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I picked up a 07 700.:smile I got it cheap, it's been used around salt water so it isn't real pretty.:x It's not terrible tho. But the P.O said that it fouls the plug every hour or 2 of running time. I thought "no problem". Well, after seeing the air cleaner(it was an oily disintegrating mess) and noticing that it had way too much oil in the oil tank. ( about 1.5 to 2 cups) I figured one or both of those things had to be the problem. I corrected those 2 issues and put a new plug in it, but if fouled it out in short order. I did a compression test and it only has 90 p.s.i. That was with a brand new quality tester. So, what should the compression be? Also if it was a valve problem, would it be hard to start? It doesn't seem to smoke, but I didn't really pay much attention to that. I'll have to go get another plug to check to see if it smokes.
Thanks for any help :grin
 

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Yes, valve issues usually cause hard cold starting; the intakes get tight.
Others will have to chime in on proper compression.

Are there any modifications? Air box, exhaust, electronics?
 

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Welcome aboard Purple and congrats on your new beast! Per the Service Manual:
 

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Did you do a dry and wet compression check? Is the plug fouled with gas or oil? You might get a #7 plug instead of a #8. Yes, you should adjust your valves for better cold starts.

WELCOME TO THE FORUM.
 

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Oil may have gas in it due to over priming causing high oil readings. Learned the hard way on that pretty quick.
 

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Discussion Starter #6
Welcome aboard Purple and congrats on your new beast! Per the Service Manual:
Thanks for the welcome
So 90 seems like way too much. That doesn't make sense. Now i'm really confused.

AS far as I can tell, it's bone stock. It starts really easy with a new plug

What's the diff between a wet test and a dry test?

The oil in the tank was sort of a gray color. Could that be gas in it? How does that happen?
 

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There is a very specific procedure listed for testing compression plus a Yamaha Compression Tester which may read differently than a standard automotive
tester. Below are the snips from the service manual.
 

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welcome to the group nice year did ya get the burnt orange and black??????
 

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Discussion Starter #10
There is a very specific procedure listed for testing compression plus a Yamaha Compression Tester which may read differently than a standard automotive
tester. Below are the snips from the service manual.
Thanks for that info, Brett. I have a riding buddy named Brett:laugh I pretty much did all those things when I tested it. Except for checking valves. It starts easy when cold, so I don't think the valves are an issue. But I will check them. It sounds like I got carbon build-up, no? That sounds alot easier and cheaper than a top-end rebuild. So, the plug fouling issue is maybe ignition related or maybe the throttle body needs a cleaning? That may be a contributing factor to the carbon build-up. I guess I need to invest in a manual.
 

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Thanks for that info, Brett. I have a riding buddy named Brett:laugh I pretty much did all those things when I tested it. Except for checking valves. It starts easy when cold, so I don't think the valves are an issue. But I will check them. It sounds like I got carbon build-up, no? That sounds alot easier and cheaper than a top-end rebuild. So, the plug fouling issue is maybe ignition related or maybe the throttle body needs a cleaning? That may be a contributing factor to the carbon build-up. I guess I need to invest in a manual.

You are welcome! Check your private messages when you get a chance.
 

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Did you do a dry and wet compression check? Is the plug fouled with gas or oil? You might get a #7 plug instead of a #8. Yes, you should adjust your valves for better cold starts.

WELCOME TO THE FORUM.


Dry compression is a warmed up motor. Wet compression is warmed up, then add about 1/8oz of oil to see if the reading increases a lot. That indicates worn rings. I wouldn't be worried about a high reading. I would almost suspect a bad gauge, maybe exchange it and do your test again.


Again, is the plug fouled with gas or oil??


If you haven't, change your oil and filter. The gray color indicates water, but there could be fuel in it too.


A #7 plug is hotter and may burn a little cleaner.
 

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Discussion Starter #15
Dry compression is a warmed up motor. Wet compression is warmed up, then add about 1/8oz of oil to see if the reading increases a lot. That indicates worn rings. I wouldn't be worried about a high reading. I would almost suspect a bad gauge, maybe exchange it and do your test again.


Again, is the plug fouled with gas or oil??


If you haven't, change your oil and filter. The gray color indicates water, but there could be fuel in it too.


A #7 plug is hotter and may burn a little cleaner.

I tested it with my old tester and thought that it was way off. I bought a new one and it was within 2 p.s.i of the old one. IDT it's the gauge. I'm not sure on what is fouling the plug. I'll check on it when I get a chance.Thanks!
 

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I put some run time on it and it hasn't fouled the plug yet. I'm thinking maybe that nasty air cleaner caused the carbon build-up, but, now that it's flowing good and clean air the carbon is burning out? IDK Hoping :smile
 

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Dunno but it's never a bad idea to have a clean air filter :)
 
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