This bike just wont run right!!

Heres what I have done so far. Cleaned carbs out very well. Wet set all floats. Checked valve clearance. All were good.

So I actually had the bike running well at one point. It was idling nice, and I took it for a test drive and it felt pretty good. But then the next day it wouldnt start, and the throttle was binding. So I took the carbs back off, and the problem was I didnt clean the gas tank out good enough before installing that too. The carbs got all gummed and varnished up again.

So I took those back off and cleaned them out real good again, wet set floats again too. I just got it all back together and I expected it run like the other day before I put the tank on.

Well no such luck. I can keep it running with the throttle if I keep the rpms around 1500 or better, but it will not idle on its own. I have the idle screw all the way in, and I still have to give it some throttle to keep it running. It feels like I am having to give way too much throttle for the rpms its running at.

What is going on here?

 

Have you checked for vacuum leaks? Throttle shaft seals and carb to head rubber boots are common places for leaks.
If you soaked the carbs in dip tupe carb cleaner there is a good chance the throttle shaft seals are dried up and leaking.

 

I didnt soak in dip. I think the manifold to head boots should be sealed up pretty good. I did Rick's method of gasket sealant-gasket-sealant-gasket-sealant-manifold. I would hope that will all that it is pretty air tight. I havent changed the throttle shaft seals, but while its running I tried spraying starting fluid around the shafts and boots and nothing changed.

It seems like it is a vacuum leak, but I have no idea where it could be.

 

Also, you didn't mention the words "bench sync".

A bench sync and running sync are necessary any time you are into the carbs.

 

Now I am starting to wonder...

What type of gasket paper do you guys use for the manifolds? The first time I did it, when it ran good until I put the tank on, I used the cork material. It was on the thicker side, and when I tightened it up the material compressed a good amount. It seemed to squish out on the sides, and I didnt really like that.

So this time I used the rubber fiber paper. It is thinner than the cork, and doesnt squish out the same way. So I thought that would be better.

But now I am wondering if the first time around was a better seal than now. What type of material do you guys use?

 

Carbs don't "varnish up" overnight. If you found gumminess or varnish you didn't clean them in the first place.

What is going on here?

-You didn't get the carbs truly clean. How far did you break them down? Primary mixture screws? O-rings on same? Emulsion tubes?

-You skipped doing a bench sync,

-Didn't do a running vacuum sync with YICS blocked (if applicable.)

-DID you submerge the still-assembled carbs in solvent? mlew is right about that.

And as far as making your own manifold gaskets, I wouldn't. Just get some real ones from XJ4Ever. How long you wanna fight this anyway? You're well on your way to membership in the "I've cleaned my carbs five times" club.

 

I did not say the carbs varnished overnight. I thought I properly cleaned out the old dirty tank, but I didnt. So when I put new fuel in the tank it dissolved some more varnish in the tank and sent that to the carbs. They were spotless and smooth when I installed, and sticky and coated in varnish from the tank when I removed them.

I broke the carbs all the way down except for removing butterflies and throttle shafts. I didnt do a running sync yet because it wont even stay running without playing with the throttle.

And I did not submerge the carbs.

 

Good.

Go back and double-check the float levels, and do a more accurate bench sync. Instead of trying to use strips of anything as "feelers" use Polock's method of the relationship to the tiny "bypass" holes in the carb throat to get the butterflies in the same position.

Then, as long as you don't have any vacuum leaks (and you're taking the time to re-attach the airbox boots) it should run well enough to get a sync. If not, then replace your homemade intake manifold gaskets and have another go.

It's not going to run right until you get it well-sync'ed. Sounds like you're close though, with your valves in spec and all.

It also sounds like you need an in-line fuel filter. $3 could save you a lot more effort.

 

Float levels was the last thing I checked before installing the carbs. They were spot on.

The airbox boots are reattached. I think for sure my problem is vacuum leak. It has to be. I am going to pick up some hose clamps today and replace the clamps that attach the carbs to the manifolds. Some of them were bottoming out so maybe they are not getting tight enough to make a good seal.

Well thats the hope anyway because I really do not want to re-do those manifold gaskets.

 

Almost sounds like varnish in the ears?

 

What are the ears?

 

Ok well I ordered new throttle shaft seal. But I decided to go pull off the 2 end seals and see how they look, and they actually didnt look too terrible to me. One of them was a little soft and seemed almost a little stretchy. The other felt pretty good. It was soft and pliable and didnt look like it had any tears or anything.

I really hope this is what the problem is though. Because if not I have no more ideas.

 

Here is an update to this thread.

I have since replaced the throttle shaft seals and got the bike all back together.

The bike is still very hard to get started. After a while of cranking I can eventually get it going. But I have to keep the rpms around 2k or better to keep it going. If they drop below that it will die. But once the bike is good and hot I can keep it idling at 1100, but only after it has been running for a while and the engine is hot. Not even just warm, it has to be hot to idle.

Once I reach this point I can shut it down and start it with no problems.

Another thing I notice is if I cover the airbox inlet port with my hand the rpms will shoot up to 6k and stay there until I let go. I also notice when it is cold if I cover the inlet I can start it up pretty easy.

Is this just acting like a mechanical choke? Or maybe the airbox is just flowing too much air? The filter in there is dirty, but I would think if anything that would restrict flow.

What do you guys think?

 

Ohh I forgot to mention I did bench sync and thats all good. Also the metering ports in bowl are absolutely clear, as well as the enrichment circuit. So that cant be a reason for the hard start.