[bigE]

Hey guys. Ive been working on a 1986 rm250 i just bought and i finally got it running today :smile: . The only problem is it that it has very little power and wont idle. I took the muffler off and that boosted the power some. Somebody told me if it wont idle it could be a problem with the reed valves. I pulled them out and the two on the ends are sticking up about a millimeter. THis is way too much isnt it? Could the reeds have that much affect on the performance? I am new to the whole reed concept so any advice/info would be appreciated

 

[n8r]

I haven't messed much with reeds, so I can't comment on that. Have you set the air mixture screw to the recommended position? Then you should be able to mess with the idle screw and make the bike idle. Also make sure you are working with a nice clean plug and you aren't trying to run old gas.

 

[bigE]

The plug is new and the gas is fresh (it may be the wrong mixture though. Im running 20:1 which i think may be a little rich). Ive been fiddling with the pilot screw. I dont think it has an individual air and idle screw. Correct me if im wrong (and tell me where theyre at ;-) )

 

[Dave2122]

Here is a quick explination of reeds. On a 2 stroke they are what meters the fuel flow from the carb to the cylinder via gas pressures in the cylinder. When a 2 stroke piston raises and lowers in the cylinder bore it opens intake and exhaust ports. This creates positive pressure which holds the reeds closed on compression stroke. On the exhaust stroke there is a negative pressure "vacume" which draws the fuel mix throught the carbs and then the reed valves.

Your reeds should sit flush on the reed blocks. If as yopu described they are not sitting flush or are cracked this negates the reeds effectivness in regulating flow. Get them changed and dial in your air screw and idle adjustment and you will be in good shape.

 

[bigE]

thanks dave. im gonna order some right now. Should i expect a significant improvement? Its really sluggish now....

 

[Dave2122]

Lets eliminate this problem and see where we are at. then we can get it dialed in. Once it is running right you will have a strong bike no doubt about it.

 

[Knoc]

#1 thing to do before ya order anything would be to check the compression

 

[Dave2122]

We can takle that after he replaces the bad reeds. If the reeds dont sit flush on the reed blocks they are no good. He could have a brand new engine and if the reeds a f'ed up it will run like garbage.

 

[Knoc]

Or the reeds could be fine and its just low compression and he needs to rebuild the top end??.. What does checking compression take all of 5 minutes?

 

[motoman]

Your 20:1 sounds extremely rich as well. My newer RM250 and most other 2 strokes will run 32:1 or leaner depending on the type of oil.
Did you check your main jet?

 

[bigE]

I took the carb apart and cleaned it. The jets looked fine, but then again i am not used to the type of carb thats in it... My previous carb expirences are with street bikes where the throttle cable is not directly linked to the jet needle..... Im still waiting on the reeds to get in. I dont have a compression checker and since i already ordered the reeds, i will wait and see if they help before i buy one.

 

[Dave2122]

Knoc if you read his first post you will see why I said to chamge the reeds.......

 

[bigE]

I finally got the reeds and installed them. They helped a little but the bike is still really sluggish. I did a compression test and its pretty low, about 75-100 psi. What all is usually replaced when doing the top end? About how much will it cost me? Will i have to mess with the bottom end too? Im thinking about just selling it. Anyone have any idea what its worth?

 

[Dave2122]

A top end if you do it yourself wil runn about $130 It is not hard to do as only basic tools are needed. Don't get dicouraged, it wont take much to sort the bike out. Once it is you will be so glad you put the effort into fixing it.

Here is the list of parts:

Piston
Rings
Con Rod Needle Bearing
Wrist Pin
C Clips
Base Gasket