85 yamaha xlv

M

mosabi

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Nov 19, 2011
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8
Location
ND
Hey all,

Thought some of you might be able to answer a couple questions I have regarding my first rebuild.

Snowmobile in question is an '85 XLV with a 535cc.

Just completed my first rebuild where I had the cylinders bored and honed to new oem pistons .20 over. Just got everything put back together and it fired immediately. I also installed new Boyesen reeds. I went to check compression and I'm just over 100psi in both cylinders, both have roughly the same compression. I have cleaned the carb (only 1 on this model) and premixed the fuel along with utilizing the oil injection.

I ran it the other night on a stand, after warmup I gave it some throttle to break the track loose from sitting all summer. I killed the engine (not from Idle) and checked the plugs. The PTO side had a carbon deposit on the metal tip and the MAG side had oil on it. Note: These were new plugs BR9ES and both are getting spark.

I started up the sled again and pulled the MAG side plug wire off so its just running on the PTO cylinder and it never lost a beat. I did the opposite so it was running on the MAG side and I needed to give it some throttle to keep it going but it did run.

My question is: Is this all normal? Will I most likely see an increase in compression after a tank of gas?

Thanks!
 
Thanks! Is it normal:

I ran it the other night on a stand, after warmup I gave it some throttle to break the track loose from sitting all summer. I killed the engine (not from Idle) and checked the plugs. The PTO side had a carbon deposit on the metal tip and the MAG side had oil on it. Note: These were new plugs BR9ES and both are getting spark.

I started up the sled again and pulled the MAG side plug wire off so its just running on the PTO cylinder and it never lost a beat. I did the opposite so it was running on the MAG side and I needed to give it some throttle to keep it going but it did run.
 
I still haven't had a chance to break in my engine yet but found out I had fuel leaking out of my pulse line, found a ripped diaphragm in the fuel pump so I rebuilt it. Perhaps thats why the mag side plug was always wet, running too rich.
 
Can anyone with drastic knowledge of Yamaha 540 fan cooled engines answer if these are by chance low compression motors?

Thanks in advance!
 
Rebuilt a SR 540 and installed in a VK...it only showed just over
100 psi ...never checked again, but runs well so far...will know
more if it ever snows ...LOL...had some trouble feeling confident
that I purged the air from the 2 oil lines from tank.
Ron
 
Ron~ Thank you for that info, makes me feel much better. We are struggling with no snow and I have yet to get the engine broke in. Can you please make a follow up when you get it broken in and let me know how your compression is sitting. I'll do the same.

Are you running a bit of premix in the fuel too? Hope you get some snow too!
 
Hi M
The orig 93 injected into the fuel line before the pump, the engine
I used was about 1985 and injects into each manifold,..the pump
has two draw hoses from tank and had trouble getting an air
bubble out of one hose ....the darn bleed screw is difficult to get
to and I tried using an oil can to prime it and popped the frost
plug from the oil pump...jammed it back and finally seemed to
get air out by removing lines at pump to let air out..
Used a heat gun to soften up the hose at each nozzle, removed
and disconnected cable from carb and held the oil drive open
while letting the sled idle , running premix, and watched it flow
out.
I will try to check compression later , if it snows...LOL
Ron
 
I'll agree that the bleed screw is useless in this sled due to no space to get to it. I still got my lines going into both sides of the manifold. Almost thinking about premixing it all the time but don't know how to effectively disable the oil pump while still keeping the tach working.

I was told the same thing by bleeding it while those two manifold lines were disconnected, holding the oil drive line wide open at idle.
 
It's a pain to go back to mixing..but I have seen them
disconected and plugged...other option is to disconnect
the cable and leave it working at idle setting and premix
at 50:1.....That way you would still pump according to
RPM but never increase to the amt it would normally give.
One reason to inject in the manifold is so you still have
oil when slowing down from Wide open throttle and speed.
Problem can be the oil injected builds up and can foul
or give off smoke when you start off again...
My 93 VK "was" injected into the fuel line before the pump.
If you don't trust your pump,,,maybe leave it hooked and
mix something synthetic at 100:1
Ron
 
This past summer I rebuilt my '85 Yamaha XLV. Due to lack of snow this winter I have only rode it a couple times (about 20 minutes total) just around the yard really.

We have a trip coming up this weekend to Lake Winnipeg to go ice fishing and I hear they got lots of snow.

How good of an idea is it to start pulling a Frabill Predator (flip over) fish house with it with not many miles on the rebuilt? I don't think its the greatest idea myself but is there any way I can hurt the motor which hasn't really been broken in yet?

Expert opinions needed. Thanks!
 
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