99 Gen 1 stalls after 20-30 minutes

[Tom Determan]

Hi guys, I'm trying to save long walks home and hours of diagnosis if possible. My buddy's 99 stalls after a short ride, last year I decided it was a poor battery and bad stator, causing low voltage after a few miles with no charging. The stator was bad, installed a rebuilt Rick's and everything seemed fine for a couple fall rides. Carbs were cleaned, jets inspected, and synched nicely last year at the same time to rule out a few carb things as the bike was recently acquired and 20 rs old.

On to this year......First nice day here a couple of weeks ago and 10 -15 miles bikes starts stalling, won't run, sit a few minutes and nurse it home. (buddy's description - he doesn't remember if the problem appeared before or after filling the tank) I had him drain the carbs and catch the contents, one carb had water in it, maybe a teaspoon or so and a few black specks were found. I decided no choice but had to verify the pilots were clean and investigate the tank and filter. He trailered the bike up here, I drove it around the block, pulled it into the driveway to idle, ran fine except for a funny misfire every few seconds, seemed like 1 cyl had an occasional misfire. RPM is stable. We pulled it into the garage and drained the carbs, no water. Emptied and scoped the tank, a few black specs down there (20 yr old bike) but nice steel, nothing abnormal for a 20 yr old tank. Pulled the carbs, found one pilot possibly clogged but overall nice condition in all 4 bowls, nothing unusual, no other contamination. The bike has an inline serviceable filter that can be disassembled, the filter looked clean. I found a main jet that was 1/2 turn loose, must be from a senior moment I guess, as I was the last guy in there. Would a slightly loose mainjet allow extra fuel to pile up until it misfires, and then start the cycle over ? That doesn't really square with the whole theory of operation on a sliding needle / closed plunger setup. Seems like a loose mainjet would behave the same as having a 500 MJ in there.

This bike starts perfect, after 30 to 60 seconds feathering the choke it idles nearly perfect, comes off throttle nicely in the garage and under load. After a good warmup this idle misfire appears. The owner also says it has a miss around 1/4 throttle but I've never driven it enough to notice. Maybe a 40 MPH city street position I guess. 37.5 pilot, 170 MJ, and needles set per Mark's (exhaust) or Yamaha recommendation, sorry I haven't pulled the CV covers off yet, but that's where I would have set it.

Summary, 2 problems - an idle misfire every few rotations in a warm engine, seems like one cyl, and engine stalls out after a few miles. Is there a common electrical issue that acts up after good heat soaking in the engine block and under the seat, air intake cover, etc ? I've never heard a lean backfire or sneeze, only this funny misfire at idle and the owner is afraid to take it out for fear of walking home. I have ruled out fuel supply, filtration and carb set up. I'm thinking a trigger coil, CDI pack or whatever it's called on this machine, or some electrical issue. I have 90 % of the testers known to man and know how to use them, just not familiar with the Vmax's quirks. Just point me in the right direction. Thank you guys.

Tom

 

[Radioguylogs]

I had some experiences that were similar to yours. They may not explain your problem, but just in case...

(1) Bike Dies -When I bought my bike it had a failed voltage regulator. I kept it on a battery tender, so it would start OK. I'd ride it for 30 minutes, then stop to top off the gas before I went home. It wouldn't start at the gas station twice, so I went looking for the problem. I replaced the battery and it happened again. Then I knew to check the regulator. Do you use a battery tender? If not, then this doesn't seem to be your problem.

(2) Miss-fire every few Seconds at Idle- My bike did this when I bought it. Like yours, it was OK until it warmed up. It drove me crazy. I sync'd the carbs and tweaked A/F idle mixtures. No joy.

Independently, I noticed the bike always seemed to take a lot throttle to get off the line, then it would surge when it got 3k RPM. I decided it must have a problem with pilot jets, even thought the dealer 'rebuilt' the carbs before I bought it. Sure enough, #3 pilot jet was totally plugged. After a carb rebuild, it idles perfectly, and it comes of the line like it should.

