KXF RMF 250 head problems

[2smoke]

As a 2stroke man I have found the head/valve problems in the new 4T quite interesting. I spoke with a friend of mine who has been working on these babies. This is what he told me I cannot verify but I thought Id pass it on.

Fine dust is the killer. Gets in through hot start cable system on KXF, RMF (Yamaha's this is not a problem as they use a rubber sealed plunger system). Gets in through top of carb (seal this up) only held by two screws and an rubber o ring, move carby vent hoses away from back wheel. Make the the carby breath through a filter in the airbox ala PC racing kit. Piston maximum 20 hours and replace.

Feel free to discuss or rubbish....I only put it up as maybe just maybe it might help someone.

 

[2smoke]

.......and be meticulous with air filter cleaning!!!!!

 

[YZ165]

Or, get a YZF and don't worry about all the bugs that Suzukawasaki haven't figured out yet!

 

[Rich Rohrich]

The Honda CRFs (both 450 & 250) have the exact same problems with valve recession, as do the YZF250s just to a lesser extent. Fine dust getting in through the carb float vents, air cleaner boot and various other places is certainly a logical reason why the hard coating on the valve face could wear away and cause the recession issues.

Lots of folks have theorys ranging from dust to cam dynamics to inadequate valve spring tension and life. All these theory have real merit but IMO it's still unclear what the root cause is. All I know for sure is, running Kibblewhite stainless steel valves with their high quality springs and titanium retainers has proven to be a very effective fix for the CRF450 and the YZF250. Doing valve jobs and fixing these cylinder heads is the bulk of our four-stroke business lately. Kibblewhite is working on a fix for the CRF250 as well as the RMZ250. Hopefully in the next month or so we'll be able to post some test reusults.

 

[2smoke]

Interesting....everyone down here seems to be moving towards trying stainless steel valves too.

He mentioned that he decided to look at valves and piston crowns through a microscope and thats when he detected microscopic dirt and rock particles affecting all those bits.

 

[Rich Rohrich]

Replacing the OEM valve seats with a softer aftermarket seats is also a good fix, just much more expensive and outside the scope of capablities for a lot of smaller shops.