Yamaha SX 700 Vmax - Problem starting when warm - Page 2 - Snowmobile Forum: Your #1 Snowmobile Forum

Captaincooter · 02-09-2012, 06:27 AM

where has cossie93 been? maybe he could update us on the latest tests, checks, or status!

Phaze · 02-09-2012, 09:42 AM

He hasn't been active on this forum since 1/23. An update would be nice, especially for the members who were trying to help.......

Captaincooter · 02-09-2012, 06:06 PM

Hey Phase,

Any probs with the pipe ends cracking on yours?

Phaze · 02-09-2012, 09:09 PM

Not yet........

cossie93 · 03-04-2012, 03:56 AM

Hi everybody!

Sorry for not giving you feedback.
I havent had the chance to make a real test.

But now i have....
I have cleaned the carbs 2-3 times. Everything looks ok. I have spark.
I ran the snowmobile last weekend and i could run it for 1 hour. Then took a long stop (2 hours) It started.
When I was going home (about 1 hour ride) it started to missfire a bit. Not on full throttle but half. Replaced the plugs and it was good again.
It seems that the plugs dont get hot enough for selfcleaning when running half throttle.
So i changed the needle to 2.5 instead of 3.0

Today it went hot (because running on ice, no snow.)
Then i stopped and it wouldnt start again.
I replaced the plugs but it didnt start.
I checked the plugs , all plugs are dry. I tried full choke when it was hot. The plugs are still dry.
So i waited 3 hours, then it started again.

Could it be some fuel filter that is clogged?
Or could it be the fuel pump ?
I havent had the chance to check the pump again when the enginge is hot.

Best regards
Marcus

**RJ Gleason** · 03-04-2012, 03:59 AM

For the no snow/low snow conditions, you would be well served to use scratchers. They will throw up enough powder to keep the engine cool and the hyfax lubed.

yamadad4 · 03-04-2012, 10:43 AM

hot to the point of the temp light flashing? could be why your plugs appeared dry.

on your next test, take along some extra fuel and prime a cylinder after you check for spark. something else is going on with your sled be it fuel or electrical related. you need to test it hot to get a better handle on the situation. you could almost simulate a test on a stand or lift.

heat soaked engine wouldnt affect the fuel delivery in theory, unless your pulse line is sucking air or you have a crank seal fatiguing from the heat. you can test the fuel pump with a vacuum pump and visually inspect the hoses and the filter. you may even consider checking the reeds for condition.

cossie93 · 03-04-2012, 11:22 AM

Quote:

Originally Posted by yamadad4

hot to the point of the temp light flashing? could be why your plugs appeared dry.

on your next test, take along some extra fuel and prime a cylinder after you check for spark. something else is going on with your sled be it fuel or electrical related. you need to test it hot to get a better handle on the situation. you could almost simulate a test on a stand or lift.

heat soaked engine wouldnt affect the fuel delivery in theory, unless your pulse line is sucking air or you have a crank seal fatiguing from the heat. you can test the fuel pump with a vacuum pump and visually inspect the hoses and the filter. you may even consider checking the reeds for condition.

Hi!
The temp light was on, but it didnt flash

How much fuel should I pour into the sparkplug hole?
Teaspoon? In each cylinder?
Or is it better with starting gas?

If I have a crank sealing leak when hot, shouldnt it also affect the air/fuel mixture so I would run lean?

I have checked the reeds, everything looked ok.

I have ordered another fuel pump so I will check this later this week when I install it.

/Marcus

yamadad4 · 03-04-2012, 05:57 PM

couple ounces is usually enough, preferably pre-mixed if available but for testing probably not as crucial. not a fan of ether or any other spray type starting fluids.

lean=reduced or lack of fuel. dry plugs? hmmm. was there any smoke coming out of the plug hole? excessive clutch temps can take their toll on the pto seal.

you have an unusual problem occuring, sometimes you need to think outside the box.

hopefully its an easy fix for you.