Does you bike seem to take a lot of throttle to get going and then surge at 3k RPM? I know you cleaned the jets already, but I wonder if they could have gotten dirty again. You have seen contamination before.

Like I said, I just mention these experiences in case they help.

-Mike

 

[MaxMidnight]

Have you checked that the fuel tank breather is clear?

How old are the plug cap and leads? Have you taken the leads out of the coil towers to check for corrosion?

 

[Fire-medic]

A hot-soak bike which stops completely and won't re-start immediately, it cranks but will-not start, is a sign of a bad pick-up coil. I's a year 1999, so it's got the newer ignition w/a single pick-up coil.

What happens is the heat causes the pick-up coil to open its broken wire, when cold, the bike will run, but once hot, the break opens, and your bike cranks, and cranks, but no-running. Let it cool for say a half-hour, and if it cranks and immediately-starts, my $'s on a failed pick-up coil.

The ohms reading should be about 100 ohms, + or -- a bit, if it varies much from that, especially when hot, and the bike has shut-off, you've found the problem.

New ones aren't cheap. There are aftermarket ones for probably 1/3 of OEM new $. Search on here for info on the source for the aftermarket coils. Here's one source:

1990-2007 Yamaha V-Max VMAX VMX1200 Stator Pick up
Part # P4901 $129.99

Replacement Part: Sometimes this is the only part that fails on your stator. This is the for the pickup coil only as shown. The rubber grommet is not included. Will need to use original rubber grommet from old pulser. To replace it pull the wires from the new pulser through and then attach the provided terminals and connector to the wires.

This part is about $300 through Yamaha!

OE number: 3UF-81670-00-00.
https://www.regulatorrectifier.com/catalog/1990-2007-yamaha-v-max-vmax-vmx1200-stator-pick-up

Poor running at idle, or off-idle, I usually find that the pilot jets are plugged. It takes a very-fine wire to clean them. Sometimes sprays will blast the crap out but if it doesn't you need to use a single strand of thin wire to poke-out the blockage. If you have any particulate material at-all in your gas tank, or visible rust, you have to remove that, and have a clean tank because if you don't, the pilot jets will quickly plug/become obstructed again.

 

[Tom Determan]

Thanks for the ideas and experiences - this is what I need.
We installed a Rick's stator last year to correct a charging problem. I may have installed a regulator too, I don't recall, but the bike starts crisp and cranks fast, there doesn't seem to be any cranking or voltage related starting and cranking issues.

This bike starts after 2 or 3 spins, idles nicely, and runs strong except for, a slight misfire on 1 ? after it's warm, and it totally stalls out after 15-30 minutes on the road. Usually when cleaning tiny pilots it's hard to know if they were clogged or not. I hold them up to light with a magnifying glass and look for a nice round pin of light. Fuel alone sometimes blocks the light. Blowing at them can sometimes clear them. I'm thinking something may have come through somehow from the fact my buddy saw a few small black specs when he drained the bowls last week looking for water. I found very little when I disassembled them and the fact that the bike runs strong and idles fine except for a misfire every few spins ??? Wouldn't a clogged pilot affect or kill that cylinder every 2 spins ? This seems "less frequent than every 2 spins" but somewhat regular in frequency.

Tank is clean and I use wires as a last resort after sprays, soaking, toothpicks and ultrasonic cleaners. But I have twisted a few strands of very fine auto wire together before ! I think the crisp start, smooth idle and strong pull hot or cold indicates clear pilots and well working carbs for the most part. If the valves are way out of whack (22K miles unknown service record) does a warm engine cause enough leakage to miss now and then at idle ?

I'll verify the breather is clear, that's a good suggestion. Would bad plug caps and leads cause problems through the full RPM range ? Plugs are new but I'll certainly look at these.

