Vmax 600 xtc engine help

M

mongaupt

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Feb 20, 2017
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NY
Hi Everyone I had a few questions and hope some people can help.

I have a 97-98 vmax 600 xtc. It starts right up and doesn't have any issues starting again later.

I did notice that it might have been running a little sluggish. It still would feel like it had power and didn't show any real issues on the trails. I thought after last ride I might need to change the plugs. I just checked the plugs and they were pretty oiled up. Also seemed to be running a little rich. I felt it was rich Because I seen the smoke coming from it.

I just put a cheap compression tester to the motor while changing the plugs and both pulled exactly 90 pounds. Seemed weird but I know that's to low for a 2 cycle motor like this. Also the pounds slowly fell after a few minutes.

The way I tested it was to screw it in and pull the pull cord a few times. Did I do this correct?

I'm planning on pulling the top end off soon to check it all out. Could the reason of the falling pressure be from the bottom end? Or most likely something with the top end like bad gasket, bad pistons, etc?

I have done many tops ends on all different sleds but scared to get into the bottom end.

Any help in the matter will be very helpful. Thanks everyone and happy riding.


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How many miles on the sled ? Both cylinders being the same is good, but 90 psi is bad. Should be around 120.
If it's a high mileage sled, may just need rings and a light hone.
 
I was planning on buying the top end kit after this season anyway. Will a light hone need me to go up in cylinder size?


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No, there is no overbore size because the cylinders are plated. So, if there is too much wear in the cylinders and the pistons get too loose in the bore, the cylinders will need to be sent in to get re-plated.
That runs about $200 per cylinder I think.
Yamaha has a spec for bore size range on the cylinders, but don't have it handy.
 
MURDER YAMAHA said:
No, there is no overbore size because the cylinders are plated. So, if there is too much wear in the cylinders and the pistons get too loose in the bore, the cylinders will need to be sent in to get re-plated.
That runs about $200 per cylinder I think.
Yamaha has a spec for bore size range on the cylinders, but don't have it handy.
Click to expand...


Didn't know that on this model. I had the 96 without reverse and the cylinders were able to be bored.

I know you can never tell without seeing it but do you believe this is a top end issue or bottom end?

The light hone is this something I need to have someone do?
I would be looking for any type or nicks or scaring correct?


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Honing may be able to be done if there aren't Many imperfections in the cylinder wall. Most guys will do a quick hone when reassmebling after new rings. It's done mainly to get rid of fine scratches, and to help the new rings seat.
I have had no problems with the bottom end of my motor so far since it was new and I have around 3700 miles.
 
MURDER YAMAHA said:
Honing may be able to be done if there aren't Many imperfections in the cylinder wall. Most guys will do a quick hone when reassmebling after new rings. It's done mainly to get rid of fine scratches, and to help the new rings seat.
I have had no problems with the bottom end of my motor so far since it was new and I have around 3700 miles.
Click to expand...


Thanks for the information.
If the walls are looking pretty good ,
Are these cheap honing tools any good?

http://www.motoparthub.com/W80560_P...e?src=Google&gclid=CMz0quiPoNICFZlKDQodppIO5g




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First off your comp is fine, The number means nothing. You did both cylinders the same way and the both tested equally. There is no right way to do it just that you do it the same each time. Warm, cold, wet, dry, 5 pulls ten pull, temp variations etc. proper technique is 10 pulls with dry cylinders and cold with throttle open for baseline numbers. Then every time you check do it the same. To do a proper leak down you need a "leak down" tester. Leaving psi in a comp tester looking for a change means nothing. Now after 4000 mi you very well may need a top end rebuild of at least rings but save that for a summer project. Your symptoms sound more in line with dirty carbs, poor oil cable adjustment, chipped reeds etc. when was the last good go through of these basics?
 
Yep, what super1c said is right on. I assumed that you pulled the recoil the proper amount of times, ect. when you got your 90psi. But each compression tester is different.
If mine was used, and it read 90psi, I would know there was a serious problem, assuming the test was done correctly as super1c stated above.
Reeds do get chipped edges easily on these motors, so good suggestion there as well.
 
Thanks for the information.
I was planning on putting new pistons.
Going over the carbs.
New reeds.
Plugs
And seals on jugs. Head. Carbs n flange.

With adjusting the oil Cable how do I adjust without going to lean.


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Try doing the same test the same way, but put a bit of 2 stroke oil in the cylinder, if you number jumps to 120-130, you probably need some new rings (and Id do headgasket while your at it)
The smoke and black colour is a sign your running rich, so carb cleaning and adjustment should be done, although the twins were setup rich from the factory.
If your pistons still look good and are original Yamaha, Id just slap new rings, wristpins and snap rings on those same pistons. If you do want to go new pistons put Yamaha pistons in, anything else and your asking for trouble.
 
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