Wrong base gasket's been blocking part of the transfers...

[SoFlo]

Well, I'm replacing the topend on my '96 RM250, that I got a few months back. Take a look at the base gasket that someone put on this bike, the wrong one for sure I think. It took me a while to notice this I admit, but still, it's obviously the wrong gasket. It's blocking alot of the transfers on the back side of the engine. I was probably losing a few solid horsepower here, and the right gasket with a new topend should really give me a boost huh?
The only thing I'm mainly wondering is what is it going to do to the jetting? More flow, so it's gonna need more gas? Or is it gonna be like more suck to the carb, so leaner jets? Either way, I'm kinda annoyed about the whole thing, I've gone on a bunch of trips with this bike already. It's the first bike I've owned, so I guess I didn't know what kinda power I was looking for out of a 250.

On the right side of this pic there's those two holes that look like coolant pockets or whatever, but they don't actually lead anywhere. On the cylinder there's no holes that line up with them.There was some oil in them from the wrong old gasket being on there. We shoved a tooth pick in there and could feel the bottom. So I guess they just save weight or something?

http://img.photobucket.com/albums/v456/2001Toomey/IMG_2083.jpg

Old gasket... Those bolt holes stretch out into the transfer area and block a ton of acreage there. :bang:

http://img.photobucket.com/albums/v456/2001Toomey/IMG_2082.jpg

New gasket... It's the right gasket for my year, and everything looks fine on it. On the coolant holes, should I cut the gasket to match the hole, for more flow?

http://img.photobucket.com/albums/v456/2001Toomey/IMG_2081.jpg

That's one reason people suggest to put a new topend on a used bike you buy.

 

[crazy4nitro]

I imagine that the powerband might be diff. now. oh and more of it...
I would not alter the gasket myself the holes might give a certain amount of restriction..(a guess)

Crazy

 

[tuckers20]

does anyone know where i can get some coloured carburettor hoses. ie, overflow and breather.

 

[SoFlo]

does anyone know where i can get some coloured carburettor hoses. ie, overflow and breather.

:bang:
Go to www.rockymountainmc.com, and why did you post this in my thread about something totally different?

Back on topic... :nod:

 

[crazy4nitro]

does anyone know where i can get some coloured carburettor hoses. ie, overflow and breather.

Umm,ya might want to start your own thread,you will get better results..

Also your Hi-jacking someone else's thread..

All due respect,
Crazy4nitro

 

[sick 96 250]

your old base gasket does look way off, the new one you have pictured is the exact same as what i had on my 96... Dont mind the anti-freeze in the pic :laugh:

 

[SoFlo]

Yep, that's what my new one looks like. I just can't believe that someone would put that gasket on there that is blocking an area leading to the transfer ports. Anyone know what those two little empty passages are that are toward the back of the engine right at split in the case?

 

[tuckers20]

its the first time i have posted something.

 

[tuckers20]

thanks tho

 

[Rcannon]

We should all pass a rule, or law.

Never take anything for granted on a used motorcycle. Wrong gasket??? Imagine that!

I just finished rebuilding a KX 125. When I opened the carb, I found Kehin jets instead of mikuni. The carb is mikuni. Oddly enough, the bike ran pretty well with the main jet 1/2 way in....

 

[SirHilton17]

your old base gasket does look way off, the new one you have pictured is the exact same as what i had on my 96... Dont mind the anti-freeze in the pic :laugh:

WOW!!!!!!!!! it looks like ur big end bearing got a bit hot :yikes:

 

[sick 96 250]

WOW!!!!!!!!! it looks like ur big end bearing got a bit hot :yikes:

Yeah that also what happens when you buy a used bike that was jetted way lean, turned out to be fine in the end, just needed a new piston and rings and ran great till i sold it

 

[SoFlo]

Anyone have a clue how much power I was down, or what it's going to do to the jetting? Make is leaner or richer?

 

[sick 96 250]

theres prob no real way to tell if you were really losing power or not untill you fire it up with the new top end and give her a spin. It could of had the bike running lean and rich with that gasket, unable to really know. As for jetting just start around the stock specs. usually 1-2 pilots size down and a few on the main will be where you'll end up. Just have dial it back in again. You should have no troubles. Good luck

 

[RM_guy]

You may not have lost as much power as you think. Granted the flow was disrupted but where and when the fuel enter the cylinder is more important than how it gets there. Remember that it is being pumped up through the transfer ports as the piston moves down so the same amout of fuel is getting into the cylinder no matter how much of a restriction there is.

 

[SoFlo]

I guess you're right. More of the mixture probably just ended up going through the other transfers. A guy on another board told me that the old gasket looked like a KX 500 one.

 

[Jman271]

That crank looks a little toasty,(blue)!

 

[Rich Rohrich]

WOW!!!!!!!!! it looks like ur big end bearing got a bit hot :yikes:

All oem japanese cranks have those bluing marks to some degree. It's from the heat used in the original crank build process.