Posted June 14, 2005 - 09:43 PM
cooper, thanks for the effort and help
Posted June 16, 2005 - 01:20 AM
You will get a few uses out of the head gasket too if you are lucky.
If there is any ridge left on the head gasket, it will seal up. just give it a light coasting of white threebond
Posted June 16, 2005 - 02:37 PM
Posted March 09, 2006 - 11:24 PM
Posted March 10, 2006 - 10:06 AM
Posted March 10, 2006 - 10:55 AM
Posted March 10, 2006 - 11:51 AM
I studied the wear patterns of my carb body, slide and plate. Just to clarify what I’m describing – the carb slide is the block that holds the needle and rides on the little wheels and the plate is the mostly flat piece of metal connected to the slide that is what breaks.
The slide plate shows most wear when the throttle is in the idle to ¼ position. When the slide is almost closed the bottom corners of the plate fit into a slot in the carb body that tend to hold the plate from moving back and forth. The carb slide itself has a bit of play and is free to move back and forth a bit in the slide guide. Since the plate is connected to the slide the plate moves back and forth with pulses of the engine but the bottom corners are held by the slots in the carb body. There is a bending force right at the weak spot - the indented section of the plate and cracks begin to form at the corners of the indented spots.
My best guess is that lugging the engine at small throttle openings and engine braking is causing the problem. With small throttle openings there’s not much velocity through the carb and engine pulses push back through the intake valves a bit due to the overlap of the cam, and push against the carb slide causing it to vibrate back and forth. At higher rpm’s with larger throttle openings the velocity through the carb is probably strong enough to prevent the engine pulses from popping back into the carb. I think the most damage is done at small throttle openings when the corners of the slide plate are trapped and engine pulses are rocking the slide back and forth.
There is quite a bit of play between my slide and the channel it rides in in the carb body. Maybe replacing the wheels would help, or maybe the body is too worn. I think that the less back and forth play the slide has in the body, the less chance of premature failure of the plate. I even thought about gluing thin feeler strips into the carb body to reduce the play.
One last important thing is the rubber O ring between the plate and the slide. I’ve heard of a few guys who broke a plate, installed a new one and it failed in a week or 2. Then they installed another one and it lasted for years. This is probably because they installed the O ring backwards. In the proper position it acts as a shock absorber between the slide and plate. If it’s installed backwards it does nothing and I think that would cause the quick failure that some guys experienced. Since they pulled it apart right away, they didn’t know which way the O ring was installed.
The YZ’s have less plate failures probably because they don’t do as much trail riding, putting along at small throttle openings.
Of course, I could be wrong
Posted March 10, 2006 - 09:59 PM
Posted March 11, 2006 - 08:24 PM
juz my 2 cents