Other Is this motor fried?

[96superjet]

On a ride at the end of the season on my 1999 GP800 and it started making some tapping noise then "whack" motor stopped. So, I finally got around to tearing it down. I didn't take pics, but the "YPVS" power valves were completely polluted with sludge (they would barely move). So after completely cleaning everything up, I took some pics and looking for recommendations. Do I need a new top end kit? Do the pistons look OK? The cylinder walls look pretty good. If I put everything back together, is there a way I can check compression without hoisting that pig of motor back into the hull? Thanks for any advice.

 

[vomitspot]

i dont see any damage
now would be a good time to upgrade to riva or rd powervalves , they warranty against defects
oem valves is common for them to break

you can check comp by hooking a battery str8 to the starter but be ready it spins as soon as you connect 2nd wire

 

[ChrisFiore15]

Looks pretty good, Def replace PVs with the kits as said above...

Did you check the pump area? Could be the root of the noises you heard.

 

[tor*p*do]

Looks like it was running a little lean to me.
And the blow-by on the pistons could
indicate the need for new rings and a hone at least

 

[ProSouth]

^^agreed, it has slight scoring on the piston, but nothing i wouldnt run. cylinder still has crosshatching but i would honestly run a hone through it and new rings also. good luck

 

[96superjet]

Looks like it was running a little lean to me.
And the blow-by on the pistons could
indicate the need for new rings and a hone at least

Yea a while ago I added aftermarket flame arrestors in an effort to increase air flow, but after some reading it appears that the "I" body carbs on the GP800 react poorly from the added air flow. Here's a link to Group K's discussion on this topic and an excerpt from the article addressing the mid-range lean condition.

"However the free breathing flame arrestors also causes a slight reduction in the inlet tract vacuum needed to draw fuel from the carburetor jet circuits. Removing the choke plates (in addition to the aftermarket arrestor) further weakens the inlet tract vacuum as it additionally increases cfm. This added vacuum loss creates a mid-range lean condition that cannot be adjusted or jetted away.

The afore mentioned loss of the inlet tract vacuum is referred to as a loss of "signal". While this inlet "signal" itself cannot be recovered, it is possible to modify the stock carburetors in a way that allows them to be more sensitive to the remaining signal that exists in the inlet tract. Such a modification is performed by Novi Performance (makers of racing carbs). This carb modification, by itself, does not result in a genuine power increase. However with this mod, the carbs will have enough "signal strength" to avoid the unsolvable mid-range lean condition that might take place with the choke butterflies and shafts removed"

So I'm gonna call Novi to see what's involved in this carb modification. As I plan on removing the choke plates (installing a primer cuz the GP800 has always been a PITA to start) and remove the "Accelerator Pump" that comes stock on the GP800. Here's a pic of the accelerator pump mechanism.

 

[tor*p*do]

probably should slap some new wrist pin bearings in it
as well, while its down

 

[badvinny]

I don't know if it is fried? Maybe it is " baked" or even "toast", probably not fried though!