DRZ 400 cranks but won't start

[Nick Sebasovich]

Ok so, the bowl is full of fuel.  When I sprayed fuel right through the carb I got the slightest bit of a rumble.  HARDLY a response. Its the most life I've seen out of this bike since I bought it. 

[Nick Sebasovich]

Another update.  While i was cranking the bike today i can feel air pushing out of the crankcase breather tube... Is that as bad as i think it is?

[jjktmrider]

That's the piston moving up/down and why they need a breather. You'll need to do something with the carb to get it to run , I doubt it was completely cleaned . Likely the pilot circuit was not unplugged. 

 

Since you have the fcr , give the bike 4-5 throttle twists to squirt some fuel down it's throat . see if it'll pop off . If it doesn't take out the plug and see if it's wet . If wet try holding the throttle open 1/8 turn while cranking and every once in a while give it a accel pump squirt .

 

 

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[Nick Sebasovich]

I pulled the carb out and with the help of a YouTube video I cleaned it myself. First time in a FCR so hopefully everything is right. I'm gonna put fuel to it and crank some more and see if it made a difference 

[Nick Sebasovich]

Also the intake valve looks like it's covered in carbon. Don't know if that points to anything or not..

[jjktmrider]

That video didn't have you splitting the carb in half did it ? I'd hope they just had you take the bowl of and take the jets out ect.. but not total teardown , the fcr is one that doesn't take too nicely when taken completely apart without complete new seals and gaskets , even then .

The carbon on the valve(s) is common as long as it's just barely enough to "look" like it has some on it , but not a thick coating .

 

 

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[Nick Sebasovich]

Well guys I apologize for the long absence.  Like i said I've been working at this when i get time and the past few days I've been hard at it again.  I built my self a little homemade cylinder leak down tester with the hose from my compression tester with the schrader valve removed and an air compressor with a rubber tip on the air chuck. i was able to fashion some that was air tight and i could use to pressurize the cylinder.  I found that with the engine at TDC and the cylinder pressurized, I have air pushing back through my carb.  Its a substantial amount, enough that i can feel it on my hand when i put it up to the carb throat.  

Am i right in assuming that i have a valve problem?

Im thinking my next step is to pull the head and inspect the valves to look for a bent or burnt valve.

Any thoughts?

[Backwoods-Bomber]

Well guys I apologize for the long absence.  Like i said I've been working at this when i get time and the past few days I've been hard at it again.  I built my self a little homemade cylinder leak down tester with the hose from my compression tester with the schrader valve removed and an air compressor with a rubber tip on the air chuck. i was able to fashion some that was air tight and i could use to pressurize the cylinder.  I found that with the engine at TDC and the cylinder pressurized, I have air pushing back through my carb.  Its a substantial amount, enough that i can feel it on my hand when i put it up to the carb throat.  
Am i right in assuming that i have a valve problem?
Im thinking my next step is to pull the head and inspect the valves to look for a bent or burnt valve.
Any thoughts?

Are you sure it's on the compression stroke?

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[Nick Sebasovich]

No I didn't verify that. Would it matter?

[Backwoods-Bomber]

No I didn't verify that. Would it matter?

Yup, if you are on the intake stroke the intake valves are open. Pull the valve cover so you can verify that the cams are at 10 and 2.

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[Nick Sebasovich]

Ok. I'll do that tomorrow. I assumed that regardless of the stroke the valves would be closed at TDC. 

[Backwoods-Bomber]

Ok. I'll do that tomorrow. I assumed that regardless of the stroke the valves would be closed at TDC. 

To do the leak down properly you will need to disable the decomp. This requires the valve cover to be off anyway. Otherwise, you will be losing air out the right exhaust valve. You will probably be able to figure this out by yourself but let me know if you need more guidance.

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[Nick Sebasovich]

So I took the cams completely out of the head to eliminate any possibility of valves being open and found that my intake valves are not seating properly and blowing quite a bit of air by them. They look extremely burnt and carbon coated. I pulled the head assuming this is probably my problem. 

[Backwoods-Bomber]

I'm kind of at a loss for how that could be the issue if you truly have 120 psi of compression with the decomp active.

 

Flip the head upside down on the work bench and puddle some solvent on the valves. Look for where the solvent leaks past the valves to confirm the issue.

 

Don't lose the cam dowels when flipping it over.

 

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[Nick Sebasovich]

I'll give it a try. Hopefully that will give me a better idea. 

They just seem like the seats are not clean enough to seal. The compression spec is over 140psi for this bike I believe. 

If this isn't my whole problem, then it's at least contributing to it. 

[ohiodrz400sm]

I'll give it a try. Hopefully that will give me a better idea. 
They just seem like the seats are not clean enough to seal. The compression spec is over 140psi for this bike I believe. 
If this isn't my whole problem, then it's at least contributing to it. 

The manual states 130 psi with decomp active.

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[jjktmrider]

That what I though , 120 may not be tip-top but should be plenty to run . I'd expect down in the 80-90'ish range to start having starting issues . Fresh rebuilt motors with rings not yet seated-in are in the 110-130psi range without a decomp and they start .

 

 

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Edited August 12, 2017 by jjktmrider

[Nick Sebasovich]

I don't know what else it could be. Im no master mechanic but I've run through everything on this bike that I can think of. I'm open to whatever you guys suggest though. I'll gladly take the advice! Lol

[ohiodrz400sm]

If you plan on keeping the bike it wouldn't hurt to rebuild the head. It is nearly 15 years old.

Beyond that, a factory service manual goes a long way. I still suspect a carburetor issue but my magic 8 ball isn't always right. There is always the dealer option if you can't figure it out.

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[Nick Sebasovich]

8 minutes ago, ohiodrz400sm said:

If you plan on keeping the bike it wouldn't hurt to rebuild the head. It is nearly 15 years old.

Beyond that, a factory service manual goes a long way. I still suspect a carburetor issue but my magic 8 ball isn't always right. There is always the dealer option if you can't figure it out.

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My plan was to overhaul the head since it's already off. The bike is clean enough that it's worth holding on to and eventually I'll sort this thing out. The carb issue is still in the back of my mind. I'm still not totally educated on this vacuum stuff. I understand the basics of it but I don't fully understand how it works and I feel like I could have a problem there. 

The manual is shipped already. Should be here Monday. 

If all else fails I might have to go the dealer route as much as it pains me to do it.