Well here I go again with engine problems,to be honest I'm starting to think this sled is cursed.I was on a trip with a couple of buds and we were on our way back to the motel where we parked the truck/trailer and I lost the center cylinder about 20 miles from being back without incident.Temps that day were cold and I'm guessing about -15 to -20 C (5 to -4 F) as it was -30 C the night before night and the sled is only jetted down one size on the mains to 145,145,147.5 and the wash seemed to be good.We were on an old railway bed that is now the trail and our average speed was about 60-65 mph,I wasn't pushing it by any means but we had been running for about 20 minutes at a constant speed up until this happened so I'm not sure where to look for problems just yet.The only thing I can see right off is that it doesn't look as though the oil pump was putting enough oil out because we had put on about 450kms(270mls) at that point and the sled hadn't even used a full liter of oil as I filled it up to verify how much it used.I checked the cable measurement and it was at 15mm!!! so if anything this should have been smoking like a chimney but it wasn't.Given that the farther the throttle is opened the more the oil pump is opened and the more oil it should have used,especially at 15mm,even though on average I probably only used about half throttle for steady trail speeds.I pulled the cylinder off and it isn't pretty and I think I'll remove the oil pump and all the lines to see if there is something blocking the flow as I dont see anything else right yet to give me an indication of what caused this.Could I be jetted too lean only one size down?Please look at the pics and give me all the feedback you can think of please.
1.Mag side
2.Center
3.PTO
4.cylinder
5.Oil tank level from full when this happened
1.Mag side
2.Center
3.PTO
4.cylinder
5.Oil tank level from full when this happened
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You were lean & the other cylinders were close to grenading too. Piston top should be very black with eraser size or larger clear spots by the transfer ports. Gotta jet er back up cus you got lucky you only lost one piston & cylinder.
daman
New member
If you look close on the pto cyl. it looks like it's just starting to burn on the
exh. side,,unless i'm not seeing that wright..
But yea..jet her back up!!!!!!!!
exh. side,,unless i'm not seeing that wright..
But yea..jet her back up!!!!!!!!
braindead1684
Member
I agree at around 10-oclock pto looks like it has a hole in it. That sux man i just had mine lean out this weekend as well. Good luck with it, i would definetly check out the carbs they might have been the main prob. Did you use a lot of gas or less then normal as well?
Thanks for the info guys.Tomorrow I'm going to take the carbs apart and put the old jets back in as well as investigate the oil pump and lines.From what I can see I used about the normal amount of gas that the sled usually burns,just going by reciepts and trip meter readings so I dont think it's lacking there.It's the oil usuage that concerns me it just doesn't seem to be enough for the miles I put on.One thing I forgot to put in my first post was that when I discovered the 15mm setting on the pump cable I set it back to 21mm (stock) and it was shortly there after this happened so it seems to me to be too much of a coincidence that it doesn't have something to do with it.Thanks and keep the tips coming.
ps: these are Weisco pistons too and I'm hoping that the cylinder will clean up without being scored.Anyone else have any experience with similar circumstances?
ps: these are Weisco pistons too and I'm hoping that the cylinder will clean up without being scored.Anyone else have any experience with similar circumstances?
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Get rid of the Wiseco pistons & run the new Yamaha sRX pistons. They come coated & coulda saved you or made the engine live a little longer.
DoktorC
Member
That was also a lean burndown for sure. Lack of oil does not cause that kind of damage. Do get rid of the wisco's..genuine Yamaha is the only way to go.
braindead1684
Member
Hey man if your in mid michigan pm me and i will hook you up with the guy doing mine its cheap and he knows what he's doing, i am dropping mine off tomrrow to get hopefully just honed and possible bored over. I was also told the same thing about the lean condition having to do with something other then the oil pump, possible seal leak or more then likely clogged fuel system.
Thanks for the suggestions guys.The only reason I put Weiscos in the engine after the last rebuild was for cost.They are/were coated and I got all 3 complete with rings,pins and wrist pin bearings for less than half what the OEMs were but I do agree that they(OEM) are by far a better way to go even though I was assured by the place I bought them that as long as I let the sled warm up lots before running it hard they would be fine 
.I've got a couple of used OEM pistons and rings so I think I'll be using one of them for the rest of this season as I still need to see if the cylinder is salvagable if not then I'm going to have to come up with another plan.Thanks.
.I've got a couple of used OEM pistons and rings so I think I'll be using one of them for the rest of this season as I still need to see if the cylinder is salvagable if not then I'm going to have to come up with another plan.Thanks.