Shafner79
New member
Well, I rode 80 miles on Saturday....sled ran 100% all morning. Stopped at the truck for a 20 minute break. Rode another mile and a half and it just shut down.....no warning, no noises, no lights....just shut off.
Tried to pull it, and it felt locked up. Turned the primary and it moved again. Pulled the plugs, and the middle plug had white specs all over it and I could see some marks around the edge of the piston.
My guess is a ring broke and clipped the exhaust port, causing it to lock up.
I will update, with pics once I get her opened up. I was running fresh 93 octane, normal temps, and the same elevations I always ride at. Only issue I had was an abnormal idle hang when stopping....
Tried to pull it, and it felt locked up. Turned the primary and it moved again. Pulled the plugs, and the middle plug had white specs all over it and I could see some marks around the edge of the piston.
My guess is a ring broke and clipped the exhaust port, causing it to lock up.
I will update, with pics once I get her opened up. I was running fresh 93 octane, normal temps, and the same elevations I always ride at. Only issue I had was an abnormal idle hang when stopping....
Shafner79
New member
Ok, so I tore into it today...
I barely used any oil...only about 3/4"-1" from cap in tank for 85 miles.
When I took off the carbs, the fuel that came out was crystal clear. Powervalve and cable are fine. There is obvious pitting on the head. The cylinder is worn, and has some aluminum build up from the piston on it, but doesn't seem to have any scratches that I can feel with my hand (possibly could be honed out??). Piston is junk but no up and down play in the rod bearing.
I took apart the fuel pump and there seems to be mixed fuel in all parts of it. Carb boots seemed to be fine, reeds looked ok. Carbs were cleaned 2 weeks ago, and had fresh 93 ocatane in it.
Any ideas on the cause? Oil pump failure? Could it really run 80+ miles on such little oil and only damage one piston?
I barely used any oil...only about 3/4"-1" from cap in tank for 85 miles.
When I took off the carbs, the fuel that came out was crystal clear. Powervalve and cable are fine. There is obvious pitting on the head. The cylinder is worn, and has some aluminum build up from the piston on it, but doesn't seem to have any scratches that I can feel with my hand (possibly could be honed out??). Piston is junk but no up and down play in the rod bearing.
I took apart the fuel pump and there seems to be mixed fuel in all parts of it. Carb boots seemed to be fine, reeds looked ok. Carbs were cleaned 2 weeks ago, and had fresh 93 ocatane in it.
Any ideas on the cause? Oil pump failure? Could it really run 80+ miles on such little oil and only damage one piston?
super1c
Super Moderator
Just a guess from reading a lot here. Did you let it warm up before you took off from the truck and hit the throttle? Looks like pic's from a cold seizure often called 4 corner seizure. Just a thought and i like learning along the way. Looks like the piston heated up and expanded faster then the jug. I would think the lack of oil would be seen in the crank first. How is the center crank rod look?
typical 4 corner seizure...... I also see it has wiseco pistons in it.... those cold seize very easily like what you have pictured there if they are not warmed up well first. The wiseco is a good piston its just they expand a little faster then does the cast cylinder and they need the extra warm up time to work without issues.
add: its also running too lean, you need to richen up the carb settings some.
add: its also running too lean, you need to richen up the carb settings some.
Shafner79
New member
I didn't realize they were weiscos....the mag cylinder is different. Burnt down from dirty carbs right after i bought it. I replaced with an oem piston.
Sled had run for hours before it broke. Took a 20 minute break, let it warm up a bit then rode off. Made it about 1.5 miles and it shut off....it's lean because it was not using any oil. Gas in carbs was clear, like straight gas.
I'll have to get a better look at the rod....like i said, no up and down play in bearings.
Any suggestions on just flushing the case or should I pull the motor?
Sled had run for hours before it broke. Took a 20 minute break, let it warm up a bit then rode off. Made it about 1.5 miles and it shut off....it's lean because it was not using any oil. Gas in carbs was clear, like straight gas.
I'll have to get a better look at the rod....like i said, no up and down play in bearings.
Any suggestions on just flushing the case or should I pull the motor?
thefindian
New member
20 minute break and a cold seizure no way only a inch of oil in 85 miles thats not good. You should be going through around a quart of oil in a full tank of fuel.
Shafner79
New member
thefindian said:
That's what I thought. Used about 3/4 tank of fuel....also clear gas in carbs.
Notice how middle cylinder is clean and pto & mag are black??
thefindian
New member
I would pull that motor all the way down and check the crank bearings out and then i would look into the oil pump i dont know if you can rebuild it or just buy a new or used one I have never had a problem with a yamaha oil pump.
Shafner79 said:
umm no, when i am talking lean, I am talking about air/fuel ratio as there is no wash marks on those other pistons at all ,very dry. Oil does not make a engine run rich or lean on the air/fuel ratio to a extent, UNLESS you have excessive oil in the fuel in which it makes the engine LEAN with more oil, because the oil takes place of the gas and more oil means less gas and it makes for a leaner air/fuel ratio.
