A forum for owners of Yamaha TTR250 trail and enduro bikes!

RAIDER · Member

What’s this hole in the front side of the engine?

pug · Guru

Pretty sure That's not meant to be there is that the front of the barrel

RAIDER · Member

This is a photo from the web just to show the location of the issue.

pug · Guru

Someone will be along that's has milled the barrel for an over bore sleeve will be along and know for sure but I think you are ok there is not alot of meat in the alloy at that point so iron barrel wall is close to the outside a mill or two it looks like this thin spot has alloy rotted away showing the barrel and that has in turn rusted and pushed more alloy away I don't think its near an oil way so a clean and a patch of JBL weld or low melt alloy welding stick would cover it easy when cleaned up and will stop it getting any bigger. But a 350 big bore member on hear should know for sure see what they have to say

-- Edited by pug on Saturday 5th of October 2024 06:24:08 AM

RAIDER · Member

Hey, thanks a lot for the knowledge, but the oil isn't coming from there, My only worry was that would water go inside the engine from that hole sort of thingy when I’m washing the bike. The oil leaking is from the decompression rubber or the cam cover rubber, will be inspecting the leak later today.

ttr steve · Super Guru

Well that is a new one on me, is this a standard 250 barrel ?

Anyone else seen this sort of thing?

ttr steve · Super Guru

RAIDER wrote:
Hey, thanks a lot for the knowledge, but the oil isn't coming from there, My only worry was that would water go inside the engine from that hole sort of thingy when I’m washing the bike. The oil leaking is from the decompression rubber or the cam cover rubber, will be inspecting the leak later today.

If oil isn't coming out, water won't get in.

TTRfan · Super Guru

I can't make out what's happening from the photo. Is the barrel properly clean?

Is it possible to take a couple more photos from different angles and distances? One with a flash that shows what's behind the holes would be good.

I recall a long time ago that I bought a Thumper Racing barrel for their "325" big bore kit. I was supplied with the wrong diameter liner such that when the barrel was bored to take it the walls were left very thin in places. You can see the cracks in the photo.

However, yours are holes and not cracks and no oil escaping.

Perhaps extra photos will help the diagnosis wink

Brian

Leaking barrel.jpg

Jeff B · Senior Member

This hole is located in the head, not cylinder. It is a weep hole for water to drain from the spark plug well. There is another weep hole on the opposite side (on the intake side). If you remove the spark plug, you could shine a flashlight into it and see light on the opposite side.

RAIDER · Member

Jeff, you are correct 100%, I took the plug out yesterday and checked and found out what it is for. For stopping water from being collected around the spark plug and they say it's also there for air flow. Well thanks again for the re-assurance.

RAIDER · Member

Thank you Brian and everyone else for the help.

ttr steve · Super Guru

Doh!

Forgot about that, but didn't look like it in the photo.