Update - 2019 kx450 top end

Duncster316
Edited Date/Time 4/19/2020 6:32am
Hey all. So, 55 hours on my kx, intermediate mx rider. Thinking about doing a top end with OEM parts, engine hasn’t been touched so far. I’m a little concerned about wrist pin fitment and a few reports of rods snapping maybe because of this issue. Bottom line, I don’t want to be riding a bike that might grenade. Not sure whether to do the top end or maybe just keep running it, or maybe look at getting rid of the bike before doing anything. I don’t know of any engine builders or shops I would really trust with this kind of thing in the North Texas area. Anyway, thanks for any input!
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CarlinoJoeVideo
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CarlinoJoeVideo 3/29/2020 8:36am
3/29/2020 8:36am
For nov/int rider, I’d think you can get well over 150 hours on that bike. There’s always freak situations, but no way to count on those.

Before I considered doing a top end at 55hours, I’d check the valves and do a leak down test.
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walent215
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walent215 3/29/2020 8:51am
3/29/2020 8:51am
I would personally go 75 hours minimum before tearing it down unless your riding WOT everywhere.
I also wouldnt Concern myself with alleged wristpin issues. Sure things can happen but we dont know exactly how these people maintain their bikes or how they ride them. Continue to change oil/ filter at frequent intervals and run clean air filters. That's your best bet to insuring reliable engine life. Enjoy riding and give your best effort on proper maintenance. If your gut says pull it down and check it, then by all means go for it. A piston, cam chain and gaskets are really very cheap and easy to install! Dont over think it!
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Duncster316 3/29/2020 9:20am
3/29/2020 9:20am
Ok, great! Thanks for the insight guys. I’m pretty ocd with my bike maintenance and oil/filters. The bike also runs great, no indications of any problems. Will keep on going and check the valve clearance.
dancolvin633
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dancolvin633 4/5/2020 8:56am
4/5/2020 8:56am
Duncster316 wrote:
Ok, great! Thanks for the insight guys. I’m pretty ocd with my bike maintenance and oil/filters. The bike also runs great, no indications of any problems...
Ok, great! Thanks for the insight guys. I’m pretty ocd with my bike maintenance and oil/filters. The bike also runs great, no indications of any problems. Will keep on going and check the valve clearance.
The one you saw of Greenguy with the rod snapped in half, remember he had 125 hours on it. And he rides a lot, and he’s prettt fast. Rule of thumb
Is 50 hours do a top end, 100 hours do a crank. You could certainly more then likely go longer, but why risk it. When cranks fail it’s EXPENSIVE.

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Duncster316 4/19/2020 6:38am
4/19/2020 6:38am
Ok, so for a couple of months now Ive been getting a little smoke during warmup. After clean and detail after riding yesterday, I started it up for a minute and it was smoking at idle during warmup a lot more than before, with pretty big puffs of smoke if I blipped the throttle just a little bit. I’m thinking it looks like top end time for sure, what do you guys think about brands of top end kits or pistons/buy all the OEM little parts? Looking for high quality parts, not on a budget for this kind of stuff. Thanks! (58 hours on it now, and I do get on the throttle pretty hard when I ride).
DynoDan22
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DynoDan22 4/19/2020 6:48am
4/19/2020 6:48am
Use all OEM parts.
walent215
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walent215 4/19/2020 8:05am
4/19/2020 8:05am
Duncster316 wrote:
Ok, so for a couple of months now Ive been getting a little smoke during warmup. After clean and detail after riding yesterday, I started it...
Ok, so for a couple of months now Ive been getting a little smoke during warmup. After clean and detail after riding yesterday, I started it up for a minute and it was smoking at idle during warmup a lot more than before, with pretty big puffs of smoke if I blipped the throttle just a little bit. I’m thinking it looks like top end time for sure, what do you guys think about brands of top end kits or pistons/buy all the OEM little parts? Looking for high quality parts, not on a budget for this kind of stuff. Thanks! (58 hours on it now, and I do get on the throttle pretty hard when I ride).
Time to open her up then I'd say with that much blow by. I've used most of the big name pistons and have had great luck with all of them . Prox, JE, vertex, Wiseco etc. The vertex I've used seem like a very good quality piston. You mentioned wrist pin issues in your initial post. Some pistons come with DLC costed wrist pins so maybe look into one of those. Off the top of my head I'm thinking CP is one that does. Not 100% sure on the others.
Paw Paw 271
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Paw Paw 271 4/19/2020 8:17am
4/19/2020 8:17am
You could have valve oil seal issues creating the smoke.

