I got stranded today! And have no idea what's up!

Ok, I'm looking for some help here - hopefully someone can offer some experience so I'm not fishing in the dark this weekend.

I've been having issues with my bike lately. In my previous post http://www.xjbikes.com/Forums/viewtopic/t=15073.html I described the problem:

"The problem was - on startup, left cylinder was firing [petcock side], right wasn't (sometimes for up to 10 minutes) - cold exhaust on right. After a while, would start to fire - puh.......puh.......puh..puh..puh..puhpuhpuhpuh. Leaked gas like a bugger. A co-worker, who rides the same bike as myself (83 maxim 400) said pull the carbs - sounds like a stuck float."

I pulled and thoroughly cleaned the carbs, completely breaking them down (although I did not break the rack) - I pulled every component I could, soaked them and the carbs (except for rubber/plastic parts, of course) in automotive dunk, sprayed everything out with carb cleaner, cleaned the jets with copper wire...they were spotless.

Monday I rode to work - rode beautifully. Idled well, and whereas before the bike used to lose power at high RPM's (over 4000) in 1st/2nd (sounded like "mmmmmmmmmmm - bwaaaaa" as it revved and then choked), it ran flawlessly - it was like having a new bike. It ran about 45 minutes with absolutely fabulous performance. Tuesday, it sat in the garage - snow on the road.

This morning - idled a bit rough - then on the way to work it started to stall out at low RPM's, and lose power at higher RPM's in the low gears. I hit a stop sign after about 10 minutes, and it stalled. Could NOT get it started again, although it would turn over.

This afternoon, I went to pick up the bike. It turned over 15 - 20 times, and on full choke with throttle full on it finally fired up. Again, it was only the left cylinder (petcock side) firing - the right cylinder did not fire until I opened up the throttle and held the RPM's at 4000-ish. As long as I kept the RPM's in 3 - 4000, it ran fine - over that, lost power, under that, started to stall. It was NOT a fun run home. As I pulled into the driveway, the RPM's dropped below 2000, and she died. I closed the petcock (on reserve), but she leaked a bit of gas after standing.

Also a lot of smoke off of the engine block when I first fired it up (see pics) - I am assuming b/c of leaking gas? There was no evidence of smoke by the time I got home.

A co-worker and fellow 83 maxim 400 owner thought initially it was a stuck float valve on the right - hence the carb cleaning. A fellow at Action Motorcycles said given the age of the bike, more likely was a worn pin in the float valve on the right (see pic - that's the left side one, though).

In the thread here http://www.xjbikes.com/Forums/viewtopic/t=15073.html, rhys had this to say:

Only thought there is that if the fuel supply is shot, wouldn't both not fire? Although I suppose the fuel does feed into the right side first....hmmm. I know that my cap does not function correctly - I filled my tank a tad much on my very first fill, and it overflowed b/c of a faulty seal (and I found out the PO's "new professional paint job" was NOT with gas resistant paint - it bubbled and even peeled in one area).

Any thoughts from out there?

 

Looks like the carburetors need to come off again.

Make sure the floats are not full of fuel and sinking. Replace the float needles and seats if you didn't last time.

Set float height to be within spec.

Clean them again while you're in there.

Is the tank squeaky clean and a good in line filter installed? If not you'll have to keep cleaning the carburetors.

 

Am i mistaken or should that float needle have a rubber tip? I'm pretty sure mine does, but it's been a few months since i pulled mine. Also did you check to make sure you're gettin spark on the right side, almost sounds like your alternator may be weak/going and you don't have enough juice to fire at low rpm.

Couple things to check.

What do your plugs look like?

 

I was just looking at your pics again. That boot from the airbox to carb looks a touch out of adjustment. Mine was the exact same way (air box was pushed too far back so the boot wouldn't reach)

Maybe check that your airbox is pushed all the way forward, to get a better seal on that boot to the carb with the clamp.

 

Neither of my float needles had a rubber pin on them...the plugs are relatively new (put in by PO when I purchased in March '08) although I have not checked the gap, and I am getting spark.

Yah, I pushed the box forward as far as I could, but that's the best I could do. The airbox was not bolted in place when I cleaned the carbs, so I think the PO tried to push it forward and left the bolts just sitting there loose. I tightened them up, and it didn't change the orientation from loose - it just doesn't seem to want to go forward anymore. But those boots are a bit stiff as well, which doesn't help.

 

Not sure what you mean by "full of fuel and sinking." How do I check that? And what is the float seat?

Again - how do I do that?

I don't know about the tank (it has a red coating inside of it?) but there is a good in line filter to the petcock.

