1989 Yamaha Exciter 570 wot Bog

[gintstone]

Hi everyone, Im a new member, gald to have finally registered. Anyways I got a 1989 yamaha exciter (38mm round slide mik's) for $400, bought a DG pipe (used for $50) jetted it 2 sizes up (was 320 now is 340 main jet) Needle is a 6DH7 on the 3rd clip position. The fuel/air screw is out 1 turn. The sled idles nice at 2000rpm and the sled runs good, except for a slight bog at wot from the midrange speed. From a dead start I can give it wot with snappy throttle response, but from the midrange to wot thats when the bog happens. I can feather the throttle through the rpm's and get the exciter to respond to wot better; either that or gas and let off, gas and let off, and also that seems to help me achieve a better wot response.
I mean, It's a beast from dead stop to wot, but then at about 40mph, it begins to bog a little until I pump the throttle. If I feather the throttle, without snapping it wide open, the exciter seems really crisp and screams, but if I hold it wot from dead stop it will go great till about 40mph, then it bogs just a bit.
I am wondering if I should get a set of exciter II needles (6FL82) and try them, or if I should just go with a pair of 330 jets. Maybe it's the floats, I set them to 18mm (eyeballed it), but decided to try to lower the fuel level to see if it alleviated the bog issue( which it didn't, only thing that helped was cleaning the needle valve and adjusting the air/fuel mixture screw) Any thoughts? Thx guys.

 

[luv 455]

Since it's the mid range i would raise the needles 1 notch witch will fatten up the mid and see if that helps. You could be a little lean in the mid.

 

[dsc577]

did it run fine with the stock pipe?are the power jets blocked off?is it a 2 piece dg,i have a rpc setup for the 2 piece pipe,pilot-45,needles-6dh4,needle jet-166-q6,needle clip 3,air screw 3/4 turn,power jet blocked off,main jet screwed directly into needle jet,
i am runnin 6fl82's with 166-q6 with my psi pipe,42.5 pilots
main jets may be a little big for a stock motor,rpc says lh320 rh 330

 

[gintstone]

it's hard to say if it rode better, seeing how I ended up getting the sled in the fall, no snow to really test it out on, got the DG pipe and installed it BEFORE I even got to take it out for the first time. I still have the stock pipe, gonna gut it and maybe put it back on. I took my seconday off today and cleaned it and found one of the helix buttons was missing, and the setting was on A-1, the setting with the least pressure. And yes power jets are deleted, along with tors. Looks like a 2 part pipe, http://dgperformance.com/models.php?modelID=162 there is a pic of it brand new.

 

[gintstone]

thx luv 455, I'll give the needles a try next, but first I gotta put the secondary back on with them new buttons and try it out. EXCITED

 

[Lasse]

I got a 1989 Yamaha Exciter-I .
Main Jet : 340
Needle : 6DH7 on the 3rd clip position.
Air screw : 1.0 turn out.
The sled idles nice at 2000rpm and the sled runs good,
except for a slight bog at wot from the midrange speed.
From a dead start I can give it wot with snappy throttle response,
but from the midrange to wot thats when the bog happens.
I am wondering if I should get a set of Exciter-II needles (6FL82) and try them, or if I should just go with a pair of 330 jets.

The Exciter-I is known to have a lean spot in the midrange that can cause burn downs.
The factory sent out a service bulletin* about this,
containing a new carb set up and deleting of the power jet system
*Se below --->

Just picked up an EX-570 ( 1988 ).
My research tells me that the jetting on these was somewhat of a disaster.
I will make sure the Power jet is disabled.
I'm open to any and all advice.
I'm also going to modify the air box.
Looks like a poor design even for then.
Say what you will, but I think I can get it to run more consistently.

Any other tricks or tips on these sleds.
I'm interested in anything.... cooling, suspension, jetting or whatever you have found to work.

1. Clean up among all the funky fuel and oil lines that Yamaha put on these sleds.
Delete the whole Oil Injection system including the oil pump.
Run 1:40 premix instead.

2. Completly disconnect the warming system to the carburettors.

3. Disconnect the T.O.R.S.-system from the carburettors.
remove all the powerjet function and parts from the carburretors.

4. Jetting:
Updated Yamaha Factory jetting for the Yamaha Exciter-I ( 87 / 88 / 89 / 90 )
Pilot jet : 40
Main jet : 320
Air screw : 1.0 turn out ( +-½ Turn )
Slide : 3.0
Needle jet : 480 P-6
Needle : 6FL68 ( Yamaha part # 239-14116-68-00 )
( And of course all the things regarding the "Power Jet" system is deleted ! )

5. Set the engine idle speed to 1600-1800 Rpm

6. Seconary clutch:
Secondary spring : WHITE
Secondary setting : A-2
Helix angle : 45 Degr.
Helix pre tension : 50 degr.