A xr250r, an unidentifiable hole...

[RhynoCZ]

Hello, lads and lasses, do you happen to know, what's this hole for? I mean the rectangular one between the two intake channels. I'm not sure what year the bike is, the owner says '89, but I think it's '85. Thanks,

https://i.imgur.com/ucBL83D.jpg
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'87 Honda XBR 500, '96 Kawasaki ZX7R P1, '90 Honda CB-1, '88 Kawasaki GPz550, MZ 150 ETZ
'95 Mercedes-Benz w202 C200 CGI, '98 Mercedes-Benz w210 E200 Kompressor

[Nemo]

Probably coolant, to prevent carb icing.
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Previously owned: Kawasaki KH125, Suzuki GP125, Suzuki GX 125, Honda CB125 TDC '83, Honda ntv 600, Kawasaki ER5, Kawasaki ZZR600, Aprilia RSV 1000 Mille
Now own: Ducati 848 evo

[Pete.]

Casting feature IMO.
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a.k.a 'Geri'

132.9mph off and walked away. Gear is good, gear is good, gear is very very good

[RhynoCZ]

The hole is 7+cm deep.
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'87 Honda XBR 500, '96 Kawasaki ZX7R P1, '90 Honda CB-1, '88 Kawasaki GPz550, MZ 150 ETZ
'95 Mercedes-Benz w202 C200 CGI, '98 Mercedes-Benz w210 E200 Kompressor

[Fizzer Thou]

As Pete said,it is just a casting mark.

As it is air cooled there is no water jacket

It is more likely the '84-'85 model,as that cylinder head is for a twin carb version,as against the '89 model which was single carb

https://www.cmsnl.com/honda-xr250r-1989-belgium_model6767/partslist/E__0201.html#results

https://www.cmsnl.com/honda-xr250r-1984-usa_model876/partslist/E++02.html#results
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Just talk bikes.What else is there?

Always have a 'Plan B'

[Snod Blatter]

The early dual carb heads have a reed valve over that hole (part of the rubber inlet manifold) which allows the cool intake charge to be shared from the slow running carb to both inlet valves, so it goes from left to right. This was abandoned somewhere around '85-'86 as it didn't seem necessary for reliability but presumably Honda couldn't be bothered changing the casting

Second picture along the bottom hopefully explains it:

https://i.imgur.com/rF4EeeQ.jpg

[bikenut]

nice article.......you may have problems looming with all that sealer everywhere......blocked oil holes ??
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nuts about bikes