fourth notch from the top of the jet - closer to the pointy end.


And again, with the choke pulled out, it runs pretty darn good. After initial warm-up. releasing the choke, it idles pretty nicely. However, when applying throttle, it spits back or coughs like it's getting too much of something - fuel or air. My guess would be fuel, but I've already proven I don't know sh*t.

 

If you push the throttle open quickly they all spit back. If you open steadily it shouldn't, and this is usually a sign of a weak mixture, as any engine needs a rich mixture during acceleration, hence accelerator jets on old cars. Try the bike as it is, unless it is really bad when accelerating and, once it has done a long ride, shut off right away, no letting it idle then, once cool, remove the plug and take a look at the colour of the nose. This will tell you how far out the carburation is, plenty of pics of how it should and shouldn't look on the net. Did you check that diaphragm for holes? This is quite a common fault and very expensive to replace.

As for that jet bridge, I'm not sure I got the terminology right but here it is, fits on top of the emulsion tube, that main jet needle sits inside it.

 

Ummm....ok. Ya know...I didn't even know there was a jet bridge till you mentioned it and pointed it out.
It kinda hides up in the carb cavity.So, needless to say I did not even know it was there -- until you mentioned it. Thanks.
I did my research. Pulled the carb today (getting really good at it)(. And dug into it. Found it covered in goo. Replaced it. Cleaned out the goo. And ....

Runs like it used to run. Absolutely no issues.

I want to thank you for your continued support and patience. I will post a couple more images and some descriptions in an effort to help someone else.
wootwoot!!!
Randall.