Strange carb problem

Well, the other day I noticed that my number 1 cylinder was not working; easy to tell since pipe was cold. So I went about checking the mains; got spark (man, that smarts), got great compression (105+psi, I say plus cuz I didnt hammer down on the connections), and so that leaves fuel. Take carbs off and give a basic cleaning. I found bunch of crud in 1st carb. The 40 jet (primary or secondary?) was clogged and the screen was completely clogged. I put it back together and money; thing works great. BUT, here's the problem, it did it again and this time it was just that the float level in the number 1 carb was real low. So I brought it back up and nice, its fixed. BUT actually its not cuz it did it again.
What would cause the float level in a carb to drop too low? Like its not refilling or something. Also, I happened to notice that the gas inlet to the carbs is between the number 1 and 2 cylinder on my bike, whereas the inlet on my 550 parts bike is between the number 2 and 3 carbs. Would this have anythig to do with it? Please help; I searched this site for the last 4 days with no luck.

 

Well, I did find a little info regarding bending the tabs of the float mechanism so as to change the level of floats. Is this how its done, and how exactly? Seems like a bunch of trail and error, which is fine with me, I just don't want to go bending shit without definate answer. Any help would be much appreciated.

 

It's trial and error.

Set one float height and verify it with the clear tube method. If it's good, move on to the next float. After you do this a few times, you have a rough idea of how much to bend the tab. Be careful though, the tab can break.

I use a pair of wide, flat jewelers pliers as it grabs the entire tab and bends it at the very bottom.

 

For getting the float pretty close dry you might find THIS topic helpful.

 

Sweet! I knew I could count on this site. Yeah, thats what I figured. That sit will be quite useful MiCarl, thank you much. I used the clear tube method, and did bench sync; other 3 seem to be spot on, while the 1 has the float sitting way too low. I will peep it out tomorrow. Thanks again people.

 

TIP:

If you bend the tab enough to know you bent it you probably went too far.

Commit only TINY bendage!

 

Having found "Clogging Crap" when you went looking would be a good reason to:
Look and see if the Petcock Tower is in place.
Install an Inline Fuel Filter.

(If you only have one Float to adjust. Pull a good-one and lay a Ruler across the Float Frame under the Tang.
Measure the Gap between the Edge of the Ruler and the GOOD Float Tang.
Match-up the one that's not right to the value of the known good one.

 

Also check if you don't have a leaky float...

 

I mentioned that one once it was how I learned they're SOLID.

Not like other bikes I have known with soldered brass floats.

 

Fitz...UR saying that the black plastic looking floats are actually solid material? They can't leak?

Secondarily, I replaced one float because the material was pitted and I thought it might be prone to leak. Which means...it can't leak and I have an extra float that will float no matter what!!!

 

Cool, thanks for all the input; I'll be sure to take all into consideration. The cylindrical filter is in place on the petcock. The tank had some problem areas and obviously contains some rust. I have an inline fuel filter on it now as well. Got to run though, old lady riden my ass. Peace

 

Hey guys. Yeah, so I took the carbs off again and checked all that stuff. I measured the float tabs to the nearest 64th, so they are close, and, to my displeasure (may be wrong word), they are the exact same. So, before bending away, I checked the mixture screws and they were all over the place. The carb in question was 3.5 turns out. Could this cause the bike to be running very lean, and thus starving the engine and creating the 'cold pipe'? The others were between 2 and 3 turns out. I put them all to 2.5 turns out. I also moved the tab .5 of a 64th (I'm sure wrong terminology, but the point is made: I moved it a little). Well, figured I'd keep up on it. Thanks for any help.

 

Yeah, so...I will answer this one on my own. Yes, having the mixture screw turned too far out will create a problem in which the float level remains too low and leans out the bike a lot, thus making for an ill performing and cold cylinder. I brought all 2.5 turns out. Problem solved. Bike sounds great. Oh, I also freed up the rear break. Which actualy brings up a question. My front brake does not make rear brake light do its thing, while the rear brake does. Is the front brake supposed to make rear brake light up? Stupid question? I presume there must be an electrical problem somewhere along the line.

 

That my friend doesn't make actual sense, but I'm glad it worked for you.

You are a candidate for a rear brake delamination !! Inspect your rear shoes before you ride again.
Your front brake lever is supposed to depress a little hidden, black switch in the brake lever perch. There should be 2 wires there.
Ride safe !!

