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DRZ400 Rear Wheel Lock Up

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Just picked up a 2000 DRZ400E from craigslist about a month ago. The bike ran great during the test drive and for about 3 weeks after. Then after a long day of riding with my buddy, we were cruizing at about 20mph and my back wheel locked up all the sudden. I pulled in the clutch and the tire freed up as i rolled to a stop with the engine locked. I then tried to start the bike and it would turn over but would not fire. Brought it to a mechanic and he said it was water in the gas tank and that the bike was running fine and that he test drive it to operating temperature (lies). When i went to pick it up I rode it around for a minute or two and it worked fine so i left. Sure enough about a mile down the road it felt like someone was hitting my back brake repeatedly and then the bike locked up again. Waited 5 min and it would start and idle in neutral for about 15 seconds before locking up yet again.

 

I have little experience working inside dirtbike engines so I need help troubleshooting this issue please!

 

Thanks, Chris

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Symptoms are piston seizure in the cylinder.  Typical to free up once cooled off.  You will probably find aluminum transfer from the piston to the bore or the hard coat is warn thru exposing the aluminum cylinder surface to the piston.

 

Recommend remove the head and the cylinder to diagnose.

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Thank you for the fast response! How tough is removing the cylinder. I have worked on carburetors before and have basic tools like socket wrenches but don't have a torque wrench. Will i have to remove the engine block from the frame?

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Motor can stay in the frame.  You will probably have to buy some tools but nothing very specialized. You will need a torque wrench at re-assembly for the 4, 10mm head bolts.

 

Some people will not touch a motor without a full set of torque wrenches for every fastener. Other people are less concerned.  You will have to trust your own judgment and experience to decide how many torque wrenches you will need.  If you buy torque wrench(s), buy good quality and of the correct scale range.  The torque you need should be within 50% to 90% of the wrench scale.  The 4, 10mm head bolts are the critical items where a torque wrench is a must.  The head bolts torque to 43 foot pounds not 34.

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Turns out the bearing that holds the camshaft and the connecting rod together went bad and was intermittently locking up!

 

crankshaft and connecting rod?

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I'm gonna be in your boat soon. A loud knocky tap is indicative of some bearing on the crank going south. I just got a hotrods crank/ bottom end kit. With your experience level I would say its above what you want to tackle, but i do encourage you to research and try it yourself....if you want to buy some tools and learn new skill. Otherwise look on here for what parts you should buy, and supply them to the shop you choose to rebuild it for you ( keeps pricing more honest ).

Bottom end kit is 340 for stock stroke and includes gaskets and some seals. I chose to replace every bearing in the bottom end while I'm there. Hotrods supplies kits for crank trans, counterbalance and water pump if you so choose. I found the pricing reasonable.

Edited by BLKRAWB

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Sorry duplicate post. Fatfingered my phone

Edited by BLKRAWB

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