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splutter, backfire then stalling

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hello, I've got bit of a problem with my bike. Its a 2000 mdl Drz400 kick start only. I've had for few years, regularly serviced etc. my son was riding it the other day and had to push it home about a mile after (so he says), it coughed and spluttered then stalled as if it ran out of fuel. There was stll plenty in tank. He couldn't get going again.

Now I have had the carby out, pulled the bowl off, taken all the jets out, given all the small galleries a blast with air and replaced the needle and seat. The pilot screw was exactly 1 and 7/8 ths of a turn out so I set it back to the same. I couldnt realy say for sure that I found anything wrong with the carby.

After putting it all back together, I was able to get it started with no problems.

i let it warm up for few minutes, adjusted the idle speed and took it for a burn. At first I thought I had fixed the prblem but then it began to splutter, backfire and stall to a stop, as if it had run out of fuel.

Any ideas? Could the valve clearances have anything to do with it? It's got me stumped. :thumbsup:

Any advice, suggestions welcome.

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valve clearance could do this if one was very tight and you were losing compression when the motor got hot. I'd start with the easy stuff first though..

make sure you don't have a plugged gas cap vent or vent line, make sure you're actually getting fuel to the carb and the petcock isn't plugged, you've got oil in the bike, etc.

go ride it, when it dies, pop the gas cap and listen and hear if you can hear a hissing like there's a vacuum there, if no, pull the petcock out of the tank and make sure it isn't all nasty and the guts of it aren't rotted out. make sure your fuel line isn't a little bit kinked and it swells shut when the engine heat hits it, eliminate the obvious before you tear into the engine.

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Yupp check hoses to the carb and the tank, I had a very almost exact problem, i changed my tank to yellow and the bike. Forgot a hose try running it on p for prime allowing gravity to feed the fuel if that works then its the hose i forgot LOL took me an hour :/

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Sounds like a failed petcock. Same shit happened to me. Set your petcock to PRI and you should ride forever. Just don't forget to take it off PRI or you'll be screwed.

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Well Ive checked the petcock, fuel line and the tank vent and there's no problem with fuel delivery to the carb. I'm wondering if the float level may be out or if I missed cleaning out a crutial air or fuel passage inside the carb. I even changed the sparkplug (just in case its a sprk problem).

I tried it again this morning and it started pretty easy cold with the choke out. Once again I let it warm up a minute or two, pushed the choke back in and tried to ride it. It popped and stalled after only getting 20 feet away! and it wouldn' start. I pulled the hot-start knob out and I got it going again but it only lasted a few seconds.

I know its hard to diagnose from only a description like this.

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UPDATE. I checked over the whole bike, stopping occasionally to scratch my head, and I spotted a wire that goes to my head lamp was freyed on its insulation and could have been shorting out against the frame. So I fixed that and also re-checked all the hoses and pipes to and from the carby. There was one small hose that looked a little kinked so straightened that up and tried again. This time no problems. It started easy from cold, I let warm up for a good 5 minuted with the choke out. When itbstarted to runa bit rough with the choke out, I gave it a bit of a rev and pushed the choke off. It sounded sweet. Good throttle response. I adjusted the idle speed a touch more and then took it for a spin. It seems to be good now.

So is it possible that the wire for the headlamp shorting was the cause? This bike is a kickstart only ( no battery). And I' also thinking I may not have been letting it get up to temperature before pushing the choke in. ( its not cold where I am. 25 degC.) The real test will be a proper ride with my lads out bush.

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im not sure what it is what its called but its got small round cover on the lhs of the carby above the float bowl. two small screws hold the cover on. It has 3 hoses attached to it. one comes from the vaccuum side of inlet manifold, one comes from upsteam of the butterfly and another smaller one that comes from the guts of the carby somewhere. This is the one was I think was a bit kinked.

This round thing looks like it has a diaphragm in it. I didn't touch it when I had it out.

What is this thing anyway?

I'll post a pic as soon as I get on a proper PC.

Thanks for all the help thus far too! great forum

tRevHead62

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Your model should have this slant body fcr....NOT a mikuni vacuum carb..your fuel tap has got on ,off and res...?

I think you are referring to the coast enrichener.?...inside the red line..

img1924largetx6-1.jpg

The coast enrichener richens the fuel mixture on deceleration to prevent backfiring...It's basically an air cut off valve that relys on engine vacuum..

The CE over time tends to become inconsistent..It can stick,the rubber deteriorates and can cause jetting issues...

Check your carb jetting are close to this..

160 main jet

200 main air jet

100 pilot air jet

EMN needle clip 3 or stock DXP needle clip 5

45 pilot jet

2.25 turns fuel screw

airbox snorkel removed

I would recommend....

Remove the coast enrichener.http://www.thumpertalk.com/forum/showthread.php?t=726110&highlight=coast+enrichener+removal

Do the Eddie Mod if it has any bogging issues..http://www.thumpertalk.com/forum/showthread.php?t=890079&highlight=eddie+mod

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I should have mentioned that the bike has had a stroker kit fitted by a previous owner and, to be honest, it may have some other mods as well. So the jet settings you advised are probably not accurate for this bike. Thanks anyway. its all very handy information.

Here's a pic of my carb. Mine has "hot-Start" valve fitted. Was this an after market accessory or was it stock on some models only?

http://i1111.photobucket.com/albums/h479/trevhead62/2000DRZ400carb.jpg

Edited by tRevHead62
fixing link to photobucket image

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2000DRZ400carb.jpg

The hose that was kinked a bit was the small one just under the rhs screw.

The bike's running ok again now. hmmm. Don't ya hate that... not knowing what exactly you did but you fixed it anyway!

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Ok.. then this would be suitable jetting for 470cc stroker/Bbore, sea level, open pipe

160 main jet

200 main air jet

EMR needle

clip 3

45 pilot jet

2 turns fuel screw

airbox snorkel removed

The CE removal and Eddie mod is still applicable...

From memory the hot start was stock on that model...

If you want to get it going way better a 41fcr, +1mm rhc/ferra valves and rhc187 cams would be suitable..all available from Master Eddie...

Edited by CraigoDRZ400sm

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