4 strokes valve work

C

cowasaki

i always hear people say that 4 strokes 250's and 450's always need valve work. my 2 friends say that they need valve work like every 30hrs on it.. Now i just dont trust their judgement on that.. so can anybody tell me how often 4 strokes need valve work? why they need valve work? and Which 250 burns up the valves the most? because im thinking about getting a 4 stroke 250:noidea::confused:
 
SRAD97750

SRAD97750

Moderator
Staff member
It comes down to maintenance.
When the "change of clearance over time" leads you to believe the valves are stretching, or the valve seats are wearing.
You check clearances every 5-10 hours and record the measurements. When it starts to look like it's wearing at a faster rate than normal, then you could need valve work.

100% depends on each rider and application. I know folks with 100K miles on their sportbikes without adjusting the valves once. I have heard of CRF250F valves needing overhaul after 30 hard MX hours. -BIG DAN:thumb:
 
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C

cowasaki

SRAD97750:
It comes down to maintenance.
When the "change of clearance over time" leads you to believe the valves are stretching, or the valve seats are wearing.
You check clearances every 5-10 hours and record the measurements. When it starts to look like it's wearing at a faster rate than normal, then you could need valve work.

100% depends on each rider and application. I know folks with 100K miles on their sportbikes without adjusting the valves once. I have heard of CRF250F valves needing overhaul after 30 hard MX hours. -BIG DAN:thumb:
Click to expand...
say you dont ride that hard just trail riding do you think that will keep the valves in better shape?
 
SRAD97750

SRAD97750

Moderator
Staff member
cowasaki:
say you dont ride that hard just trail riding do you think that will keep the valves in better shape?
Click to expand...
They will be in better shape compared to a MX ridden race bike.
But you really have to do the proper maintenance and measure the valve clearances regularly on any 4T. Otherwise you're always going to be guessing. -BIG DAN:thumb:
 
James

James

Staff member
I'd say that the most important thing is making sure that you keep your air filter clean/changed often.

For easy riding I'd probably go 50 hours on the piston and 100+ on the valves. Just keep an eye on the valve clearances, especially if it begins to start hard.

Also buy an hour meter, it's the only way to accurately tell how many hours you've put in the bike.
 
M

MikeinFresno

the Hondas are the hardest on the valves, my KTMs are not too bad only needing adjustment every 30 hrs or so on my RFS series motor and 50 hrs or so on the XC4 series 250 motor. This is valve adjustment times, not valve tear down and rebuild times.

the worst thing you can do is to not keep up with the adjustments and that will eat your head n valves up real quick.
 
snowflake

snowflake

04-08 CRF250R's are the hardest on valves. I have one. I don't have a total hour count on mine but I bought it summer 2012 and promptly put an hour meter on it, after 15 hours (mixture of mx and one really fast desert track I spent over-revving for the entire race) the intake valves were trashed. I had stainless steel valves installed last year, I'm about a season and a half in on that work and its still going strong with the valves in spec (haven't adjusted them other than for the fact that I changed camshafts)

Good air filter maintenance coupled with keeping it off the rev limiter and you can easily see 100+ hours out of a set, and their are aftermarket solutions, one is the stainless steel route I went, which adds weight to the valve train so it will rev a little slower. Then there are companies like Fast Heads that offer revised valve seats (different material) that claims to have also fixed the problem.
 
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T

TurtleShifter

Since were "whipping them out" I think that Yamaha did a great job with their WR valve train. Just last May was the first time I even cracked open the head on my '07 WR450. Never even had them adjusted. Bike was still running strong, starting easily. Just decided it was time to put some YZ cams in the bike, do a little port job, a slight bump up in the piston. My motor guy, Paul at ASRacing, said the valves looked worn but said I could re-use a couple if I wanted to. Chose not to.

Been happy with the motor on this bike. Had a YFZ450 quad I took to Glamis all the time. Same thing. Motor ran strong and never did any valve work to it. It was an '04 and sold it in '08 still going strong.:thumb:
 
snowflake

snowflake

TurtleShifter:
Since were "whipping them out" I think that Yamaha did a great job with their WR valve train. Just last May was the first time I even cracked open the head on my '07 WR450. Never even had them adjusted. Bike was still running strong, starting easily. Just decided it was time to put some YZ cams in the bike, do a little port job, a slight bump up in the piston. My motor guy, Paul at ASRacing, said the valves looked worn but said I could re-use a couple if I wanted to. Chose not to.

Been happy with the motor on this bike. Had a YFZ450 quad I took to Glamis all the time. Same thing. Motor ran strong and never did any valve work to it. It was an '04 and sold it in '08 still going strong.:thumb:
Click to expand...
I have an 01 WR250F that, shortly after I got it, shat a crank, upon rebuild and years later, never once have those valves had to be adjusted.

It sits a lot now these days but when I do ride it, it only takes about 4 kicks to initially start it
 
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