99 yamaha srx 600 blues once warmed up it wont rev past 7000 rpm loosing comp.

P

panterahead79

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Hey Folks,

Well Ive got a few problems with the srx 600. It has ran fine all season untill last week. We went out for a while last week.Then it started bogging down to 7000 rpm on any wot. Once it starts it wont quit untill I shut the sled off for a while. I havent seen any light codes from the gauges other then the 3 at start up.

Now every time I take it out. It Is fine for about a mile or so then it starts the bogging again. I always let it warm up good before I take it out. So far...

I changed the plugs
I changed the belt the old one was probally well worn but no major defects.
I went through carbs no plugged jets everything still seems to be insync.
I pulled the power valves none stuck no pull throughs replaced them last year from repaired ones on here. Looked surpisingly clean other then the milky residue?"I'll post a pic"
After my bone head move last night of starting with pulling pvs I remembered I was gonna do a compression test would of saved me some time starting there.
So after all the other stuff I'am deff losing comp on cyls readings of 110 90 110 last check was 125 give or take on all 3.

I used my fancy inspection cam wish it took pictures.

All reeds seem to be intact.
Pistons have some clean spots on them like what happens with a head gasket leak on a car. Over all though look normal no melting spots
that I can see with cam.

I really am having problems finding parts this year last year I could find about anything for this sled. I cant find a rebuild kit or pistons even the wiseco site dont list one for the 600. They list the 700s I can only seem to find oems and they are super pricey. Does anyone know a wiseco or spi part number for a rebuild kit or a piston and ring set for the 600?
I can still find the gasket kits but If I need pistons seems to be sol except for the oems.

Thanks
PH
 

I haven't ever looked myself but have read on here that OEM is only option for the 600 as no aftermarket company makes them. I have also read on here about getting pistons coated to bring them back into spec. With those comp numbers (110,90,110) down from 125 you need to get a better look before it grenades.
 
check your stator when it does it.your high speed coil is bad when hot.mine did the same.
 
do all 3 powervalves have that milky grease on them?

on your compression check does it come up higher once the sled is warmed up? what happens if you shoot a shot of like wd40 into the cylinder and then recheck with guage?

have you looked at the flywheel to see if its rusty on the magnets on outside?
 
Hey all,

Devil that sucks they dont have an aftermarket piston. I will pull the heads sometime and get a better look at what is actually going on. I hope pistons are not beyond repair. As oems seem to be anywhere from $120 up per piston

Densrx I will see if I can check the electrics when warm but not sure if I will get same results on the lift (Its been raining all day now and looks like its gonna stay warm so wont have any snow to test )

Captn Hopefully I can get away with just the rings and a gasket kit.

Mrviper Yes all 3 pv's had that milky residue on them. Leaky head gasket maybe? I will try the wd 40 or some fogging oil and retest comp. I will also try it when sled is warm that may be a little bit before I get gas put back in. I havent looked at stator yet to see if its is rusty will do this at some point

Will 700 srx heads bolt up to the 600 bottom end? Just throwing around ideas.

I'm not exactally sure how I want to proceed at this point. Guess my season is over this year I was supposed to go to Cadillac this Friday Thru Tuesday but thats pretty much ruined now :whine:

Thanks for all your input I will let you know what I find as I go

PH
 
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Yea 700 jugs Pistons and heads will bolt on the case but you need the 700 cdi and will need to rejet reclutch etc.

I think they only make Oem pistons as well, I couldn't find any aftermarket ones.

Do the wet comp test like mr viper said. If the numbers are drastically higher you need new rings and or Pistons. Sounds to me like you might be burning a little coolant as well.


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Hey all,

I ran the comp test with some fogging oil and I get about a 10 psi increase across the board 119/112/119 ish. So I need to get some rings and a gasket kit at very least.

As far as 700 kits I can find a wiseco kit for a 700 part # SK1270
Displacement: 696cc
Bore - Standard: 69.00mm
Bore - Actual: 69.00mm
Bore - Oversize: STD
Stroke: 62.00mm
Cylinders: 3
Treatment: Hard Coat Annodize
Note: Pro-Lite
Note: Nikasil Bore

Is this not correct info for a 98-01 700 srx? I think there is a spi kit also if I remember correctly.
I dont know if its really worth going the extra money and work to go that route of changing the heads and cdi etc... It would be nice to have a sleeper though lol. qDepends what I find when I take the time to pull engine to me there is no sense in changing rings with out changing crank seals / gaskets also.

Ph
 
Hey all,

I found some more info I pulled heads and middle one has burnt the top of piston off on the front exhaust side by the rings. All the pistons look to me like it got leaned out on all cylinders. The middle center inside head gasket looks like it is super stretched out. The cylinders look good from what I seen except some scaring on the clutch/pto side. All of the heads look crazy clean to me. I will post some pics of everything I can see thus far. I really dont know what I'm going to do I put way to much in this sled last year already.

20150306_184316.jpg20150306_184401.jpg20150306_184411.jpg20150306_184420.jpg20150306_185136.jpg
 
the pistons being burnt off the front edge is from too lean of jetting and or too low of octane fuel for the jetting thats in it, it gets hot and it begins to burn the crown edge back. The good news is at least you caught it before it exposed the ring and melted it and then it gouges the cylinder and you have a reall expensive mess going on.
What else i see is one was drinking antifreeze and washing all the carbon off the piston top. it also can be from a way rich condition where it will also wash the carbon off the top and your heads being super clean as you noted leads me more to antifreeze then anything else, it can either come from the o-rings or the base gasket. they get white a nd fuzzy overtime and begin to leak.

yamaha oem pistons for a srx600 are like $115 each. I would go ahead and pull the cylinders and replace the base gasket,o-rings and new pistons/rings and it should run for a very long tome. Youll need to go thru the carbs and see what jetting is in it to prevent the burn back of the pistons in the future.
 
Like mr viper said check the jets to see what it has. When I bought my srx I got in the carbs and noticed the main jet was a 135 on the pto cylinder, then I noticed the fuel screw was turned almost all the way in. Previous owner must have been trying to lean that cylinder out for who knows what reason. Then this fall when I replaced the rings I noticed the pto cylinder was different from the other two. A lot cleaner. So he must have burned it down and then had it fixed and sold it. My point is you never know what the previous owner could have done. Also I have seen so many people too cheap to use premium fuel, I mean really spend the extra 2 dollars, for the added safety. Anyways, I'm sure if you do everything mr viper said it will last a long time. It will be well worth it in the end.
 
Hey guys,

I wonder if it was the oil I had to use on last top off or oil pump. That caused the lean condition I normally run amsoil interceptor and had to use dominator. I always have run 93 ultra gas w ethanol when I fill up local it the best I can get in my area. When up north we ran non ethanol 91 I think is what it was. I will go back through carbs I didnt do a complete tear down this last time because the looked really good inside. I forget what jets were in the carbs didnt take note last year but it has always been on the rich side of things.

Do you think I can get by with just buying one piston or do I need to get all three? Also what can I dump down in the cylinders to protect them for now Im sure I got some antifreeze in bottom of case at this point. It is going to be a lil while before I get my funds for this project so I put everything back together for now. Can I put the atf down in there or should I just use the fogging oil?

Thanks again
ph
 
Get the coolant out and get some kind of oil down there. I'm running stock jetting and it is just a little rich but good for 10 below


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If they show signs of wear or any damage they need to be replaced with new or good used, go over things with prejudice, check everything as you reassemble, Ive rebuilt 15L engines worth tons of coin and I've seen some "wizardry" in those tear downs let me tell you,
 
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