where are you? If you are in Pokhara, go see Matt from Hearts and Tears, if he can't help you he may know who can...

Just got to Kathmandu

Edit: the starting is coming and going again but I did just notice that when I touched a drip of petrol from the carb overflow after it had been sitting for a day that it was thick and red and looked all the world like the k&n air filter oil. I started using it after I had issues but it's been ages since I've used proper foam air filter oil so it could just be one more thing contributing to the "crap (bad petrol, etc) is getting in the fuel and making it run badly" problem. Since there seem to be a lot of honda CFL's around here I may try a search for proper foam air filter oil and put to bed the air filter questions once and for all.

Maybe the focus on a clogged or over-oiled filter is misplaced.
Is the carb overflowing? Float level may be too high. Not sure about the DRZ but other DR models have a tendency to have a sticky needle valve or a faulty o-ring on the fuel input.
It's good practice to shut off the fuel tap and let the carb fuel level drop when the bike is being parked-up.

Another thing to check after all the carb work is the pilot screw. Maybe it's not been replaced in the right position. But then this would affect tick-over throttle not half-full throttle.

I only ever used engine oil to oil my air filter. I would wash it in petrol and washing up liquid, dry it for 24hrs in the sun or somewhere warm.

Then put it in a plastic bag and drizzle a few glugs over it, (like you would drizzle oil over vegetables before putting them in the oven), then massage it in.

It was never enough oil that it ran off the sponge filter nor accumulated in the bottom of the air box. The airbox would be greasy but never a build up.

The carb has overflowed twice now, both times while parked overnight. I asked the mechanic about the float when he took the carb apart and he said it was fine. Unfortunately the DRZ has no off - it's vacuum operated so it just stays 'on' all the time.

maybe you could put a clamp on the fuel hose overnight. Does sound like a float issue..

Tap needs a refurb; diaphragm probably holed but where are you going one of them!
You need to be aware that fuel might leak into sump. Again, I'm not certain how likely on a DRZ. If it's leaked into the air-box you'd know already.

Clamping the pipe overnight is a good idea. Or remove fuel hose and insert a bolt and secure with a jubilee clip.

Looks like you'll have to check the float and needle valve. A *gentle* dressing of the needle face with very fine sandpaper should be helpful if it's worn . Then test float movement is shutting off fuel. Does the float move freely and is not punctured.

thanks all for your help, I think we're getting closer to the answer with the petcock/fuel tap. One of the loose screws that the mechanic pointed out was actually on the back of the petcock, which I never noticed because the screw head sits in the back. In addition according to thumpertalk it looks like the petcock on the DRZ is prone to failure, and they all recommend getting a cheapo Yamaha Raptor petcock as a replacement (which has an 'off'). If it's the petcock, that'll fix it, if it's not and it's the float that's broken (even though the mechanic checked), well at least then I could easily shut it back to 'off' overnight. It looks like I might even be able to get one ordered from China.

I would vet carefully info from Thumper Talk. There are some experts there but plenty of clowns too. Stay with the experts.

I owned a DRZ-E and kept a friends S model running for about 10 years, so bit of background on this bike.

With all the well meant suggestions here ... you may end up chasing your tail, headed off to the weeds, opening several cans of worms along the way. :helpsmilie:

A careful approach is needed now. Think it all through.

I doubt too much oil on the K&N was ever an issue. I hate K&N filters and would never use one ... but it's what you got ... and .. if you keep it clean and LIGHTLY oiled, it will be fine unless riding constantly in severe dust behind trucks or several other bikes. The K&N does not filter dirt well, more oil will not help for long.

The engine may suck a tiny amount of oil in ... but that would soon be burnt up. I'm guessing the rich running/fouled plugs are caused by something else.

I would replace the complete O ring set in the float bowl. I think there are two or 3 O rings, including the one on the float stem where it plugs into the bottom of the float bowl.

