Coywolf 80 Posted May 21, 2023 Report Share Posted May 21, 2023 i have been fixing up an old 1975 dt100 enduro motorbike which i dragged out of a scrap yard a few years ago....it was totally seized up, i did eventually manage to get the head/barrel off after a hard job and it needs a top end rebuild the crank was fine....the engine is now sitting on the shelf ready to work on at a later date..... after some research an mx100 engine is a bit more lively and bolts straight in....so i did find an 1980 engine in America that i had it sent to me, i opened it up to check it was all good which it was....clean bore no scores good piston and rings....it was .25 on the piston so 1 oversize whereas the dt was .50 at 2 oversized.... the dt was premix and the mx came with the oil pump and cables attached, i took them off and just did a premix of 40.1 to try the engine and after 4 kicks it started..... now.....i want to run the oil pump this is the 1975 dt carb, I'm assuming the nipple that i have put the red arrow to is the oil inlet....as all the other carbs for the dt the oil inlet is were i have put the red circle, or could it be in that white circle that someone has blocked what was the oil inlet off....or is that a bung from the factory....i can't find any info on the 1975 carb over here anywhere, but on the Yamaha dt forums they are saying the nipple i have put the red arrow to is for a breather pipe and not for oil.....which is confusing me, also the only hole in the carb inlet is the one i have put the red circle and red arrow which has a small deep seated jet and normally the hole for the oil usually comes out were i have put the white circle....usually an oil nipple has ribs down it to grip the pipe and breather nipples are smooth...i didn't really won't to take a chance and possibly seize the engine....i'm just after a bit of reassurance really even though i'm pretty sure it is an oil inlet and not a breather like they are saying on the dt forums....anyone know anything about these carbs? 2 Quote Link to post Share on other sites
Arry 18,631 Posted May 22, 2023 Report Share Posted May 22, 2023 Tilly don't know if this is any help. YAMAHA DT100A 1974 SERVICE MANUAL Pdf Download | ManualsLib WWW.MANUALSLIB.COM View and Download Yamaha DT100A 1974 service manual online. DT100A 1974 motorcycle pdf manual download. Also for: Dt100a 1976, Dt100c 1976, Dt125a... Cheers Arry 1 Quote Link to post Share on other sites
Bakerboy 3,258 Posted May 22, 2023 Report Share Posted May 22, 2023 It's the oil inlet, my BIL rebuilds bikes, he knew what I was on about before I showed him the pic 2 Quote Link to post Share on other sites
BEARINATOR 2,825 Posted May 22, 2023 Report Share Posted May 22, 2023 As said oil inlet 1 Quote Link to post Share on other sites
paulus 26 Posted May 22, 2023 Report Share Posted May 22, 2023 The auto lubes are a pain in the arse on the mx just cap it off and run it pre mix, That way you will know the exact mix. Quote Link to post Share on other sites
Chid 6,377 Posted May 22, 2023 Report Share Posted May 22, 2023 44 minutes ago, paulus said: The auto lubes are a pain in the arse on the mx just cap it off and run it pre mix, That way you will know the exact mix. 1 Quote Link to post Share on other sites
Coywolf 80 Posted May 22, 2023 Author Report Share Posted May 22, 2023 13 hours ago, Arry said: Tilly don't know if this is any help. YAMAHA DT100A 1974 SERVICE MANUAL Pdf Download | ManualsLib WWW.MANUALSLIB.COM View and Download Yamaha DT100A 1974 service manual online. DT100A 1974 motorcycle pdf manual download. Also for: Dt100a 1976, Dt100c 1976, Dt125a... Cheers Arry thanks arry, just what i need for any other info bud....this service manual didn't come up over here when i was trying to find any answers mate.....thanks bud 1 Quote Link to post Share on other sites
Coywolf 80 Posted May 22, 2023 Author Report Share Posted May 22, 2023 2 hours ago, Bakerboy said: It's the oil inlet, my BIL rebuilds bikes, he knew what I was on about before I showed him the pic thanks bakerboy.....that's a big help bud... Quote Link to post Share on other sites
Coywolf 80 Posted May 22, 2023 Author Report Share Posted May 22, 2023 2 hours ago, BEARINATOR said: As said oil inlet thanks bud....much appreciated.... 1 Quote Link to post Share on other sites
foxdropper 17,092 Posted May 22, 2023 Report Share Posted May 22, 2023 Need to stick a drill up the winky valve mate . 2 Quote Link to post Share on other sites
Coywolf 80 Posted May 22, 2023 Author Report Share Posted May 22, 2023 1 hour ago, paulus said: The auto lubes are a pain in the arse on the mx just cap it off and run it pre mix, That way you will know the exact mix. hi paulus, when you say a pain in the arse....do you mean unreliable or inconsistent.....have you had one fail and damage a motor, also what premix ratio did you run, people say for safety run at 32.1 and others say 40.1 would be fine..... Quote Link to post Share on other sites
Coywolf 80 Posted May 22, 2023 Author Report Share Posted May 22, 2023 54 minutes ago, Chid said: thanks chid..... Quote Link to post Share on other sites
stumfelter 3,032 Posted May 22, 2023 Report Share Posted May 22, 2023 That is definitely, I repeat definitely not for the autolube! That is the breather for the float bowl. There is also an overflow for the float bowl which is on the bottom of the carb. I'll check some pictures and get back to you but the auto lube pipe often connects into the inlet manifold. 1 Quote Link to post Share on other sites
stumfelter 3,032 Posted May 22, 2023 Report Share Posted May 22, 2023 1 Quote Link to post Share on other sites
stumfelter 3,032 Posted May 22, 2023 Report Share Posted May 22, 2023 The autolube feed goes directly into the cylinder on dt's. I knew that pipe on the carb wasn't right as I restored a 175 a few years back. 1 Quote Link to post Share on other sites
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