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stnkbg1

Looking for advise on my YZ engine build

13 posts in this topic

Those of you who saw my other thread know that I killed the big end rod bearing on my YZ400. I'm now in the process of figuring out how to rebuild it. I'm planning on replacing the crank assembly, piston, cylinder, and all associated small parts and seals. I do not want to do anything with the cams or valvetrain as everything there is in great shape, and I dont feel like spending extra money on something that's not necessary.

To give some background on how I use the bike, it's a plated motard and I ride it on the street a lot. It mostly sees commuting duty during the week on surface streets, and some canyon carving on the weekends. Sometimes the weekend rides are a couple hundred miles or more. Occasionally it sees freeway use, for up to about 30 miles at a time. Very rarely I swap dirt tires on and take it out to the desert. Reliability is the number once concern for me, so I'm looking for whatever will get the job done without putting undue stress on the motor. I'm not worried about power, as it's always had more than enough. However if I can get more power for similar money without compromising reliability......hell yeah I'll go for it.

So here are the options as I see them.

#1-build back to stock. Highly unlikely. It'll still cost at least $850, and I'll be back where I started.

#2-get new stock crank and Lukes 420 big bore kit. Also unlikely, mostly because the next 2 sound like better bang for the same buck, and maybe more reliable, you tell me.

#3-Build with stock 426 crank,piston, etc - Basically I'll get a stock 426 motor. Would be a bit more power than the 400, and I cant see any negatives as far as reliability. In fact with the bigger rod/piston bearing I suppose it's possible that it'll be slightly more reliable, at least in that one part.

#4-Use 426 crank, with Lukes 444 big bore kit- Go all out right? It'll cost about $150 more, but it'll be more powerful, and hell just damn cool. I wonder about reliability though, plus with the added expense I can get a vapor and actually keep tabs on how hot it is, how illegally fast I'm going, rpm, etc.

So I'm looking for advise. Basically right now I'm trying to decide between options 3 and 4. Both are extremely tempting in different ways. Both are an upgrade from what it was. One is a bigger power upgrade, but the other may be more reliable. That's my debate right now.

Thanks

Dallas

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Considering reliability is key, option 3 would be my first choice, then 4 and 1. Given the option of doing any of these 3, I'd take 2 off the list.

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Reliability!! Stock is the best.. Wonder if the lukes 444 engine vibrates allot!! I would also run the new cams with the decompression on them too.. If your gonna spend 1200.00.. Man another 1000.00 you can have a Fo Fiddy..03 model.. But if you love the 400 I guess try the 444. Whatcha got to lose? Except Money.. LOL!!! Good luck..

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Option 3 looks good. The stock 426 is very reliable as long as you keep the oil fresh.

The jury is still out on the 444 kit. I have a little less than an hour on mine. They have awesome power on the bottom, but seems a little flat in the mid and top. Maybe its my jetting, but the 426 had more hit. I'm changing needles today, so hopefully I'll figure something out.

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Wonder if the lukes 444 engine vibrates allot!!

I haven't noticed any vibration differences between the 426 & 444.

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Option 3 looks good. The stock 426 is very reliable as long as you keep the oil fresh.

The jury is still out on the 444 kit. I have a little less than an hour on mine. They have awesome power on the bottom, but seems a little flat in the mid and top. Maybe its my jetting, but the 426 had more hit. I'm changing needles today, so hopefully I'll figure something out.

The bike is a 400.. 97 98 I'm guessin

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The bike is a 400.. 97 98 I'm guessin

They didn't have a production 97 model so it would have to be a 98 or 99 model.

You can turn a 400 into a 420, 426, or a 444.....all it takes is money. :banghead:

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Reliability!! Stock is the best.. Wonder if the lukes 444 engine vibrates allot!! I would also run the new cams with the decompression on them too.. If your gonna spend 1200.00.. Man another 1000.00 you can have a Fo Fiddy..03 model.. But if you love the 400 I guess try the 444. Whatcha got to lose? Except Money.. LOL!!! Good luck..

Like I already said, I'm not swapping cams. I actually dont mind the decomp lever. It sounds like a stock 426 is my best bet, and yeah I could just buy a 450, but it wouldn't already be street legal in CA.

Dallas

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Like I already said, I'm not swapping cams. I actually dont mind the decomp lever.
You don't know what you're missing.

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I ride the bike around town, with no ignition key. The decomp is my way of keeping honest people honest. If they cant start it, they cant ride it away. It's also the way I keep friends from riding it, "if you can start it, you can ride it" :banghead:

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As far as reliability of the 444, I ave about 2500 miles on mine with absolutely no issues. The 13.5:1 comp ratio protests sometimes if I run cheap gas, so for your type of use I would suggest the 12.5:1 comp ratio. The engine revs a bit slower with the bigger piston, as there is more mass to move and change direction. From my perspective, it kind of "calmed down" the more hyper behavior that the hot cams added. As far as vibration, I can't tell a difference between the 444 and the stock 426 (nor between my 444 and my riding partner's 400). The forged pistons that come with the Luke's kit (wiseco) are a bit noisier than the cast stocker, but that will be the case with any forged piston.

As far as camshafts, I see your point about the stock decomp lever...you might want to think about dropping 2 bills on a hotcams intake, though. Gives you more across the board, a bigger midrange hit, and quicker rev with the big bore than stock. Again, 2500 miles of big bore and hot cams, mostly desert riding with some pavement and DS events, and no issues at all.

Obviously, my vote is to go big or go home.

Where in Cali are you located? I'm in Palmdale. If you're anywhere close, you're welcome to come swing a leg over the beast and try my set up to see if it's what you want...

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I ride the bike around town, with no ignition key. The decomp is my way of keeping honest people honest. If they cant start it, they cant ride it away. It's also the way I keep friends from riding it, "if you can start it, you can ride it" :banghead:

thats exacley why i love mine :busted:

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