What did you do to your Yamaha today?

yes, and the fuel is new, it hasn't sat in the motorcycle, it ran perfectly until a fifth something to electric system, as i changed everything i assume, that only the Pickup coil can be still an issue-not changed yet.

The spark is very strong, and the lighting on the motorcycle works as it should, but the spark is very "messy" it doest have stop-go, motion, it sparks almost random, but very fast, almost like it doesn't stop sparking when the piston moves downwards.

 

You could try an auxilliary tank to see if it runs.

 

The crazy spark tells me there's an issue with the little analog "computer" in the TCI module and it might be firing very late in the cycle. It should be one very distinct spark every crank rotation just a few degrees off TDC while cranking. The little analog "computer" as it's known is a ceramic thick film integrated module that sets up the timing curve and each is tailored to the engine displacement meaning a 650 TCI won't have the same curve as a 750. I don't know how well a 550 TCI will work with your 500 but I'd say give it a try. Just make sure the wiring is correct.

 

Spent waaay too long rebuilding the front callipers on my 650 seca. As usual, took ages to bleed all the air out (well, enough so that I have what can be called a brake. It doesn't need much, just enough to ride it down the road for storage. It hasn't run for two years so will need fresh fuel and a battery.

 

Yesterday was in the high 50s but kinda gloomy looking. So I decided it was warm enough in the garage to pull the Yamaha's carbs. I really appreciate how the 45-year-old airbox-to-carb boots are still flexible and supple; they don't make rubber like that anymore!

Unfortunately, I found no explanation for the #1 carb overflowing last Friday morning. Nothing lodged in the float valve, no damage to the needle, reasonable sag on the float (compared it with the other carbs, which did not overflow), and carbs (internally at least) clean as a whistle.

Since I had to turn the rack upside down to reach the screws, there is a chance that any piece of debris that held the #1 float valve open has retreated back upstream, so I suspect the next thing will be to pull that carb off the rack and clean the fittings.

But not today: it's sunny and supposed to hit 65º this afternoon... and I have two other bikes that could use a last warm-weather ride!

 

One more thing I should mention... because I live in the heart of the corn belt, where non-ethanol fuel is by and large not an option, I installed float valves with metal (vs. rubber) tips. Shame nobody makes ethanol-resistant Viton® tipped needles for this bike, but I suppose ethanol was a new thing in 1980. Since Len recommends all-metal needles for people who live in corn country, I assume they are not the source of the problem. I could not see any marks or anything on the needle. I suppose I could pull the valve seat and see if there's any sign of damage there...

 

There was a "gasohol" experiment back in the early 80's using ethanol mixes but it died off and I don't think Yamaha sourced alcohol resistant needle tips. That being said I've never had an issue with mine but I'm a stickler for fuel filters and I do drain the carbs when storing the bike for the winter.

 

I remember trying a tank of the early "gasohol" in 1982 (I think), in my '76 Water Buffalo. The bike ran on it just fine, but the stuff frothed and foamed in the tank and I found I had to go on reserve at the half-tank mark because everything above reserve was foam. Weird. Modern E10 doesn't seem to have that problem, so there must be various stabilizers in it.

The rubber tips on my Maxim's original float needles dissolved as I was cleaning the carbs, probably because they'd sat for 20 years with gas (and whatever it turned into) on them. My first set of aftermarket needles had rubber tips, which also disintegrated quickly upon exposure to E10 (or were simply junk in the first place; they were from Amazon). I then went to the ones I have now, which are solid metal tips and seemed to work OK, at least until #1 started overflowing.

Given that carbureted bikes made in the last 20-30 years have had rubber-tipped float needles that were ethanol-tolerant, I'm kind of amazed that nobody's matched-up one from another bike that will work in the XJ650.

 

So is this a thing now - float valves in our XJs destined to leak due to E10 fuel (you can get E5 in the UK, but that's as good as it gets)?
For my maxim on Mikunis it's even worse, since the valves themselves are sealed with rubber o rings...

 

Just a random thought but maybe there's a small engine carburetor needle that would work and have similar characteristics with respect to length diameter and so on? Small engine carbs I can think of with a hard tipped needle are the Briggs updraft, Tecumseh horizontal shaft to the mid 70's and Onan generators with the opposed twin. CCK/CCKA/CCKB (generator and utility service), B43 & B48 used on the Emerald generators. I have an Onan Emerald-II 6.5KW commercial and know it has a hard tip needle that works against a soft rubber seat that has deteriorated to the point of no fuel control, carburetor is made by Mikuni but I have never given this any thought until now.

 

You're lucky to only have to put up with E5.......in the USA, just about everywhere it's E10 and up to E15. Reduces gas mileage, too.

