NTM 450X Valve clearance help!!!

[Jim Dettman]

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Is it worth putting new cam chain guides in it?? 

 Inspect them carefully.   If they show any signs of cracking, replace them.

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Also, is Kibblewhite valves still the best choice?? I know I don't want the stock ones. 

 Yes, you don't want TI valves.  SS and most still like the Kibblewhite's

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Lastly, whats the story on pistons??

 OEM piston and rings.   You can use a TRX piston if you want 3 rings.  Trade is that it won't quite rev as fast, but you'll have better oil control.

Jim.

[amcjen]

Jim, you’re always a wealth of knowledge. I really appreciate your replies. Thank you!

[bullittman281]

Hello,

I've got some more questions. When I drained the oil it looked like normal dirty oil. It had the typical metallic wave when swirled just like any other oil I've drained. It did NOT look like gold dust. Measuring the rod side clearance I get .021". I'm under the impression that .022" is MAX. Does this number really mean anything?? Everything else seems tight. I can't detect any play anywhere else. The mains seem tight w/o pulling the side cover and the rod is tight otherwise. The small end measure .750" ~.75025". This is using a mic and a snap gauge. .750" flies through and .7505" wont go. There is a tenth or two wear out of round on the rod small end. Its not much but it is detectable w/ the snap gauge. The pin that came out measures very close to .748. That gives .002-.0025" clearance. Again, I don't know if that's significant or not.

I spoke w/ a machine shop about measuring the cylinder and its nearly perfectly round and straight at 3.7795" to 3.780". It looks good. Not sure how Honda sizes pistons. I know Yamaha has a,b,c,d depending on bore but the difference is tiny.

I also spoke w/ him about the head. He's an automotive shop but knows of/about Honda and their valve problems. The problem is pervasive. He was unwilling to look at it any time soon and much prefers not to as its too much work for the pay. I can't blame him. I'll see what the motorcycle shop says tomorrow. Let me know if any of this means anything.

 

Bullittman

Edited February 25, 2020 by bullittman281

[Jim Dettman]

.021 on the rod clearance is fine.   Max is .030.  Standard range is .012 - .030.  So you are fine there.

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The small end measure .750" ~.75025". This is using a mic and a snap gauge. .750" flies through and .7505" wont go. 

This is not so great...you are smack on the service limit of .750.  Spec is .7487 - .7494.

You are supposed to replace the crank if it's over the service limit. On the pin, the limit is .747 and .002 is the correct pin to rod clearance.

On the cylinder not so great either.   While you are under the limit of 3.7805, taper and out of round is limited to .0004 and you are at .0005.   Again, right on the border.

It's great you are taking the time to check everything carefully so you know where you stand.  Most don't bother.

Unfortunately, it's looking like you have a fairly worn motor in just about every aspect.   It's a tough call on how far to go with it.  Certainly the valves need to be taken care of, but beyond that, not sure how much more you'd want to do with it.

Both the cylinder and the crank are right on the border of needing to be dealt with and given the state of things, it leaves you wondering about what kind of shape the seals and bearings are in.   I'd say you are right on the border line of a complete rebuild, and I know you didn't want to sink a ton of money into this.

Jim.

Edited February 25, 2020 by Jim Dettman

[bullittman281]

Hello,
Good or bad I'm gonna roll the dice on the crank and run it. $430 to rebuild the head w/ stainless valves. I'll put a new piston and cam chain in it while its apart. I've got to study the guides and tensioner closer to make sure they are good. A new tensioner is ~$80. I'll see what I do on that.

The motorcycle shop works on tons of these things and their comments were the cranks rarely cause any problems. If nothing is galled up and looks good they run them and have never had trouble doing that. They figure if one goes bad its always the big end and not the wrist pin that fails.  If I can get a top end's worth of hours out if it first before a total rebuild I can live w/ that. That would be a few years worth of riding. They only stock the stock valves so I'll have to wait on shipping of parts but hopefully in a couple of weeks I'll have all back together. 

 

Bullittman

[Jim Dettman]

FWIW, I think you are making a good call.   I wasn't going to sway you one way or the other earlier, but that's what I'd do. 

Just stay on top of oil and filter changes, keep an eye out for any gold flakes or changes in oil level, and ride it.   At a guess, you should be able to get a couple hundred hours out of it with a fresh piston, rings, and pin.

Jim.

[bullittman281]

Hello,

Thats good to hear. I did flinch and ordered a cam chain tensioner being I have no accurate history. Hopefully next week I get all of my parts an I can put it back together. Maybe the stupid weather will improve by then as well. Winter could end....... 

Thanks.

Bullittman

[Leardriver]

A bit of philosophy on repairing it to run for a while. 

It is absolutely the wrong thing to do in any textbook to put new SS intake valves and springs in without cutting the heads. Away from the textbook, in the real world, it is done successfully quite often enough on an X, and lasts for 10 years of flogging. So, $150 for new intake valves and springs without cutting the seats if you are tapped on budget, and I would bet on a long lasting great running bike. It would not be the worst gamble you ever took.

In Colorado, at high altitude, a pipe or muffler is pure bling. Years of dyno testing by me shows that the stock exhaust flows all of the air that the bike can use above 2500 feet, and the thin air negates any gain. You would normally hope to gain 1.5 HP at red line down at lower altitude, you will not in Colorado. Seat of the pants gains are wrong, and perhaps exist to ease buyers remorse. Plus, you are on a budget, save your money for the valves. A good running stock X is terrific.

Speaking of good running, a 158 main jet, a stock 45 pilot, and the fuel screw at 1 7.8, and never touch it again. 

Edited February 28, 2020 by Leardriver

[bullittman281]

Hello,
This is all good!! I'm working a line on a stock exhaust. I HATE noise and that seems to be what most aftermarket stuff does. I'll certainly trade some HP for a quiet bike. The low end power on this thing is intoxicating. Its probably too much but there is no kill like overkill. Your jetting numbers look good. It came too lean to run w/ a 145 main and a 50 pilot. It starts well but the 50 pilot is too rich. I stuck a 160 in it to get it to run and it absolutely rips. I'll have to experiment with your numbers when I get it put back together. Any recommendations on needle and clip position?? I have no idea what a stock needle is. I'd have to pull it apart to see whats in it now.

Speaking of power, how much do these things actually make stock? I've not found too many good sources. I'm just kind of curious. I know max HP means little as its the off idle power this has that has my attention but I am curious.

 

Bullittman

[bullittman281]

Hello,

Just for an update I finally got all of my parts and the head back from the motorcycle shop. I got it all put back together and running tonight. I haven't had a chance to ride it any more than around the block but it runs and sounds good. The stock exhaust is SO MUCH better than the "racing" can that it had on it. It was call the cops loud. I've got some more details to work out but so far it runs. Thanks for all the input!

 

Bullittman

[Jim Dettman]

[35000km 05 X]

i had 60 000Km on a 05 stock bottom end in that time i put 9 sets of rings in and 5 piston cylinder was still good 

i still ride it 

but i spending more time on the CRF 250x then the 450x

i think the motor are very reliable