Need Help! Tuning issue 98 KDX200

[zepplin153]

WHAT IS GOING ON??????

I rebuilt my 98 KDX 200.

It idles fine
Low end feels ok
As soon as the power band starts to kick engine runs like crap.
It wont rev on out and power sucks

Please help me trouble shoot this.

Quick reference edits (below is info added after my original post):

I update here to save reading all posts. So, use this as a quick reference. But, if you read the entire post there are many great tips if your problem sounds like mine.

- my major problem was the power valves and jetting issues, but the major thing was the power valves. They were in backwards..... Thanks to the backwards manual. *note* the sub valve with the groove near the top of the shaft actually goes on the right along with the sub valve actuating rod that has the o-ring on it. they both go together on the right side as if your were sitting on the bike. (The manual actually says the sub valve with the groove goes on the left, that is wrong).

- Do not chemical dip the kdx carb. They have a hidden o ring on the jet block which will loose its seal if you dip. I found several others which claimed same problem as me. Carb ran like it was rich and they could not jet it away.

- found the jet block o-ring from http://www.sudco.com for $5.00. they have a minimum order of $25.00 or a $5.00 handling fee. Part number is 021-532. BTW it is like 4 seals all conjoined as one thing so that one part will cover you.

- for me, in tennessee, after a rebuild involving boreing and replating, rejetting my carb solved the rest of my problems. I am running 45/155 with the needle clip on the second from top groove.

- The posts here were very helpful and ultimately the path to a solution and a ride-able bike.

[Julien D]

When you bored it, what did you bore it to? What piston did you install?

What is meant by "a little rich with oil"? What ratio are you running, and with what oil?

Sure sounds like a power valve issue. If you remove the pipe and the actuating gear paw thingie, you can operate the valves by hand and observe through the exhaust port the movement of the KIPS valves. At full open, everything should be.. well, fully open.

Sometimes when a clapped out engine is rebuilt, the jetting may have been set for clapped out mode. It could be that your main jet is entirely too rich and needs to be changed. So there's another possibility.

[Varmint]

Are you sure you aligned the KIPS paw gear correctly? Were you sure the support the shaft when you removed the left-handed threaded nut? If you snapped that during disassembly, the PV system will not open causing the symptoms you are experiencing.

[zepplin153]

When you bored it, what did you bore it to? What piston did you install?

What is meant by "a little rich with oil"? What ratio are you running, and with what oil?

Sure sounds like a power valve issue. If you remove the pipe and the actuating gear paw thingie, you can operate the valves by hand and observe through the exhaust port the movement of the KIPS valves. At full open, everything should be.. well, fully open.

Sometimes when a clapped out engine is rebuilt, the jetting may have been set for clapped out mode. It could be that your main jet is entirely too rich and needs to be changed. So there's another possibility.

-bore: not sure would have to ask the place where i had it done. I installed the piston they recommended with the cylinder, but, again I would have to ask exact size. Would a different bore have that effect or need different jetting?

- A little rich: Manual calls for 32:1 I have a 2.5 gal gas can so 10oz is 32:1 i put 12oz so like 29or30:1

- Power valve issue: I rebuilt this thing from the inside out. Before I started putting cylinder back on bottom end I triple checked the Power valves timing and function. I dont know what else I could do to them. To answer your question, yes I could see the valve open completely.

- Jetting: I am not sure if the jets have been messed with at all or not it is used. "160" is on the main jet. If the main jet is too rich, would it run like crap throughout the entire power range or just in the top end like that? BTW what is "clapped out?" What other symptoms would i need to listen for if its jetting?

if it is the valves.... what am I looking for? It seemed to be in perfect working order and timing was set..

Thanks so much for you input. I am stummped

[zepplin153]

Are you sure you aligned the KIPS paw gear correctly? Were you sure the support the shaft when you removed the left-handed threaded nut? If you snapped that during disassembly, the PV system will not open causing the symptoms you are experiencing.

I dont fully understand what you mean here. Please explain more (sorry). I did not bend the shaft if thats what you mean. Also, I did not snap the nut. It all seemed to work great before I finished the rest of the engine. Smooth action.

- If it is the valves what should I look for?

[rbates9]

- no clamp for where the carb connects to cylinder intake

This is most likely not your problem but it will be shortly if you don't address it.

From the sounds of it you have not done any jetting to this bike. There is a jetting guide in the jets and needles section. Use it.

On the left side of the cylinder there is a round slotted cover for the KIPS. Remove that cover and start the bike, rev it up (you will need to rev the bike up past 5000 - 6000 RPMs to see it move) and watch for the shaft to move. If it does not then the KIPS is not working.

I would start with these things and go from there.

[zepplin153]

- no clamp for where the carb connects to cylinder intake

This is most likely not your problem but it will be shortly if you don't address it.

From the sounds of it you have not done any jetting to this bike. There is a jetting guide in the jets and needles section. Use it.

On the left side of the cylinder there is a round slotted cover for the KIPS. Remove that cover and start the bike, rev it up (you will need to rev the bike up past 5000 - 6000 RPMs to see it move) and watch for the shaft to move. If it does not then the KIPS is not working.

