94 RM250 Piston hitting cylinder head.

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12/12/2018 11:22 AM

Picked up a 94 rm250 used. Had no piston. Bought new wiseco kit (67mm stock. 89-95 rm250 piston kit) for it. I I noticed a new hot rod crank rod in it as I installed the piston. Anyway I get it back together and the piston is about an eighth inch(1/8)high out of my cylinder. Now I checked the vin# it's a 94 frame and I know my engine is between 90and95. I also took a piston out of a 1990 rm250 thinking maybe I got the wrong piston but the piston I pulled from a running 1990 rm250 was also coming up about an eighth of an inch out of my cylinder. I have to use like 5 base gaskets to make the cylinder flush with the top of piston edge. Anyone ever get this before?

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12/12/2018 4:10 PM

Call up hot rods and ask them if they make a long rod for that engine. Does your head look like it has been machined or is the still the factory casting?

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21.5 350 XC-F
96' XR600r

12/13/2018 7:03 AM

It looks all stock. I'm prety sure the rod is the same size on 89-95 rm250. Maybe the head was shortened (squish)? Is that a possibility? I just want to know if I can put a base riser on there. It takes like 5 base gaskets to get the cylinder flush with the piston edge.

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12/13/2018 7:06 AM

I would just use the multiple gaskets but it leaks air and runs lean. Also coolant leaks if I stack all those gaskets together. I was thinking of making a plastic or rubber gasket about 1/8 inch thick. Maybe that will work?

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12/13/2018 7:09 AM

I'm trying to remember.... Is the piston flush with head gasket o rings at tdc or flush with the aluminum?

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12/13/2018 7:59 AM

It either has a stroker crank in it or a long rod.

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Race Bike: 2018 KTM 350SXF

Other Bikes: 1985 CR80R, 1990 CR250R, 1998 PW80, Yeti SB130LR.

Sold: 2016 YZ250F, 2012 CRF250R

12/13/2018 12:25 PM

Ryan_Glatz wrote:

I'm trying to remember.... Is the piston flush with head gasket o rings at tdc or flush with the aluminum?

Anyone know On a stock rm250 with piston at tdc where does the piston sit?

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12/13/2018 12:27 PM

You do have a cylinder head gasket right?
Stroker crank, long rod, or cylinder was machined down. The hot rods crank could be the wrong year.
You can call cometic they can make an aluminum spacer to get you straight.
I would aim for 1.1 -1.2 mm squish.
Measure your base gaskets, use one on top and one under the spacer.

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12/14/2018 12:15 AM

Not an actual gasket. It's the 2 o rings but yeah I got em both on. The cylinder head is not bolted on and I turn the engine by hand the piston is pushing the cylinder head up about an eighth inch. Is the squish band on both top and bottom of cylinder? I never had to measure squish. I know the cylinder head is squished out lol. There ain't a ridge inside where the dome starts to go up to the plug anymore from being sanded or serviced so many times or it was really warped and it took that much to get a level surface......

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12/14/2018 1:32 AM
Edited Date/Time: 12/14/2018 1:40 AM

Ryan_Glatz wrote:

Not an actual gasket. It's the 2 o rings but yeah I got em both on. The cylinder head is not bolted on and I turn the engine ...more

it definitely sounds like is very possible it has a long rod/stroker kit in it as has been implied...The cylinder head issue sounds like someone milled the cylinder head and didn’t set squish, or had enough squish with a cylinder spacer installed and was milled as a way to return the compression to stock or higher... it is possible the person re-assembling it prior to you didn’t realize what he was doing and installed a long rod, or it is possible he lost the spacer for the cylinder during re- assembly (reason for not installing piston?) ... Also to check squish you measure distance between the cylinder head (the flat area outside the dome) and the top of the piston... solder or clay (what I’ve used) work great as ways to obtain this measurement... using the above method requires the head to be installed though which sounds like it’s impossible in your situation...

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12/14/2018 3:27 AM

Ryan_Glatz wrote:

Not an actual gasket. It's the 2 o rings but yeah I got em both on. The cylinder head is not bolted on and I turn the engine ...more

Paul_Pitzonka wrote:

it definitely sounds like is very possible it has a long rod/stroker kit in it as has been implied...The cylinder head issue ...more

That makes sense the cylinder wasn't on it when I got it. Actually the whole bike was apart. Maybe the spacer got lost along with the carb seat and Airbox.... Lol

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12/15/2018 11:54 AM

Head machined and was set up for a flat top piston is my guess

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12/15/2018 2:19 PM

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12/15/2018 2:28 PM

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12/15/2018 2:29 PM

You can see the head gives no clearance at all. It's been shaved one too many times

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12/15/2018 2:50 PM
Edited Date/Time: 12/15/2018 2:51 PM

Ryan_Glatz wrote:

You can see the head gives no clearance at all. It's been shaved one too many times

I’m definitely going with it’s stroked... that piston is way above deck height... do you happen to remember what rod is in it?

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12/15/2018 3:03 PM

Ryan_Glatz wrote:

You can see the head gives no clearance at all. It's been shaved one too many times

Paul_Pitzonka wrote:

I’m definitely going with it’s stroked... that piston is way above deck height... do you happen to remember what rod is in it? ...more

I'm with Paul, there is no way that piston should be above the deck like that. Something is wrong, either the rod or the piston.

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2018 KX450F
2005 KX250
2003 KDX 220
1984 KX 80
1982 RM 80
1980 RM 80
1977 XR 75
1969 Honda Mini 50

12/15/2018 3:15 PM

Ryan_Glatz wrote:

You can see the head gives no clearance at all. It's been shaved one too many times

Paul_Pitzonka wrote:

I’m definitely going with it’s stroked... that piston is way above deck height... do you happen to remember what rod is in it? ...more

Just know it's hot rods I'll go pull cylinder off and see if I can find some numbers or something else on it.

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12/15/2018 3:20 PM

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12/15/2018 3:22 PM

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12/15/2018 3:24 PM

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12/15/2018 3:28 PM

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12/15/2018 3:32 PM

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12/15/2018 3:43 PM

Hot rods ck105 it fits my bike. My piston is right. Could this bike be a rmx.... But even if it is..... isnt 94 rmx 100% innerchangeable with 94 rm250??

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12/15/2018 3:47 PM

Vin# JS1RJ16A8R2101244

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12/15/2018 4:13 PM

Ryan_Glatz wrote:

Hot rods ck105 it fits my bike. My piston is right. Could this bike be a rmx.... But even if it is..... isnt 94 rmx 100% ...more

1994 rm250 says suzuki vin decode. The rod is right the piston is right.......

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12/15/2018 5:06 PM

Ryan_Glatz wrote: Photo

Base of the cylinder has been milled off... that cylinder has been worked on before notice the 75 ground into the side... also look at the height between the engine displacement tag and the base compared to a stock cylinder..Photo

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12/15/2018 5:18 PM

Ryan_Glatz wrote: Photo
Paul_Pitzonka wrote:

Base of the cylinder has been milled off... that cylinder has been worked on before notice the 75 ground into the side... also ...more

I see. That's my problem. Thanks for pointing that out. It may have taken another week before I noticed that.

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12/16/2018 7:08 AM

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12/16/2018 7:14 AM

Ryan_Glatz wrote: Photo

Cometic never answered back on my enquiring about making a base riser and I want to ride....... This should work but what you guys think. Jigsaw? I got cork gasket for bottom and top of it...or just paper gasket if my thickness target requires it....... Any opinions?

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