Time for a new top end...what else?

Discussion specific to the 1995 - 2006 KDX200 (H Series) and 1995 - 2005 KDX220R (A Series) models sold in the USA
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Trackdog
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Time for a new top end...what else?

Post by Trackdog »

The time has come for new piston and rings. Clean up the KIPS, rebuild the carb.
I have been told to do a "port and polish" I am aware of the KB head mod, but he's retired.

Also doing a suspension upgrade from stock. I am guessing springs for my weight(150#) and GOLD VALVES.

I need and want to keep the stock exhaust.
New Hampshire does not allow any mods to the exhaust on their trails. I like the bike now, it's very quite. But not knowing what a pipe would do, I am curious and welcome opinions.

How about reeds?

As many are scaling back on spending for now, it is not going to be an open checkbook rebuild this time, so I would to try to keep costs down where I can. Which, is not typical for me, but cost of living has gone way up and keeps rising.

So I am open to some budget minded suggestions for over the winter upgrades.

Thanks
Trackdog
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2004 KDX 200
2004 KX 125
1986 CR 125
1994 DR350
1998 VFR
2004 DUCATI S4R
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Re: Time for a new top end...what else?

Post by KDXGarage »

Damn, your bike looks good. I suggest try not to scratch it. :-) Keep it looking good.

I would suggest reading up on FRP Offroad to consider Jeff Fredette doing port work / maybe head work (not sure if he does that too).

Have you measured your sag? Are you 150 pounds or are you 150 pound with full riding gear, extra tools, parts, water backpack, etc.?

Why are your forks so high in the clamps?
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John_S
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Re: Time for a new top end...what else?

Post by John_S »

Unless you have to have more power I would keep it just like it is and freshen it up with a top end, clean kips, and new reeds. Doing the work yourself that should be less than 200 for everything including new coolant and you’re ready to go.
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Trackdog
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Re: Time for a new top end...what else?

Post by Trackdog »

KDXGarage wrote: 04:23 pm Nov 24 2022 Damn, your bike looks good. I suggest try not to scratch it. :-) Keep it looking good.

I would suggest reading up on FRP Offroad to consider Jeff Fredette doing port work / maybe head work (not sure if he does that too).

Have you measured your sag? Are you 150 pounds or are you 150 pound with full riding gear, extra tools, parts, water backpack, etc.?

Why are your forks so high in the clamps?
Not scratch it.. :grin: My buddies say the same thing about ALL my bikes.I buy and older, neglected bike, pour my heart and wallet into it, and presto! Looks like a brand new bike! Then all my friends laugh, and say, now what are you going to do with?

150#, just me, naked if you need to know that. No gear. I am just riding trails behind my house now, plan on some track days next year, maybe a J Day or two. I have not set the sag yet to be honest. I know, that's one of the first thing that need to be done. But after the winter long build, I just wanted to get a ride of two in. Then send the suspension off for a rebuild, re-valve and re-spring. I did pull the forks of and change the oil, but that's it.

As to fork height, I am vertically challenged...and I would like to be able to sit on the bike and have my feet reach the ground.
The kid I bought the bike from was short too. He installed a Kouba Link to lower the rear. I dropped the nose a bit for my comfort
I know this will effect steering, make the bike turn in a little quicker, may reduce stability on high speed straight line tracking, and the whole lowering the bike effects a bunch of other stuff.
The trails behind my house range from wide open power lines, to very tight, deep mud, littered with tree roots, single track. Being able to reach the ground with my feet is needed at times.
I am open to suggestions.

I am aware of Jeff, grew up idolizing and reading about him and Larry.
I got a couple small things from FRP. I hope he continues support fans of the KDX!
But I have a local Kawi dealer where the guy that runs the shop raced a KDX for years, and his Dad is a machinist that works there.
He suggested the port job and he can do it there.
2004 KDX 200
2004 KX 125
1986 CR 125
1994 DR350
1998 VFR
2004 DUCATI S4R
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Re: Time for a new top end...what else?

Post by KDXGarage »

After full riding gear, you may be OK. Just keep it in mind when doing the sag.

