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98Thumpin400f

oil pressure check?

24 posts in this topic

I just completed a top end rebuild on a 98 YZ400F moments ago and I am wondering if there is a quick way to make sure I am getting oil to the top end manually before I crank it up and don't have oil pressure for some crazy reason.

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You can try loosening the top oil line and kick it over real fast. I'm not sure if that would work, but if you had oil pressure before the rebuild chances are you'll have oil pressure now.

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Thanks 642MX I will give that a try. I took the drain plug out already and kicked it over by hand to see if it would pump any oil out that way but did not have any luck. I may not have been turning the engine fast enough to generate any psi. The reason I am so concerned is because I bought the bike used and before I could even ride it I had to tear it down for the rebuild. I just don't want to have to go right back into it. Thanks again for the input I will crank it up for the first time tomorrow and see what happens

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If you look on the rear of the cylinder head on the pipe side just in front of where the oil line connects, there is a green 10mm bolt. This bolt plugs the oil passage and is used to check exactly what you are asking. Remove it and then stroke the kickstarter a few times until you see oil come out of the hole. That means you have oil pressure to the top end. Reinstall the bolt, wipe up the mess and crank 'er over! :thumbsup:

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If you pre-lubed the parts as you assembled the motor again, then there should be no problem with following the manual's directions on checking oil pressure. Loosen the top oil pipe bolt and start the bike, within seconds you should have oil seeping out of that connection. I would give it 15 seconds, and if nothing, shut it off and investigate.

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Bear in mind when you do the check that you probably have no oil in the oil filter well, and it takes something like 75-100cc to fill that. Only then can oil go beyond that point to reach everything else, and kicking it manually is a slow way to get it there. You may, if you're worried about it, want to lay the bike on its left side, remove the cover (leave the filter in place) and mostly fill the well with oil. Another thing you can do to possibly speed up the initial delivery is to loosen the feed line until oil runs from it to prevent there being a bubble blocking things up momentarily.

But, as Butta said, If you lubed everything to begin with, and it's put together right, there's no reason to think it won't push oil up fairly quickly. Just keep the revs down for the first 30 seconds and see if it leaks at the top oil fitting while it's loose, you'll be fine.

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Thanks for all the input guys. I definitely pre lubed everything good so that should not be a problem. Here goes nothing.

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Another thing you can do to possibly speed up the initial delivery is to loosen the feed line until oil runs from it to prevent there being a bubble blocking things up momentarily.
Gray, I'm curious as to why you and the guy who posted before you would recommend breaking the seal on a fitting that uses two crush washers (listed as single use in the manual) when the factory has supplied a simple means for checking oil flow? :thumbsup:

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I believe the manual says to crack the top oil line if you feel it is necessary to check the pressure.

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I believe the manual says to crack the top oil line if you feel it is necessary to check the pressure.

yup! infact IT SAYS TO DO IT EVERY TIME YOU CHANGE THE OIL.Seems a bit of a overkill to me but what the heck.I'm not sure if the new ones still have that part in there but my kids 04 does. :thumbsup:

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Gray, I'm curious as to why you and the guy who posted before you would recommend breaking the seal on a fitting that uses two crush washers (listed as single use in the manual) when the factory has supplied a simple means for checking oil flow? :thumbsup:
The 400 does not have the oil pressure check plug you refer to, as your 450 does (which BTW, also seals with a copper washer), and the manual calls for loosening the top oil fitting as a check of oil pressure.

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I believe the manual says to crack the top oil line if you feel it is necessary to check the pressure.
Why? The bolt I referred to is about 20mm away from that fitting and provides access to the exact same oil passage fed by the tube. I have this bolt on my '04 WR and my bro has it on his '03 YZF. Both our manuals say to use it to check oil pressure. Did Yamaha do away with it on later bikes? If so, I see the point of Gray's answer, but if you have this bolt then that is the best way to check rather than risking a leak from the crush washers used on the oil line banjo bolt. The check bolt even has a copper washer on it like the cooling system drain bolt in the water pump cover. The main reason to use a copper washer is as a fluid seal. :thumbsup:

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The 400 does not have the oil pressure check plug you refer to, as your 450 does (which BTW, also seals with a copper washer), and the manual calls for loosening the top oil fitting as a check of oil pressure.
Well, then, I defer to your superior knowledge on the "older" stuff. :bonk::bonk::thumbsup: I didn't realize this bolt was such an innovation for Yamaha! :thumbsup:

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The '01 YZ250F got it first. The copper washers probably are less an issue than the slight and repeated twisting the happens at the joint of the oil line and the banjo fitting as the bolt is loosened/re-tightened. Apparently, these are brazed together somewhat better than the old British lines were.

...And no more "older" jokes :thumbsup:

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...And no more "older" jokes :thumbsup:
Ooh, a rare display of emotion from the Grayster! :thumbsup: Just so you know: 8/1958, class of '76. Nuff said. :bonk:

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Just so you know: 8/1958, class of '76. Nuff said. :bonk:
Just a pup! Be a little more careful, and you could live to be my age! :thumbsup:

:thumbsup:

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Just for every body to know from my experience the oil psi check was a success but on the negative side I now have a oil gushing banjo fitting so I have found that you should have some extra washers on hand to avoid missing a ride if you loosen one!! I am glad I joined this forum I have achieved great knowledge from all who have helped :thumbsup:

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Mine lasted a few times before it spontaneously started leaking. The good news is that they are cheap and easy to replace, I just hope the dealership has it in stock for you.

:thumbsup:

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The 400 does not have the oil pressure check plug you refer to, as your 450 does (which BTW, also seals with a copper washer), and the manual calls for loosening the top oil fitting as a check of oil pressure.

Thanks for taking care of my light work, Gray! :thumbsup:

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yep read the manual cyclewriter, it says crack the line, and banjos are not truly one use, only if the get to crushed, or seep

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