WOT RPM fluctuating 06 rev?

[kinney31]

As stated 06 rev 800 with 2500 miles. 100 miles ago the wrist pin clip broke and took out my cylinders. With the miles I decided to replace the crank (Big John) supplied that. After getting the cylinders re nic'd new pistons new domes (rkt) we put her all back together. Took it on a test ride yesterday and it is real snappy and runs pretty good, but if you hold wot it fluctuates between 7500 and 7800 rpms. Nothing has changed just freshened up, clutching, jetting and so on. Back to fluctuating at times it spikes above that 75 and you can feel the power. Power valves are clean, checked reeds, boots, and primary cleaned and team secondary is good. what are your thoughts power valve selenoid possibly not allowing the valves to open all the way and sometimes breaks free and opens all the way? Sled was towed out about 32 miles and filled the engine compartment full of snow, which might of allowed water to leak in. Any help would be appreciated.
Also when we had the motor out we did a vac test and the motor held,so i know its not sucking air in.

 

[DOOin it]

What pistons are you running in it? is it a wat wat wat sound?

 

[kinney31]

running spi single ring. No it feels almost like the belt is slipping but its not.

 

[DOOin it]

I've had this same problem with my 05 800!! went through the same thing and it ended up being the spi pistons!! Put oem pistons back in and ran like a champ.

 

[kinney31]

Last ride we rode maybe 25 miles and it broke a ring so i replaced the piston and took it back out and its doing the same thing?I adj the clickers extreme the other way and the rpms stayed the same. Thats what leaves me to believe it has something to do with the power valves not opening. Here is the history of the sled
1) sled broke wrist pin clip, took out cyls, and head. re nic cyl, new pistons, new domes, new crank. Had it on the stand in the shop reving it up and it had a fluctuating throttle on the stand but never fluctuated up in the mtns on the ride below.

2)took sled out prob 40 miles the o-ring on the head broke and started to over heat the motor. Packed snow around the motor and limped it out. The sled ripped that day no fluctuation of rpm's. Got sled back to shop and the pistons smeared slightly so in goes new pistons and rings cylinders were fine. Put it on the stand and no flucuating rpms thought we were set.

3)To the mtns we go after unloading sled it throws check eng light. Then doesn't come back on the rest of day. The first 8-10 miles it had a fluctuating rpm and not a whole lot of power in the bottom end, than the sled came to life normal rpm's. My initial thought was i put too much race fuel in and over octaned the motor not allowing it to heat up the pipe. it ran normal for about an hour and lost a cyl,so I limped it out pretty mad at this point. Pulled the motor out and the pto piston broke a ring. Cylinders wer fine checked by the local shop re hoaned the cylinders, did a leak down test and everything passed. In goes new piston and rings.

4)And here is the latest test ride report which started this thread. Sled feels real snappy in the bottom end but still has a fluctuating rpm even under load on the flats etc. It never stopped flucuating the whole ride like it did on the above ride. On the way down it ran real hard hitting full rpms at times. Now the funny thing is its accelerating while it does it sometimes! My thoughts are that the power valves on the above ride werent opening in the beginning of the ride. After a while of warming up the eng compartment maybe they broke loose and the solenoid started opening all the way. Than the ring broke , might be a fluke who knows.

 

[monstermachine]

Exhaust valves

This may sound dumb but make sure the weep hole on the exhaust valves line up with the hole on the cylinder, also check the valves while idling if you can see the rubber boot in there moving too much it could have a damaged seal

 

[kinney31]

update

Decided to throw OEM pistons back in! And......... it runs perfect who would of thunk. The spi pistons after 20 miles look horrible compared to the 2200 mile take outs. Also the spi pistons and rings were hard on the cylinders, there is a bit of blow by on the piston that had 50 miles on it, I know the rings werent seated yet. But the oem pistons did not skip a beat from the beginning. Not trying to bash just giving the results I had after 5 spi pistons. Just a family guy trying to save a dollar and ended up spending more after all.

 

[DOOin it]

Man i'm glad you had good luck with that!! the only other thing i found weird with the RKT head was that i droped ten jet sizes guess its more effecient than the stocker!!

 

[kr]

Did you guys ever figure what was different about the spi's that caused the issue?..wall clearance, skirt dimensions, ring gap, ect? Theyve (spi's) always worked great for me...getting ready to do set of dual rings right now.

 

[DOOin it]

Did you guys ever figure what was different about the spi's that caused the issue?..wall clearance, skirt dimensions, ring gap, ect? Theyve (spi's) always worked great for me...getting ready to do set of dual rings right now.

Never was able to tell a diffrence between the two!! i've put them (spi's) in a couple 600s and some other 800 and they worked great no issues. not sure what the deal was!! maybe weight between the two or something was off just a hair.

 

[kinney31]

I took out my thermostat and plugged the return on the bottle so my sled runs cooler. The spi's would not transfer heat to the cylinders. May be bad rings who knows. I do know one thing I will NEVER put cheap pistons in a motor ever again. It's a no brainer 5 spi pistons sled runs horrible. 1 set of oem and it runs perfect. I should have listened to Kelsey at RKT from the very beginning he warned me!

 

[towny]

Decided to throw OEM pistons back in! And......... it runs perfect who would of thunk. The spi pistons after 20 miles look horrible compared to the 2200 mile take outs. Also the spi pistons and rings were hard on the cylinders, there is a bit of blow by on the piston that had 50 miles on it, I know the rings werent seated yet. But the oem pistons did not skip a beat from the beginning. Not trying to bash just giving the results I had after 5 spi pistons. Just a family guy trying to save a dollar and ended up spending more after all.

WOW! What the heck my 06 has been doing the same thing and it started after I put in SPI replacment pistons???? Was able to clutch around it but never totaly got away from the Waaa Waaa Waaa when pinning it WOT! Hummm I wander what the differance is?? Has great compresion and the pistons fit the bores real nice. I have an SLP head on it and was thinking it was causing the problem?

 

[kinney31]

Towny

Not sure if it's the head or not? My sled has a rkt head, dynoport pipe and can, slp ported cylinders, and v force reeds. It never skipped a beat untill 2300 miles the wrist pin clip broke.I tried the cheap pistons and my motor did not like them. I had the cylinders re nicd, after pulling the cylinders off 3 times it's not pretty what the spi piston's did to the cylinders they look like they have 2000 miles on them and they only have 150 max. Pretty sure it's the pistons.....

 

[RKT]

I took out my thermostat and plugged the return on the bottle so my sled runs cooler. The spi's would not transfer heat to the cylinders. May be bad rings who knows. I do know one thing I will NEVER put cheap pistons in a motor ever again. It's a no brainer 5 spi pistons sled runs horrible. 1 set of oem and it runs perfect. I should have listened to Kelsey at RKT from the very beginning he warned me!

ANY internal engine component ,IMO, is like choosing a doctor... You do not want to "skimp" on the product to save a buck, because it will cost you in the long run EVERY TIME..

ANYTHING Made in China (even if they put it is a different box with a USA Name like some) should NEVER be installed in your engine!! They simply do not work correctly.

Glad you found your problem...