My KDX is running great except it has a slight bog (booaa) when running at about 1/8 throttle and then suddenly yanking it open. It quickly recovers, just hesitates for a short moment. I have tried everything with jetting, now sitting with needle mid pos, 158 main and 45 pilot air screw 2 turns out. Temp about 28 deg celsius, elev 1300m. I have tried 42 pilot , needle 2nd from top and down to 155 mains and back up to 160. Is this slight hesitation normal.
Slight bog
- Thread starter Hoffies
- Start date
Yep, that's pretty normal. The sudden blast of air when snap the throttle WFO is leaning it out, then the fuel follows and evens things up and off you go. Roll on the throttle.
You might try leaving all else alone and running the air screw in to about 1/2 turn and see what difference that makes. But if you get it rich enough to get rid of that bog, you might find it blubbery at cruising speeds.
The only other thing I would check for is an air leak. Not likely if you say everything else is great, but it's still possible.
You might try a different needle if you're still on the stocker. CEL/DEL are a good bet for an H series bike. I'm using a CGK in my E series. These needles are all much richer off-idle and should help.
You might try leaving all else alone and running the air screw in to about 1/2 turn and see what difference that makes. But if you get it rich enough to get rid of that bog, you might find it blubbery at cruising speeds.
The only other thing I would check for is an air leak. Not likely if you say everything else is great, but it's still possible.
You might try a different needle if you're still on the stocker. CEL/DEL are a good bet for an H series bike. I'm using a CGK in my E series. These needles are all much richer off-idle and should help.
When was the last time the reeds and silencer packing was inspected/changed? Have you tried the choke to confirm its a rich or lean bog? Vintage Bob
dirt bike dave
Sponsoring Member
- May 3, 2000
- 5,348
- 3
It's a small displacement bike with a carb full of compromises, not an EFI 450.
Totally normal to get a short bog if you whack the throttle open from 1/8 to WFO.
No use trying to jet it away. Any improvement is likely to cause other problems elsewhere, IMO.
Rolling on the throttle and giving the cluch a quick stab to build up revs is going to get you all there is to get out of 200cc of 20+ year old technology.
Totally normal to get a short bog if you whack the throttle open from 1/8 to WFO.
No use trying to jet it away. Any improvement is likely to cause other problems elsewhere, IMO.
Rolling on the throttle and giving the cluch a quick stab to build up revs is going to get you all there is to get out of 200cc of 20+ year old technology.
dirt bike dave said:
There you go making sense again Dave. ;)
Mmmhmm, makes perfect sense. But I have to disagree, as usual. A proper keihin needle and methodical jetting = no off-idle bog. The stock kawi 1173 needle is crap and belongs in the waste bin.
With proper tuning and perhaps a little modding there is PLENTY more to be had from that 200cc motor :).
J.
With proper tuning and perhaps a little modding there is PLENTY more to be had from that 200cc motor :).
J.
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Is the air box and silencer stock? Does the bike still have the oem throttle? A quick turn throttle can make any trail bike bog. Everything you can do to make that trail bike run better/modded, will likely shorten the service time also. Except normal jetting! An mx 250 top end shows replacement at 3 races, or 7.5 hours. What is the stock KDX200 schedule? That is how much range it can be modded?
- Thread starter
- #11
I thought it may be the case as I have spent many hours trying to get rid of this short bog, I never noticed it in fact, have had the bike 4 years(since new), untill I did very tight cornered trail, with no high speed stuff and chasing friend on quad. Ive cleaned carb, tried higher octane fuel, jetted all jetting/needle/air screw up and down, replaced muffler material, short bog persists. Apart from that, the bike is really enjoyable to ride. Like the KDX rattle, seems like this slight bog/hesitation is part of the KDX? With no accellerator pump I suppose it is expected?
I would try the needle, what the heck? And raising the compression/head mods will shorten the engine life.
whenfoxforks-ruled said:
Yeah, most the kdx200/220 head mods are more to clean up and improve the squish than adding compression. Of course you could opt for high compression if you like, but most the time this would require race fuel.
What year is this KDX?
The KDX is a trailbike, it runs on regular gas. Turning this into an mx bike is what a lot are basically doing with their mods, whether they realize this or not. A lot are old mx bar room theories, shot to hell a long time ago. This bike is so basic, changing the grips can seem like a mod. The head, between stock and race gas has plenty of room for changes, and run on premium. It can probably be reshaped and keep the CC's the same? But, dropping a few CC's will make a huge difference in the throttle. And taking an MX race bike, to the trails, detune it like a KDX. Dropping the oil ratio in the name of spooge is backward engineering! Doesn't JD have a grab bag of needles and jets for this model?
He does. I can tell you of my experience with squish band mods on my 200. Better throttle control, slightly more power everywhere, still running premium pump gas. For what I spent on it, it was well worth it. It did not make the bike more "mx like", but rather more controllable and with more grunt and more over-rev.
I have done a good many mods on my KDX, and ALL of them are geared towards aggressive woods riding, not MX. I think stating that modding a trail bike makes it an MX bike is too general, although I do see where you are coming from.
As always, strongly agreed on the point of spooge as related to oil ratio.
I have done a good many mods on my KDX, and ALL of them are geared towards aggressive woods riding, not MX. I think stating that modding a trail bike makes it an MX bike is too general, although I do see where you are coming from.
As always, strongly agreed on the point of spooge as related to oil ratio.
reepicheep
Member
- Apr 3, 2009
- 670
- 2
Ditto Julien for the Eric Gorr "more better everywhere" mod for my 225 setup. Lost nowhere, gained everywhere, runs great on normal premium. I mix it between 32:1 and 40:1 depending on how good the oil is. Haven't noticed a difference beyond that the Klotz smells the best. :)