 

Yeah, well, actually it did not fix the problem. Damn thing. I mean, it did work for a little longer and after sitting for a while and starting four times, though this last time it was same problem: 1st cylinder runs cold. Actually, if I remove the dimple between the carb and cylinder, it makes no difference on that cylinder when its cold on that side. When I just set the float level it runs perfect; then, after sitting, its low again. I'm lost. Well not exactly; I imagine the little improvement was from the very slight bend I did to the float tab, so I will go back to the drawing board and go little more. After seeing if the float has gone up from work I did. I hope all this makes some sense. Please keep helping and I'll keep trying. Oh, and thanks for the assisstance with front break, though not sure what meant about rear brakes. The rear brakes look great; it was the little shaft part that moves pads was frozen.

Please stick with me...I need you.

 

Do a "Live Float-Height Observation.
Hook-up a fabricated Vinyl Hose rigged with a Right-angle Union and a short section of Windshield Washer Hose to keep the jig on tight to your Number-1 Carb.

Observe what happens to the Float Level as you run the Bike.

If you have not removed the Float Valve Bodies, ... do so to examine the so-called "Beenie-screen" Filters on the Valve Body.

Eyeball the Geometry of the Float Pin as the Tang lifts and lowers the Pin within the Float Valve.
If the Pin is "Cockeyed" and not centered. Change the Wire Hanger to the other side of the Tang and get the Up-down movement centered.

Fabricate a "Liquid-separating Vacuum Bottle" and Vacuum the Pilot Air Passage out through the Pilot AIR Jet.
[Inspect the two AIR Jets to insure they are properly placed!]

 

http://www.xjbikes.com/Forums/viewtopic ... ation.html

You need to read this thread about the 28 year old rear brakes.

 

Damn! That would suck to have your brakes lock up at some unforseen moment. Thanks for the heads up; they didn't look like it was happening, but they are as good as changed.
Ok guys, back to the carb issue. I'm really stumped here. I have not set up the live float observation or vac thingy yet, but I will. What I'm looking for now is a little more brain picking. Which way does one bend the float tab if the desired effect is a higher float level? I bent it downwards twice now; once very little (<64th) and again more (2 or so 64ths) I know the measurements aren't right, but just wanted to give idea of how much I've bent. Did I go the right way? I seems as though the float level went down farther than originally. Of course it ran great everytime after, and few times after, I set float manually. I just can't figure out which way to bend for sure, and want more info. Also, could the root of my problem be some sort of vac leak (maybe wrong term) within the carb (like a torn boot)? Or, remember, I have a 550 tci in for now (having 650 fixed), could that be my problem; some sort of timing issue? That one is a reach, because seems to me that since it runs good when 1st set float, that its not a timing issue but instead fuel. People, I want to state again how thankful I am for all imput.

 

Wow that sounds confusing. The skinny, if it helps: How does the float work in conjunction with the brass pin thing with the rubber point on it? And, which way does one bend the float 'tang' to get a higher float level? Lol, thanks much

 

Well, if you orient all parts right side up, then bending the tang down gives a higher float and fuel level.
And yes, we are used to confusing verbiage.
Carry on.
Check with the clear tube method. It's the only way.

 

usually if you bend that float tang enough to see it's different, it's too much
floats on the bench, float side up, bend the tang up to make the fuel level go up (thinking thinking thinking) yea thats right

 

Thanks guys. I mean, I bent it downwards if imagining that the carbs were on the bike and in running form. Yeah I'll get on the clear tube method tomorrow. Its just really confusing me. It would seem that I bent the tab a fair amount, and anyway, what would cause this carb to come so far out of tune? Whatever though. I'll keep plugging away.

 

Hey I found something out that is definately of question. I went out to start the bike and like ussual itstarted right up. Now, the 1st carb didn't work, so I put my finger over the small oval-like hole at top of carb (you know?). Well, that did it, cylinder works great. Now, what does that hole do, and what could be up with it to cause this? Thanks much

 

Are you missing a Pilot Mixture Screw???
What is this "Oval-like Hole" you speak of?

 

OK, GOT IT! Guys, this problem has been twistin my mind; there is no reason the damn thing should not be working. I took off the carbs and float bowls 1 and 4. I noticed 4 was dripping from the needle valve, while 1 was not. Unreal, explains it all, #1 was clogged about .5inch into the gas feed hole. Yes I have put inline filter, but obviously had not for past 30yrs. I will start it up after work tomorrow and pray that its fixed, which I bet it is. Thanx a bunch for stickn with me through another one. Not enough can be said about the information highway.

