CR250 making a noice

[Tonyklem]

I have an 89 CR250, and i just got back on it for the first time since my ACL reconstruction. i had to clean the carb and adjust the ar screw etc to get it running again. it has fairly new gas in it and it runs strong.
Theres 2 problems though
1. When i get up into a high RPM it sort of flattens out. if i sit still and rev it high, it does the same thing. if i rev it up high for a bit it will "clear up" and rev normally for a bit. could this be my jetting or what?

2. there is a wierd noise coming from the engine, cant tell if its from the cylinder or the gear box. its sort of a slapping/clunking noise. i never heard this before when i was riding it and i have no idea what to check or adjust to see if it makes it better

let me know what you guys think.

oh, and the prev owner said he just rebuilt the topend this last summer and i havnt been riding it much at all.

 

[oldfrt613]

Seems like every used bike sold has a fresh top end ( to some this simply means new rings ). I'd pull the cylinder and check the whole thing. If everything is OK it will only cost a set of gaskets. There is a distinct possibilty that the lower rod bearing is worn on a bike that old, check it too, if it comes apart your looking at major engine damage. The bike is probably flat on top because the jetting is a little rich.

 

[Tonyklem]

hmmmm. i figured about the jetting. but its wierd how this noise was NEVER there until now. seems kinda funny. i might tear it apart next next weekend.

 

[Tonyklem]

anyone here done a top end on an 89 cr250? I've never done one before and I'm trying to get an idea of the difficulty. i have replaced transmissions, clutches, and axles in cars before, im just not used to bikes yet :D

 

[TimberPig]

2 Stroke Top End

That should give you an idea.

 

[Tonyklem]

thanks

 

[Badgadjit1]

not bad at all...bike are easy to work on....pretty self explanatory.

 

[Tonyklem]

ok good :)

 

[Husky Texan]

Bad main bearing and bad crank seal. The bearing is causing the clunking noise, the seal is the reason you are running rich/flat. I bet it smokes a good bit too.

 

[Tonyklem]

Where exactly is the crank case seal. How far do i have to disassemble the engine to get to it?

yes... it does smoke pretty good before it warms up.

anyone know where i can get a good deal on an entire gasket kit for my engine?

 

[TimberPig]

This explains an entire bottom end rebuild, but if only the crank seals are bad, you have to remove the clutch and primary gear to get to the right side, and the entire flywheel and stator for the left one.

Bottom End Rebuild

This tells you how to check the crank, to see if the bearings are going south too, or if only the seals are shot.

Crank Checking

 

[kennycr250]

try service honda for parts, they have a forum on here.