95 RM 250 rebuild need to know...

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Budget_89KDX
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95 RM 250 rebuild need to know...

Post by Budget_89KDX »

Ok my little brother bought a 95 suzi rm 250 a month ago from the "STEALERSHIP" known as world of power sports.well it would not idle so when he took it in for the recall on the vent hoses and while there he tells them it won't idle they said they would take care of it.well he gets it back last weekend and we ride today.got about 8 miles from my house out on the river and the thing starts pinging and then lost all power and died.he went to kick it over and its like taking the plug out and kicking it over.so I go get him in the truck brought it to the shop and did a compression test and got 45psi not good.also the plug is greyish white and charred definately lean.he called them and they won't admit to leaning it out and want almost as much as he paid for the bike to rebuild it.so I found a namura kit with gaskets and all for 90 on ebay and am going to rebuild it what do I need to look for on these when rebuilding them?do they have power valve setup?how simple are they to rebuild?what am in for on this basically?
Ipaman
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Post by Ipaman »

Well it a typical two stroke, so once you pull the cylinder head you will have to inspect it and then the piston and rings. I would replace your piston, rings, and wrist pin bearing. It is very possible you will need to have the cylinder honed, or sleeved. There are places online that you can send them to. Hopefully it just got too hot and burnt the rings up and that is it.
gregp
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Post by gregp »

That bike definately does have a power valve. Once you get the top end replaced, you will have to figure out if the bike is jetted correctly. An RM250 should not sieze, or pinch the ring just by trail riding it. So, either the piston and ring was very old, and worn out, or the bike is jetted very lean, or both.
One of the problems with issues like yours, is that you do not know the history of the bike at all. Is it the original bore size? Has the cylinder already been sleeved, or replated? You will need a bore gauge to find out for sure, before you go ahead and buy a new piston and ring. Also, if the cylinder has been sleeved already, you may need a different ring composition than the original. (A hard, coated cylinder uses a softer ring, an iron sleeved cylinder uses a harder ring - I think) Wiseco used to offer all of this information in their free catalog.
Been there. Done that.
2004 Dual Sported KDX200
1999 Ninja 250 (Daughter's)
1996 DR 650 (stock, mostly street use)
Budget_89KDX
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Post by Budget_89KDX »

So how does this suzis power valve work?I can't Seem to find much info on them.all I can tell u is that when he bought the bike it was running real rich and wouldn't idle but I hadn't had time to look at it and then the dealership called him about a recall so when he took it in he told them it wouldn't idle and said to look at it.when he got it back I put a brand new plug in and we went riding yesterday I wanted to see how it was jetted since we hadn't had a chance to ride the kdx or rm much yet and then it blew up.I gps'ed it and we weren't even 2 miles from my house I thought we were farther.but yea so what do I need to know about when rebuilding this bike?is the pv like the kips?is there anything special about it?I honestly plan to just pull the jug and head swap pistons,wrist pin,and rings and have the bore checked providing there's no gouges.are these plated like the kdx's?I'm used to my yamaha blasters easy to work on and cheap.if anyone can give me as much detail on the particulars of this motor id appreciate it.
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Post by Budget_89KDX »

Btw my hundred dollar kdx has held up like a champ.lol
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Indawoods
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Post by Indawoods »

Lol! WOPS blows! They were bought out by a car dealership and they know 0 about bikes. They probably put straight gas in the bike....
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Post by fuzzy »

In general it should be the same as the KDX, but the PV will most likely be easier to deal with since it's much less complex (and functional). Bike should have nickel bore, and just like the KDX replating is generally preferred over sleeving. When you inspect the damage, assess as to whether or not enything dropped into the lower and...If so, you'll need to be splitting the cases. It may be time for that anyway since lower end hours are unknown.
'91 KDX 200 Project $300 KDX
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Budget_89KDX
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Post by Budget_89KDX »

Ok I tore it down last night and it literally melted the rings to the wall in places and there's A build up of ring material in spots on the jug.the piston is definately fried.so basically he don't have a lot of cash for toys with 4 kids and house so I'm looking for cheapest most reliable route.will a sleeve be ok?for half the price of sending it off to be replated we can have it sleeved is there any drawbacks to this?on the bright side this engine was down apart and layed out on the bench in 80mins.
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Post by KarlP »

I suspect it is piston material on the cylinder, not rings.

You may be able to clean up the cylinder and be good to go with new piston and rings.

This doesn't help with the "why it melted in the first place". You really need to figure that out or it may happen again.

I'd prefer a replating to a sleeve.
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fuzzy
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Post by fuzzy »

Indeed, you could have bad crank seals causing the lean condition. Inda could be right, you could've had a lack of oil sieze. If the plating is not scored, you can get siezed aluminlum off with muratic acid....Just make sure it doesn't touch ANY aluminum you care about!! I've seen cold-siezed cyl's come back to life perfectly with this method. Drawback to the sleeve is less life, less cooling, and worrying about whether or not the sleeve installer knows what they are doing (can ruin powervalve, etc). You maybe able to ebay a good cyl for what replating costs.
'91 KDX 200 Project $300 KDX
'95 KDX 200 Project $600 KDX
'94 WR 250 Always a project
gregp
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Post by gregp »