I really like the pickup coil idea, the description fits the problem for the stalling. Easy to measure ohms although that might not be a 100 % proof test. Cheap and easy to just replace.

Back to jetting, the needle is a SS needle with no markings, a 1+ mm nylon and thin aluminum shim under the clip in the 2nd groove from the top, so this seems to be on the fat side. This was probably part of the Mark's exhaust add, any thoughts on the mfr and good starting point for 800 ft ASL and 50 to 90 F ? In my original post I mentioned a 1/4 throttle issue, maybe I should put the clip on top or change that shim.

 

[MaxMidnight]

Would bad plug caps and leads cause problems through the full RPM range ? Plugs are new but I'll certainly look at these.

I really like the pickup coil idea

I'm suggesting that you cover the basics before you dive in deeper as it is ost likely these that are causing the problem. If they are OE then some or all of them may not be working optimally.

Whilst you may like the pic-up coil idea you need to establish that they are faulty before considering replacement.

First rule of diagnosis 'Act on facts and not hunches if you want a first time repair'.

 

[Traumahawk]

Lets start with the basics. When it stalls, take off the fuel cap. Is there a whoosh of air? That means a plugged vent line.

 

[Woody]

Bad fuel pump ?

 

[crolf]

Replace or disconnect the tip over valve.

 

[Tom Determan]

Bad fuel pump ?

Fuel pump was replaced last fall, pumps nice and strong.

 

[Woody]

Fuel pump was replaced last fall, pumps nice and strong.

Good

 

[Fire-medic]

When it quits 'hot,' the ohms on the pick-up coil should be out-of-spec from stock. That value is 110 ohms plus/minus 10%, from the factory manual. That is assuming the pick-up coil is the culprit. When the bike quits from an open circuit to the pick-up coil, you are no-longer measuring the resistance of the pick-up coil device or its complete wiring.

I agree with Max Midnight, throwing parts at it is not an efficient nor cheap/inexpensive way to approach the issue in any circumstance. I've had two bad p-u coils in 27 years of VMax, multiple ownerships.

Traumahawk, your avatar is just an X on my screen, do you have another to throw-up?

I forget what the OP has for main jetting? The Dynojets are higher numbers, compared to the same size OEM Yamaha jets. I think the Dynojets have a DJ prefix before the #. If you have a 5-groove slide clip/needle, you have aftermarket needles. Stock was for USA bikes just one groove ("Groovy, dude!") Since you are above sea level, dropping to one-smaller main jet size for your minimal height above sea level-differential would probably help, from stock, BUT! How your current jets are in size is what you need to determine first. Then compare that to the stock (probably 152.5) Yamaha jets, and you are operating from a point of information. I have a UFO 4/1 on a stock engine, and am running essentially at sea-level (Miami FL) and I've dropped-to 147.5 and the bike runs well. Stock settings are a bit-rich for carburetor-equipped bikes from the 1980's, to allow the bike to live, as the fuel helps to keep the engine cool. Lean bikes run hot, and too-lean will cause problems of an expensive kind. Too-rich just wastes fuel, assuming that the bike pulls cleanly.

If my bike begins to idle poorly and it's synched properly, the first thing I'll check, after spraying the carb boots to see if I have an air leak (the mis-firing cyl will have a noticeably 'cool' exhaust compared to the properly-firing others) is to drain the float bowls, looking for water or particulate contamination. Drain the hoses into a clear container to closely-examine the gas for water/contaminants.

If I have any suspicions based upon that, I won't hesitate to tear-down the carbs to access the pilot jets. Yes, holding them to a light source should show you if they are obstructed. If a air pressure hose won't blow them clean, either replace it or use a fine wire to poke the obstruction out. Use your light source to confirm a clean bore.

Having a properly-synched set of carburetors is primary. Having valves set properly is too. A bike with out of spec valves usually runs poorly everywhere, because the cylinders aren't sealing at the combustion chamber. Backfiring through the carbs is easy to spot.