Won't idle.

What size are they?

 

don't know, haven't taken one out for many years

 

I was going to make one myself but found a guy on Ebay that makes a nice aluminum one with o-rings for $33.

 

If you're not idling now, then blocking the YICS ports isn't going to fix that. [EDIT} Unless there is a vacuum leak at the YICS mainfold.

A 4-1 will make it a tad lean (not much though), and since the baseline for the idle mixture screws is for the stock exhaust, and most of the time we end up at 2 3/4 turns out you might need 3, or to go up one size for the pilot jet.


If you really want to mess with the tool:
home-made-yics-tool-diagrams.72713
@chacal also sells them, including OEM quality seals.

Keep in mind that hardly any of us use the thing, and the one member that I'd trust to rebuild my carbs has his sitting on a shelf still in the wrapper.



Merged so we can keep track of what's going on.

 

Ok.....im getting really good at pulling and replacing these carbs. A skill I hope to carry on to my other bikes. I was doing some reading and I found that there are o rings in the pilot jet bores. I never even saw them. So I got them out and found 2 that were flat, and one that was flat broke. I went ahead and purchased a full rebuild kit complete with o-rings and new jets. I'm tired of fixing someone else's f***up. I wanna fix my own f***ups damit.
I've got a colortune on the way, and a few other parts, and tools.
Now, I also read another post where the o.p. was having basically the same issue as me. Then, dudes neighbor pops in and tells him to adjust his timing chain and switch to a higher octane. As far as I know, the choice in octane won't keep these bikes from idling. But I was curious aboyt the chain adjustment. And how I would check it.

 

The camchain on yours adjusts automatically.
The machine was engineered to run on low-test pump gas. Increasing the octane is just a waste of your money.

The idle mixture screw o-rings are often ignored, and will cause no end of trouble unless they are in good condition. Vacuum operated carbs are intolerant of vacuum leaks.

 

your motor will not benefit from high test fuel.



it is located under the carbs. you will see a bolt with a lock nut on it pointing 90 degrees out of the adjuster if it is adjustable.

if it is an automatic adjuster it may need to be removed and cleaned and reinstalled.

 

this link shows how to adjust if it were adjustable
http://www.xjcd.org/650H_engine_maintenance

 

My new rebuild kit came in today. I'm going to tinker with that tonight. My colortune also came, so it's going to be an interesting 24hrs.

 

With my MAC 4-1 I have to run almost 5 turns out. If you're at 3, that's prolly why it won't idle.

I bet it you raise the idle screw in enough it will, but if you touch the throttle it will never come back down.

 

when the mix needle needs to be open to many turns you have to go up 1 size on the pilot jets.
at 5 turns out I think you are at that point to change the pilot jet .

 

+1

 

+2

 

I have a jet drill set, I'll try going up a size on the old jets and see where that takes me. Worse case scenario I'm back to square one with my new set. Spare parts are fun lol

 

I hope you have a drill press or some way to make sure that all four of those jets end up being the same size. Best of luck with that and I hope it works for you.

 

Which pilot jet am I supposed to increase? I'm overthinking, and need clarification. Is it on the top end under the diaphragm?

 

There is only one pilot fuel jet, and if you aren't aware of that and where it is, then you need to slow down and not do anything until you understand where all the parts are and how they work.

Carbs and Fuel System

IN THE CHURCH OF CLEAN

THE SECRET LIFE OF CARBURETORS

Inside your Carbs

To answer your question directly, the pilot fuel (commonly just referred to as the pilot) is covered by the flost bowl, and is the smaller (numerically) of the two fuel jets.

 

My confusion is derived from the picture of the upper jets, That someone had labeled as the pilot. Thank you for clearing that up.

 

the jets onder the diaphragm are air jets.
1 jet is the pilot air jet the other jet is the main air jet.
both the air jets supply air to be mixed with fuel before fuel is dispensed.

the pilot jet circuit has a pilot air jet a pilot fuel jet and the mixture screw.

the main jet circuit has an main air jet, a main fuel jet and an aspirator tube (emulsion tube) under the main jet.

the pilot jet runs the bike to around 2000-3000 rpm which is when the main jet starts to kick in.

 

Is worked!! I went up a jet size and she started right up, without choke. I have her purring like a kitten. FINALLY. I suppose it was the exhaust mod throwing it off. I'm about to get my gear on and take it for a spin to see how well I got her dialed in. I just finished a running sync