What is this on my engine, is there supposed to be a hose or a plug? 03 yz250f

Related:
Create New Tag

11/25/2017 2:06 PM

I'm currently replacing the radiators and hoses on my 03 yz250f, the guy before me had the radiator jacked up pretty bad, and the hoses were leaking from that.

So while looking at my bike I noticed this little thing sticking out of the engine, what is it?
Photo
looks like maybe a plug or hose was there. But I don't know.
A google search didn't help much...

Also on the topic of what is that, what are the screw/bolt holes on the engine? Photo

Photo


Thanks
Ben

|

2003 Yz250f.

11/25/2017 2:15 PM

That hole in your cylinder is where a manual decompressor lever would have been for 2001 and 2002 bikes. For 2003+ the decompressor was housed internally to the camshaft, so no need for an external mechanism. But, Yamaha had a bunch of cylinder heads to keep using, so for 2003 and 2004 bikes, they would have had a rubber plug jammed in that hole, with a pinch bolt to secure it. Obviously the design doesn't age well as many people lose the plugs over time, and then your bike spits oil out of that hole.

Go to Ebay and get a cnc'd aluminum plug for $10. It will fit nice and tight in there. Oh and that boss up there by the hole is used to secure the bracket for your manual decompressor.  No need to worry about it.

As for the bosses on  the lower engine cases, I'm not sure.

|

11/25/2017 2:21 PM

Check motosport. They have diagrams for oem stuff.

|

11/25/2017 2:31 PM

Micahdogg wrote:

That hole in your cylinder is where a manual decompressor lever would have been for 2001 and 2002 bikes. For 2003+ the decompressor was housed internally to the camshaft, so no need for an external mechanism. But, Yamaha had a bunch of cylinder heads to keep using, so for 2003 and 2004 bikes, they would have had a rubber plug jammed in that hole, with a pinch bolt to secure it. Obviously the design doesn't age well as many people lose the plugs over time, and then your bike spits oil out of that hole.

Go to Ebay and get a cnc'd aluminum plug for $10. It will fit nice and tight in there. Oh and that boss up there by the hole is used to secure the bracket for your manual decompressor.  No need to worry about it.

As for the bosses on  the lower engine cases, I'm not sure.

What should I search on eBay to find that?

|

2003 Yz250f.

11/25/2017 2:32 PM

mxb2 wrote:

Check motosport. They have diagrams for oem stuff.

I looked, but didn't see anything, thanks for the suggestion though.

|

2003 Yz250f.

11/25/2017 3:46 PM

mxb2 wrote:

Check motosport. They have diagrams for oem stuff.

BENDOWANDS wrote:

I looked, but didn't see anything, thanks for the suggestion though.

Np man, maybe try Yamahas direct site.

|

11/25/2017 4:49 PM

|

11/25/2017 5:02 PM

Micahdogg wrote:

That hole in your cylinder is where a manual decompressor lever would have been for 2001 and 2002 bikes. For 2003+ the decompressor was housed internally to the camshaft, so no need for an external mechanism. But, Yamaha had a bunch of cylinder heads to keep using, so for 2003 and 2004 bikes, they would have had a rubber plug jammed in that hole, with a pinch bolt to secure it. Obviously the design doesn't age well as many people lose the plugs over time, and then your bike spits oil out of that hole.

Go to Ebay and get a cnc'd aluminum plug for $10. It will fit nice and tight in there. Oh and that boss up there by the hole is used to secure the bracket for your manual decompressor.  No need to worry about it.

As for the bosses on  the lower engine cases, I'm not sure.

X2

Paw Paw

|

11/27/2017 10:40 AM
Edited Date/Time: 11/27/2017 10:41 AM

Similar to the decompression lever from an earlier model, I believe the holes in the engine cases just ahead of the cylinder were for an external oil tank as found on older models. My '04 had an internal sump engine, and that design may have begun in '03.

Yamaha may not have needed to change out that right-side engine case for any other reason and decided to keep the bosses on there for cost savings.
It's also entirely possible that the engine case is shared with another model that requires something there.
In any case, I wouldn't be too worried about any missing pieces.

|

Braaapin' aint easy.

11/29/2017 11:04 AM

BENDOWANDS wrote:

I'm currently replacing the radiators and hoses on my 03 yz250f, the guy before me had the radiator jacked up pretty bad, and the hoses were leaking from that.

So while looking at my bike I noticed this little thing sticking out of the engine, what is it?
Photo
looks like maybe a plug or hose was there. But I don't know.
A google search didn't help much...

Also on the topic of what is that, what are the screw/bolt holes on the engine? Photo

Photo


Thanks
Ben

Look up on a Micro fiche... 2004 Yamaha YZ250F in the Camshaft Chain Pic.... Plug
90338-18064-00 Runs about $4... Call TCD in Clarkston Mi... They should have some in stock. They did when they used to be called TECH-CARE. I'm not sure the Yamaha's used a screw. I think that was the Suzuki/Kawasaki's when they used the same plug. Good luck.

|