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DRZ400E Piston Scored barrel due to overheating

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I just spent AUD$1600 getting a new piston / barrel and all the other parts that go with it, due to my engine overheating, and scoring the barrel.

2003 DRZ-400E

I am trying to find the cause.

I did recently install a new 25L tank, but that should not be the problem, other people have this tank and have no problems. I am going to install the original tank to make sure.

Any ideas?

One mechanic said that it is running a bit lean. (don't know if it is related, but sometimes it backfires, and sometimes when idiling when I rev it, it will stall)

Unfortunately, I am not mechanically minded, and cannot check it myself. (hope to learn tho).

I am going to take it back to the suzuki dealership tomorrow for them to investigate.

But I don't want this to happen again due to overheating.


Running to lean

Cooling system problem

Raidiators/pipe blocked


Any input is greatly appreciated. I will post some pics of the barral / piston tonight.

Thanks for reading.

At the moment, I am :banghead::banghead::lol:

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Thats not good. I have an 05 E and it has overheated a few times. It has boiled over twice so far. Both times were on the dunes with engine working hard and little wind. It has also gotten pretty hot on the trails a couple times also. Started popping out of gear. I put an 80mm high flow computer fan in front of the radiator but behind the radiator guard. I think it helped but I am going to put one on the other side and switch it. I also put on a kx500 radiator cap that does nothing to keep it cool but will keep the fluid in a little longer if it does get hot. I dont really know what else can be done. Oh I also put in the Engine Ice coolent but did not see much difference with that.

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It has to be extremely hot to cause an issue like that. No coolant? I have lost a head gasket before and was riding until I heard a noise. Sounded like a rattle. Turned out it was coolant slowly working its way into the cylinder and instantly boiling off.

Anyways bike was extremely hot. Like...... light a fire hot. Nothing catastrophic happened at all...... so what makes you so sure that it was overheating? Just because you boil over some coolant doesn't mean it took out the motor. Just curious????

Should have just bored out the original cylinder and got a bigger piston while you were at it. 436cc sounds yummy. Cheaper probably too.

Strollerking maybe try using some Water Wetter and keep your bike inside at night so you don't need antifreeze. That should help a bit.

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Post sum pictures of the piston and barrel

I think it is more probable that

A Pease of metal chipped of an internal part of the motor

dust got into the motor

Or a oil starvation problem maybe blocked oil jet

The barrel can be repaired & replated

So don’t throw it away , sell it if you don’t want it

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The dealership said it was due to overheating. I thought it might have been from lack of oil.

After the piston/barrel/etc was replaced, I test rode it, and went back to the shop, they said it is running hot, and should not run this hot. Tonight I put the original tank back on to prove that it is not the tank that is the problem (they thought it might be the new 25L tank). I am taking it to them tomorrow with the original tank on, to find the problem. fingers crossed it might just be something small (jetting or so, some ppl said it was running Lean), the day this actually happened, I was riding on the road for an hour or so @ 100km/h, pulled over for a rest, and then heard the noise? I was actually 1000m higher altitude than normal, and the oil was low (did not check it)

Either way it is not good, and cost me a packet :banghead::banghead:

I want to find the cause tho, and really appreciate your help and comments.

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Don't know what temperature. E model has no guage, but they did not test it. Where should they test it anywayz?

I did about a 10 min ride, and the radiators were hot, could not touch for more than 0.5 -1 sec.

They did not say anything about the oil pumping :-(

I want my bike back and fixed :-( not a good experience for first bike :banghead::banghead:

Whats your opinion? Oil related or overheating due to running to lean or not enough cooling....

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Better than 90% chance its an oil problem

That’s the piston that is smeared over the side of the barrel in pic 2

I would be testing the oil pump and confirming the spray nozzle wasn’t blocked

Is the underside of the piston like a burnet barby plate

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Got the bike back. I was contemplating the 440 kit, but I chose to go back to stock.

She runs very well. Sounds a bid deeper??

But I am very happy to have the bike back, missed her so much! Got to look after her now.

The bike shop was suspicous of the larger (25L) fuel tank that was the cause.

But I am putting my money on the low oil level as the cause. So I must maintain and not do that again!

Back to riding :banghead:

Thanks for your help guys!

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