Paw Paw
Duncster316 4/19/2020 4:44pm
4/19/2020 4:44pm
Thanks for the replies guys! Paw Paw, would you suggest maybe doing a valve clearance check first and see what they look like, adjust as necessary and re check for the smoke?
jeffs
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jeffs 4/19/2020 6:16pm
4/19/2020 6:16pm Edited Date/Time 4/19/2020 6:17pm
This seller on ebay has a great deal on CP piston kits. I'm planning on buying one of these real soon.
Seller information
azquadparts (14784 )
100% Positive feedback
Details about
18-20 Kawasaki KX450F KX 450F 96mm Stock Bore 13:1 RACE Coat CP Piston & Gaskets

Item Information
Condition:
New
Price:
US $239.99
https://www.ebay.com/itm/18-20-Kawasaki-KX450F-KX-450F-96mm-Stock-Bore-…
Paw Paw 271
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Paw Paw 271 4/19/2020 6:52pm
4/19/2020 6:52pm
Duncster316 wrote:
Thanks for the replies guys! Paw Paw, would you suggest maybe doing a valve clearance check first and see what they look like, adjust as necessary...
Thanks for the replies guys! Paw Paw, would you suggest maybe doing a valve clearance check first and see what they look like, adjust as necessary and re check for the smoke?
You can do that, but it will not have any effect on the issue of valve seals leaking.

Paw Paw
kb228
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kb228 4/19/2020 6:54pm
4/19/2020 6:54pm
Best pistons are JE & CP Carillo. The carillo kits come with a DLC coated wrist pin and easy to install wrist pin clips which is nice. I run them in both of my kx’s.

You need to figure out what the smoke is exactly. Valve clearance doesnt create smoke. Your issue lies in this list:
Valve stem seal damage
Valve guide wear(unlikely with your amount of hours)
Blown head gasket
Cylinder damage
Ring end gap too much(indicates ring wear)
Warped gasket surface

If you want to make it easy, order up a CP piston kit, prox top end gasket kit, and then measure your cylinder bore and ring gap before assembly. Run a ball hone through your cylinder to create crosshatching so your rings seat. Ball hones will not remove material - just adds the hatching. Check your gasket surfaces by getting a sheet of marble and sticking 400 grit wet sandpaper on it and run it in a figure 8 with light pressure. Any warpage will show immediately. You can even sharpie your gasket surface before hand to make low spots even more obvious.
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project racer 4/19/2020 8:12pm
4/19/2020 8:12pm
Never hear much about checking out the heads much when suggestions are given. Valve seats concentric ? Valves measure out ? Springs not sacked? Stem seals and keepers good ?

The power in a four stroke is made in the head. Just seems like it would come up in rebuild talk to maybe freshen the head at top end time.
Duncster316 4/20/2020 7:49am
4/20/2020 7:49am
Thanks so much for the info everyone! So, Looks like CP and OEM top end kits readily available, question - it appears the CP kit ups the compression from 12.5/1 to 13/1. Would there be considerations with that level of change? Maybe dumb question, should I run non synthetic/semi for the first hour after rebuild? Thanks for the help, I don’t have any experience working on four strokes until now.
kb228
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kb228 4/20/2020 1:59pm
4/20/2020 1:59pm
Duncster316 wrote:
Thanks so much for the info everyone! So, Looks like CP and OEM top end kits readily available, question - it appears the CP kit ups...
Thanks so much for the info everyone! So, Looks like CP and OEM top end kits readily available, question - it appears the CP kit ups the compression from 12.5/1 to 13/1. Would there be considerations with that level of change? Maybe dumb question, should I run non synthetic/semi for the first hour after rebuild? Thanks for the help, I don’t have any experience working on four strokes until now.
Run full synthetic. No concerns going to 13:1. Run premium gas.

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