Some fresh shock oil will help it out, too.
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billie_morini
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Re: Time for a new top end...what else?

Post by billie_morini »

Track dog,
We are same weight. Best thing I did for suspension was get springs for forks & shocks for my weight. Forks & shocks received internal parts replacement & new oil. This included nitrogen charge for rear shock. Adjusted clickers and am very happy. No Gold Valves or expensive parts.

For reeds, I'm using Boysen Dual Stage. They run rich and required minor carb tuning. Most important thing to do when rebuilding carb is replace jet block o-ring.

My engine's cylinder was replated by Millineum to OEM spec. They also cleaned the power valves, gapped the rings using the piston I ordered from them, and sold me a Wössner piston and OEM caged needle bearing for piston pin. I prefer Wössner over Wiseco pistons based on road racing experience when I was younger. Wiseco had some quality control issues back then.
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Re: Time for a new top end...what else?

Post by Trackdog »

billie_morini wrote: 03:18 am Nov 28 2022 Track dog,
We are same weight. Best thing I did for suspension was get springs for forks & shocks for my weight. Forks & shocks received internal parts replacement & new oil. This included nitrogen charge for rear shock. Adjusted clickers and am very happy. No Gold Valves or expensive parts.

For reeds, I'm using Boysen Dual Stage. They run rich and required minor carb tuning. Most important thing to do when rebuilding carb is replace jet block o-ring.

My engine's cylinder was replated by Millineum to OEM spec. They also cleaned the power valves, gapped the rings using the piston I ordered from them, and sold me a Wössner piston and OEM caged needle bearing for piston pin. I prefer Wössner over Wiseco pistons based on road racing experience when I was younger. Wiseco had some quality control issues back then.
billie
Thanks for the advice billie!
I am old school, so I was thinking Wiseco. Was not aware of the QAQC issue.

I was going to run OEM on the reeds, but after some research and talking to others, I am leaning on aftermarket. How many hours on the Boyesens ? Notice a considerable difference? As long as I can retain the stock pipe I will try aftermarket.
Did you just swap out the reeds or get a new cage as well?

My bike has a Keihin PWK 35 carb. I pulled it apart and cleaned it, reset the float height, but I did not have a jet block gasket with my rebuild kit. Such an important component, why was it not in my kit?
My o3 KX 125 has a Mikuni TM, and that got a new JD jet block gasket! I was aware before hand when I rebuilt that carb as the the jet block gasket has issues. That carb got some other JD bling as well.
I will order a jet block gasket and get that done!

As far as suspension, when I got the bike, I replaced the fork oil with a 5w based on my weight, but either the springs are too light or I need a heavier oil. The forks seem to be under-sprung in stock trim. I will follow your advice and get new springs front and rear for my weight.
2004 KDX 200
2004 KX 125
1986 CR 125
1994 DR350
1998 VFR
2004 DUCATI S4R
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Re: Time for a new top end...what else?

Post by Trackdog »

FYI
I dropped those forks, way too much leg showing...not high speed stability at all!
2004 KDX 200
2004 KX 125
1986 CR 125
1994 DR350
1998 VFR
2004 DUCATI S4R
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billie_morini
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Re: Time for a new top end...what else?

Post by billie_morini »

Trackdog, you've experienced how tremendously soft the front fork springs are. They are too light for our weight. Since you changed the oil, you probably saw the long (tubing) spacer. The springs are so sad, that increasing spacer length does not remedy poor performance. Thicker oil will not help them either. Fork spring softness is partially why you experienced no high speed stability. Meanwhile, the rear spring is for riders that outweigh us by 30+ pounds. So, stock suspension is way out of balance. I now have springs on front and rear for our weight. Oil in my forks is also 5 wt. I most frequently use Maxima Racing Fork Oil (blue label). Oil in my shock is Race Tech's Ultra Slick oil in 2.5 weight. It's truly possible to feel this oil is more slippery than the Maxima I use.

In addition to re-springing the suspension for my weight, I also shortened the forks and shocks so I can solidly touch the ground. I love this!