All of these posts are right on the money. With any luck, once you get the cylinder cleaned up, and remove the galled up aluminum from the bore, the bore will be fine. Then you will just need a piston and ring (is this a 1 ring piston?)
Then, make sure you run plenty of 2 stroke oil, and if the bike is jetted on the rich side, it should last a while.
Once you get it going again, tell your brother to try to ride the mid-range, and not rev the motor to the moon, because tight budgets and high strung MX bikes do not mix well.
He really should have bought a KDX if reliability and budget performance were his goals, but, you already knew that...
The last RM I took apart (a 1998 RM125) had a guillotine style power valve that was much simpler than the systems on out KDX's, but it still had broken pieces.
2004 Dual Sported KDX200
1999 Ninja 250 (Daughter's)
1996 DR 650 (stock, mostly street use)
Budget_89KDX
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Post by Budget_89KDX »

Nah the cylinder is gouged pretty good.I don't think I'm going to use it as is it'll definately need to be sleeved.we don't race them just trail ride and an ocassional trip to the mx track in casey.and yea I've been looking the pv over on this and it uses two ports and is much simpler than my kdx but it wasn't even hooked up the junky plastiic clip that attatched to the arm wasn't hooked up so this thing oughta be night and day after a rebuild.
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Post by Budget_89KDX »

Btw I'm about to start tearring my kdx down for the rebuild this winter what can be done to make me equal to or as fast and powerful as this rm 250 or is it even worth the cost or possible?
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Post by gregp »

"There is no replacement for displacement" LOL. If you want to make your KDX competitive with a 250cc MX bike, you will need an FMF rev pipe, and porting. Even then, the best advantage you will have is that the KDX will be more nimble.
With the little plastic clip missing on the RM's PV link rod, the valve would be free to flop open and closed randomly. I would think that it would eventually just get stuck in one position with carbon deposits.
2004 Dual Sported KDX200
1999 Ninja 250 (Daughter's)
1996 DR 650 (stock, mostly street use)
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fuzzy
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Post by fuzzy »

There is most likely a span of years where the cyl are interchangeable. Figure this out, and score one on ebay. I looked for one for my WR, and scored an entire freshly rebuilt motor, for $300.

The chapest way to make the KDX run like a 250 is to go spend $1500 on a 250 to have along side the mighty KDX. You can definitely spruce a KDX up a lot, but don't expect to ever make 50hp. More than enough to overpower the chassis, and conditions it was meant to be ridden in? Yes.
'91 KDX 200 Project $300 KDX
'95 KDX 200 Project $600 KDX
'94 WR 250 Always a project
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Coop
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Post by Coop »

I'm sure there are a bunch of sites like this, but I always use this one when researching parts (not buying):

http://www.powersportspro.com/pages/par ... amaha.aspx

A quick check there says 93-95 use the same cylinder.

Sku Model Description Req Price View
11200-28850
RM250 (1993)
Assembly: CYLINDER
CYLINDER MODEL P (SKU: 11200-28850) (Supersede: 11200-28860) 1 $681.42
11200-28850
RM250 (1995)
Assembly: CYLINDER
CYLINDER MODEL P (SKU: 11200-28850) (Supersede: 11200-28860) 1 $681.42
11200-28850
RM250S (1993)
Assembly: CYLINDER
CYLINDER MODEL P (SKU: 11200-28850) (Supersede: 11200-28860) 1 $681.42
11200-28850
RM250S (1994)
Assembly: CYLINDER
CYLINDER MODEL P (SKU: 11200-28850) (Supersede: 11200-28860) 1 $681.42
11200-28850
RM250S (1995)
Assembly: CYLINDER
CYLINDER MODEL P (SKU: 11200-28850) (Supersede: 11200-28860) 1 $681.42
Budget_89KDX
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Post by Budget_89KDX »

Yea sleeving it won't half of the 700 for a new one from wops and he's set on not spending a cent with them.so I think he's sleeving it and ill just put another piston and topend set in and call it a day.
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Post by Budget_89KDX »

As for the fmf pipe what's the difference from the dyno port I have?I looking to atleast hang with him on a straight run these are my current mods see if you Think I should or could improve on these?new 0.020 over replated topend,previous owner says minor porting(whatever that means),and head milled,dyno port header,pro circuit silencer,boysen reeds,uni 2 stage filter,no lid on air box,kips is intact and working correctly,45/158 jetting,CGL jet needle 2nd clip from bottom.the bike runs great and wide open I can manage stay about 4-6 bike lengths behind him,but on the trails I run circles around him and my kdx is much more comfortable than his rm suspension wise.I went on the rb site from here and was questioning whether or not his carb and head work was worth it?
gregp
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Post by gregp »

You have almost all of the recommended mods for your machine.
The only mods left are:
1) A full aftermarket reed cage - V-Force or Boyeson RAD. I have used them both, and they are comparable. Going against public opinion, I would say that the RAD valve worked better for me (stronger"hit"). I have not tried running my current V-Force cage with the "loose tension" reed setting yet, though.
2) Fredette porting. 'Nuff said.
3) RB carb and head modifications - These will give you a much "cleaner" running motor, but probably will not help in your quest to match power with an RM250.
4) Suspension mods. If you spend most of your time *off* of an MX track, Race Tech Gold Valves or similar treatment will make your bike soak up trail garbage much better.
Love your KDX for what it is: an excellent trail bike. Do not try to turn it into something else or you will be disappointed and broke.
2004 Dual Sported KDX200
1999 Ninja 250 (Daughter's)
1996 DR 650 (stock, mostly street use)
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