97 Mountain Max 700 triple question

[Bunn]

My brother owns a 97 Yamaha Mountain Max 700 triple that has been a great sled but has developed a strange issue as of late that is intermittent.The sled has just over 2000km. The issue we are having is one cylinder(pto side) is over oiling,yes that is correct,only one cylinder is over oiling.The other two cylinders are oiling properly and spark plug color is good.It has triple pipes and oil is spraying out of the pipe tip and out the seam all over the engine bay.It seems to only happen when working the engine hard and at higher rpm.I am a Ski-doo guy and know them inside and out.I am a little confused on how this engine injects oil.The oil supply line runs to the oil pump then a small line runs up to the fuel pump.Is this where the mixture happens?Does anyone know exactly how this injection system operates so I can better understand.Also,has anyone come across this before? The spark plug for the cylinder is covered in oil,I know it's oil and not fuel because it does not evaporate.Any help is greatly appreciated.

 

[TROLLCAT]

oil mixes at the fuel pump no worries there
a bad plug, or your compression is low on that cylinder
check these things

 

[Bunn]

Compression is 135psi for all cylinders.I did change the plug and also the coil(always carry an extra)...spark tester shows good "bright" spark.Just baffles me that only one cylinder is doing it.Injection cable has been checked and is proper set.Is there a metering valve inside the fuel pump that can possibly mess up?

 

[SRXtreme]

Check reed valve and clean carbs. It's not an oil problem but an ignition/fuel problem. The combustion cycle isn't being done efficiently.........SRXtreme

 

[Bunn]

I had the carbs off earlier this year to clean and check them.Verified float buoyancy and proper height.Reed valve where also removed and inspected at that time.Unless I am missing something,or over analyzing the situation,I'm baffled.I think fuel as well because it has strong spark.The cylinder runs about 5-7degrees f lower than the other two.The fact that I don't know these carbs very well leads me to believe I am missing something.Does anybody know someone in Calgary that has a lot of experience with these old engine/carb set-ups?

 

[Lund]

Your problem comes from the carb. you might want to change the needle seat and seat needle as they tend to wear in carb's. This will cause uncontrolled fuel to enter the intake and essentially causing a flooding issue with that cylinder. Your engine is a triple so its not as noticeable as a twin.
Personally i'ed replace all three in the carb's.

 

[ttpowersports]

My brother owns a 97 Yamaha Mountain Max 700 triple that has been a great sled but has developed a strange issue as of late that is intermittent.The sled has just over 2000km. The issue we are having is one cylinder(pto side) is over oiling,yes that is correct,only one cylinder is over oiling.The other two cylinders are oiling properly and spark plug color is good.It has triple pipes and oil is spraying out of the pipe tip and out the seam all over the engine bay.It seems to only happen when working the engine hard and at higher rpm.I am a Ski-doo guy and know them inside and out.I am a little confused on how this engine injects oil.The oil supply line runs to the oil pump then a small line runs up to the fuel pump.Is this where the mixture happens?Does anyone know exactly how this injection system operates so I can better understand.Also,has anyone come across this before? The spark plug for the cylinder is covered in oil,I know it's oil and not fuel because it does not evaporate.Any help is greatly appreciated.

so couple questions,
it's over oiling, so is it following the plug on the pto side?

does it idle fine and run fine if so for how long before it over oils, and when this happens, again , does it foul a plug?
2000 km is not a lot those 700 were bluet proof , however with the triple pipes, they we're know to spit oil residue out, due to lack of a good exhaust seal, take the pipes apart and use high temp exhaust silicone on them joints, it was usually cyl-pipe gasket that wee the worst, but we would apply a liberal amount on all. Exhaust gasket due to this. Also the single choke rod would also occasionally stick. Apply pressure to it and ensure it isn't partially open, this too would cause a rich issue.
You may want to ensure with the pipes that the resetting specs were followed. If one carb is set too rich that would also result in what. Your experiencing

T

 

[Modman]

so couple questions,
it's over oiling, so is it following the plug on the pto side?

does it idle fine and run fine if so for how long before it over oils, and when this happens, again , does it foul a plug?
2000 km is not a lot those 700 were bluet proof , however with the triple pipes, they we're know to spit oil residue out, due to lack of a good exhaust seal, take the pipes apart and use high temp exhaust silicone on them joints, it was usually cyl-pipe gasket that wee the worst, but we would apply a liberal amount on all. Exhaust gasket due to this. Also the single choke rod would also occasionally stick. Apply pressure to it and ensure it isn't partially open, this too would cause a rich issue.
You may want to ensure with the pipes that the resetting specs were followed. If one carb is set too rich that would also result in what. Your experiencing

T

Same questions - it is fouling the plug or just getting oil on the outside of the cylinder? if its just oil (cosmetic), then make sure the pipe is sitting properly on the flange and seal it well with high temp silicone. If its fouling the plug, then I would check the jetting spec, you might need to stagger the jetting especially with triple pipes. Depending on where the coolant enters and leaves the block, one cylinder is typically hotter and therefore you wind up with staggered jetting. If you were riding in warmer temps or higher elevation, then its going to be rich and you will need to back down the jetting.

 

[SRXtreme]

5-7 degrees isn't alot. How are you measuring temps?pyro's or infared?

 

[Bunn]

infrared in several locations on the head,cylinders and exhaust,all within 5-7F.

Yes at times it will foul a plug.But you can swap a plug and it runs fine.Even after you run it hard,it doesn't seem to have a huge power loss.I pulled the ignition wire,grounded it and runs poorly to compare.It's really an odd situation.

Yes,the exhaust seems have always leaked a bit and makes a mess always.

I have done a couple things and will review what we find after taking out this weekend.

Thanks for all the responses....I will let you know what happened this weekend.

 

[Barry Barton]

I had yamahas for years the sled has a enricher switch it does stick quite a bit just clean the cable easy to do also check the enricher rod that hokes the carbs together one might not be set right.

 

[Bunn]

So Barry Barton,you win.The choke cable(enricher) is holding on and when you push down,problem goes way.Just adjusted cable and presto,problem no longer present....thanks everyone for the ideas.