Ok I have an o1 ds 650 and for the last month or so It has bee running like sh**. So I figured ok its time for a good tune up. So I removed the carb and cleaned it up put it back on and same thing. Next I pulled the valve cover and did the valve clearance check all was in spec yet which I couldnt beleive. so put it back together and also changed oil. So Im still stuck with a shitty running machine, dont know why. So then I bought a dynojet kit and rejetted and DJ needle and still the exact thing. So does anybody have any suggestions.
Here are the symptons. Starts and idles ok. but when it is warmig up the engine will like kinda stumble or stall for a splite second but not die out almost like a small backfirs in the carb or something, not quite sure. Next when I drive it it does not have as much power as it should kind of doggy. Then when it gets to 5 grand or so it really starts to stumble an dogg way down. Help me Please.

 

you might want to check compression and your spark plug as well

 

Do I have todo anything different than doing a compression test on a car. I have a snap-on compression tester. I heard from someone that I have to do something to disable the compresion release valve or something along those lines. Also what should the compression be? Dry? and Wet test?

 

fdl just an idea i came across on mine the boot between the carb and intake dry rots and gets brittle. ??? do you have a ground to motor. from what ive read the early models have ground problems.

 

I am not sure the test methods on a atv i would think they would be about the same as on a car but don't qoute me on that one. and as for the compression i am not sure maybe some other guys on here might be able to tell you.

 

I think its 185 psi cranking omr(oldmanracing) would know more on this he can break it down more.

 

is the problem intermitant or consistant.? check comp when cold , and after warmed up. also when changing plugs check spark from both coil's, i'v seen coil's go bad on other machines and work until warm. if it misses when warmed up, and comp is down , only when warm, if you are going to rering ect. also have a valve job done, just in case your valve isnt sealing when hot .
for testing spray wd 40 around the boot and the intake where it meats the head. if the idle jumps or stalls one is bad boot or intake gaskets , not saying that is your problem. and just add a ground or two, to be safe , it wont hurt. just to rule out the basics , make sure your pet **** is't partaly cloged. limiting flow. last read your plugs , what are they saying, lean, rich ,water, ect. i would put your carb back exactly like it wasw until you find the prob, then tune it with a jet kit, your carb was adjusted for the temp, and running right befor i assume. i am not a ds expert. but this should get you started. and i'm also curious to know what omr think's
he seem's to know the machine well . good luck .

 

I had added a few grounds last year when I had trouble with the CDI getting fried. Then all was good upuntill now, so yea grounds are good. the carb diaphram was good I did all that basic stuff and now rechecked and all seems good. But Ill try the other suggestions.
Thanks

 

My recommendations:
#1 Needle Assembly
DJ Third groove down from the top of needle.
Below clip - white washer and at bottom thick washer
Above clip - thin washer
When installing make sure small spring goes over end of needle.

#2 Good plugs
Boot that goes over the end of plug stem must hold plug firmly.
Take off boots from plugs and with a spare plug check for tightness
If plug falls off with a very small shake - plug holder is worn out.
To replace - with flat screwdriver - the inserts screw out. Be careful, there is a floater behind holder. Looks like a small round fuse.
Reinspect and try again to install over a plug, you should be able to tell if it is in need of replacement. Very little drag when worn.

Try these 2 recommendations and let me know the outcome.

OMR

 

I will definately try these out thanks.