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View Full Version : 91 RM 250 Need to Know



350Xrider
08-20-2003, 01:27 AM
"Too much preload on the spring. On the left side of the cylinder is a dial that controls the spring preload for the exhaust valve system. The preload doesn't have that great of an affect on the engine's powerband, but too much preload will prevent the valves from opening, which causes a lack of top-end power."

I read this on on another site and I have a 1991 RM 250 and I need to know how to set the pre load on the spring they are talking aboutand how many turns it should take. Any help would be appreciated. Does anyone know if you will see a noticeable performance gain out of adjusting this? Any other suggestions on how to get more power out of a 91 RM 250 cheap? Thanks a lot

YTZ250#1
08-20-2003, 11:29 PM
It sounds like a power valve adjustment of some kind.I'm not sure how to do it but some of my friends might,I'll check in to it.My 89rm250 had an
fmf pipe and uni filter when I got it,it was plenty fast.Be sure to change the rings and or the piston often.A little over a hundred bucks to keep
it fresh every year beats buying a new cylinder.They are around $400
and there not borable.

lushatc200x
08-30-2003, 11:51 AM
hehe hate to tell u this bro but if you pay 400 dollars for a cylinder your an idiot. and they can bore them and resleeve them. a bore is 40 a sleeve is 80 and to press it in is 100. sounds more along the lines at about 220 bucks. then there is a 70 dollar piston and a 20 dollar head gasket.add all that and you got little over 400 in it all together.

MR ATC
08-31-2003, 12:08 PM
hehe hate to tell u this bro but if you pay 400 dollars for a cylinder your an idiot. and they can bore them and resleeve them. a bore is 40 a sleeve is 80 and to press it in is 100. sounds more along the lines at about 220 bucks. then there is a 70 dollar piston and a 20 dollar head gasket.add all that and you got little over 400 in it all together.

i hate to tell you this, but if you sleeve a nikisol cylinder your the !@#$%. when you sleeve these cylinders you lose power. the sleeves heat up faster and get hotter. not the best for a two stroke racing motor. that is why the factories no longer use steel sleeves in the production motors.


350Xrider it has been a while since i had RM's ( i raced 89-92 125's and 250's) so i'm a little rusty on the subject but the spring sets the tensino for the power valve if i remember correctly 1/4 turn is the limit of adjustment. but to be positive i would get a service or owners manual to be safe.

YTZ250#1
09-01-2003, 10:06 AM
Thanks Mr ATC.I wanted to say somthing to lush,but figured it would get deleted or edited out anyway so I did'nt waste my time.And to think he
called me the idiot.

lushatc200x
09-02-2003, 08:48 PM
gee there i never said you were an idiot know did i. NO :rolleyes: and mr atc i know that u can sleeve them i dont know about all this they over heat stuff cause if you had a bike with that bullshit plating (<my opinion) and you really scar up the damn cylinder the bike shops cant replate them they tell you that it has to be resleeved. i had a kx80 that needed it done and they said it couldnt because it was scared to bad. besides that none wants to pay 300 bucks to have it replated everytime they lock their top end up. its easier to resleeve it. my cr 500 is bored 40 it has a sleeve in it and it doesnt overheat. it stays at operating temperature. and i was under the impression that the nickle plating was just a smoother surface than a metal sleeve. either way im right about resleeving. :)

MR ATC
09-02-2003, 09:36 PM
your CR 500 does not overheat because you do not ride it hard enough.

the dealership tells you to resleeve so they can make more money off of you. 100% profit on the sleeve and 50% profit on labor.

whoever told you 300 for plating is overpriced but it is still cheaper then your 400 estimate.

the only benifit to sleeves is it allows you to run your piston to the point of wearing out your cylinder and then boring it. thus the lazy mans way of maintaing things instead of replacing piston and rings when needed.

even if you wear out a nikisol cylinder it can still be bored and replated.

TimSr
09-02-2003, 09:47 PM
Whether its $250. $300, $400, or $500, I think the point YTZ250#1 was making is a very valid one, without arguing the details, which is that by maintaining piston and rings on a regular basis will make your cylinder last longer, as a new top end for unboreable cylinders costs a lot more than what most of us think of as chump change no matter which route you take to fix it.

lushatc200x
09-03-2003, 10:54 AM
in reply to mr atc i ride that 500 hard enough. im slow through the woods which means that it should definatly get hot but it doesnt. i ride the roads as fast as it will take me. that will keep it cool but we usually do woods riding and im not that fast through there and so far no overheats. thanks to honda. making quality stuff. and about changing pistons and rings. thats good yes good but what happes when you wear your cylinder out of round cause all you do is change the piston and ring instead or refreshing the cylinder itself. no saying you would have to do that everytime no but after a while the trailprotrailprotrailprotrailpro wears out ya know. oww a sleeve is 80 a press is 100 and a piston and ring is 70-75 max. it only comes to around 255 or 260. i was told 300 to replate the cylinder. honda and a private bike shop told me that. the bad thing about nickle plating is that after a while when the stuff wears a bunch it will flake off in chuncks. or it will wear smooth to wear the piston actually hits the jug itself. in short term whats derectly behind the nickle plating. and that could cause the piston to seize up.

MR ATC
09-03-2003, 11:42 AM
lush i was not trying to insult you. you do not ride the 500 hard enough to overheat it...unless of course you ride harder then any national pro ( David Baily, Ricky Johnson ect.) or any Desert racer.

as far as wearing out a nikolsol cylinder well i raced 125's and changed piston and rings once a month if not sooner yet none of my cylinders were wore out. its simple maintenance like Tim said. yes it will eventually wear out but by then the cost to replate is not a bad expense for something that last years.

just like air cooled motors are a thing of the PAST so is steel sleeves.

if you put a sleeve in a standard nikolsol cyliner you WILL lose power and heat disposition.

const42
11-25-2003, 03:18 AM
you are correct but it is not that much of a power loss but I would replate it and move on as this plate will last along time if the bike is maintained.
and I am sorry but if someone wanted to bore my cylinder for 40.00 I would go get my drill and do it my self j/k lol but you do get what you pay for and there equipment can not be that advanced to charge so little when you take in 1 cylinder thx.point being you generally get what you pay for.hell I could coat hanger my whole bike togather and save $ but then what did I really save when I tried to get out cheap and had to redo it every year?