christoph21
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Posts posted by christoph21
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Sounds like the carb fairy has been round to your spot and chased them pesky gremlins away
I'd say. It finally came for this one and not the first Honda i had. . .
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hrrmm.. vacuum leak? are your vacuum ports capped on your intake boots, intake boots snug, etc, etc.. clean the carbs and run it around the block a few times? is your throttle cable getting hung up and pulling the butteryfly open a little? if it's routed through the fork wrong it will do it.
What? Nothing of that. I've already repaired that. The bike runs swell now and it's consistent.
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I would still recommend adjusting them with it running if you can at all get it set up to. Then you can actually find the best setting. When the idle is highest that is about where you want it. You might go back just a little in from that point if you want it slightly lean (slightly lean is not really a bad thing at idle) but running gets it best. When it's right it will drop right back to idle when you let off, no hanging at all. The idle hanging high is a prime sign of it being lean.
I was going to tune up the carbs today but as i was letting the bike idle it just kinda fixed itself. I dunno, i kept the screws out 3.5 turns and everything was great. I put on 60 miles and when i got back it was revving clean and idle perfectly.
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If it's anything like mine was, after sitting 13 years (prepped for storage first) the seals in the top end all turned to rubber rocks. I had to replace all the external rubber seals (cam seal, the rocker rod seals etc) to get the hemoraging to stop (it's the only way I can describe it). On mine the seals that had oil against them while stored all seem to still be fine, and I think I still need to replace the valve seals yet, but the major leakage is gone (90% was from the cam oil seal).
I'll keep that in mind. I'll be checking that out first thing sunday hopefully
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My experience with exactly the same symptoms was that I was still way lean. I setup so I had gas with the tank lifted enough to get to the idle mix screws and then adjusted them out till highest idle and starting back down and then came back to the highest idle coming down. I did this to both carbs and had to turn the idle speed WAY down in the process as it went from 1200 RPM to almost 4000 just by adjusting the mixture. I ended up about 5 and 5 1/2 turns out on the mix screws, I know that is way out from spec, but what works works.
If you haven't replaced the o-rings on the idle mixture screws you probably need to, but try adjusting it first just in case.
Yeah i figured i needed to keep turning. I have the screws about 3.5 turns out from bottom and i still noticed a little sticking at the 3k line but it comes back down. I think i'll take it out another half turn and that should do it because it's running pretty good right now aside from the 3k thing.
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it means a weak mix, pilot jets up to 4k then main jets take over after that.
idling issues are nothing to do with the diaphram, the idle sytem are notoriuos for clogging up especiallly if you don't run with an after market fuel filter inline twixt the tank and carb.
try anti clockwise unscrew the idle on top front of carb 2.5 turns from bottoming out
All right. I took the idle mix screws out 2.5 turns like you said. I started it up. It was a good low idle then i gave it some throttle and it went back up and hung at 3500, 4000 RPM or so. What should I do? Should I keep turning the screws out by a half turn and trying again?
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Unscrew the idle mixture screw? I take it that's what you meant. Any tips on removing the cap?
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Well, the bike DID run great. I'm have idling and revving issues again. There are no cracks in the carb boots now after I siliconed them. The jets are clear and floats are set accordingly. I have NOT looked at the venturi slides. I suspect one has a bad vacuum seal. This would lead to a high idle/rev problem yes?
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Anybody know of a recurring oil leaking issue with and 81 ( or comparable) xs400? the bike has been sitting for 15-20 years inside, stored free of gas and after running it for a day it leaks oil considerably. Do you think it just needs time for the seals to become moist again and expand?
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Yeah I forgot to connect the hose to the carb boot. I was anxious after cleaning the carbs out so when it didn't start i panicked and jumped on here. thankyfully it was a quick fix
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Nevermind. I fixed everything just fine. Damn vacuum petcock...
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Hello all. I have recently restored my third bike, a 1981 Yamaha xs400, and I just got it started up today for the first time. Currently, the bike starts right up with the push of the ignition switch, but does not idle on it's own. Also, when holding the throttle at one point, the bike can sometimes rev up higher and higher on it's own. I just cleaned all the jets in the carbs, floats and everything else EXCEPT the venturi slide as the screws were in rough shape. The venturi seem good though because the carb was already pretty clean when i got it and they slide pretty smooth. Any specific methods to remedy this?
I know I probably need to adjust the idle screw but i'm not familiar with yamahas quite yet so a walkthough would be great. thanks
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Oil leak
in Classics
Posted
Do you have the part numbers for the rocker rod seals and the cam seals? That would be really convenient for me thanks