Stock silencer on 1990 KDX200 OK?

Marsh · Mar 25, 2004

1990 KDX 200 with FMF gold series pipe, stock silencer, boyseen reeds, air box lid removed, clean oiled UNI filter, and extensive porting.

I have been wondering if the stock silencer in this combination could be a problem. Should I spend the $ and get an aftermarket unit.

Pros, cons please. I am trying to tune this thing in. I bought it last month and it does not run like it should. I am tuning the carb up right now and I am hoping the port job was not done poorly.

Another question: What effects will I feel if the port job is done wrong? Right now all I can see is the intake runner is hogged way out and smoothed considerably. Makes me nervous.

Thanks.

G. Gearloose · Mar 25, 2004

Who did the port work? A hacker or reputible shop?
Where is it missing power?
What are your jets, needle?
Have you replaced the packing in the center section? It wraps around the perferated core, only about 3" wide.
Do you have any compression numbers?

I don't think the stock silencer hold it back any.

Marsh · Mar 25, 2004

The porting was done by someone I did not know personally but he does ride a bit. He is not a pro bike machinist though.

The bike doesn't idle well. I need to set it to rev quite high and every now and then it will still fall off and stall.
There is a flat spot from closed throttle to 1/2 when in the low gears when you crack it fast.
WOT is sputtery with little power. It does not have much power up there.
Overall the bike is not impressive at all. I rode my buddy's 2003 220 and wholey carp, that thing is a rocket compared to this. It was like comparing a diesel VW jetta to a corvette. Really!

Anyway. I am hoping the porting is not the problem but I have long road to tell. With all the mods mentioned the bike still has it's original jetting: 48 pilot, 150 main, 1172 needle in the 2nd from bottom position and a #6 slide.

Last night I installed a 155 main and a 1173 needle in the middle position and hope to test things out tonight after work.

Thanks for the reply, hopfully this will shed more light on things.

The silencer. So I can repack the centre section of the stocker? How do I get to it?

Thanks.
Marsh.

G. Gearloose · Mar 25, 2004

That needle, clip, with that pilot sounds fat from idle through mid.

One more thing, is the airbox uncorked?
If not, even the 150 could be fat at rpm, and lean at low rpm, giving you fits.
Uncork the airbox (if applicable) and try the 155.

Sounds like you needed jetting before 'hogging' out the jug.

The silencer disassembles easily, just take all the bolts off it, the internals might be gummed in, but it should all slide apart, out the rear.

The porting thrown in a big fat wildcard into the mix.

fuzzy · Mar 25, 2004

I don't think the stockers use packing?.....At least I've enver touched one due to this assumpion.... :think:

G. Gearloose · Mar 25, 2004

I found a 3x6" +/- piece in mine, relpace it occasionally, I could hear the difference when it got spooge-saturated. Fixed the spooge since, of course.

Marsh · Mar 25, 2004

What is meant by "is the airbox uncorked"???????????

Not sure.

Also. What are the tell-tale signs of rich or lean as far as feel. I can read the plugs well enough but I am interested what is felt in each situation.

Also. These bikes like the B8ES and B9ES plugs. Yes?

Thanks folks

Marsh..

G. Gearloose · Mar 25, 2004

They tend to like the b8es when jetted right, b7es can cause preignition, and B9ES when flogging the bike hard in the sand of on the ice.

The airbox lid should have the snorkle removed and 5-6 1/2" holes drilled the the lid, minimum, else excessive vacuum in the airbox causes the jetting to go rich at high RPM, the equivelent of 2 to 3 jet steps. Jetting down for that condition makes it dangerously lean at lower rpm, a bad mix and fustrating performance result.

jssport · Mar 25, 2004

stock silencer mod

I don't think your problem lies with the silencer.

I modified my 90 stock silencer and I'm very happy with it. I just cut out the middle pipe cross section reaasembled it, no packing... works great, not too loud, spark arrestor intact and working.

It's just a straighter, more direct route out.

CaptainObvious · Mar 25, 2004

jssport said:
I don't think your problem lies with the silencer.

I modified my 90 stock silencer and I'm very happy with it. I just cut out the middle pipe cross section reaasembled it, no packing... works great, not too loud, spark arrestor intact and working.

It's just a straighter, more direct route out.

I did the dame thing, but I shortened it by 5 inches at the same time by removing the entire reverse flow section and cutting the shell with a saw.

rethnal · Mar 25, 2004

The stock silencer doesn't present any adverse effects at all except weight and I for one like having a spark arrester on the bike.
And as someone said one time "If your that concerned about weight... go on a diet"

Stock silencer on 1990 KDX200 OK?

Marsh

G. Gearloose

Pigment of ur imagination

Marsh

G. Gearloose

Pigment of ur imagination

fuzzy

G. Gearloose

Pigment of ur imagination

Marsh

G. Gearloose

Pigment of ur imagination

jssport

CaptainObvious

Formally known as RV6Junkie

rethnal

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