Author Topic: YZX500 Project  (Read 51181 times)

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Offline scottysg

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Re: YZX500 Project
« Reply #30 on: February 25, 2016, 04:22:33 AM »
It's not the needle that is the problem... It's the tube that it goes up and down in... It is a jet. , and when the needle wears it out it makes it impossible to get fueling right....

Motorrad I see now what you mean. I hadn't even thought that could happen. Ill take a look at it and see how loose the needle looks in there.

I checked kips while running and the arm is moving like it should. Looking into the exhaust, the ports seem to line up right when its moved, so I'm fairly confident kips is not the issue. however I am new to kips.

Thank you,

this probably isn't the culprit...but,
did you happen to notice if the center "flapper valve", at the top of the exhaust port was opening fully as well, when you were checking the side valves?
over time the pins get worn and that valve won't function fully....in other words, if that center "flapper valve" can't open fully...it'll choke itself to some extent under full throttle because the exhaust port opening will be to small.

This engine only has the 2 barrels, theres no center valve.

Thank you,

Offline Foxx4Beaver

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Re: YZX500 Project
« Reply #31 on: February 25, 2016, 04:27:06 AM »
my bad...chalk that up to me not paying attention. :lol:
Excuse me, ma'am...but you've got extremely nice legs!!!...what time do they open???                                                                                                               https://www.youtube.com/watch?v=n8tCgN3aryQ

Motorrad

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Re: YZX500 Project
« Reply #32 on: February 25, 2016, 05:07:46 AM »
Not sure why. But I've seen more k5's with the worn needle valve than other modernish bikes.......  Now old bultacos... Don't get me started...

Offline scottysg

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Re: YZX500 Project
« Reply #33 on: February 25, 2016, 05:14:03 AM »
Not sure why. But I've seen more k5's with the worn needle valve than other modernish bikes.......  Now old bultacos... Don't get me started...

Its clearly because there is so much fuel gushing through to the massive engine. Its natural erosion like the grand canyon except it only takes years not millions of years. :p

Offline scottysg

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Re: YZX500 Project
« Reply #34 on: February 25, 2016, 05:27:14 AM »




The needle jet looks pretty good, but I can't say I know what Im looking for.

Offline scottysg

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Re: YZX500 Project
« Reply #35 on: February 25, 2016, 07:57:42 AM »
My stator plate came loose! The screws were almost all the way out and timing was like 15\20 degrees off. The plate was flopping around. Miracle nothing catastrophic happened and incredible the bike even ran. Realigned the dot, used red instead of blue loctite, and the thing ran much better. Im sure I could benefit from fresh reeds which I will order after my next paycheck, and I need to get my jetting dialed in, but Im relieved that Im on the right track now and can focus on tuning.

Thank you guys so much for your help along the way, this has been an extremely fun process and I couldn't have done it without your support!

Offline Foxx4Beaver

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Re: YZX500 Project
« Reply #36 on: February 25, 2016, 07:59:32 AM »
 :lol:....sweet.
roost on!
Excuse me, ma'am...but you've got extremely nice legs!!!...what time do they open???                                                                                                               https://www.youtube.com/watch?v=n8tCgN3aryQ

Offline umberto

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Re: YZX500 Project
« Reply #37 on: February 25, 2016, 09:18:14 AM »
Glad you had an "ah-ha" moment.  It's such a great feeling when you start getting the motor headed in the right direction.  The guys on here are so good about helping you out with questions and sharing their knowledge.  I'm pretty sure most of them have forgotten more about KX 500s than I know.   :-D
Perhaps I have a dirt bike addiction?

03 KX 250/88 KX 525/2017 KX250F - Goliath
17 KX250F/04 KX250
04 KX 250 - Lunchbox's Bike
05 KX 125/144

Offline umberto

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Re: YZX500 Project
« Reply #38 on: February 25, 2016, 09:23:56 AM »
Not sure why. But I've seen more k5's with the worn needle valve than other modernish bikes.......  Now old bultacos... Don't get me started...
Can those tubes be replaced, or is it time for a new carb at that point?
Perhaps I have a dirt bike addiction?

