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YZippy

New 400F Owner...Need feedback.

17 posts in this topic

Hi all. I have just purchased a 98 YZ 400F after a 6 and one half year lay off. Came off RM 250 and was planning to purchase another 2 stroke, but came across a deal too good to pass up. Since I have no real experience with a thumper I thought this would be a great place to seek advice. Any feedback would be appreciated. Looking forward to visiting here.

Oil. What do you recommend. I am leaning toward a synthetic after reading several articles. I saw Motul , Spectro, AMSOil Honda , and Yamaha oil at the shop. Any recommendations.

Flywheel. Shocked at how light the flywheel is for a 4 stroke. Any experience with Flywheel weights. 60% of my time will be in the woods.

Gearing. Right now it is a 14-49. Not sure if this is stock. The previous owner hasn't mailed me the shop manual yet.

Graphics. Factory Effex Graphics look great except on the tank. Gas spills got em. What is good to use to glue them back down??

Thans for any replies. I'm sure I'll be here often as I get more seat time.

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Congratulaion on the new bike and welcome to the board and back to riding. I bought a 1998 YZ400F in 1998 and I loved it. You will love it too. I will try to answer some of you questions when I wake up. Enjoy Mark

Oil I used yamalube 4R and i have used Motul also, I lean more to the semi-synthetics but that just me. I like that the petrolieumMot

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I have an '01 WR426 with an '04 YZ450 auto decompression exhaust cam and a carb accelerator pump diaphragm which has a longer pin to limit accelerator pump volume. It revs just like a 2-stroke with no bog off idle and it's faster in the woods than before these additions. These were probably the best additions I've put on it. I found all the p/n's & info needed here on thumpertalk.

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Im also a new 99 YZ400f owner. Do they make the same exhaust cam for our 400s, or is that a 426 only part? Also, where did you get these parts?

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I looked up the cam, thanks. Is it just that easy, or are there other mods involved? Does this make the starting easier like the newer bikes? If this is all it takes, then I have a nice off season project.

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Thanks! Im having a bit of trouble reading the links (theyre a little small and blurry) I know Im getting old but damn! -Jim

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Thanks! I found the almost 100 page discussion on the 450 decomp. cam swap. I read until my eyes hurt and it sounds like this is the way to making the bike JUST right!! When I get around to it, I will be doing the mod. :D

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Oil. What do you recommend. I am leaning toward a synthetic after reading several articles. I saw Motul , Spectro, AMSOil Honda , and Yamaha oil at the shop. Any recommendations.

I wouldn't use Honda oil in your Yamaha, just because...but all of the others you listed will work fine. Just make sure you get a good viscosity, 10w40 or 15w50 works best. Personally, I use Maxima Maxum4 15w50 in my YZ250F. Its an ester-based 100% synthetic racing oil. Really good stuff.

Flywheel. Shocked at how light the flywheel is for a 4 stroke. Any experience with Flywheel weights. 60% of my time will be in the woods.

For woods riding, I'll reccomend an 8oz flywheel weight to help you out in the tight stuff. You can get them through Dubach Racing. And, in case your not satisfied with the tractability of the 8oz, you can send it back for another weight and all you will have to pay is shipping and handling.

www.dubachracing.com

Gearing. Right now it is a 14-49. Not sure if this is stock. The previous owner hasn't mailed me the shop manual yet.

Yes, I am almost positive that is the stock gearing for that bike. For woods, you may be good to go with that. If you need more torque, gear down (more teeth). I doubt you'll need more top-end, but if you do I'd go with a 48-tooth rear sprocket. Dont forget whenever you change out one sprocket, you have to get a whole new set. That includes front/rear plus a chain. Otherwise it will wear out way to fast. Unless your an experienced mechanic, get a Clymer manual. Its much easier to understand.

www.clymer.com

Graphics. Factory Effex Graphics look great except on the tank. Gas spills got em. What is good to use to glue them back down??

Personally, I use Loctite Super Glue. It'll NEVER come up again. :D

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Wow!! Thanks for the info everyone. I hope in a few months I can help someone else. I had a Stealhy 12oz weight on my RM 250 and it transformed the bike. It was a 5 minute job. When looking at their sight the 400 had either a drill and tap option or send them the flywheel. THere has to be a easier way!! Anyway. Thanks for all the replies

Jeff

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Wow!! Thanks for the info everyone. I hope in a few months I can help someone else. I had a Stealhy 12oz weight on my RM 250 and it transformed the bike. It was a 5 minute job. When looking at their sight the 400 had either a drill and tap option or send them the flywheel. THere has to be a easier way!! Anyway. Thanks for all the replies

Jeff

No problem, enjoy your 400F...its one of my favorite bikes! :D

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I would really look at the timing chain. If it hasn't been replaced I would recomend installing a new one. There was a rash of chain failers a year or so back. Chains were getting stretched out and jumping timing. A new chain is only like $35. Something to think about.

I would also start replacing all the fluids in the bike. Fork / shock oil. Brake fluid, Antifreeze...the works. Its amazing how nasty brake fluid gets over time.

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If I was to properly flush the old stuff out, would it be a good idea to run silicone brake fluid, or is this a bad idea? Ive used it in some of my cars and trucks because of the way it doesnt attract moisture. Not to mention its not corrosive.

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I'm lucky....it has a new Timing Chain and newly changed fork and shock oil along with new piston/ring, water pump impeller and shaft and new bearings in the bottom end.

It was a bear to crank today. Did the drill...decompress... kick about 10 times....gas on...bring to top dead...decompress.....move about 1 inch....release....bring up the kick starter and kick like I mean it. The choke wants to pop close constantly...What's up with that?? Am I missing something?? Noticed some radiator overflow today. Probably need to flush.

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