Captaincooter · 03-04-2012, 09:25 PM

such weird intermittent things to me sound electrical. I had an EXT that would nt charge the battery properly so the EFI would act up. After a whole season of greif and chasing coils, and stators I found a short in the main wire harness. Like Yamadad said, think outside the box

cossie93 · 03-05-2012, 06:55 AM

Quote:

Originally Posted by Captaincooter

such weird intermittent things to me sound electrical. I had an EXT that would nt charge the battery properly so the EFI would act up. After a whole season of greif and chasing coils, and stators I found a short in the main wire harness. Like Yamadad said, think outside the box

Yes, I am trying to be creative. (I have changed the Stator to a new one)
I think it seems like a fuel problem because of the dry sparkplugs (even after 10-20 pulls with full choke)

I will try the priming the cylinders and see if that works, will probably do it next weekend because i am working on the days.

Otherwise i am getting more and more into thinking about yamdad suggestions about a bad crank seal when hot. And that doesnt seem very funny because of all the work.
I have tried to spray starting gas around the intake and it doesnt seem to make any difference in idling speed. So the intakes seems ok. I am not sure if i tried to spay near the crank seals.
It i have a leak there should the idle rise when i spary starting gas near it?

/marcus

yamadad4 · 03-05-2012, 07:02 AM

yes, you will hear a noticable rpm increase. during your testing, try spraying at warm up, after its warm, and again with the engine hot.

spray behind the secondary as well as in the area of the recoil. the recoil side is a bit harder to reach with the spray, try several different angles.

cossie93 · 03-17-2012, 10:44 AM

Hi!

The new/used fuel pump is installed so i will test this as soon as possible.
The problem is that almost all the snow is melted away by now.

I will report more on this when I have tried it again.

Best regards
Marcus

SRX 700 · 03-17-2012, 03:45 PM

If most of the snow is melted, try running on stand and see how it runs. Seems fuel related to me.

cossie93 · 01-14-2013, 03:22 PM

Quote:

Originally Posted by cossie93

Hi!

The new/used fuel pump is installed so i will test this as soon as possible.
The problem is that almost all the snow is melted away by now.

I will report more on this when I have tried it again.

Best regards
Marcus

Still problem starting when warm.
1st try was running about 1hour. Mostly on idle but i ran some short runs 5mins or so. Throttlerespons and engine felt fine. Stopped some times and it started again. (Was minus 20 degrees celsius)
2nd run was running on the ice and in the forrest. After a while it felt like the engine didnt pull as good it did when it was cold. Sometime it also missfired, Top speed on ice with about 10cm snow was just about 105 -110 kph when it felt like that. When i stoped it at my place it didnt start after a lot of pulls / without and with choke.

If it is something with the electronics, do youg guys have any idea what to check. I have a new stator so that should be ok.

I am sorry if i havent updated this thread in a while but havent had the time during summer/autumn to test the machine....

mmsrx · 01-14-2013, 05:20 PM

Try spraying WD-40 or something like it between the clutch and the motor pointing it at the crank. If the motor revs up your seal is gone. Usually when your seal is gone it is because the crank bearings are wearing. This also affects the fuel pump because your pulsar line pressure will drop.

yamadad4 · 01-14-2013, 06:50 PM

oem or aftermarket stator? is the flywheel clean and rust free? ground connections making good contact?

from there your back to fuel delivery. kinked vent or supply line, bad fuel line in the tank at the filter, etc.

cossie93 · 02-17-2013, 02:48 PM

Hi everybody!

The startingproblems when Engine is warm is now fixed.

I pulled the Engine out of the snowmobile and changed the lower end sealings on all the cylinders.
I also changed the headgaskets. (the old one gave correct Reading on compressiontest)

One of the cylinder had some spikes / damage on the top of the cylinderhead and also some spikes/damage to the pistion.
That cylinder was also a litte wet. (Some cooling liquid?)

Thank you all for your inputs on my problem.
I hope that this will give some inputs for others with the same problem.

Best regards
Marcus