03 KX 250/88 KX 525/2017 KX250F - Goliath
17 KX250F/04 KX250
04 KX 250 - Lunchbox's Bike
05 KX 125/144

Offline scottysg

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Re: YZX500 Project
« Reply #39 on: March 01, 2016, 09:06:10 AM »
Glad you had an "ah-ha" moment.  It's such a great feeling when you start getting the motor headed in the right direction.  The guys on here are so good about helping you out with questions and sharing their knowledge.  I'm pretty sure most of them have forgotten more about KX 500s than I know.   :-D

It is amazing to have a resource like this. 20 years ago you were on your own for the most part. Now a guy like me who knows nothing can put a bike together and get riding quickly thanks to helpful guys on here.

Speaking of which, please take a look at this youtube video and let me know if I'm getting closer with my jetting. 168 main, 60 pilot, 40:1 927, 70 degrees at sea level. I had the timing on the center mark with a 170 main and it didn't want to rev on top. I retarded the timing halfway between the center and retarded notch and put the 168 in. It doesn't blubber at wot as much anymore. i just don't want to go down too much and run lean. Plug chop to come after I get the seat of the pants tuning dialed in.

https://www.youtube.com/watch?v=AWk4577qW50

Offline umberto

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Re: YZX500 Project
« Reply #40 on: March 01, 2016, 10:11:47 AM »
It sounds good, but I would still do some plug chops just to make sure.  Better safe than sorry for sure, especially with the less common 1988 motors we have. 
Perhaps I have a dirt bike addiction?

03 KX 250/88 KX 525/2017 KX250F - Goliath
17 KX250F/04 KX250
04 KX 250 - Lunchbox's Bike
05 KX 125/144

Offline scottysg

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Re: YZX500 Project
« Reply #41 on: March 03, 2016, 08:56:51 AM »
It sounds good, but I would still do some plug chops just to make sure.  Better safe than sorry for sure, especially with the less common 1988 motors we have. 

Good call, I want to keep as many of these alive so our species does go extinct :)

Check out this shot of my plug chop: 69 degrees, sea level, 40:1 maxima 927, 168 main, 58 pilot, air screw 1.5 turns out, fresh filter, slightly overcast\foggy.

Got the bike warmed up for about 20 minutes, shut it down, pulled the plug, put a brand new one gapped to 22 thou (manual says 24 but Ive had better results with 22, does anyone possibly know why). Started it up, rode to the end of the block not at full throttle but pretty quick, turned around, wound it out to the top of 4th, pulled the clutch\hit the kill, coasted back to the toolbox, and this is the result. Not seeing a perfect 'ring' like I've seen on the internet. Also, since I'm doing this on roads (ahem in mexico) I didn't want to have it wound to the top of 5th for 1 mile at wot like I've read I need to. with my gearing thats like 120 lol. I don't know if this would lead to my test giving inaccurate results.

Let me make a guess before the experts tell me what the plug actually says: The motor is running slightly rich at wot based on the carbon deposits that have lightly covered the whole tip of the ceramic. I could go down 1 size on the main, but for safety, its probably best I stay with this size.

Alright guys, let me have it-what is going on in my engine! Thanks for the tips :)




Offline scottysg

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Re: YZX500 Project
« Reply #42 on: September 09, 2016, 06:51:56 AM »
The bike is running great! My computer got stolen which is why its been challenging to get pics up. In any case, I rebuilt the motor, got the crank balanced and bearing seat repaired at crankworks, the bike is very smooth. after lots of experimenting with heat wrap im pretty settled. the bike is now just a rider, not a project anymore which feels great. though its almost red sticker season so knowing me ill have this apart again soon riding other bikes. it pulls very well. if i could get it to hook up... my friends dont ride behind me anymore and tires dont last very long out here in californias rocky terrain. the frame seems to be holding up well to the extra weight. i have a big desert tank too so this was never planned to be a light bike. im a tall but very light guy so i just point it and hang on! its been a fun journey to get this done.

If anyone has questions about the work or problems please let me know, im very happy to share what ive done :)


The problems with this build seemed never ending


this is why you shouldnt hit doubles on a street bike...


killed my old dc welder, got this fancy new one and i recommend it to others


proud over my creation! (heat wrap not finalized in this photo, im using much less now)