I would start with these things and go from there.

Clamp: I ordered a new one. should be here thurs.
Jetting: worked great before The rebuild: would having my cylinder replated make enough difference to need new jetting?
Kips Cover: I will try this... I know the cover you speak of very well. It has new piston and rings... will it be ok to rev that high yet?

Thanks for the feedback

[rbates9]

will it be ok to rev that high yet?

My break in process involves starting the bike, letting it warm up with a few blips of the throttle to keep it cleared out, check for leaks, shut it down, check levels, ride as normal.

I personally think that the "break in process" is way over rated. I am a heavy equipment mechanic, I have rebuilt many diesels that get the same treatment as described above and live a long happy life. To each there own but I just can't bring my self to taking the time to "season" an engine. What do you think is going to happen with a long drawn out break in process that won't happen with just normal riding?

[zepplin153]

- no clamp for where the carb connects to cylinder intake

This is most likely not your problem but it will be shortly if you don't address it.

From the sounds of it you have not done any jetting to this bike. There is a jetting guide in the jets and needles section. Use it.

On the left side of the cylinder there is a round slotted cover for the KIPS. Remove that cover and start the bike, rev it up (you will need to rev the bike up past 5000 - 6000 RPMs to see it move) and watch for the shaft to move. If it does not then the KIPS is not working.

I would start with these things and go from there.

DID THE KIPS TEST. They open just fine. It looks normal when under no load. Once i get on the bike, at the point they should open they don't (as i watched while riding). Please tell me this is a carb thing.

[rbates9]

The kips is a rpm related part. If it works when sitting still it should work while your riding it as well.

[zepplin153]

The kips is a rpm related part. If it works when sitting still it should work while your riding it as well.

Only when the engine has a load, like When I am riding, the power band never comes, therefore not enough RPMs to open the valves. Do you think this means there is not the right fuel getting to the engine?

Or, would it act like this if the power valves, or sub valves, are not timed correctly?

[Julien D]

Incorrectly timed valves could cause it, yes. If you have no luck resolving, and aren't sure about your kips timing, you can post up a pic through the exhaust showing valves open/closed and someone can tell you.

Also, that 160 main jet is likely to be way too big. 155 might be a better starting point.

[KarlP]

How much time is on this rebuild?

A freshly replaced piston/plated cylinder will often not rev out right away. Don't push it too hard to do so.

160 does sound big.

[scheckaet]

160 is big.
Read on the jetting guide in the jet and needle section.
the main has the most effect at wot.
if the kips actuates when you rev the engine then your kips is ok (whether you stand still or ride), the timing could be off.
FYI the manual has the left and right sub-valve wrong, they show the right on the left and vice versa.

[zepplin153]

160 is big.
Read on the jetting guide in the jet and needle section.
the main has the most effect at wot.
if the kips actuates when you rev the engine then your kips is ok (whether you stand still or ride), the timing could be off.
FYI the manual has the left and right sub-valve wrong, they show the right on the left and vice versa.

Wrong?!?!?! Are you kidding me? It says how to identify them my their markings. Is that the section that is wrong? or is the diagram wrong?

BTW 160 is stock for my year. My dealer only has 150 avail for now. I would have to order 155. any input.

Thanks for sharing. I know its got to be something simple like this.

[scheckaet]

depending on which manual you got i forgot to add.
if you install them and use common sense ( with or without a book) you will see if it works the way it should.
I'll see if i can take some pics tonight of my cylinder with the subvalve correctly installed.

"160 is stock for my year" doesn't mean it's right for your bike and your riding conditions

[Julien D]

I would not advise dropping all the way down to a 150. 155 is safe for most people, you could end up going as small as 150, but you want to be sure and do some plug chops to make sure its not too lean. See the jetting sticky in jets and needles.

[zepplin153]

I have printed the jetting thing. I plan on trying those checks tonight. I will let you know what I come up with later tonight or tomorrow.

[KarlP]

If it won't rev out cleanly you'll have a hard time following that jetting procedure.

Patience, man! I think that fresh rebuild may need a little more running time before it will rev out. You did not say how much time you've got on it since the rebuild.

[zepplin153]

If it won't rev out cleanly you'll have a hard time following that jetting procedure.

Patience, man! I think that fresh rebuild may need a little more running time before it will rev out. You did not say how much time you've got on it since the rebuild.

I have had maybe an hour on it since first cranked. I read you suggestion about it not reving out because of how fresh it is but you are the first person I have ever heard say that. Not saying it doesn't happen but is this really a likely possibility? By the way, I mean no disrespect by questioning your idea. In fact I am quite grateful you have taken the time to share it. Its just a first. Neither myself nor others I know have heard of this. I was actually so intrigued with the notion that I called a bunch of my buds after you posted that to share it with them.

I hear you on the patience thing man! Its hard. It took me nearly a year to get it to this point and to be so close makes me insane.

I have a brief story about the bike that is kind of funny. check it out if you have nothing better to do:
http://kdxrider.net/forums/viewtopic.php?f=100&t=12403