I know, I know. It may be a Keihin thing that the jet block O-ring is an extra. But, it's important to control this variable by replacement.

The Dual Stage Boysen reeds were installed on the OEM cage. I'd read somewhere, maybe this forum, that this is adequate. I think there are 75 hours on these reeds. Ditto for new top end. I only know this because I stumbled into this bit of recorded data the other day while having another frustrating experience trying to use the TRail Tech Vapor instrument that came with my used KDX. :grin: As far as notice improvement, I cannot say. I installed the Boysen reeds pretty early on and set out to properly jet the bike. The young man I bought the bike from tried to cure bad jetting with a colder spark plug. Unbeknownst to him and me (until forum members shared a model-specific detail), is the jet block O-ring was leaking. I'd rebuilt the PKW33 carb not knowing this O-ring existed. It wasn't until the jet-block O-ring was replaced that it was possible to properly jet the carb.

All in all, I'm not out to break records or bones. Therefore, i don't seek maximum performance. Couldn't use it at this age, even if I had it. I want heaps of reliability and only a little bit of extra spiff.

About old school and pistons. Wiseco, a US company, has been manufacturing pistons for about 60 years. Wossner, a German company, has been manufacturing pistons for about 40 years. Not such a big difference when talking about forged pistons according to the quality control programs both companies has. I once lived in Germany and conducted heat transfer research in an academic institute. In relation to my work, I spent some time with engineers at Daimler and Siemens, too. I'm very confident with Wossner forged pistons. Discounting the goofballs that caused their own failures with Wiseco pistons, my road racing team partner and I saw piston failure in the mid-1990's in his 4 cylinder, 4-stroke monster engine. Some of the individual Wiseco pistons (excessively) expanded at different rates in differing dimensions. Bad things followed this behavior. We raced for many years at Laguna Seca, Sears Point, Thunderhill, Buttonwillow (in California). My racing partner also raced at Streets of Willow (CA) and the (newer) track at Pahrump (NV). After I stopped racing to work in Germany, he raced annually at Phillip Island (Oz). Point to this information, is we weren't hacks. We were careful about what we ordered and built. While Wiseco bit my racing partner, I didn't suffer the same disasters in my heavily hopped up 2 cylinder, 2-stroke engine that was built with Wiseco. I'm sure in a KDX, Wiseco is absolutely fine. I simply developed a distaste for Wiseco and was also exposed to some different stuff when living & working on the Continent.
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Re: Time for a new top end...what else?

Post by Trackdog »

Hey billie,
Thanks for the details!!!
Is it the KDX that attracts such a nice group of people?!?
I would like to think so.
My experience here and elsewhere with respect to the KDX has been overwhelming!
It was the bike of my dreams when I was a teenager(in the 80's). I finally make the money to afford the things I have always wanted and chatting with like minded folks has been worth the wait.
Thank you KDXRIDER!
2004 KDX 200
2004 KX 125
1986 CR 125
1994 DR350
1998 VFR
2004 DUCATI S4R
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Re: Time for a new top end...what else?

Post by Trackdog »

attached is some gratuitous pics from my past for billie. This when I was in my 40's and at my fighting weight of 130#
The good ole days!
Coincidentally, this is when I was in the best shape of my life...minus the copious amount of beer consumption.
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2004 KDX 200
2004 KX 125
1986 CR 125
1994 DR350
1998 VFR
2004 DUCATI S4R
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Re: Time for a new top end...what else?

Post by MoonStomper »

Beer is GOOD for your health and don’t forget it!

… sweet road racing pix, always wanted to try that.
~^~^~^~^~^~^~^~^~^~^~^~^~^~^~^~^~^~^~^~
Let the good times ROLL!!!!!!!!!!!!!!!!
‘99 KDX 220 / '03 KDX 200 - @%@ '18 Trek Slash 8 @%@ ‘22 Rieju MR300 Racing

BLACKSBURG, VIRGINIA USA
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billie_morini
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Re: Time for a new top end...what else?

Post by billie_morini »

TRACKDOG IS MY NEW TRACK HERO!

Muy gratuity for sharing fab fotos!
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