power valve missing

[unclefista240]

rem

 

[IndyMX]

You should be able to get the parts at bikebandit.com

 

[sick 96 250]

if you run without the power valve you will have no top end. Did you buy this bike cheap or something recently? Dont just replace the piston and rings without doing the PV.

Just out of curiosity, which O-rings are you speaking of that leak? If your talking about the head then yeah, your bike may fire up for a second then die, your pulling coolant down into the bottom end and cutting out the spark.

Still confused on how you have a bike with the PV missing and never noticed it.

 

[sixds]

if you run without the power valve you will have no top end. Did you buy this bike cheap or something recently? Dont just replace the piston and rings without doing the PV.

i thought the powervalve opened up to make more top end? and when its closed that helps with bottom end, no?

 

[sick 96 250]

if the power valve is disconnected, when you get into the higher RPM's it will not open to give you the flow you need for the higher RPM's, having no top end.

So no PV, no top end, unless something else crazy is going on

 

[sixds]

yes, but he said the powervalve was missing completely, not just not working.

 

[IndyMX]

if the PV is completely missing, as the OP said, you'll have no bottom at all.. Top end won't be affected.

 

[dirt bike dave]

Check to see if the bike has big bore conversion. Not sure about the RM, but a large over bore on some bikes requires removing the PV.

 

[_JOE_]

Check to see if the bike has big bore conversion. Not sure about the RM, but a large over bore on some bikes requires removing the PV.

My 02 just needed shaved down for a 265(2mm over). I dont see why one would remove it completely.

 

[dirt bike dave]

My 02 just needed shaved down for a 265(2mm over). I dont see why one would remove it completely.

Maybe his is bored to 310. If you needed to shave it to go from 250 to 265, do you think you could go to 310 without removing it? BTW, his '95 also has a different motor than your '02.

I'm just throwing out ideas why someone would remove the powervalve in a dirt bike. Besides accomodating an over bore, the only other thing I can think of is the PV was worn out and busted, and they did want to spend the money to repair properly.

The poster said the 'bike seemed to run OK' even with a worn out top end and no PV. Would it run OK in this condition on a stock bore? Maybe not, but it could with a 310 kit.

 

[unclefista240]

yes its completely missing. i havent owned a bike this new nor have i been on a bike in a while so it seemed to run ok to me. does anyone have a head complete with the valve?

 

[unclefista240]

finally done

so i bought powervalves for a 1995 rm 250 (since mine were missing) only to find out that my cylinder was from a 1992. i bought a new piston and waited a few months till i came across a cylinder with powervalves like new,a few hours but in great shape, so i got it all together ,after cleaning measuring and lubing, couldnt get it to start by kicking so i drained the gas put it where it could get warm then pull started it behind my three wheeler. i had to put it in third to get it to turn over. its got the most compression ive ever seen. igot it started but only ran it for a while . when i mixed the gas out in the cold it was like a wad of molasas? thats why i warmed the gas first( heated porch, not blow torch) im gonna do a compression test when shes broke in . form what i could tell its a completely different bike. kansas weather sucks.

 

[mox69]

Well normal gas won't thicken when its cold out. Even gas mixed with oil should not be noticeably thicker when cold. I would say you have bad gas or oil. I would go pickup brand new gas, and mix in some good 2T oil.

Also, if this thing is freshly rebuilt and put back together correctly it should fire right up. If you have to tow it behind something to get it to start, that indicates there is probably something wrong still. Trying to start it like this will only make the problem worse.

 

[Blink-182]

if u left it for a few months with fuel wouldent that mean it would have gotten gunky in the carb?

 

[BigRedAF]

if the power valve is disconnected, when you get into the higher RPM's it will not open to give you the flow you need for the higher RPM's, having no top end.

So no PV, no top end, unless something else crazy is going on

I think what your saying is improper power valve operation equals less power.

If it stays closed you will have less top end, bottom end will be unaffected.

Completely missing is a mystery. The channels that the valve rides in would cause turbulence and screw a lot of things up.

 

[tyler_43]

lol the only time I've ever heard of somebody completely removing the powervalve is when they use the engine in a shifter Kart :P

 

[unclefista240]

yeah like i mentioned the power valve was gone completely,and the cylinder was off of a 1992 and my bike and the power valve i purchased are 1995. and yes its all back apart to address the starting issue, its just too damn cold.oh i also found out that it has a hotrod crank so i figure whoever had it before suffered a catastrophic? failure and patched it back together....

 

[tyler_43]

freaky...

 

[mxcrazed]

I bought a cylinder for my 89 cr250 it was ported and polished and bored to the largest size wiseco makes with a sleeve and the valves were removed and replaced with these aluminum plugs that were machined to fit the cylinder and port matched and they looked beautiful

also it appeared to have been run on alcohol I think it was out of a shifter cart but no confirmation i was gonna have it resleeved but then i would have to get port work done again maybe i can get by with a hone

 

[tyler_43]

yes that sure sounds like a kart cylinder... the plugs give it away. That thing will be tuned of sheer top end so I'd advise the port work if you want it in a bike... maybe send it to eric gorr and get him to tune it a lil' more for bottom?