yz head vs wr head???

Whats the difference? I bought a WR motor off ebay a while back because mine went *BOOM* and i finally got the new one in the bike but i noticed slight differences in the head i took out and the one i put on. The Decompression thing is smaller and there is a nipple on the head next to the carb. Where does this nipple go? catch can? What are the flow differences?

What years?? The newer WR's have the a.i.s fittings, The head shape and valves are the same so that shouldnt be a issue.

My bike is a 2000 WR400F and the motor i bought off ebay was a 2000WR...or so i thought. The head is different then the one i pulled off. Anybody have a PDF manual for the 2000 YZ?

The nipple on the left side of the induction manifold is for the old style hot start tube (I believe all YZ/WR 400s should have it). The tube runs from the nipple to the frame mounted hot start knob/valve which in turn plugs into a nipple on the air box boot.

The nipple on the left side of the induction manifold is for the old style hot start tube (I believe all YZ/WR 400s should have it). The tube runs from the nipple to the frame mounted hot start knob/valve which in turn plugs into a nipple on the air box boot.

I dont think i have the old style hot start. I have a red lever on the carb for my hot starts. The bike is back together now and with it idling with the choke on that nipple with blow air out of it and the bike will die. I start it back up again and put my finger over it and the rpms will go down and the bike will die again. So where exactly should that nipple plug into?

You need to plug that hole...if the head was off the bike I would suggest drilling out the nipple, tapping the hole and plugging it with a bolt. That's what I did to run the 400 head on my 426. Since it's already together, just go to AutoZone and get a cap for a vacuum port and install it. I would glue it on with some Permatex No 2 and put a hose clamp or zip tie over it as well.

You need to plug that hole...if the head was off the bike I would suggest drilling out the nipple, tapping the hole and plugging it with a bolt. That's what I did to run the 400 head on my 426. Since it's already together, just go to AutoZone and get a cap for a vacuum port and install it. I would glue it on with some Permatex No 2 and put a hose clamp or zip tie over it as well.

i tried plugging the hole with some tubing and a golf tee too see if it would help and it seems to only make it worse. It wouldn't kick over at ALL, choke in or out but when i took the tubing off it kicked right over with the choke out. Then if i put the tubing back on the hole with the bike running it instantly dies. also if i put the choke in it while its running with the tube off it seems to die also. I might have a problem further down the line someplace.

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