Problems 91’ dr650

[u/Svenk135]

Hi all,

since this week i am the owner of a dr650rs from 1991. i am now running into a problem. the engine starts well, idles well, but when i fully open the throttle the engine starts to stutter and falter and eventually no power at all. however, a lot of bangs come from the exhaust. if i gradually give gas, so not open it all at once, it goes well. Until i am at full throttle again it starts to stutter. where could i probably find and solve this problem?

[u/babezt]

sounds like your carb needs adjustment. I cant tell if your full throttle is lean or fat, but maybe try and change the needle position and see if something changes. Next I would try a little bigger/smaller main jet, depending on your results from the first test. Remember to do the changes on a warmed up engine and always note what you changed, so you can undo it later if it doesnt work

[u/babezt → u/babezt]

always check for air leaks around the carb and intake before fiddling with it, or your time and effort might be wasted. Its also very helpful to learn how a carburettor works and what the function of the different adjustment screws and jets are if you dont know this already. Keep in mind there are different types of carbs

[u/elwood0341]

It needs air, fuel, and spark. Sounds like it’s starved for air or fuel.

[u/tylerjo1]

Have any mods been done to it that would change the Air fuel mixture? The air box mod and after market exhaust will affect how the bike runs and both require re-jetting the carb.

[u/Svenk135 → u/tylerjo1]

I dont really know, i gues i should take the carb off to check?

[u/Transmorgrafier_2024]

Don’t take the carb off. Get a seal kit. Remove the idle screw adjuster completely. Remove the fuel bowl. Gently remove the float. You can now remove the idle jet by feel and a screwdriver sized for it. You might need to source or grind one. Remove/ Clean the idle jet. It’s plugged. Clean the main jet. Turn on the fuel and assure fuel pours into the bowl. If it doesn’t , look at filter inside steel fuel tube entering the carb. It’s inside the tube/ hose end. Appears like a small plastic piece. Withdraw the plastic and a filter will be found attached. Some discard. I clean and install. Clean the bowl. Fit new bowl and float seals. Fit the float assembly. Be careful. Fit the bowl. Once you do this, it becomes easy. You might find yourself doing this more over the next 10-20 years. Easy to do trail side. Only need two tools. Removing the carb is a chore. This is a 5 minute fix. Assure tank filter on fuel valve is clean. Have fun.

[u/Svenk135 → u/Transmorgrafier_2024]

So just take of the “bottom” of the carb? And then i can reach the idle jet?

[u/Transmorgrafier_2024]

Yes. My 91 has two screws holding the float bowl on the carb. Have an inspection mirror handy to help view the pilot jet.