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Gotcha, that makes sense - thick clingy oil to catch all the dust and shite going through the airbox. I'll pull the filter and haul the old girl round the block a few times, see what gives. Looks like the apocalypse outside, I swear it's raining upwards. I'll leave the ride till tomorrow, 20 degrees and sunny on the forecast. That's more like it.
But then again I have been invited to a barbecue which inevitably means that the weather will go to shit.
Ok. Pulled the filter out the airbox and went for a ride yesterday.
Damn.
Different bike. Throttle response way smoother, much less boggy, just way more fun. Really felt much better.
So today I’m going to properly clean the filter (I bought some mineral spirits yesterday - will that do it?) but don’t have the right filter oil, I’ll pick some up next week.
I’m also going to pull the carb and switch out the main jet for a smaller size. Let’s see.
Yep use dawn to ckean then get filter oil. Ct has kn and it works well. It red too so you can see how much you put on. The other option is 2 stroke oil. It works. Regular motor oil can worj too in a pinch. Apply and if you can squeeze out excess thats the best. Ie a foam filter. But a cotton wire like a kn you need to spray and let drip then put back.
Thanks for all the help with this gents, it really helped me out once again. Took the bike out again without the filter just to confirm how everything ran and sounded, then got to work on the carb. Turns out you can get to the jets while leaving the carb in situ -
It means removing a bunch of crap from the other side (namely starter relay assembly, some hoses need to be rerouted and the gas tank shimmed up by 3-4") but it's doable. Switched out the 155 jet that I'd previously installed for a 150 -
and buttoned it up again. You have to be careful that the dowel pin holding the floats in place doesn't dislocate but again, doable. Pulled the plug, gave it a good clean with a wire brush and carb cleaner, and once everything was back where it should be I went out for another ride. Big difference - so much smoother, crisper and with far better throttle response. Still had a fair amount of black exhaust when I cracked the throttle, but it's maybe significant that the air filter was not installed. I'm hoping once it's cleaned and reinstalled that the air/gas mix will balance out a bit better. I'll also pull the plug again and see what it looks like (didn't have time last night).
Overall - to anyone reading this that has a thumper and is staring down the barrel at carb work - it's not as hard as I made it out to be. Especially as the jets can be accessed (on this KLR anyway) with them still in the bike.
Edit - On second thoughts, once the air filter is installed I'm now thinking the bike will run richer if anything and therefore the black exhaust probably won't die down. What would you suggest the next step? Dial down the jet - or play with the needle shim? Or the air mixture screw?
From that read it looks like most of these 685's are running 142-145 mains.
From ADV Rider:
"I've used my A/F meter (wide band O2) on doz of KLR's. I generally end up with the following final settings using KLX needle. Folks report they average 47-50mpg in mixed riding.
KLX needle 2nd clip
142.5 main jet
7/64 drilled slide
Fuel screw adjusted for max rpm's (generally 1.75 to 2.25 turns out)"
Jim, what is the stock jet for the bike? rule of thumb generally is +1 step for more open exhaust, and likely +1 step for the larger piston. I looked at BB but it has various #'s from 142-150 with 2 step increments, so if your bike started with a 142 +2 would be a 146 so my guess is you'll end up there or maybe a 148 with the snorkel removed. 150 may be too rich. But if you are using aftermarket jets the sizing steps may be different from oem. You'll need a conversion chart.
Cheers Mike, I think you already hooked me up with the conversion chart so it should be pretty easy to figure out what size the DynoJet jet is compared to OEM. I'll have a look later, thanks fella
Yezzir.
ADV Rider is a ridiculous treasure trove of information it's just so huge it can be a PITA to sort through it.
I've never messed with a dynojet kit (i like to stick OEM on carbs) but if it's as rich as it seems if it were me I'd toss the stock bits back in and see what you get, then maybe bump the main up a couple notches. Stock shouldn't be lean enough to hurt anything with testing.
Carbs are a tricky bitch, sometimes you make change after change only to find out that stock works best, or that you needed to actually drop down a jet size instead of go up. I fought a 400F forever until someone finally told me to actually drop the jets a size and bam right on.
Yezzir.
