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WhiteEagle78

YZ400F seat replacement and idol issues....

10 posts in this topic

Hello everyone,

I recently picked up a 98' YZ400F. Have not had a chance to do any real riding yet, so im not 100% on how much I like it obviously, but it sounds good when its running... and a lot lighter than my old 86'XL600R!!! Changed out the oil and filter with Spectro Golden 4 and a K&N oil filter. Flushed the cooling system and filled it with engine ice. The bike sounds great when running, but wont idol without dying... idols for about 5 seconds and then stalls... have to keep playing with the throttle, the air filter looks pretty clean... but maybe its isnt breathing good enough.

There is loooots of sag in the shock, and it sounds kinda dry and "scrapey" when going through the stroke... might have to tear it apart maybe. Still have to lube/grease all the fittings, cables and bearings and find a place that can sell me high grade bolts to replace the exhaust and skid plate bolts that are missing.

The one other major thing I have to do is replace the seat which is ripped and is hard as a rock!!! Dose anyone have any recomendations as far as good aftermarket upgrades for the riders rear??? Thanks for any help....

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maybe clean the carb. i have a 99 yz 400f in parts. two seats one SDG the other stock in good shape plus many goodys , alm. sub frame carbon fiber air box oil in frame block off hinson basket no crank, head or valves most parts in good shape.

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Yeah, Ive never dived into a carb very far... but it looks like Im going to need to learn how. The bike sat for a while, Im sure its a bit gunked up inside. Maybe even send it to Zip Ty... everyone seems to like there "secret mods" How do you like the SDG seat? Is it a little softer and more grippy than stock? Ive seen a few on ebay for pretty good deals.... seems like a popular choice for the riders rear.

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I just recently purchased a 99 yz400f and it could not hold an idle. I sent the carb out and had them replace everything in the carb (the needle, the float, all the seals, and the jets). after the fix and clean, the bike had no problems holding an idle!!! (after I got the thing started!!!).

About the sag issue, I would have the rear spring changed for your size and weight and at the same time get the shock rebuilt. it sounds like the shock is just old and needs to receive some much needed TLC.

I had my rear spring replaced and the rear shock rebuilt for about $75 (not including parts).

Patrick M.

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The more I read through these posts, the more it seems like i need to yank the carb and send it to Zip Ty. For $100 do they clean the whole thing and replace worn o-rings and the such.... or do they just do a little "secret" mod and send it back???

As far as the shock goes.... yeah, I think its just been worn out. I think one of the previous owners did some enduro racing with it. The forks seem to have been re-sprung and taken care of well.... the shock seems to have been neglected and worn out pretty good. I guess I'll just have to pull it and find a place somewhere here in the bay area that can give me a good price on a fresh shock rebuild and the suspension should be riding nice once again.

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The bike sounds great when running, but wont idol without dying... idols for about 5 seconds and then stalls... have to keep playing with the throttle, the air filter looks pretty clean... but maybe its isnt breathing good enough.

I've got idol issues too, I can't choose between Ricky or Bubba! Ok, seriously, does the carby still have the fuel screw, sometimes they can unscrew and fall out?

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I live in the bay area and i found a guy by the name of steve at 650 racing in redwood city.

I dont know his phone number off hand but you can get it off his website at www.650racing.com

I heard a lot of good things about his from the local MX Riders!!!!!!

I hope this helps!!!

Patrick M.

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I've got idol issues too, I can't choose between Ricky or Bubba! Ok, seriously, does the carby still have the fuel screw, sometimes they can unscrew and fall out?

Gotta give some major props to Ricky... was stoked to see him win his last supercross race in SF :thumbsup:

Im going to pull the carb this weekend, sense there are a few nuts and bolts that have rattled off this bike... I will surely be checking to see if the fuel screw fell out... would be to much of a suprize I guess

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I live in the bay area and i found a guy by the name of steve at 650 racing in redwood city.

I dont know his phone number off hand but you can get it off his website at www.650racing.com

I heard a lot of good things about his from the local MX Riders!!!!!!

I hope this helps!!!

Patrick M.

Thanks for the shop recommendation. Checking out the link shows me a new riding place to (Coyote hills) might be a little closer than Hollister.

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Im going to pull the carb this weekend, sense there are a few nuts and bolts that have rattled off this bike... I will surely be checking to see if the fuel screw fell out... would be to much of a suprize I guess

You can check if the fuel screw is there if you loosen and tilt the carby, and a torch might be handy. If it's gone, you may aswell buy an aftermarket easy adjust fuel screw. http://shop.thumpertalk.com/product_p/fms02.htm Going by the picture, you'll also need to buy a spring and o-ring for it too.

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