DR350 Bog off idle - Wrist Twisters
 
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post #1 of 8 Old 07-16-2014, 05:55 AM Thread Starter
Milites Gregarius
 
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DR350 Bog off idle

Are there any carb experts in the house?

I acquired a 1999 DR350SE (street legal model). It has some erratic behavior. It starts and idles great. Initially you could start down the road and at random times it would stutter a little but would pick up and be back to normal.

Yesterday it was running pretty good. I stopped for 10 minutes and took off again. I made it about a mile before it just died. It would still start and idle fine but any throttle input would kill it immediately. Pulling the choke would kill it.

Once I idled it the mile or so back to the house and let it cool. I pulled the plug. It's obviously rich (very black). My feeble mind understands there is an idle circuit and a main circuit so it appears my problem is the main. I figure a disassembly is required to clean/check but I don't know exactly what I'm looking for. It would seem that a clogged jet would make me go lean but it's obviously rich.

Any pointers would be appreciated.

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post #2 of 8 Old 07-16-2014, 12:35 PM
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Generally there are 3 circuits. How it works is depending on your engine rpm and throttle input, you will have an overlap of at least 2 circuits most times.

If it's running really rich and bogging down then you either have something holding the float open, the wot circuit stuck open or an issue with the diaphragm.

Best thing to do is just tear apart the carb, remove all rubber pieces and boil it in either water or water/limon mix for 10-15 mins, dry everything out with compressed air and reassemble.

When installing the diaphragm be sure to lube it with atf!

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post #3 of 8 Old 07-17-2014, 04:47 PM
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Not sure about yours, but the keihin carbs on my '85 nighthawk had three circuits like Pvster said (4 if you include the choke circuit). If you're mechanically inclined I'd recommend taking it apart and cleaning. I haven't tried the boiling method, but I do know that a high-pound test fishing line (nylon) is great for cleaning all the little holes and ports - just poke it into the holes and see if anything gets pushed out. NEVER use anything that could scratch the body (guitar wire, etc).
If you're less technical/want to try a "quick" fix, shut off the gas valve, run the carbs out of gas, detach the gas hose then fill the carbs (through the hose) with Seafoam. Probably want to leave it overnight if you do this.
My guess though is that you're probably better with disassembly since an occasional problem would indicate that its probably something other than just gummed up gas (maybe a piece of rust?).

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post #4 of 8 Old 07-18-2014, 06:41 AM Thread Starter
Milites Gregarius
 
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I appreciate the input. I found the cause of the super richness. There were some "shims" (looked like plain old washers) on the needle. Stock size jets for the off road version (but larger than the stock SE jets). I'm thinking a P/O had some kind of exhaust on it. Anyway, it's not running rich now but it's still bogging off idle. Now once it gets passed that bog it'll fly. I'm making progress. Going to go ahead and pull it apart for a soak. Thanks for the tips.

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post #5 of 8 Old 07-18-2014, 10:30 AM
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Did you turn your idle screws out a bit to lean out your idle mixture? Also Try tapping the bottom of the carb bowl when on idle and see if it helps, will tell you if sticking float and or stubborn float needle.

I may not have a lot to say but it doesn't mean I don't listen.
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post #6 of 8 Old 07-18-2014, 03:49 PM
Milites Gregarius
 
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Quote:
Originally Posted by amchev View Post
I appreciate the input. I found the cause of the super richness. There were some "shims" (looked like plain old washers) on the needle. Stock size jets for the off road version (but larger than the stock SE jets). I'm thinking a P/O had some kind of exhaust on it. Anyway, it's not running rich now but it's still bogging off idle. Now once it gets passed that bog it'll fly. I'm making progress. Going to go ahead and pull it apart for a soak. Thanks for the tips.
Glad to hear your making progress with it. And when you figure out the bogging off idle please let us know the cause of the problem. Because I have a 98 dr350se

image-3678768721.jpg

and In the 4 or 5 months I've had it, it would from time to time (twice so far) run very rich from idle to just above but after 2500 rpm to would be perfect. But after a week or so it would stop. So Since it is a intermediate problem I assume it is a sticky float or vacuum slide but I've been to lazy to pull it apart.good luck with her though

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post #7 of 8 Old 07-21-2014, 07:48 AM Thread Starter
Milites Gregarius
 
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Bog off idle was due to the air box snorkel being removed by previous owner. Apparently the "shims" on the needle were to compensate for that. With the shims removed it was popping on decel (lean). I put my hand over the air box hole until I got the bike to respond to throttle correctly. I used a piece of plastic and duct tape as a temp fix for the hole size. It runs great now and the spark plug looks good. My friend is going to look into either replacing the snorkel or getting a real jet kit for the open air box.

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post #8 of 8 Old 07-23-2014, 05:09 AM
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Pilot jet, replace it with one 2 sizes larger.

Put the shim(s) back in, forget the snorkel, should be fine.

Oh - Float position is important, be sure it's right while you're in there.

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