Rough idle start

[TyeGuy]

I vaporblasted, rebuilt, and rebalanced my vm22ss carbs. I?m a little inexperienced with carbs, which is why it took me so long to rebuild them because I was so thorough with the process, but since the rebuild, I feel my bike takes a lot more effort to start/warm up. With the choke fully on, it takes a few kicks to start( it used to start on the 2nd-3rd kick). I also have to leave the choke fully on for a solid 5mins before I can switch it to half choke without it dying. After a few minutes with choke fully on, the RPMs will raise to about 2500, I?ll then start to close choke about half and let the RPMs drop to about 2000 RPM. Then when I attempt to close the choke completely, I have to roll on the throttle a tad bit to keep it from dying. If it dies, I have to position choke back to half open and let it warm up longer until it can idle without bogging down.

Once it?s warmed up with choke complexly off though, the bike idles perfectly around 1750 RPM. What can I do/inspect to help it start smoother? I?m gonna try to sell the bike soon, and would like it to start easy in front of a potential buyer.

 

[tom203]

A warmed up idle of 1750 is far from perfect- with functining pilot circuits and at least a bench sync, an idle of 1200 should be no problem. I suspect the pilot circuits are clogged forcing you to rely on "choke" longer than necessary.

 

[Big T]

Did you clean them per the VM tutorial?

 

[Steve]

What are your air screw and fuel screw settings?

Do you have stock airbox and exhaust?

.

 

[TyeGuy]

A warmed up idle of 1750 is far from perfect- with functining pilot circuits and at least a bench sync, an idle of 1200 should be no problem. I suspect the pilot circuits are clogged forcing you to rely on "choke" longer than necessary.

Sorry for my absence. You're right its not. I had my idle screw too high. I guess I left it high after I synced my carbs or something. I adjusted it, and it does idle fine at 1200. Sorry for the confusion.

But it still seems to warm up a little rough.

 

[TyeGuy]

Yes I did, I followed bwringer's guide. http://gsarchive.bwringer.com/bikecliff/images/vm_carb_rebuild.pdf

 

[TyeGuy]

yeah I have the stock airbox and exhaust installed. My pilot air screw is 2 screws out across all 4 carbs. When I sent in my carbs to get vaporblasted. It took off the factory seal on the pilot fuel screw. But the mechanic who vaporblasted them wrote me an email telling me he noticed them and although the seal was cleaned off, he set them back to 1 1/2 screw out. I think I checked them at 1 1/2 screw out when I was reassembling the carbs. I hope I did anyways.

 

[Big T]

Pilot fuel screws should be 3/4 of a turn out.
Plus, they weren't removed for cleaning?

 

[TyeGuy]

Pilot fuel screws should be 3/4 of a turn out.
Plus, they weren't removed for cleaning?

I double checked what my mechanic actually said, and I was wrong. He checked what they were turned out to before he removed them for cleaning, he recorded the pilot fuel screw was 1-1/4 out, not 1-1/2. Bwringer's rebuild insturctions states to set them 3/4-1 1/4 turns out. I honestly can't remember if I left them alone or screwed them 1/4-1/2 turns in.

Aside from using the choke a little longer to warm up the bike, I don't have any running issues. It doesn't backfire, or pop. The bike doesn't starve for fuel when I let off the throttle and come to a stop, and the bike idles well at 1200RPM. So I would think my pilot fuel screw is set correctly.

Now that I lowered my idle to 1200. I could check my spark plugs and see how my mixture is. That would determine if my pilot fuel screw was set wrong, but then again, I'm still in spec of my pilot air screw turned out 2 turns.