ADV Rider is a ridiculous treasure trove of information it's just so huge it can be a PITA to sort through it.
I've never messed with a dynojet kit (i like to stick OEM on carbs) but if it's as rich as it seems if it were me I'd toss the stock bits back in and see what you get, then maybe bump the main up a couple notches. Stock shouldn't be lean enough to hurt anything with testing.
Carbs are a tricky bitch, sometimes you make change after change only to find out that stock works best, or that you needed to actually drop down a jet size instead of go up. I fought a 400F forever until someone finally told me to actually drop the jets a size and bam right on.
No kidding? Drop a jet size huh, who'd'a thunk it. Maybe I'll end up down that route too. The good news is that accessing the jet is really easy on this KLR, and I bet if I rotate it the other way I could probably access the slide and needle too if necessary.
I'm a member of ADV Rider but yeah, there's a lot of wading to be done over there. I should definitely dig deeper though, you're right - there's a ton of great info there. Thanks again man
The reason for dropping a jet size is because you went up in bore, but remained the same size on the carb. There is significantly more vacuum pulling through the venturi, which is pulling more fuel. Making the carb slide hole more open is supposed to reduce some of that effect for the main. It's also possible the vacuum is pulling the main up early, so you are running off the pilot and main together and too early. If you open up the exhaust and airbox more, or forgo the airbox altogether for Uni filters, then it's possible you would have to do the opposite. If you're trying to do all of this just in the garage at idle on center stand, then you may not get the right information. You'll really need to ride it to figure out your mid and upper range on throttle.
No kidding? Drop a jet size huh, who'd'a thunk it. Maybe I'll end up down that route too. The good news is that accessing the jet is really easy on this KLR, and I bet if I rotate it the other way I could probably access the slide and needle too if necessary.
I'm a member of ADV Rider but yeah, there's a lot of wading to be done over there. I should definitely dig deeper though, you're right - there's a ton of great info there. Thanks again man
When you free up the air passages you reduce the amount of vacuum required to suck x amount of air through the carb, this means less fuel gets sucked in and you need to jet richer for intake/exhaust mods. (usually)
The big bore kits on the other hand will increase the vacuum.
This causes both more air and fuel to get sucked in. In certain situations it’s likely that the fuel flow increases more than air flow and you could end up rich even on stock jetting. It’s all about the Bernoulli’s principal.
You guys explain so nicely the effects i experienced when boring out the xs750 and xs11. Since i dont know shit about physical principles it felt odd needing to drop the needle to the bottom on the xs11, and go back to stock jets. Might even have to drop a size before its 100%
Thanks again for all the help and explanations, really gives me more understanding of how the carb actually works. Didn't get round to playing with the jet today but did figure out that the jet I have in there now is a DynoJet 150 (down from 155). That's the equivalent of a Keihin 165.
Did however get myself a can of PlastiDip and turned those butt ugly white side covers a rather splendid black -
Never used PlastiDip before but I like the texture when it dries. Hopefully tomorrow I'll have time to get back to the carb - I'll switch the jet for a smaller size, clean that filter (I followed your lead Irk and ordered the foam filter cleaning/oil set you suggested) and see what gives. Getting closer.
Plasti-dip is great stuff. 165 is way large and likely your rich issue. I'd get a Keihin 150 and try that as it was the large side of stock on the BB parts listing.
I'll try that - the DynoJet kit came with a bunch of main jets so I'll keep dialling it down until I lose the cloud of black smoke from the exhaust and the plug stops fouling.
Speaking of which, does anyone have an idea why the bike occasionally stalls? It'll do it pretty randomly but usually when I'm decelerating. Coming up to a stop sign, traffic lights. that kind of thing. But it can also do it when I'm just going down the road. Happened about 5 times in 15 minutes yesterday. I'm still keeping the bike local so I'm not at speed when it happens, but it's a bit unnerving - and I look like a right wally when it happens next to a beer terrace full of people. Not a cool look at all.
I could be the rich condition fouling the plug enough to make it quit. but it sounds more like a bad connection in your ignition circuit. I had an old fuse that would randomly disconnect and kill the bike only to reconnect seconds later and start back up. Also a lose ground can cause the same thing. Check all your wires for routing/chafing connections etc.
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