Make sure you have not lost any little rubber items.
Most common problems are old O rings (that may look OK to naked eye) and a clogged Pilot jet. The Pilot jet can be hard to clean and may LOOK like it's OK ... If you can, get a NEW one.

A word about Chinese parts. NOT GOOD! Many in the DR650 and DRZ community have had problems with Jet and O ring kits of Ebay from China.
Some may be OK but I know that some are NOT. If you can get OEM Suzuki, I would.

Try these guys to start:
https://procycle.us/bikepages/drz400.html#fuel

I doubt your petcock is the problem. It's more likely the O rings in float bowl.
Make sure you account for ALL of them. You will need good pics of the Carb.

Don't try to work on the Carb with it ON the bike. Take it off.
Obviously bad fuel is a concern ... and has faked out plenty of mechanics including me.

So, really try to make sure the fuel is OK. Water would be the real enemy. Grit and crap can be filtered out ... but water not so easy.
Remember, it's heavier than FUEL so it collects at bottom of fuel tank or float bowl.

Make sure your fuel filters are clean and flowing. I've forgotten if DRZ-S has an internal fuel filter like the DR650 does? The one on the DR650 is hidden and some miss it. Not sure on DRZ400 ... but check on that.

Check the Air Cut off thingy and make sure that little O ring is in there. Procycle has a kit if required.

You may have an inline filter as well, plus your petcock stem is a filter too. All must be checked and clean.

If you carb leaks it will eventually fill your crankcase with gas. Not good! So either the vacuum feed petcock is faulty or the O rings are bad in the float bowl or little rubber "needle valve" thing is worn or has crap collected in it's seat.
Poor quality or ill fitting O rings can also cause problems. The Pro Cycle kits are pretty good but OEM Suzuki is ALWAYS best.

Once you get it running make sure you run filters and filter the fuel you get through nylon stockings and try to find some sort of additive to put in fuel to absorb moisture. Don't use too much! The locals must have something that works.

Sorry for long diatribe!
All the best!
bier

Thanks a ton for the detailed response! Btw my air filter is a foam one, but I'm using k&n oil on it sInce its the closest I can find to foam air filter oil.

The DRZ doesn't have an internal fuel filter, just the screen on the petcock, which was clean.

The fuel here is very bad, I don't think it's possible to get a verified good tank which makes it all much harder to diagnose. Even if it doesn't have dirt or water it's very low octane. At least I've been guaranteed that since kerosene no cheaper than petrol in Nepal that unscrupulous station owners won't try to doctor the fuel like they do in India.

I'll try ordering a o ring set, I'm getting a friend to send me a parts shipment from Europe soon anyway - but that's at least a month off. (And even then I'm having a really hard time finding the right parts - at the procycle shop are you looking at the carb repair kit?) Until then I guess it's unhooking the fuel hose every night when I'm done for the day. I'm mostly doing trekkimg now though so it shouldn't be THAT much of a hassle, even if it's a bit hard on the hose.

Looks like ProCycle has all sorts of things for your bike ... jet kits, carb rebuild kits and more. I'd look it over and see what you think would help. If you have specific questions I would email ProCycle ... very good customer service there!

They may be able to steer you to parts you need and possible solutions.
They ship really fast but I imagine the real issue is getting past Indian or Nepalese customs in a timely manner.

I missed the no K&N filter part, sorry. ANY light oil is FINE for oiling your air filter.
Too bad about the fuel. If local bikes are running on it, your DRZ should too.
Enjoy the trekking! Once your bike is sorted should all be good! :D:D:D:D:D

Posting in case someone has the same problem.

It turns out it was the carb, which had been getting worse and worse while I waited for parts - I took to Kathmandu Motorcycle Workshop (which is a great shop) with the carb rebuild kit. When they had it out they verified that the seals around the float were leaking (by blowing into the fuel line) and showed me how worn all the o rings were. They put it all back together and now it's starting (and running) much better.

Of course then to celebrate I promptly got a flat tyre :(