Bad Hesitation

Vincent

Vincent

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Aug 29, 2015
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Ontario Canada
Hesitation

Well, all good things must come to an end.
My super reliable Venture is sick.
The terrible midrange hesitation I experience briefly last weekend has returned. At the time turning the carb heaters back on seemed to have stoped it leading me to believe the carbs had Frozen up. WRONG! Funny I was able to accumulated another 80 trouble free km over a few days before it reappeared lastnight.

It starts well and idle ok, seems a bit rougher though.
As is revs to 5000 - 6000rpms it misses and hesitate. Sometimes it improves but then eventually worse again. Tried giving a bit of choke but the motor just wants to die. Funny thing is it runs as if the choke was stuck on a bit. Plugs tell a different tale. #1 is very dark, where #2, & 3 look lean, dry and light in colour. Almost like a vacuum leak.

Things I have done today.

-Checked compression 115 psi on all three. No change there.

-Drained all gas till the tank was bone dry and refilled with fresh 91 octane.

- Removed and completely cleaned the carbs again! They were spotless ofcourse. Double checked all setting. Everything was fine.

- Inspected the carb to reed rubber boots. No cracks, in good shape.

- Verified no kinks in fuel lines.

- Tried three difference sets of plugs. The last ones I bought last night.

- Checked for vacuum leaks all around the carbs, boots, base gaskets with a can of carb cleaner. Idle never changed.

-Thought maybe #1 coil, wire or boot was misfireing (Because it's much darker then the others) So I switch the coil, wire and boot with a spares. No change.

Any other ideas?
 
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Did you cheek the in tank fuel filter when you drained the gas, before you re-fuled? Was there any crap in the bottom of the tank? Did you check reeds? Did you try new plug boots? Those symptoms sound like either a fuel issue or possibly stator... or chipped reed could maybe do that. Its weird that it came and went like that. Was the outside temp the same when the problem happened both times? The one and only time i froze my carbs up it didn't want to run at all. It would barley move past a slow roll, backfiring ect...
 
It's a new fuel filter from the yamaha dealer. I installed it last fall. Tank was vacuum cleaned at the same time. Reeds were not checked. Plug boots were replaced by the previous owner. Maybe due again.

Like you said it's weird it completely disappeared then suddenly came back.
 
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It has run very well in mild or very cold temperatures for hundreds of kms. Like I said #2 & 3 look lean. It first happened in -25 c and reappeared in -7c.
 
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The key to this mistery lays in these spark plug colours. Something is wrong with #1 PTO side.
 

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Been checking coil, wires and plugs ohms. I used two different multimeters and got the same numbers on both.

Primary resistance measured on 200 ohms scale .
All three coils showed full continuity.
Didn't get the 0.05 to 0.07 ohms suggested by my yamaha book.

Secondary resistance with spark plug boots still on. Measured on the 20k ohms scale.

#1 coil assembly 9.0
#2 coil assembly 11.0
#3 coil assembly 10.8

One question. Do you measure from the female or the male connector? I used the female. Don't know if that's correct.

I know the boots are supposed to be removed but I think they were glued. I can't get them off and was concerned too much force mite damage them.
 

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I had a similar hesitation that was caused by bad plug caps and moisture getting in there. New caps 5 ohm(maybe it's 5k?) from local auto parts store all three $15 and she runs like a top.

Sent from my XT1080 using Tapatalk
 
Are you saying that measuring the primary wires is showing zero (or near zero) ohms. If so you may need to replace them. They should read between 0.36 and 0.48 ohms at 68 degrees F. Are you using the smallest ohm setting? It may be on too high of a setting to measure less than 1 ohm. You may have to use a different meter that measures lower values.

Secondary wire should be measured to the male connector and 5.4K - 7.4K ohms - if you leave your plug caps on they should read between 10.K - 12.4K ohms. The one with only 9K ohms is getting suspect. I would test the caps by themselves and possibly just replace them as nst115 suggested.

Somehow I have a feeling that you issue might be deeper, but start eliminating things one at a time.

I would test the stator coils. That doesn't cost anything but a little time.

Are you still running a battery? Is it in good shape?
 
Ya. I'm starting to realize exactly that. When I try to measure off the male connecter to plug boot, I have a hard time finding continuity from #2 & 3 coil. But #1 easily . I managed to finally rip off the plug boots. They were very stuck and I damaged one. Cut a 1/2 off each wire, and after that all coils measure 3300 to 3400 ohms easily.

If this is the case it would mean #2 & 3 plugs were misfireing at times and are actually lighter in colour because of fuel wash. Hope it's my fix!
 
I was replying to snt115 there.

On the primary circuits I ment I measure good continuity with no resistance. So actually shows 0 ohms on the lowest settings of two different meters. But they are both cheap 35$ ones.

Right now with all the plug boots off, the coils all match my yamaha Manuel's ohms specs. Good enough for yamaha good enough for me.
The boots are all really suspect at this point and will all be replaced.

Yes, next I can check, flywheel, stator, etc......

My battery is 2 years old and hold a charge well.

Thanks for all the help guys. I learn more with every step.
 
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Which sled is this, and what year manual do you have?

btw: those plug caps thread on and off.
 
Ding said:
Which sled is this, and what year manual do you have?

btw: those plug caps thread on and off.
Click to expand...

For a 2000 700 Venture.

And yes I knew they were screwed on, but the rubbers had bonded badly over time and caused damage to the boots as I tried to unscrew them.
 

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That looks like a Clymer's manual. I am not sure how accurate the information is in it.

My manual (Yamaha official service manual) shows different values. Maybe some others can chime in. I believe your sled has the 175W charging system.
 
I'm sure you are correct about the charging system wattage. As fare as the book it is Clymer. Some info Is likely inaccurate.
 
Awsome guys. I'm going to get this figured out and fixed! Still lots of snowmobiling season left.
 
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