 

Hey Rick, its the one at the rear of the carbs, with air boots removed, at the top, right above the main bore to the carb. It seems as though when I pluged that hole it created a vacuum and sucked up more gas, though this only temporarily worked. It did, however, lead me to the conclusion that something was very wrong and eventually to my last post. Thanks again to all that viewed and put in advice.

 

Put a Cap on it.
That's a Vacuum Testing Port.
If that's open, the Hole is getting way too much air.
Just use a 1-1/2-Inch piece of tight-fitting hose with the hose-end plugged-up with a short Hex Bolt.
Cap it.
Then, see how that Number-1 Hole fires for you.

 

I think he means something in the carb throat, upwind of the carb. (you know, the rear)

 

Without a photograph, ... it will be difficult to assist you.

The Yamaha Drawing shows Std. Carbs on the Bike.
Hitachi's.
You may have Carbs that somebody grabbed off from a California Bike that has the "Coasting Circuit" Tube.

You'd still have to seal that fitting.
Get a picture of what we're dealing with so we all know for sure.

 

Hey guys, just wanted to clear this up so you not wasting your time. The problem was a block in the left side of the fuel feed line (about .5" into where fuel feeds carb). I not sure how I missed it before, or even if its something that just happened. Anyway I stummbled upon it after not draining all fuel from fuel line. Oh well, I'll take it! Thanks again guys. PS: where does a guy find new rear brake shoes around here?

 

Hey thechuck
I would say that every price posted by chacal has been the best bargain and availability is as fast as any shop. Remember, dealer shops do not stock parts for 1980-1990 bikes.

 

Yeah and I believe it, but thats where the problem lies; I can't find that info anywhere. I know I'm challeneged, but damn.

 

Although this might not be the problem, I think it's still worth mentioning:

From what I've heard, 100 psi is death's doorway for a motorcycle engine (hopefully it'd be 120-150), and absolute compression is not as important as relative compression (125,125,125,125 is better than 125, 140, 140, 140), the difference between any two cylinders shouldn't be more than 10(?) psi. So I think it would be worth while to get a good reading on all four cylinders.

Also, yeah if you don't know the exact terminology, post some pics (500x500 pixels max), link to diagrams, etc...someone will chime in with the exact terminology and can help you alot quicker. Also, when someone else looks at this thread for advice (and doesn't know the terminology either) they'll learn quite a bit too!

Chacal has a "catalog" in the Forums section: Forums-> XJ4Ever - Supporting Vendor -> XJ MAXIM, SECA, AND TURBO PARTS CATALOG. He will also be very receptive if you send him a PM (personal message) asking what you need and giving him the Year, Model, even VIN number on the bike. He knows his stuff, and just about everyone on this forum goes to him for parts (I know I do!)

 

If you are significantly below the 119 psi Minimum Compression you are taking a risk that could result in a Catastrophic Failure.

The Compression is necessary for making Power.
More importantly, Compresssion PREVENTS the Piston from continuing-on in a straight line when the Piston reaches the Top of its Stroke.

The Compression SLOWS DOWN the inertia of the Piston's Upward movement ... applying an Air Brake to the Upward Forces and preventing the Piston from continuing Up and Out of the Engine on its way to the Moon.

A below Minimum Compression Value is going to allow the Weight of the Piston to PULL >> Upward >> against the changing in direction of the Connecting Rod.
THE ROD WILL BE EXPOSED TO THESE OPPOSING FORCES and begin to Fatigue.
Eventually, the Piston will win the fight.
The Connecting Rod will break.

And, that will be all she wrote!

 

Now wait a minute. . .
If you're running hard, turning eight grand, then close the throttle, you know, for maximum engine braking, what's happening to the piston/rod assembly on the exhaust stroke??

It's not pushing against 100 PSI for any kind of braking. I'd say close to zero PSI on the exhaust stroke, then to NEGATIVE 12 PSI as soon as the intake valve opens, at 18* BTD Center, which should suck the piston right up to the head.

And it does this over 60 times per second without fail.
(for almost 30 years too)

 

Look carefully and you'll see a Red Line on the Tach.

An Engine in good condition is designed to handle stresses to its Engineering Limit.

If the Engine weren't pushing against compression there would be no Engine Braking.
I'm writing down -12 psi in case its ever a Jeopardy question.

 

Whoa.... all this technical data makes my head hurt... :?