PLEASE help me with my acceleration problems.

19Brendan81

Member
Mar 6, 2005
153
0
Hello All,

I have just had my bike looked at by the local mechanic and he isnt sure whats going on with it. Its doing two things wrong, first if you put it in neutral and hold the throttle wide open, it wont rev out. It revs right up, probably to 6000rpm but then its like its on a rev limiter, and it cuts in and out, but the revs arent dropping much in between this happening (the cutting in and out) Secondly, decent acceleration from idle to just before powerband is a non event. Sometimes this continues into band, but generally band is good…nice and loud and pulls hard. Strangely enough power and torque before band are still fine, but it just wont rev up quickly enough for it to pull the front wheel up. This is really my main concern, I don’t really care that it wont free rev until it explodes.

As I said, power seems fine, for instance on the weekend I was riding it in the mountains near where I live and I was able to tow my cousin on his WR400 up a long hill (not really steep but it would **** you if you had to walk up it) BEFORE the bike came into band, I could accelerate and decelerate as necessary without having to clutch it (1st gear). Later, I dinked my cousin up a long (1km) properly steep hill, (low range 4wd) just into power band, ½ throttle,…again, no worries.

The bike has….
-Brand new 1 week old KIPS valves….less than an hours use.
-6 month old piston and rings with hardly any hours on them, less than 10 hours from me and according to the guy I bought it off even less from him.
-good compression
-brand new plug
-aftermarket reeds (not sure which brand)
-Stock Pipe but gutted.

The mechanic says the Jets are all stock (122 main and 45 pilot sound correct for a 1991 model???) and that the reeds were not closing properly but he has since reversed them and they are now. The bore sleeve/nickel plating is VERY tired…and has some hairline cracks between a couple of the ports, but I am not convinced these would be causing the significant low RPM acceleration probs that I am having.

For the love of god please help me with this damn dirt bike before I do something desperate. :(

P.S Sorry for the long post but I really am at the end of my tether. :bang:
 

Benesesso

Member
May 11, 2005
30
0
Try regapping the spark plug down to ~.018 or so. My 1986 just would not fire past 1/2 throttle opening until I did that. Guess my ignition system is getting weak.
 

04kdx200

Member
Mar 30, 2005
209
0
All the above, plus get a spark arrestor with packing in it. Loud does not mean more power. A straight flow "muffler" will not help anything in the low rpm's.
 

G. Gearloose

Pigment of ur imagination
Jul 24, 2000
709
0
First the airbox lid must be modifed for more air else any jetting is futile, but can the 122 before you frag it.
 

TriniG

Member
Feb 5, 2002
69
0
Wait, hold on. Your bike is in the Australian market, not US. Right? Gearloose is suggesting changing the main, but that is dependant on the size Carb you got. Both my KDXs (220 and 200) are Japan domestic market that, believe it or not, come with 29mm carbs with 123/124 mains and 45 pilot. Most threads about jetting in this forum are US Market with larger 35/36mmcarbs that use 155 main jets. So before you go changing jets, make sure what carb you got that has size appropriate jets. Both my bikes are a little rich with 123/124 mains.
 

19Brendan81

Member
Mar 6, 2005
153
0
Yeah It has got a small carb on it. The KIPS weren't timed correctly, but I dont think they will be whats causing this problem. Im more concerned about the state of the Cylinder, I pulled it off yesterday to get the KIPS timed correctly, and its in a S$%# state. The Plating is worn through down the bottom and there are a couple of fine cracks between the exhaust ports. Again, I dont think would be the sole problem but it has to be contributing. Any ideas on what a Fredette 225cc big bore kit is goin to cost me?? (American Dollars will be fine).

Thanks for the suggestions so far guys, and thanks in advance for any more that come.
 
Top Bottom