The ethanol typically makes the older Buna rubber products SWELL (quite a bit sooner than it begins the disintegration process). Rubber-tipped float valve needles, when they swell, can "seize" themselves in the float valve brass seat bore, resulting in flooding or fuel supply cut-off. On the Mik float valve seats, the swelling won't be an issue, as that will actually seal them tighter, but of course they'll most likely be useless once you "prise" them out during a carb teardown.

 

@Simmy, as requested, pics of the 650RJ. Not nearly as pretty as your stuff but it has not been treated as well in its past either. It will now see more love and care, and use. Yes, know the fuse panel is crooked on the air box cover but I didn't want to be splicing and extending the wires either. It had been "installed" in its previous life, the connectors just had the wires inserted but not crimped in place and wrapped with tape. Now crimped and soldered and shrink tubing insulated. Fortunately the main bundle had mouse damage only to the tape wrapper and not to the wires themselves.

 

That’s a great bike @Fuller56
Rear fender intact is a good sign
Exhaust looks good to

 

a little rusty but not beat up, a little rough around the edges but should be good solid bike. Intact headlight! I recently acquired a no title RJ in much better cosmetic condition but mechanically questionable. No bolts in the cam sprockets so that is going to be interesting.

 

Well, I filled up the tank with fuel, pickled it with Stabil, then changed the oil and filter, hooked up the battery tender, and put her to bed for the winter. Once salt has hit the roads here in NE Ohio, I usually don't ride again until a couple spring rains clear it off. Sigh.
I do plan to do a valve clearance check/adjustment over the winter, and send the carbs to hogfiddles for his expert diagnosis/cleaning/rebuild. Although I've done the carbs many times myself and feel like I know them inside and out, I just can't get the girl to run like the screaming banshee she was prior to 2008... the year I got her back non-running from my ex-wife, who stored the bike outside and let the fuel turn to gel in the tank and carbs. It was a nightmare I'm sure I've told before.

 

Possible... I was thinking more along the lines of some post-Y2K carbureted bikes in the approximate cc/cylinder-carb diameter range of the XJ. By the year 2000, E10 was the default gasoline in much of the USA, so by then I would expect the Japanese manufacturers to have switched over to ethanol-tolerant rubber parts.

I don't know that rubber-tipped needles are particularly necessary; all-metal needles are available and mine seem to work just fine except for this one carb that started gushing on my last ride. They might be essential for something like a rubber-mount Harley motor, which thrashes pretty violently, but I can't seen the XJ's inline four vibrating anywhere near enough to require a special float needle.

Still haven't gotten around to pulling the rack apart and looking for a piece of debris upstream of the float valve. That's still my working assumption about the cause of my carb overflow, especially since I don't have any inline filter at the moment (I did not install the little mesh domes when rebuilding the carbs, and all summer long I was telling myself I needed to install a disposable filter in the fuel line but never got around to actually doing it) and the problem appeared immediately after flipping to reserve. I just need a day when the weather's warm enough to work in the unheated garage and otherwise crummy enough to not go riding or do yard work.

 

Today is the last day of fall... 51º today, 30s starting tomorrow and running out till the end of the two-week forecast (and 3-5 inches of snow this weekend). It's also dreary and damp out, and I took the other two bikes for nice rides over the weekend, so I decided to take a closer look at the carb that overflowed.

When I pulled out the float valve seat, the smoking gun was sitting there:



A little bit of rubber, about 3/16" long. It's a bit too big to actually sneak through the float valve, but I think it dangled in there far enough to hold the valve open when the carb was anointing my foot with gas. Then it retreated back into the passage when I had to flip the carbs over to pull the bowls. I fished it out, then pulled the seats from the other three carbs. No sign of junk in them. I also checked the fuel line (which I replaced a couple years ago). The end was a bit ragged, so I kinda suspect this fragment adhered to the line after I cut it and then bounced around in the fuel passage until it caused mischief.

If these needle/seat sets had come with the little mesh dome filters, the carb wouldn't have overflowed... but the seats that come with the all-metal needles don't come with the filters. Nor do the filters I had (from a set of valves with rubber tipped needles) fit on these seats--the groove they are supposed to clip into isn't wide enough. So, I took off the fuel line, made sure there were no more rubber fragments clinging to it, and reinstalled it... and put an inline filter in there to catch any crud that might be in the bottom of the tank.

I am debating whether to pull the rack apart just to clean all the fuel fittings. I didn't find any debris in the other three carbs, so it's likely this scrap of rubber was just the one thing. But I have all winter... and, now that all traces of fuel have evaporated from the carbs, I can bring them into the house on a cold day and dissect them in comfort before re-installing when it warms up in the spring. I probably ought to do that... and repeat the "wet" level setting before putting them back on, just in case.

 

That's all it takes.