 

As for the float filling up with fuel question. There might be a pin hole in the float. You can check it by putting the float in a bowl of water and see if air leaks out and the float sinks. If it does sink. Then you will need a new float. I don't know if you can patch the hole or not.

There is a screen in the petcock but that is not enough. You will need a seperate inline filter in the fuel line from the petcock to the carbs. Its cheap and you can get it at your local auto parts store.

As for the float height I don't know what is should be on the 400 maxim
On my 650 its 17.5 mm plus or minus .5mm
I'll have to look up the exact specs for your bike.

 

I had to actually rest my boots on the box (airbox not in the grove of the boots) and used some liquid electrical tape to seal it. Only way i could get it to not leak air at the carb. I MIGHT have been able to push my airbox up enough, but i wasn't gunna risk it leaking.

 

Ahh, so we're talking about the actual plastic float...that makes sense. I'll need to check that.

Sorry, that's what I was trying to say - I have a separate inline filter from the petcock to the carbs - I think I said from the tank to the petcock, didn't I. Sorry for any confusion.

 

Sorry, that's what I was trying to say - I have a separate inline filter from the petcock to the carbs - I think I said from the tank to the petcock, didn't I. Sorry for any confusion.

Ok cool. Now just check those floats.

 

For the last sort-of unanswered question: Not all float needles have rubber tips, some are just plain brass depending on the brand.

 

So am I correct in saying it is the considered opinion of most here that the problem is probably due to an issue with a float/float valve/float needle?

 

If you spilt fuel from the tank it went over the motor, in between the fins etc, the ( smoke ) will be the fuel / paint mix burning off, it will clear on it's own.

 

Sure sounds like it, OR with nothing more complex than a persistent piece of CRUD that has become lodged under one. It's just that anytime anyone mentions that their carbs have "been cleaned" these questions come to mind. Float levels are a "set it and forget it" kind of thing, until some mere human comes along and disturbs them, then they may need readjusting. Bits of crud can get stuck in a float valve very easily, hence the need for a fuel valve to begin with plus the need for an inline fuel filter.

Did you ever pull the plugs during all this? I would be curious to see if the right side was obviously way rich, it would tend to confirm the initial diagnosis (a misbehaving float.)

 

If you're spilling fuel these are the culprits. Only other thing would be a cracked carb body or leaking fuel runner.

The seat is the thing the needle slides in and closes off against. Depending on the carburetor it may be captured by a screw or threaded in.

Then the float needs to be set to regulate the fuel to the proper height in the bowl. You really need the service manual to get the specs and proper method of adjustment.

 

How would I tell if the right side was way rich?

I was pretty meticulous in the cleaning, so I don't think I introduced any new material - that being said, it is entirely possible I did not remove all of the old CRUD, either...when it comes to the float valve, I cleaned the needle, the brass housing the needle sits in, the screen, and thoroughly soaked/sprayed out the hole it slides into.

 

Just a quick confirm, no rubber tips on my float valves either

Otherwise, carbs can never be "too clean" so pull them and give them another look, something last time may have been loosened and later broke free to clog up something...

I cleaned mine 3 times the first year...

 

I must be remembering things wrong then hahah like i said it was quite a few months ago i had mine out

We still need to know what the plugs look like on right and left side Maxim. We need to know the colour of the insulator (White or sooty black)

 

I'll try and pull them tonight to take a look

 

I was viewing this sticky http://www.xjbikes.com/Forums/viewtopic/t=150.html and came across this:

I have that vacuum line going to the petcock...now, it seemed fairly squashed when I removed the tank. So I straightened it out. I wonder....if it was kinked/restricted, would that cause issues? Removing the tank, having it straightened, may have caused it to run well, then it sitting a couple of days, deforming to its squashed shape, may have mucked it again? Now, I don't see how it would result in fuel leakage, but...

 

If it was kinked enough it would block the vacuum that operates your petcock. It would be a lack of fuel rather than an abundance.

Now, if you had the manifold hose attached to the BOTTOM of your petcock and had it on prime well that would cause some issues heh.

 

Wait now; we may have been jumping to conclusions.

WHAT IF the smoking at startup has NOTHING to do with this issue, but is the result of some valve cover "weep" but lead us to think the carbs were leaking.

We've had no other evidence of "an abundance of fuel."

Did you switch your petcock to "PRI" when this happened? "ON" and "RES" are vacuum operated, "PRI" is not.

If you pinched the vacuum line the bike would act like it was running out of gas unless it was on "PRI" is this a possibility?