Thats not a oilpump problem but more like a oilpump incorrect cable adjustment, whats the gap on the oilpump cable set to,??? I will bet its 23-24mm, the bigger the gap, the leaner the pump runs.
so whats the carb setting on this engine? pilots,needles settings and mains?
thats a pretty light seizure, doubtfull it wiped the crank by just the look in the pics, usually when the rod goes its also a very dark color before turning blue and the wristpin bearing will be all but gone first. I would STILL obviously check it but from what I can ONLY SEE from pics its doubtfull it went that far.
forgot to add, the reason the center piston top is so clean is from a few of the situations:
1.) antifreeze leak into that cylinder, youd need to confirm it by looking at spark plug would yield some green fuxzzy coloring on ground strap, this also reduces the oils ability to protect it from scoring like yours did, as the antifreeze washes away the oil film.
2.) very rich running on either pilot,needle or main, but also can be a high float level in that carb, this makes it run rich all the way thru. Possible choke pluger leaking on that carb/cylinder causing excess fuel to be sloshed around, too much fuel can also be a problem and wash off the oil film from you having a lean oilpump cable setting.
if you can answer the few questions in post , we can narrow it down pretty quick as to the real cause so it doesnt happen again. you need to check those specs I asked about to get to the solution.
edit add: spark plugs are LEAN, this sled has the wrong jetting in it for starters! I see you also have a cold air kit, that makes it leaner right off the bat and the jets have to be larger, let me know what the specs are and we can solve this so it doesnt happen again. The other 2 cylinders are pretty close but too lean yet and when the temp woulda dropped into the teens they woulda been in trouble as well. Theres a few threads in the tech section where i have some plug pics of what you need to look for.
1.) antifreeze leak into that cylinder, youd need to confirm it by looking at spark plug would yield some green fuxzzy coloring on ground strap, this also reduces the oils ability to protect it from scoring like yours did, as the antifreeze washes away the oil film.
2.) very rich running on either pilot,needle or main, but also can be a high float level in that carb, this makes it run rich all the way thru. Possible choke pluger leaking on that carb/cylinder causing excess fuel to be sloshed around, too much fuel can also be a problem and wash off the oil film from you having a lean oilpump cable setting.
if you can answer the few questions in post , we can narrow it down pretty quick as to the real cause so it doesnt happen again. you need to check those specs I asked about to get to the solution.
edit add: spark plugs are LEAN, this sled has the wrong jetting in it for starters! I see you also have a cold air kit, that makes it leaner right off the bat and the jets have to be larger, let me know what the specs are and we can solve this so it doesnt happen again. The other 2 cylinders are pretty close but too lean yet and when the temp woulda dropped into the teens they woulda been in trouble as well. Theres a few threads in the tech section where i have some plug pics of what you need to look for.
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Shafner79
New member
mrviper700 said:
Jetting is M: 152.5 C: 150 P: 150
Pilots 42.5
I will check oil cable adjustment tomorrow. (My 1st thought was cable)
Devilin AblueDress!
New member
Use of ES versus ECS factor into this at all?
trailanimal
New member
hello 79, I have a 98 with alot of your mods and had an identical middle cylinder melt down, since then I have adjusted my oil to 1.25 quarts to a tank, spacers under #3 clip on the needles and run a 155.0 center with 152.5 m & p. I also run BR10ECS for those high speed runs with 4 strocks on the lakes or big temp drops at night. hope this helps. Oh no other engine damage resulted.
Shafner79
New member
mrviper700 said:
Could the choke plunger cause a higher idle? It seemed to idle hang a bit every now and then. I also have a 3" riser, but the cables don't seem too tight. They can still move around, and I know 3" seemed to be the max without adding longer cables.
Shafner79
New member
trailanimal said:
Thanks! I think I will change to those jets, and look in to the needles. Does running the BR10's have any effect during warmer temps? Is that too hot?
BR10s are a "Colder" plug then the 9s that most people run and are the plugs originally specified for the 1998 SRXs.
Most people switched to 9s to avoid fouling plugs and Yamaha changed to 9s as well on later model SRXs.
I also use BR10ECS in my 2002 SRX as I do a lot of high speed runs for long distances on rail beds and lakes and have experienced ZERO plug fouling issues in 1000s of miles.
Most people switched to 9s to avoid fouling plugs and Yamaha changed to 9s as well on later model SRXs.
I also use BR10ECS in my 2002 SRX as I do a lot of high speed runs for long distances on rail beds and lakes and have experienced ZERO plug fouling issues in 1000s of miles.
trailanimal
New member
Bob is correct 10's allow the engine to run cooler, so if your spanking some new sleds in the trails or on the lakes they offer alittle more protection, I also had some periodical idle hang so I turned the fuel screw's out to 1 & 7/8's and she will pure all day at 1600 to 1800 and I noticed when I hold the throttle at 2500 to 3000 it's the sweetes sound ever.
X2 on oil cable..I would check to make sure its in spec or even if its stuck open esp since u have a 3 inch riser..I put a 2 inch on and in the garage cables seemed fine with movement..however after a trip I began to have a bad idle hang mid way through the trip which I found weird for my sled..looked into it and found the cable stuck wide open giving me lean conditions and idle hang..just somethng to think about
Shafner79
New member
Just pulled floats, needles and top hats... top hats had a good amount of slime on them.
Shafner79 said:
I remove these filters on all my Yamaha sleds that have them as in my mind the tank filter is sufficient and they can slime over and cause mysterious melt downs...
Works for me..