I've read a few posts that stated the valve clearance on the 660 engine used in the Raptor and Grizzly can get LESS with time, indicating something is awry with the valve or valve seat. I just read an magazine article where some outfit built a 686 Grizzly, and they say the OEM valve springs are too weak, allowing the valve to bounce on the seat and cause damage. Another post said the intake valves were deforming because they're too soft. So which is it, or is it a combination of both? How many of you had to have valve/head work done because of this issue?

 

My intake valves were slightly tighter but still had some clearance, exaust valves were within spec. I adjusted them after about 20 hours.

This is not an unusuall situation. My VW racer has Titanium valves Hardened seats & trick springs & also does this, it did this with stainless valves also.

This is just a normal situation wtih the heating & cooling down of dissimialar meatals.

 

I have at least 200 hours and the intake valves tighten up but the exhaust valves have never been adjusted since new because they are always within spec.

/NotuRaptor

 

It is a very common problem for the intake valves to tighten. I just got into the motor on mine and the intake valves are trashed !! It does look as thou the spring pressure is too low. The valve seat area has been bashed all to badly. I have seen this on race cars and usually higher comp. springs take care of it. I haven't found a harder valve available, and the stoke ones are on back order along with the higher pressure springs. This leads me to believe this is becoming a common problem as more people get into there motor. If you have a new one I would suggest getting the springs to save on money and maintenance later on.

 

2strokeDiehard,
Thanks for the heads up. I never saw this phenomenon with my Ram Air IV GTO, and it had a Crane Zip 510 solid lifter cam in it. Maybe it's got to do with the aluminium heads on these things, but then again I did not have valve clearance issues with my 300 FourTrax.