If that is indeed the problem, your smoking is probably a minor oil seep somewhere (my '81 is starting to develop them now that I pound its little ***a$@*** down the freeway with great regularity) that burns off after a 10 minute ride and takes 3 hours to seep down to where it can smoke again.
***Edited by Robert. C'mon Fitz, language! Thanks!***

 

Here's the photos of the plugs, as promised - the left (petcock side) is on the left, and the right is on the....well, right. The right one is the side not firing. I rubbed the business end on the paper in the second photo - you can see all of the soot buildup there.

Well, I'm pretty sure it's gas, because

1.) It reeks of gasoline
2.) It feels like gasoline
3.) The cardboard I threw under the bike before was soaked with gasoline
3.) It smelt waaaay nastier than burning oil, the smell of which I am very familiar with thanks to a Dodge Aries I owned once upon a time

 

OK, so we WEREN'T jumping to conclusions you definitely have an overabundance of fuel. So if the bike HAD been running fine and then this suddenly started, it does point to a sticking/stuck or polluted float valve, or as someone had suggested, you may have a float with a hole in it, and it fills up with gas and quits floating. SOMETHING has you running way rich.

Remember too, since this is a YICS motor, a HORRIBLY rich condition on one side will show up on the other as well. Both plugs could look like that even if the problem is only one carb, if that carb were puking enough gas into the motor.

I think those carbs gotta come off. You need to check the float heights, both statically (dry) and then with fluid (mineral spirits is safer than gasoline if you're doing it on the bench.) You may take them apart and find a main jet laying in the bottom of the bowl, you never know...

 

Agreed, take em off and inspect/adjust

 

How do you check the float heights? And, as I don't yet have a service manual or my xjcd - anyone got the specs?

As for inspection - I had them apart last saturday and had a good look over. Now, everything (as far as I know) was where it was supposed to be, but is there a few things I should specifically be looking for?

 

Well, it was definitely running rich...I went to remove the tank today to pull the carbs again, and it was empty. I ran a tank of gas in only 19km! That's got to be some sort of record...I thought I would switch out that (upside down) oil filter while I was at it - and found my oil full of gas. I would guestimate I had close to a litre of gasoline in my oil....

So, I checked the floats for leaks - a-ok. So I bit the bullet, or bought it, rather - at $90 a pop, I picked up two float valves and put them in. I found it interesting how the old ones could fall out if I turned the carb over, while I had to push the new ones in b/c of the o-ring fitting nice and tight. Who knows, maybe that was part of the problem.

I had no way of checking the float heights, as I don't have a service manual nor the knowledge how, so we'll hope they're good to go.

In terms of getting the carbs on/off - two pieces of advice to share: someone advised me to remove all of the airbox bolts in order to be able to slide it back further - I removed the two on top, and the one by the battery - made a HUGE difference. As did the advice of the guys at Action Motorcycle, which was to spray/work some wd-40 onto the airbox boots to soften them up a bit. I have a MUCH better fit of the boots onto the carbs than when I put them on before - in fact, they're seated better than when I bought the bike.

I'll fire it up tonight (had to go get some gas in the jerry can) and take it for a test run tonight or tomorrow - I'll let you folks know how it goes!

 

I guess you found out were your gas went to.

 

If your crankcase filled up with gas you have more than just a sticky/problematic float; your petcock didn't shut off (unless you left it on "PRI.")

If the petcock had shut off, only the carb with the stuck float could have emptied itself into the motor. You got a whole lot more than one float bowl's worth of fuel in your oil, which means it kept flowing.

Float heights are checked two ways; one "dry" adjusting the physical location of the float when it stops in the 'up' postition, then again by attaching clear tubing to the drains and seeing where actual LIQUID ends up when they shut off.

Somebody recently did a rather nice photo post showing float height checking I'd find it for you but my 'search-fu' is at low ebb this morning.

Check your oil level RELIGIOUSLY before every ride until you get this fixed, no need wrecking the motor.

 

Thanks all for your help!

Bigfitz, when I parked I left the tank on reserve - I assumed that b/c that's what I flick it to when I remove the tank that's what I should have had it on when it was parked?

Anyways, I ran the bike last night for 20 min, and this morning to work (only about a 15 min ride). It seems it might be a tad rich - but, it fired on the first push of the start button, sounds a lot smoother while running (no cylinders firing only periodically), and I could open the throttle wide open in 1st/2nd without it dying above 3000rpm (something that I could not do before). We'll hope she holds out, and that I've found the culprit!

The moral? 26-year-old float valves may not function as intended.