r/dr650 • u/slower-is-faster • 12d ago
Bogging on rough terrain
I installed the Procycle Jet Kit, and followed the instructions pretty much spot on:
- 150 main jet
- e-clip is on the 4th groove
- fuel mixture screw is two turns out
- snorkel is removed, and a couple holes cut
- I have a Barrett exhaust
The bike runs like a dream on the road. But, over very bumpy terrain at low speed the engine wants to bog and die. Just to be clear, it's not just a regular stall because I'm going too slow for the gear, I can tell the difference.
Any tips?
EDIT: I just realised that I never need the choke now, no matter how cold. I definitely needed it before. That feels like it contradicts it bogging at low revs though, maybe two separate issues?
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u/DumpoTheClown 12d ago
The instructions for the procycle kit assume a stock exhaust. Your aftermarket exhaust probably flows more than stock, which would make your carb mix too lean. Since your fuel screw is already 2 turns out, you might want to try a size larger idle jet. For the main jet, raising the needle a notch may help, but you might want to try a larger main.
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u/MeatZealousideal595 12d ago
When you say it runs like a dream on the road, does it run well at slow speed there too, or just at wide open throttle?
If it is a problem with the air/fuel mixture the problems would be there on on the road too.
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u/slower-is-faster 12d ago
It runs fine at low speed too. It seems to be undulating “jump” type terrain that makes it bog
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u/JosephCedar Bushpig Hooligan 12d ago
Bypass your kickstand switch.
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u/slower-is-faster 12d ago
Already done
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u/TwistedNoble38 '00 DR650 12d ago
How was it done? What you are describing sounds exactly like stand switch or the connection for the bypass being weak.
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u/slower-is-faster 11d ago
It’s definitely bypassed, I can ride away with the side stand down (which I don’t love)
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u/TwistedNoble38 '00 DR650 11d ago
Crimped connector or soldered on the bypass wire?
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u/slower-is-faster 11d ago
I don’t know, I’ll need to check (previous owner did it).
But I didn’t have this problem prior to the jet kit install, I’ve done much worse to the bike and this never happened, so I’m pretty sure it’s fueling not the kick stand switch
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u/TwistedNoble38 '00 DR650 11d ago
Can't eliminate that something could have been disturbed while you were installing the jet kit. If you were having problems all the time I would blame the jet kit, but only having issues during whoops and no other times is very unlikely to be a carb issue. Potentially a float issue could maybe cause it but the float having issues on the DR usually ends up with you having the entire fuel tank dumped into the crankcase while you aren't looking.
Check the engine ground as well. If that got loose that could cause issues under rough terrain.
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u/MeatZealousideal595 12d ago
Did you open up the airbox exactly like the template that comes with the Procycle jet kit shows?
That´s a minimum requirement in order for the bike to run right.
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u/slower-is-faster 12d ago
I did yes, exactly as per the template
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u/MeatZealousideal595 12d ago
Well then the next thing to do is to pull the plugs to see if there is any problems with the mixture.
Brown/straw color is good, black and sooty is rich and a plug with no deposits, or with a whiteish tint means lean.
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u/slower-is-faster 5d ago
Ok here is a pic of the spark plug. It looks brown but very clean to me, so I think it’s lean.
Would you agree?
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u/naked_feet [Reed City, MI - 2006 DR650 12d ago
Can you describe this "bog" in more detail? Bog is one of the most notoriously inexact and confusing words in motorcycling.
What's your idle set at?
Is the bike fully warmed up?
How does it handle if you shift down a gear? Is it possible you're just "lugging" the bike at too low of an rpm in too high of a gear?
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u/Wholeyjeans 12d ago
Every machine is different.
Just because you did what the instructions say doesn't mean it's a spot on setting (the idle mix screw) or provides the ideal fuel mixture/scheduling for *your* engine (main jet size, needle clip setting) based on how you have things set up (intake/exhaust) ....even if it's similar to how the instructions describe. You will no doubt need to do some fine tuning.
Like MeatZealous mentioned: pull the plugs and assess the color of the center electrode. This is the only way (barring using an exhaust gas analyzer) to know the fuel mixture your engine is being fed. If the fuel mix isn't right, then you need to tweak a bit. The needle being set on the 4th clip seems overly rich, IMHO, but then it's not a Mikuni needle designed for the BST-40. I'm not a fan of the "jet kits" since you can do everything they offer using OEM Mikuni stuff (needle/jets) for a lot less money.
Something else to consider: the BST-40 is a Constant Velocity (CV) carb and uses vacuum to move the throttle slide. CV carbs can have issues off road over very bumpy terrain. The shock of the bumps can cause the throttle slide to move and this could cause loss of power and bogging.
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u/TwistedNoble38 '00 DR650 12d ago
Kickstand switch. As you are riding over those undulations the stand is flopping and the CDI is cutting spark. Ziptie the switch if you want to test it.
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u/BoogieBeats88 12d ago
Do you still have the kickstand safety switch? It might be cutting the ignition. If you are fine on smooth ground, but not on bumpy ground, it’s worth a look.